Overheating for the third time

[Michael]

I went to pick up my latest truck last Friday. We checked all of the fluids then pulled it off and got it started. Soon after we were on the interstate and pushing 55, I noticed the temp was pushing 230. I backed out of it and it went down some. We pulled over at the next exit and idling nothing was boiling out and the gage went down to 180. We didn't really think it was as hot as the gage was showing so we got back on the road. I have done a search and read about the main causes, but I have a few more questions.

As soon as I got home I took a inferred thermometer and checked the temperature of the new truck and compared them with the chase truck. Everything on the new truck was 10 to 20 degrees hotter than the chase truck. The oil pan, motor, transmission, and transfer case were all 180 to 190 on the new truck and 160 to 170 on the chase truck. The new truck is a M35A2 W/W that has had the bed swapped with a van body and has a bridge plate on the grill. The chase truck is a M35A2 without winch and without the back tarp or bows.

Do you think the extra weight and wind resistance of the shop body and winch would cause this much difference in running temp? The new truck will also out run the chase truck. Were you would floor the chase truck on a hill and it would still lose speed, the shop van would actually increase in speed. I was trying to run 50 and found myself at 55 at the top of some hills that would have slowed the other truck down to 45. Will turning the fuel up cause it to overheat?

 

[mhodges]

Is the new truck a direct drive tranny vs the chase truck being OD? that's the only scenario I can think of- explains the acceleration difference at least, and in theory, the motor would have to turn faster to hold the same speed on flat ground- thus running a hair hotter???? might be something to look into, but I'm just speculating....

 

[Michael]

They have the same transmission. The new one just seems to have more pep than any of the other ones I have driven. (which isn't that many)

 

[Michael]

Here are some pictures:

 

[DanMartin]

Swap gauges and sensors from both trucks and see if the problem follows the sensor/gauge or stays with the truck...that will tell you if you really have an overheating problem or just a bum sensor/gauge. If the problem follows the swap, swap back the gauges and that will tell you if it's the gauge or the sensor.

Also consider testing out the thermostat...you can do that in a glass bowl with boiling water...to see if it's opening properly.

When you topped off the fluids, did you purge the cooling system correctly to get all of the air out of the system? I believe there is a procedure in the TM about that.

If all else fails, consider having the radiator and system flushed and rodded professionally.

 

[txdodge43man]

I think the truck with more pep probly had the IP truned up to compinsate for the extra weigtht which would cause more fuel to be injected in to the engine and give you a hotter engine temp. that what I think

 

[Michael]

I think he just poured about a half gallon of water in it. I now think the gage is working because it was so much hotter than the other truck. or is 20 degrees really that much different?

 

[txdodge43man]

Half a gallon low is really not bad for that big of a radiator. An 20 degrees I personal would not worrry about.

 

[Barrman]

Did you check your hubs, e-brake and drums? I know it shouldn't go faster with something dragging, but a turned up engine having to overcome a constant drive train drag will make more heat.

A week or so ago, I helped Kwai bring a M109A3 across Texas from New Mexico. It was 104 degrees or higher most of the trip. The temp gauge was flirting with 220 on the long up hill runs. However, I could tell by feel and sound the difference between 210 and 218 on the gauge. 210 the truck still had power and that last little bit of pedal left still produced more noise. Just a hair below 220 however and the engine felt flat and once in a hill, no amount of pedal movement produced more noise or umph. 5 minutes at idle and the gauge was back to 180 and it would take 30 minutes of hard hills before it got back up near 220 again.

Just something to give you a reference.

 

[beaubeau]

Be sure to check Air cleaner for obstruction and or dirty. Also until U run old fuel out of the tank and run good fresh diesel through, don't worry obout it too much. Remember, a diesel wants to WORK Hard!!?? Phil

 

[WillWagner]

Re: RE: Overheating for the third time

I think he just poured about a half gallon of water in it. I now think the gage is working because it was so much hotter than the other truck. or is 20 degrees really that much different?

