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Topic: 7.5 Onan Quiet Diesel gen problem...UPDATE

Posted By: Cloud Dancer on 08/04/10 11:54am

7.5 HDKAJ11502H
A030461876

All these years, it's worked perfectly. I've done all maintenance myself. Recently, it started shutting off by itself, after running 20 to 30 minutes. It made no difference if the main tank was 1/2 or full. And, there was no sputtering, just a sudden shutoff, the same as when I turned it off.
I went to the book to clarify the fault code system, of which I had learned about in these forums. I really couldn't completely understand what it was telling me. So, I just started doing the full maintenance routines, since the parts don't cost THAT much anyway. I did the oil and filter first, then the fuel filter and air filter. Then, went to the cooling system, and had a little bit of trouble filling it, so I started it up to circulate the coolant. I let it run, and it quit on its own after about 15 minutes. On restart, it would quit immediately. Of course, the red light was blinking slowly, like asking me to read the code. I got 3 blinks, short pause, 3 blinks, long pause,....and repeat. I took it to mean 33, which speaks to an overheating problem. So, I finished filling the system by using the squeeze bulb that I use for filling my batteries (it's got a small neck below the pressure cap). Then, I filled the overflow tank to about half way between the 2 marks.
This time it ran for about 2 hours and I figured it was all OK. This was 3 days ago. Today, I tried it, and it ran for one hour and quit. And, it's giving me the same fault code, again WITHOUT any detectable sign of overheating.
During all these tests the output voltage was 119 to 121 depending on the load which I tried one and two air conditioners plus one or two TV's and one time I turned on the microwave oven. The problem does not seem to be load-related. And, the battery voltage is normal (at the battery box and the monitor panel).
I sure would appreciate some help with this one, as I really can't go anywhere without a reliable generator. Thanks

* This post was edited 09/02/10 08:51am by Cloud Dancer *


Willie & Betty Sue
Miko & Sparky
2003 41 ft Dutch Star Diesel Pusher/Spartan
Floorplan 4010
Blazer toad & Ranger bassboat


Posted By: JFG on 08/04/10 12:09pm

On the fault code, when it blinks three times.. push in on the stop button momentarly and release to get the second tier fault code.
did you chk or change the air filter?


Fred



Posted By: Cloud Dancer on 08/04/10 12:40pm

JFG wrote:

On the fault code, when it blinks three times.. push in on the stop button momentarly and release to get the second tier fault code.
did you chk or change the air filter?



That's the part I could not comprehend (second tier). I will attempt to learn how, per your instruction.

Yes, I changed the air filter.


Posted By: Cloud Dancer on 08/04/10 01:23pm

JFG,

I went out and waited for it to quit running. As soon as it did, the slow freqency red light came on, then I depressed/released the stop button and got the same 3 blinks-short pause-3 blinks as before, then I depressed/released the stop button again (which I had previously tried) and got NOTHING, no light of any description. And that is what had confused me before.
THEN, I restored the fault light by depressing the stop button 3 times within 5 seconds (per manual instruction). I get a 3 blink-pause,3 blink-pause,3 blink-pause,...continous,...so then I depress/release the stop button to go to the second tier, and I get the 3 blink,short pause,3 blink long pause, and repeat.
Is this a 33, or is it not going into 2nd tier? Or, maybe I'm not following?
Thanks


Posted By: Cloud Dancer on 08/05/10 07:11pm

NOT fixed yet,....I'm trying to find out how to check if the water pump is turning (if belt has failed?).
The Onan factory does NOT offer any tech help.


