Engine/Transmission (1998.5 - 2002) Running Hot

[BroncoMarc]

I towed my Bronco about 400 miles this weekend and my Ram was running pretty hot.



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It was almost always on the line at the top of the normal range. I'm guessing that's about 210. When I was pulling a long hill it would sometimes peg the temp gauge to 240. If I got off the gas, after 5 or 10 seconds it would drop quickly back down to 210. There were a couple times I had a semi right on my a$$ and I couldn't slow down so it was up there for about 30 seconds.



I found that turning the a/c off helped a little bit, and turning overdrive off on the hills helped, but that limits my speed on hills. It was in the low 80s outside which I'm assuming was the major contributing factor since the last 3 times I towed it didn't do this. That also made it pretty hot when I turned the a/c off.



I checked the coolant and it was full, but a little dirty. . I'm going to try a flush and fill and see if that helps any.



What else could be wrong? Am I always going to have to turn off overdrive to make it up hills without over heating? That seems like it puts me too close to red line just to keep up with traffic.



My friend has towed with his 97 a lot more weight and a lot faster without trouble. I know. . I was following him in my Bronco and I couldn't keep up on the hills!



Mine is a 98. 5 (Jan 98 build date), 24v, auto, 4. 11 gears, stock tire size and no bombing. Currently at 99,550 miles.



I need to figure this out. . My friends with powerstrokes were pulling away from me when I had to slow down!

 

[Texas Diesel]

I would suspect your fan clutch is not engaging. When it got hot you should have heard the fan engage.



How bug clogged is your radiator? Mine was 75% clogged before I cleaned it and installed a bug screen ( here we go again )

 

[RustyJC]

1. Defective thermostat (pretty common).



2. Bad fan clutch.



3. Fouled cooling system (water and/or air side).



Pulling a 13,500 lb 5ver in the Texas Hill Country, we run about 1 needle width above the 190 mark. Unloaded, we run about 1 needle width below the 190 mark. The fan clutch kicks in about 195 or so, and the temperature will drop like a rock when it does.



Rusty

 

[BroncoMarc]

The fan clutch theory sounds promising. Could it be that it's just engaging when the temp is too high? When it did go back down it dropped from 240 to 210 in about 2 seconds.

 

[RustyJC]

We had a bad fan clutch on our previous V-10. It wouldn't engage until about 230 or 235. Like yours, the temp dropped pretty quickly once it did engage, but it would kick off about 210, so the engine would run between 210-235 degF in stop-and-go towing during the summer. We replaced it with an aftermarket clutch and solved our problem.



The other thing to consider is that the thermostat may be sticking. If it doesn't open until 240, the temp would drop very rapidly as well. The more common failure on these thermostats, however, is that they won't open fully - they hang up at about half-travel.



Rusty

 

[K_Arts]

Marc,



You may want to check out this thread. Maybe it will help you out.



Overheating



Kev

 

[PCrable]

mreiter,

I would agree that it sounds like you could have a problem with you fan hub.



As far as the fan "engaging", it's really always at least partially engaged. The fan is on a fluid coupling hub. As the fluid in the hub gets hotter, the fan will turn at a speed closer to the engine. When the hub is cool, the fan will still spin at about 15% of the engine RPM. When it's hot, it will get up to 85% of engine RPM.



When the engine is hot, you should be able to hear the roar of the fan.



I have the Horton, but I'm not sure that I would spend that type of money again on it. It's either fully off spinning freely, or fully on at 100% of engine RPM. When the engine temperature hits 200 degrees, the Horton has an electric clutch that engages it and it runs at the engine RPM until it drops back below 200. You can definitely tell when the Horton starts up ans shuts down.



There are also some "Snake Oil" types of coolant additives you could try at places like AutoZone. These claim to reduce the engine temperature by up to 40 degrees, but buyer beware...



--Phil

 

[juicedcummins]

It's a safe bet that it the t-stat.

The early 24 valves had a bad batch including mine and it's a 99.

I also went the fan hub route first because the stealer in all his wisdom fiqured it was the cure. {WRONG}

If the t-stat isn't opening up enough it will not heat up the rad quick enough to tell the fan clutch to engauge when it is suposed to.

A t-stat is a cheap easy fix if you can spare about 10 min.

A fan clutch is $$$ and unless it is covered with oil [on the front],or the bearing is gone it is more than likely OK.

 

[Big_Daddy_T]

ditto on the tstat. lost mine. all my diesel mechanic friends told me i was delusional and the tstats never go out. it would get very hot and drop like a rock. there is a chime in the dash that signals when temp hits the redline. i also have the horton and like it. the other day the horton ate its power supply not cool. i think the idea is not to spin the engine above 4 grand with the fan engaged. it flexed out and ate the wires like a weedwhacker eats your toes when you wear your sandles,not funny when it happens to you.

