Engine/Transmission (1998.5 - 2002) Running hot. Did I screw up?

[BK]

Kevin,

have you changed the T-stat?



My temp never ran really hot, but when towing or pushing it hard around town, temp regulation wasnt really tight. My Jeep GC acted the same. Both were slow to warm up in the winter.



I changed the Tstat on both and my warm up times seemed like they cut on half and the temp regulation was much tighter.



My Ram's Tstat only had 20K or so miles on it. It was in one piece when it came out. My Jeep's has 115K miles on it. . it was more than over due...



I've read reports here on the site that when members went to take out the factory installed Tstat,, they were in terrible shape with only 10K-50K miles on them.





Just a thought from my experiance and from what I've read here on TDR.

-bob

 

[rblomquist]

Hey guys.



I just got back from a round trip towing the travel trailer to San Diego and I swear my fan is not working either. Some of the mountain passes the temp needle was right up against the upper "safe" mark which doesn't seem right to me. I would think even with 100+ degree temps when you're at speed you should be able to run between 2 and 2. 5k on the tach without getting that hot.



- The t-stat is a cummins part and is less than 9 mo old.



- I've never to my knowledge heard the fan come on, even towing 12000lbs up and down these passes. Also, don't they zap a lot of power? Never noticed any power loss while driving (unless it's on all the time?)



My 2 primary questions are:



1. What makes the fan come on i. e. mechanical or electrical/ECU?



2. How do you test whether or not the fan is coming on/the fan clutch is good? My fan seems to have some drag when you spin it by hand.



I have to take the truck in for the exhaust manifold TSB and will have them check the fan out if it's something I can't test. Don't suppose the fan clutch is considered part of the engine for warrenty.



p. s.



I was going to post a fresh thread on my problem but I found this one and since it's pertinent to my problem I figured it was a good place to start.

 

[bmoeller]

1. It is thermal like an old home furnace thermostat. Has metalic spring on the front of it that senses the temp change and some how it engages the clutch.



2. Have never tested one so someone else will have to try to answer that one. Even when disengaged, there is still some drag.



When you get the exhaust manifold replaced, you may want to get an ATS 3-piece so it won't crack or shrink again. This is the cheapest place I have found so far. Don't know if the price has changed since they updated their site. Was around $400 even + s/h. http://www.mrbobsdistributing.com/ats.htm

 

[GWHaley]

While trying to diagnose overheating problems on Cat backhoes, I found that debris between the raditor and the trans/hydraulic cooler mounted in front of it caused the problem. I realize our trucks don't normally run in quite as dirty conditions, but that is one place where I would check.

 

[Loren]

This is my theory, I repeat, THEORY, on how the fan clutch works:



The fan clutch thermostat (the metallic spring mentioned by bmoeller) senses the temperature of the air that is exiting the rear of the radiator. If it senses that the radiator air is too hot, it engages the fan to cool the radiator.



In order for this system to actually cool your engine, as opposed to cooling merely the radiator, you must transfer the engine heat into the radiator. A few things that I can think of can cause this not to happen.

1) A thermostat that is not opening properly to allow coolant to flow into the radiator.

2) A bad water pump.

3) Any other flow restriction.



If the hot water is not getting to the radiator, the radiator will remain cool and the fan clutch will not engage, even though the clutch is operating properly.



An easy item to troubleshoot is the thermostat. You can remove it and heat it in water to see if it opens. If it's not fully open by the appropriate temperature, it's bad. Or you can remove it and run the truck with no thermostat to see if the fan clutch then engages, or if the temperatures are closer to normal climbing a steep hill.



Troubleshooting the water pump is more difficult, but I'm sure there are forum members who can make suggestions on how to do that.



It sounds to me like at least a couple of overheating problems mentioned on this thread are not the result of a bad fan clutch, even though the fan clutch is not engaging when the engine is hot. Check for flow.



Loren

 

[KevinK]

I did take my truck to the dealer Friday and they thought that the fan clutch was o. k. They did want to pull the radiator and clean it for me. They also wanted to change the thermostat. All of this for only $600 bucks. I declined. On Saturday, I pulled the radiator and could not believe how plugged up it was. I should have taken a picture of it and posted it. There was a nice circular pattern that matched where the fan lines up that was completely plugged over roughly 30% of the area. The rest of it was loaded with a significant amount of junk. The engine side had a fairly thick film of road grime over large areas too. It's no wonder the thing was overheating. This is a truck with just over 43K miles on it. I took it to a car wash with an engine degreaser and it cleaned up very well. I also decided that this was a good time to relocate my drip bottle, because it looks like most of the engine side sludge was caused by the bottle.



Kevin

 

[plongson]

Thermal Fan clutch low-down...

First, to inspect a thermal clutch...



1. ) When the engine is cold, turn the fan by hand. You should feel substancial resistance. If it turns free when cold the clutch is no good.



2. ) Look for dirt accumulation around the center of the clutch (greasy dirt) at the point where the bi-metal spring sits. If "Crud" is present it is a good indication the viscious liquid is escaping the clutch.



3. ) If either 1) or 2) is indicated, replace the clutch...



This is how they work...



The main players are:



1. viscious liquid (VL)

2. bi-metal spring (BMS)

3. labrinth raceway (LR)

4. metring widow (MW)

5. resevoir for viscious liquid (RVL)



The BMS is attached to a small shaft that controlls the MW in the RVL. When cold, all the VL is in the RVL. The hot air coming through the radiator unwinds the BMS opening the MW letting the VL enter the LR. The clearances are very close, and the VL being forced into the LR, via centrifugal force, effectively locks the clutch. The VL is free to circulate around the circuit. When the air from the radaitor cools, the BMS closes the MW and the VL is forced back into the RVL (by centrifugal force) ready for the next time it is needed.



Loosing the VL (very thick and looks like STP) causes the clutch to loose the locking ability and attracts all the dirt at the center by the BMS. Usually it is the small seal on the shaft that lets the VL escape...



Hope this helps...