Posted By: kg5388 on 08/05/10 10:56pm

open access door on bottom of genset and look at the crank pulley with a flashlight do you see the belt in the pulley or a broken belt in the bottom

broken belt will cause fault code 1 or 33 to flash

check coolant level
check radiator and fan for being clogged/obstuction
check belt
check wire on coolant temp sensor for coming off and touching ground
ohm sender for proper resistance
test replace thermostat


Posted By: Cloud Dancer on 08/06/10 04:33pm

kg5388 wrote:

open access door on bottom of genset and look at the crank pulley with a flashlight do you see the belt in the pulley or a broken belt in the bottom

broken belt will cause fault code 1 or 33 to flash

check coolant level
check radiator and fan for being clogged/obstuction
check belt
check wire on coolant temp sensor for coming off and touching ground
ohm sender for proper resistance
test replace thermostat




Thanks for taking the time to help me.
I checked the coolant level again, and went through the procedure of clearing the vent hose. I 'pinched' the overflow hose with a needle-nose visegrip, and with mouth pressure I could hear a faint gurgle. The system appears full.
I started it cold (95 degrees ambient), and it ran for 12 minutes. I restarted it 6 minutes later, and it ran for 7 minutes. The fault code, the way I read it, is 33.

I found the pulley and the belt(appears to be 3/8 or 7/16 V-belt). The belt looks fine, even when gen is running.

In order to check the sensor wire I would need to know how, and the same for the thermostat. This is mostly because I have not removed any of the sheet metal.

Am I at that point, where I need to start removing the cover panels? This unit is on a front pullout, but I'm not so sure the panels will clear (would need to try, I suppose).

A stuck thermostat is something I can imagine would produce these symtoms. Which makes me want to ask the question, is a faulty thermostat likely?

Thanks for all answers and suggestions. I wish I was there.

Willie


Posted By: kg5388 on 08/06/10 09:39pm

I have never changed a thermostat except for routine maint.

most of the time its the temp sender

slide the genset out and remove the top you will have to crawl into the hole to remove the screws on the back side of the top.

the sensor mounts in the thermostat housing

remove the wire from the sensor
ohm the sensor post to the neg battery connection
*F OHMS
69* 750
86* 600
104* 450
122* 420

32* the ohm reading should be close to 1300ohm remove and put in ice and water and ohm between threads and post

sensor is not precise so all readings may be +/- 10%

be careful removing sensor as they will corrode and break off in the housing and is hard to get out


Posted By: Cloud Dancer on 08/08/10 06:18am

kg5388 wrote:

I have never changed a thermostat except for routine maint.

most of the time its the temp sender

slide the genset out and remove the top you will have to crawl into the hole to remove the screws on the back side of the top.

the sensor mounts in the thermostat housing

remove the wire from the sensor
ohm the sensor post to the neg battery connection
*F OHMS
69* 750
86* 600
104* 450
122* 420

32* the ohm reading should be close to 1300ohm remove and put in ice and water and ohm between threads and post

sensor is not precise so all readings may be +/- 10%

be careful removing sensor as they will corrode and break off in the housing and is hard to get out



The above format is what I truly appreciate. And, I'm looking forward to getting inside the green box and really start diagnosing in earnest.
Right now, I have to put everything MH on hold while I attend to some other matters and projects that are also pending.
I will get back to you as soon as I do something with this latest information.

Thanks for your knowledge and time.
Willie


Posted By: Cloud Dancer on 08/09/10 07:20pm

Back on the job.
I removed the top panel, and can't figure out why I had been so hesitant (was not too difficult). Right away I saw a serious kink in the coolant filler hose (a definite A-HA moment). So, I used my big squeeze bulb to finish filling it up. BUT, it was full! Then, I drained the system to verify that it was full. Yep, it was full.
I ohmed the water temp sensor, and had another A-HA moment. I started to remove it, but it would NOT budge. I drilled a 1/2 hole in the internal plastic divider so I could get a straight shot at the sensor (to use a 19MM socket and extension and ratchet). Nope, still will NOT budge.
So far, everything is as Kevin said, so I have to ask: Do you think that using an air impact gun(tool) would be a good idea? Any suggestions?
The housing seems to be made of high-impact plastic, and I'm very afraid of breaking it. Which begs the question, how difficult of a job is it R&R this housing? I can feel that there's 3 bolts that attach it to the block, but it might require removing the water pump.
Man, my small jobs always turn into big ones.