 

[Motorhead]

I agree on above . Change thermostat. If your radiator fins are pluged up, the air flow is cut and the fan clutch works off of the heated air that flows thru the radiator to engage it. When you clean out the fins use a hose nozzle but clean it from the fan side to the front. We had drivers at UPS that delivered country routes and in the bug season the drivers sometimes had to stop in their day to clean the radiator fins. It's not healthy for your engine to see the high temps that you are seeing. Also you ck the fan clutch, See if it has drag when you try to turn it by hand. Also look for dirt and oil from the clutch on the shaft and on the radiator side of the clutch.

 

[BroncoMarc]

I did some testing last night. I put some cardboard over the radiator, then drove around for awhile to try to get it hot and see if I could hear the fan spinning up. I think I heard it, but it wasn't that loud. I couldn't even get it very hot. I don't think it got over 200. Guess I need to be pulling a load to get it hot.



I think I'll try replacing the thermostat and doing a flush and fill first, then the fan clutch if that doesn't work. I found the fan clutch for $39. 99 at Advanced Auto, so it's not that expensive.



My fins look pretty clean. Only a couple small spots bent over and a few bugs.



__________________

- Marc Reiter

1998. 5 Dodge Ram Cummins Turbo Diesel - stock for now

http://www.broncomarc.com/ram/

 

[Texas Diesel]

Be sure to post what you do to fix it. TIA

 

[Roger rodbolt]

If the thermostat is working properly the fan clutch will rarely even engage whiling pulling such a light load. I'm on my third or fourth thermostat in less then 70,000 miles. Cummins has changed design and suppliers and I would recommend getting a 180 degree Cummins t-stat, checking the date code for fresh stock and buying/carrying a spare. Please let us know what you find. Larry

 

[Motorhead]

If you need a fan clutch, Stay away from the CHEAPOS!! I learned first hand you get what you pay for. Tried one on an Econoline that I had and the thing always ran hot until I got an origional equipment style. Solved the heating prob. You won't get the fan to engage with cardboard over the radiator because the fan clutch needs the heated air flow from the radiator to work. Try the thermostat first and flush the system and the radiator fins. We have some 12valve package cars at my UPS center and I haven't seen the mechanic replace any fan clutches yet, just thermostats. A few of our trucks have the Horton electric fan clutch on them and when they cut in, if you're not expecting it, the noise has scared me for a moment.

 

[BroncoMarc]

I haven't solved this problem yet, but I may have found a cause.



I tried rotating the fan with the engine off. It only would spin a couple inches before the resistance from the clutch stopped it.



Then, I took it out for a drive with cardbord over the radiator and towing my Bronco. As soon as the temp hit 240 I pulled over, shut it off and spun my fan again. It was no different. It spun a couple inches and stopped. Then I fired it back up to let it cool down!



Shouldn't the fan clutch have been locked up at that temperature? Does the fan really make that much of a difference when I'm doing 70 down the highway?



Next thing I'm going to try is taking it to the car wash and cleaning up the radiator.



__________________

- Marc Reiter

1998. 5 Dodge Ram Cummins Turbo Diesel - stock for now

http://www.broncomarc.com/ram/

 

[Motorhead]

I repete! The fan clutch won't engage with the radiator blocked off! It needs the heated air flow to heat the fluid in the clutch to engage. 240 degrees is VERY BAD for your Diesel engine! Did you change the thermostat yet? The fan clutch is probably ok with the drag that you describe. If you can't find the problem, I would seek a professional. Repeted over heating will come back to bite you.

 

[WyoJim]

mreiter... . ITS THE DAMN THERMOSTAT... A 5 minute fix with an 8mm socket... . Sheeez

 

[Motorhead]

Time to un subscribe from this thread. I had hoped that he would have taken our advice by now!

 

[BroncoMarc]

Man. . that's harsh. . Besides... half the people are saying thermostat and half are saying fan clutch. I forgot about the whole cardboard thing on the last test. . It's been a while since I read my own thread.



I haven't been able to find a thermostat yet. I changed my coolant, had an autozone thermostat, but they sold me the wrong one. None of the other parts places list a thermostat. There's not even a Dodge dealer close that has one. I need to find the local Cummins shop.



__________________

- Marc Reiter

1998. 5 Dodge Ram Cummins Turbo Diesel - stock for now

http://www.broncomarc.com/ram/

 

[jwdeeming]

It may NOT be the thermostat. I have high temps when towing as well, and have done the 180deg thermostat (from Cummins) and the only difference is it runs cooler unloaded. Soon as I tow, the temps shoot right up where they used to be and the only prevention is to run the heater full blast.



I am trying to understand the fan clutch operation and looking for options. It seems to me I'm not consistently hearing the fan kick on at 190. Still looking.



The thermostat really is a quickie. You could probably order it from a Cummins dlr and have it shipped if you don't have one close. The part number for the 180deg is 3954194 and should be about $18. Do the thermostat first so these other guys don't shoot you. Good grief - the heat is making people grumpy around here!