Depends. 20 degrees is alot if it is at 230. A half gallon of coolant won't make a difference unless it was 100 degrees outside. Best advice, make sure the gauge is correct. Electric gauges are known for malfunctioning. Use a known good mechanical gauge to verify. If the truck with the box on it runs way better than the cargo truck, chances are the fuel rate is increased. Take a close look, maybe it is an LDS, not an LDT. When the box was installed, maybe the engine was upgraded. A slow steady increase of temp. to the point of pushing coolant usually means a radiator is plugged. A quick heat no matter what the load is usually a stat. A quick heat and cool is usually a stat missing.
HTH, Will

 

[Jones]

RE: Re: RE: Overheating for the third time

At running temp. open the radiator cap safely (rag or towel folded over to cover the cap and cut down on steam or hot water burns) and stick a candy thermometer into the top tank. That should give you a pretty accurate reading. If it and the gauge are off then just isolate the problem to sender or gauge. If they're pretty close then check the thermostat in hot water with a candy thermometer so see at what point it opens. DO NOT place the thermostat in water in a bowl and micro-wave them. Don't laugh, I've seen it attempted.
A thermostat stuck closed will restrict flow and overheat the engine. A thermostat stuck OPEN will not provide enough restriction to allow heat to transfer from cylinders and head to the coolant and will also lead to overheating.
If the thermostat is working correctly then look for collapsed hoses or ones that have delaminated on the inside with the inner layer acting like a dam.
If all this is still checking out OK then it's time for a flush and maybe radiator work. Core sand from the casting process, if not completely removed-- or rust build-up, will plug water jacket passages giving you hot spots.

 

[littlebob]

RE: Re: RE: Overheating for the third time

Just for reference, while working on mine, which did not overheat before. I took the radiiator off to paint it and used an A/C coil cleaner to try and clean it out
the inside and it was a big nono. Now I have to take it off and have it rodded out because I loossened up some crud that was very comfortable where it was.
Anybody got an idea of what a shop would to this on such a large radiator?
Live and Learn,
littlebob

 

[OPCOM]

RE: Re: RE: Overheating for the third time

Call around and ask if the shops do radiators for 18-wheeler trucks and bulldozers and the like. That's the shop you want.

 

[cranetruck]

RE: Re: RE: Overheating for the third time

Drain and replace the coolant.
For all the driving I have done, with heavy loads too, I have never seen the temp exceed 208°F (my highest observed reading). I use a digital thermocouple thermometer for reference at times and the dash gauge agrees with it.
Turning up the fuel will dramatically increase your EGT, so be careful inthe hills.

 

[sermis]

RE: Re: RE: Overheating for the third time

Has the radiator been painted? I did not have a heat issue on my truck until I painted it. Now with 95+ outside and running hard 60+ on the road I saw it almost at 230.

 

[Michael]

RE: Re: RE: Overheating for the third time

The truck didn't have much fuel in it so we stopped for fuel just off base and put $100 and a qt of fuel conditioner/cleaner in it right off the bat. I did forget the e brake and leave it on for the first leg on the interstate but releasing it had little effect. The radiator has been painted but it doesn't look like too thick of a coat as compared to the rest of the truck. I was concerned about the winch and bridge plate blocking a lot of air, but then that is the correct location, so it shouldn't be a problem. The air cleaner looks new through the mushroom hole. Bjorn, I think you are saying the turning the pump up will increase EGT but not coolant temp?

Like I said in the title, this is the 3rd time for this topic. Did any of the other original posters ever find out the cause of their overheating?

I may get a chance today to try some of the other suggestions. Thanks for all the input.

 

[FSBruva]

RE: Re: RE: Overheating for the third time

Just because you "release" the parking brake in the cab... that might not actually translate to a released brake? That's what my dragging brake problem was.

Matt

 

[cranetruck]

Re: RE: Re: RE: Overheating for the third time

.....Bjorn, I think you are saying the turning the pump up will increase EGT but not coolant temp?.....

The high EGT should not effect your coolant temp very much, it is only a momentary condition (hopefully).
The cooling system on the multifuel is pretty effective and the 208°F mentioned above ocurred when I was driving a long uphill stretch with a load of lumber with my radiator cover in place.

Fresh coolant, 50/50 glycol and distilled water will help make the system more efficient also.

 

[Michael]

I finished fixing this truck over the weekend and thought I would post what I did. I replace the thermostat because the old one didn't open up as much as the new one when I tested them side by side, but it wasn't by much. I also took the radiator to a shop and had it boiled out. I think that was really the problem. In retrospect, I wish I had just flushed it out myself as was suggested. But, with the price of antifreeze, I didn't want to try that and it still need more cleaning. Now you have to work it to get it up to 180 and it won't hold it at idle. Now I am worried about what the EGT is since it has so much more power than my other truck.