Thanks for any help you extend.
Willie

BTW I drove over to Cummins/Onan and bought a thermostat, sensor, and belt. I also ordered a Service Manual for this model. It cost $15,...and these other parts were not as expensive as I had guessed. If only I could remove that dern sensor.


Posted By: kg5388 on 08/10/10 06:42am

spray some penetrating oil like PB blaster, kroil or liquid wrench on it and place your socket on it and tap lightly with a hammer do this several times to allow oil to penetrate.
don't use an impact hammer.


Posted By: Cloud Dancer on 08/10/10 08:05pm

kg5388 wrote:

spray some penetrating oil like PB blaster, kroil or liquid wrench on it and place your socket on it and tap lightly with a hammer do this several times to allow oil to penetrate.
don't use an impact hammer.



Last night I had already started the Liquid Wrench penetrating oil procedure, and I continued this morning. I followed your instructions on the tapping, penetrating oil, and trying to loosen the sender. It finally started turning, and I was able to unscrew it off. Except, the internal 'bulb' was corroded stuck, and broke off. I had to stuff an oiled rag into the thermostat housing(to catch the chips), and then drilled it out with my long 3/8" drill bit. Then, had to size the hole to original .396" diameter.
I put it all back together, with new sensor and thermostat, carefully filled it with coolant, and cranked it up.
It ran for 25 minutes and quit. I waited 5 minutes and restarted it. It ran for 10 minutes and quit. The fault code is still 33.
In other words, there was no change in the symptoms.
So, the thing that comes to mind is that if it's still overheating and commanding a shutdown, perhaps it's a pump impeller that's faulty, somehow. Heck, I don't even know how to check to see if water is circulating.
But, I'm glad I went through this process of elimination. With 1,058 hours, it was time to do it anyway.
And, I truly appreciate it. You've helped me a lot. It's just one of those things, where I have to continue with the education.


[image]

[image]


Posted By: kg5388 on 08/10/10 08:08pm

did you have the top off when you ran it? that will cause it to overheat.

you need to check the temp when it shuts down


Posted By: Cloud Dancer on 08/10/10 09:16pm

kg5388 wrote:

did you have the top off when you ran it? that will cause it to overheat.

you need to check the temp when it shuts down



I had it completely buttoned up. I even plugged the hole I made in that plastic partition. The radiator is clean, the pump pulleys and belt are intact, everything visible is as it was when everything was working normally.

Check the temp? Oh how I wish it had an ole analog temp gauge that I could do that with. All I have is a infra-red thermometer gun with laser sight. So, how/where do you check the temp?
Thanks


Posted By: Cloud Dancer on 08/11/10 09:11am

What I'm saying is that I not only don't know the standard procedure of monitoring the exact temperature of the coolant, I don't even know at what temperature the Onan system commands it to shut down.
I find nothing in the owner's/operator's manual to help me with this.
Also, it might seem that I'm 'stubbornly' directing my attention to a possible malfunction of the cooling system. However, there ARE two main developments which drive me to still suspect something in the cooling system. Firstly, there is the fault code (33). Secondly, the duration of the two 'runs' is consistent with what I would suspect would occur if the engine was overheating (25 minutes followed by 10 minutes).
Question: Do Onan specialists use a temperature gauge that hooks up to the 'electronic box', in order to monitor the exact temperature?
I ask because I noticed in the manual that some vehicles(RV's) come equipped with a remote control panel which has water temp and oil pressure gauges.
Thanks


Posted By: kg5388 on 08/11/10 10:10am

i just lift the top and hit the thermostat housing with a temp gun.

96bounder30e has the parts and service manual for your genset send him a pm at the top right of the page and he will email it to you for free


Posted By: Cloud Dancer on 08/11/10 12:36pm

kg5388 wrote:

i just lift the top and hit the thermostat housing with a temp gun.

96bounder30e has the parts and service manual for your genset send him a pm at the top right of the page and he will email it to you for free




I requested a copy of the Repair/Service Manual, but apparently Bounder is not yet in service...[emoticon]

Meanwhile, I ran the temp test.
The starting temp, at the thermostat housing, was 92* and the ending temp, one minute after it quit, was 240*
True to form, it quit after 26 minutes of running.
I'm scratching my head, thinking. On the surface, the 240 sounds like a reasonable cutoff temp,....but I don't have any reference, other than the normal running temp of the 8.3 Cummins ISC, which is 200 to 210.
If I assume that this Onan quits due to a command due to overtemp, then it kinda puts me back where I started. Or, I can look for something OTHER than those items I've replaced:

Low water level? The only thing there that I can imagine is the kink in the long filler hose. I suppose I could shorten it and that would keep it from kinking.

Water not circulating? The only thing I can think of is removing the water pump and checking it.

Obviously, I need more ideas, more info.

Thanks


Posted By: Cloud Dancer on 08/15/10 09:44pm

I'm still working on solving the overheating problem with my 7.5 Onan QD, and I'll have an update soon. But, I wanted to post this photo for Kevin, as he's been helping me via PM.
The photo shows some buildup 'stuff' that came out during one of the times that I drained the system.


[image]


Posted By: Canadian Rainbirds on 08/15/10 10:23pm

I must give you full points for all this effort. I would have just taken the rig in for $ervice and paid the required gazillion dollars!






Posted By: Cloud Dancer on 08/29/10 05:15pm

I have NOT found the fix to my Onan overheating problem. Apparently, this problem is rare enough that I haven't found anyone who has run into something similar.
I haven't even been able to verify that the controller is programmed to shut down whenever the temperature reaches 240 degrees. Onan's customer service does not give out technical information unless you're a registered Onan dealer/repair station.
The ONLY commanded shut-down fault code that it has ever produced is #33. Plus, every time that I've taken a temperature reading, it's been 240* at the thermostat housing (right after it quits). This is the reason I'm still looking at the cooling system. The next thing that I was going to do is replace the water pump, ALL hoses, plus remove the radiator and have it taken apart and cleaned (radiator shop).


Posted By: Big Katuna on 08/30/10 10:53am

Appreciate the update. Good luck and I'll be watching for the good news!


My Kharma ran over my Dogma.


Posted By: Cloud Dancer on 09/02/10 08:49am

I have been doing other things, consequently the Onan overheating problem was on the backburner.
I had posted what I was going to try next, but when I found out the price of the water pump and all hoses, I went into the re-thinking mode (back to basics, where I should've been in the first place).
I tackled the job of removing the radiator. It was more time-consuming than I had imagined. It's "sandwiched together TIGHTLY, and ALL panels have to come loose so that they can be moved away from the radiator. Apparently, not many 7.5 Onan owners have ever had this problem. And, I say that because nobody on the forums suggested the removal of the radiator.
I don't want to get my hopes up too much, but I gotta say that I have reason to suspect that a partially clogged radiator might be the cause of the overheating. I dropped off the radiator at Blanco Radiator Repair, and they will do a full service on it. Meanwhile, I'm rigging up some fittings so that I can do a thorough back-flush routine on the engine block.
I will report later.


[image]

[image]


Posted By: CA Traveler on 09/02/10 09:40am

Excellent thread, thanks for all the information. I'm wondering what all that "stuff" is and how to remove any remaining and how to prevent it from occurring. Any ideas on this? Any idea from the radiator guy or Cummins?

Cloud Dancer Did you replace the hoses? On a car a weak hose can collapse and cause overheating.

kg Tomorrow I'll be running my 7.5 for 1+ hours to charge the batteries. Is there any place (short of panel removal) that I could stop the gen and measure the coolant temp with a IR? I'm thinking of it as a reference point for Cloud Dancer or anyone else. Like removing the rad cap and measuring the overflow tank liquid temperature. Not as good as the measuring the thermostat but a possible quick reference.

Summary to date: 2003 7.5 Onan, 1058 hours, fault 33, thermostat temperature reading 240 degrees when the gen quits. Apparently not the thermostat, temperature sensor, drive belt or water pump. "Stuff" in the cooling.


2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob



Posted By: kg5388 on 09/02/10 10:51am

about the only easy access for a temp reading is the brass coolant drain under the genset

Don't remove the cap while its hot or while it's running the vent hose from the thermostat housing to the fill neck will spray coolant out several feet

just like a car the antifreeze also stops corrosion but just like it looses it's freeze protection it will loose it's corrosion protection.

there are test strips available for testing coolant

check out

coolant training

for coolant

and
Fleetguard products and training

for all other products and information on everything from coolant to fuel to testimg


Posted By: Big Katuna on 09/02/10 12:08pm

Wondering if you changed out the coolant at the recommended intervals (4 years?). Also am wondering if there is a hose on the intake side of the water pump. I have had the spring corrode away then the hose collapse under a vacuum on a car before.


Posted By: PaulJ2 on 09/02/10 01:34pm

How is the radiator cooled? A fan driven by the water pump pulley or maybe by an electric motor? Helped a friend repair a diesel generator in his Prevost MH. An electric motor in his case had stopped running. Radiator was cooled by a fan drawing air through the radiator and out a vent duct.


Posted By: Cloud Dancer on 09/02/10 04:43pm

It's back together again, and the test run has started (at 5:15 local).
It's powering two air conditioners and two old TV's and the Direct TV receiver with TracStar in-motion antenna. It's a hot day, and the the sun is beating down on the generator-end of the motorhome.
The radiator WAS partially clogged internally, so there's reason to believe that this might solve the problem.

The only hose I replaced was the filler hose, which was a straight piece of 3/4 hose from the factory, AND it was kinked. I replaced it with a formed hose which I found at the O'Reilly Parts warehouse(they let me search for one that worked). Here's a picture of it:

[image]




The fan is directly attached to the gen rotor/flywheel, and looks like a paddle wheel. It sucks air in the front and pressurizes the "box", and all the air goes out through the radiator:

[image]


Posted By: Big Katuna on 09/02/10 06:10pm

Great info. Did you change the coolant out per the Onan PM schedule? Just curious.


Posted By: Cloud Dancer on 09/02/10 06:30pm

Big Katuna wrote:

Great info. Did you change the coolant out per the Onan PM schedule? Just curious.


All maintenance on this unit has been "by the book". The only time that tap water has been in the system is recently when I flushed the system with a garden hose (after I had installed a radiator cleaner additive). Also, I did NOT replace the radiator hoses. Today, I also flushed the engine block with tap water (3 times), but I blew out the last load of water with 7 psi air pressure. Then, I filled the system with a different brand of 50/50 antifreeze than previously used.

BTW it has not quit yet. If it goes 5 hours I'll shut it off and probably call it fixed. We'll see.


Posted By: MaxThrust on 09/03/10 10:40am

Well? Inquiring minds want to know...did you finally nail it?


Mike ">
My computer beat me at chess, but I beat it at kick boxing!



Posted By: Cloud Dancer on 09/03/10 01:05pm

Yes, I believe it's fixed. It ran 5-1/2 hours, just like normal (I finally shut it off, got sleepy).
I asked the radiator guy, but all he said is that you'll go crazy trying to figure out where those mineral deposits come from. He said he flow tested it(low pressure), and that almost half of the tubes were not flowing. He had to boil it and rod it twice. The tubes are tiny, doesn't take much to clog them.

The real test will come next time I go to Lake Amistad, where I usually run the generator for 48 hours. If it makes that schedule, THAT'S when I'll celebrate.

Now, I have to get back to the Norcold 1200 project (replace the cooling unit).

Thanks to everyone for all the help.


Posted By: CA Traveler on 09/03/10 04:22pm

Per above post here's a reference temperature on my 7.5 Onan. 80 deg day, 26A output and the brass drain plug was 160 degrees. When we get a heaver load/hotter day I'll take another measurement but I wouldn't expect anything over 190.


Posted By: Cloud Dancer on 09/03/10 06:08pm

CA Traveler wrote:

Per above post here's a reference temperature on my 7.5 Onan. 80 deg day, 26A output and the brass drain plug was 160 degrees. When we get a heaver load/hotter day I'll take another measurement but I wouldn't expect anything over 190.


Same test, same place, but at 96* ambient, and after running about 2 hours (AFTER the fix), was 170*


Posted By: kg5388 on 09/04/10 10:22am

if you still have it where you can get the top off how about hitting the top and bottom radiator hoses with the temp gun and see what the difference is for future problems or for someone who uses the search function and finds your thread.

also the joint where the black front and the top meet that runs down next to the overflow tank and the screws across the top seal them with silicone.

run a small bead to seal the crack and squirt a little under the screws before tightening.

the ac condensation and rain will leak into these places and runs right into the inverter plugs and shorts out the plugs.

also you will see beautifully maintained rvs for sale then pull out the genset and there is large paint bubbles with rust surrounding the bolt heads and it looks real bad


Posted By: Cloud Dancer on 09/06/10 09:51am

kg5388 wrote:

if you still have it where you can get the top off how about hitting the top and bottom radiator hoses with the temp gun and see what the difference is for future problems or for someone who uses the search function and finds your thread.

also the joint where the black front and the top meet that runs down next to the overflow tank and the screws across the top seal them with silicone.

run a small bead to seal the crack and squirt a little under the screws before tightening.

the ac condensation and rain will leak into these places and runs right into the inverter plugs and shorts out the plugs.

also you will see beautifully maintained rvs for sale then pull out the genset and there is large paint bubbles with rust surrounding the bolt heads and it looks real bad



I need to explain, and confess, that once I finally found something that I could relate to as something that was old-school and "made sense" I was no longer enthusiastic about 'numbers' which had no useful meaning to me.

Here's my conclusion:
If there's a commanded shut down of a 7.5 Onan QD, and the fault code is #33, the most important temperature reading that you can take is the 240 degree at the thermostat housing (immediately after it quits). This will verify that the controller commanded the shut-down DUE TO OVERHEATING. If the pump belt looks OK, I would then drain the coolant and LOOK inside the radiator(disconnect the upper radiator hose at the side of the top radiator tank).

In my case, if I had FIRST performed these steps, I would've removed the radiator right away (for a complete cleaning service, at a radiator shop, $50).
This way, in 3 days I would've been where I am (which took me 3 weeks).

I'm NOT saying that I have absolutely solved my overheating problem, as the true test will come later. ALL I'm saying is that I would've used the "wasted" two weeks to work on my dead Norcold 1200 frige...[emoticon]

Kevin,
You helped me more than you might realize. In the first place, I was VERY hesitant about taking the panels off my "like-new" Onan. You got me over that pretty quick. ALL the things that you helped me with, I enjoyed doing, and it gave me a lot of confidence. I now feel very comfortable with working on any part of the Onan (the mechanical part).
I feel grateful for all the help. Thanks again.


Posted By: kg5388 on 09/06/10 10:02am

Cloud Dancer wrote:



Kevin,
You helped me more than you might realize. In the first place, I was VERY hesitant about taking the panels off my "like-new" Onan. You got me over that pretty quick. ALL the things that you helped me with, I enjoyed doing, and it gave me a lot of confidence. I now feel very comfortable with working on any part of the Onan (the mechanical part).
I feel grateful for all the help. Thanks again.


Not a problem All of us here are glad to help and the genset part is even easier to fix as long as you have a good ohm meter
the big thanks is to you for giving us the proper information to help
your welcome
Kevin


Posted By: CA Traveler on 09/06/10 10:04am

CD Understood. I suspect that if someone had a overheat problem they would see temperatures on the brass drain that were much higher than you and I measured. And this is a very quick and easy test.


Posted By: Cloud Dancer on 09/06/10 01:11pm

CA Traveler wrote:

CD Understood. I suspect that if someone had a overheat problem they would see temperatures on the brass drain that were much higher than you and I measured. And this is a very quick and easy test.



Actually, that's really NOT how it works, in the case where the radiator is partially clogged (7.5 Onan QD). That's the reason why the PLACEMENT/location of the temperature SENSOR is critical. It should always be at the nearest location to the output of the hot water, that's PRODUCED by the heat manufacturer(the engine).
What you have is a water pump that is NOT constant displacement, which means that in order for it to produce the designed mass flow of water, the designated radiator and hoses must be free of obstructions.
Assuming that the air flow through the radiator is normal, each tube in the radiator that is NOT clogged will continue to cool the water that is flowing through it. However, the amount of heat REMOVED from the engine will LESS than normal, and that's why the water temp at the sensor will indicate higher than normal. Whereas, the water temp on the 'cool tank' side of the radiator will still indicate near normal temperature. Therefore, IMO the drain cap is not a useful place to 'take the temperature'.
IMO what would be the most helpful is a water temperature gauge that you could monitor all the time. When reading analog gauges, I'm a big believer in "trend following". It sure helps to predict whenever trouble is brewing.


Posted By: CA Traveler on 09/06/10 05:56pm

Quote:

Whereas, the water temp on the 'cool tank' side of the radiator will still indicate near normal temperature. Therefore, IMO the drain cap is not a useful place to 'take the temperature'.
Sorry but it doesn't work that way. Everything is hotter, engine, coolant and radiator. 240 degree coolant going into the radiator means that it WILL not be adequately cooled and WILL be above normal at the drain.

If I had a over temperature code (with full fluid) and did the quick and easy drain measurement and got 170 as you did after the fix I would conclude that it was not likely related to the coolant fluid. The very next step would be to measure the thermostat temperature which of course involves panel removal. Then on to the obvious like belt, sensor and thermostat.

Unfortunately we don't have a brass drain plug reference but if I measured 200+ I would be concerned that the engine is indeed hotter than it should be.


Posted By: CA Traveler on 09/06/10 06:04pm

kg CD brings up an interesting point. Is there any place to install a coolant sensor and oil pressure sensor that could be connected to gauges? While these may not be ideal locations a significant variance could prove very useful.


Posted By: kg5388 on 09/06/10 06:38pm

just order 300-5027 remote panel with full gauges

it comes with hour meter, start stop switch, oil pressure, temp gauge and battery voltage


Posted By: Cloud Dancer on 09/06/10 08:15pm

CA Traveler wrote:

Quote:

Whereas, the water temp on the 'cool tank' side of the radiator will still indicate near normal temperature. Therefore, IMO the drain cap is not a useful place to 'take the temperature'.
Sorry but it doesn't work that way. Everything is hotter, engine, coolant and radiator. 240 degree coolant going into the radiator means that it WILL not be adequately cooled and WILL be above normal at the drain.

If I had a over temperature code (with full fluid) and did the quick and easy drain measurement and got 170 as you did after the fix I would conclude that it was not likely related to the coolant fluid. The very next step would be to measure the thermostat temperature which of course involves panel removal. Then on to the obvious like belt, sensor and thermostat.

Unfortunately we don't have a brass drain plug reference but if I measured 200+ I would be concerned that the engine is indeed hotter than it should be.


I'll betcha you that if the automatic cut-off system is working normally (shuts the engine off at 240 degrees measured at the thermostat housing) you will NOT read more than 173 degrees at the brass drain cap.
I ran the tests myself, and did the research myself.
And, I stand by my statement: The brass drain cap is NOT a good place to "take the temperature".
Of course, I fully understand that everyone has the freedom to diagnose a problem any way they choose.

I'll post a report on how mine goes after I run the final test.


Posted By: kg5388 on 09/06/10 08:55pm

the main thing to gauge any cooling system is engine outlet coolant temp to the radiator or top radiator tank temp versus lower radiator tank or coolant inlet to waterpump.

if for example ( just pulling temps out of the air ) you have 130* brass drain cap then the engine temp of 200* the radiator has a 70* cooling temp drop and is cooling the coolant enough to maintain correct engine temp

now if you have 130* brass drain plug temp but the thermostat is not open all the way and is restricting water flow or the radiator is stopped partialy up externaly or internaly the engine temp could be in excess of 200* you still have your coolant drop but not enough circulation to cool the engine depending on load
My wifes van will run at 210* right now but if you turn on the ac it will overheat just turn off the ac and it will run 210* I pulled the radiator cap and at 78,000 miles you can see the coolant passages stopped up so now I get to pull the radiator and have it cleaned

If Willie would have measured upper and lower tank temps I bet they would have been very close together causing the overheat and if he checked it now there is a big temp difference


Posted By: Cloud Dancer on 09/06/10 09:20pm

kg5388 wrote:

the main thing to gauge any cooling system is engine outlet coolant temp to the radiator or top radiator tank temp versus lower radiator tank or coolant inlet to waterpump.

if for example ( just pulling temps out of the air ) you have 130* brass drain cap then the engine temp of 200* the radiator has a 70* cooling temp drop and is cooling the coolant enough to maintain correct engine temp

now if you have 130* brass drain plug temp but the thermostat is not open all the way and is restricting water flow or the radiator is stopped partialy up externaly or internaly the engine temp could be in excess of 200* you still have your coolant drop but not enough circulation to cool the engine depending on load
My wifes van will run at 210* right now but if you turn on the ac it will overheat just turn off the ac and it will run 210* I pulled the radiator cap and at 78,000 miles you can see the coolant passages stopped up so now I get to pull the radiator and have it cleaned

If Willie would have measured upper and lower tank temps I bet they would have been very close together causing the overheat and if he checked it now there is a big temp difference



Kevin,

On the 15th of last month I sent you this private message:

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So, back to today's test. I put the top panel on and cranked it up. To follow your instructions, 22 minutes later (still running), I quickly lifted the top and shot the temperatures that you requested. The stat housing was 210*, top of radiator was 225*, bottom of radiator was 210*, and the brass drain cap(on hose that comes down from pump) was 170*. Keep in mind that all this is still minus the tstat that I had previously removed.
NOTICE that these temperatures are lower than before. The genset KEPT RUNNING, and running. Such that 2 hours and 30 minutes later it was still running, and I decided to take another set of readings. The first was the bottom brass drain cap, it was 172*. Then, I removed the top panel, and started taking readings up there. The tstat housing was 230*, but was now CLIMBING (due to removal of top panel, apparently). About 3 minutes later, it QUIT. I took a reading, and the tstat was up to 245*

SO, even though, at this point, I do not know exactly what caused the big change in cooling, I tend to lean towards the possible 'clearing out of some partial restriction in the flow of coolant, internally).
Therefore, I will continue to do some more 'chemical treatments', and flushings, of the system.
I will report back after I do all this and run some more tests.
I gotta say this is the first day of seeing some good signs of some kind of progress.
Thanks for everything, talk to you later.+

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And, your reply did NOT say anything about my temperature difference between the top and bottom of the radiator. Therefore, I assumed that if there was something in the way of a 'red flag' there, you would've mentioned it.
The thing is, nobody seems to know what the "normal" readings should be. I couldn't even find anybody who knew at what water temperature the controller is programmed to shut down the engine. These numbers do not appear in the service/repair manual. Do you have a source for these numbers?

* This post was edited 09/06/10 09:29pm by Cloud Dancer *


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