Engine/Transmission (1998.5 - 2002) 2002 HO Thermostat problems?

[twheat]

Hi guys! Tonight I was pulling a 5% grade hill unloaded in 5th gear. When I crested the top my water temp had shot past the usual 190 degree mark. It was halfway between 190 and the last white mark before the red 240 mark. I was probably 210 degrees would be my guess. My egt was 1000 and boost was 15psi when I noticed this. I had my foot into it pretty good. When I let off the gas to go down the other side the temp went down to the usual 190 degree mark. I have never seen this before. Is this a sign of my thermostat going out? I am making a 1000 mile trip next weekend towing an enclosed trailer and was thinking about just buying a thermostat kit to take with me. What one should I buy? Thanks for the help!

 

[KcoleKennyc]

It probably would not hurt to change the thermostat if it is old but I don't think that you have a problem. Mine goes up pretty good when pulling uphill.

 

[Missouri Mule]

If you are going to get a thermostat get it at Cummins.



Reading my factory service manual for my 96 the thermostat starts to open at 181 and is fully open at 203. Temps above 203 are controlled by fan and ambient tempature.



With the breather tube in front of the engine oil residue can clog the radiator. I would start there by pressure washing it.



I would check out fan clutch by spining the fan if no resistance is felt you need a new fan clutch.

 

[twheat]

I guess I should have also added I did a coolant flush and pressure washed the radiator less than a month ago. I have had this truck for just over a month so I have no clue what the age of the thermostat is.

 

[Sticks]

I guess I should have also added I did a coolant flush and pressure washed the radiator less than a month ago. I have had this truck for just over a month so I have no clue what the age of the thermostat is.

No, Missouri Mule means remove the radiator from the truck and wash the externals. Your intercooler side is probably caked in the center with silt, and the engine side is caked with oil around the outside edge.

 

[twheat]

No, Missouri Mule means remove the radiator from the truck and wash the externals. Your intercooler side is probably caked in the center with silt, and the engine side is caked with oil around the outside edge.

Yup I did that, I removed the whole unit to pressure wash it. There was a circle of oil the size of the fan shroud from the blow by bottle. I got rid of the puke bottle by hooking a hose on to that and running it down by the front diff.

 

[CAPTPHIL]

Every time mine has done that, it has been the fan clutch. Normally the thermostat failure will show up as the temp. gauge not moving when it opens and closes. Make sure you take your eng. # with you to get the proper one. If not you can windup with one for a med. duty app. that will freeze your butt off in the winter.
Good Luck, CAPTPHIL
01 3500 2wd 647000mi bombed boathauler

 

[Tractorat]

I was having kind of the same problem a couple of years ago. When I tried to pull a 10% grade pulling my TT, it started to get so hot, I turned around and went a different way.



I washed the radiator a few times and got minimal results. So, I just put in a new cummins thermostat. Problem went away.



Im convinced that a lot of engine temp problems that have been blamed on the radiator getting build up from the puke bottle can be fixed by just changing the thermostat.

 

[CAPTPHIL]

I have had to replace mine every 75k to 100k. Engine vibration causes them to fail over time. Have to replace fan clutch more often. It is easy to check it. Friend of mine just completed frame off restore on early MGB Great toy.
CAPTPHIL

 

[twheat]

Ok heres the update. Today I bought a new thermostat and installed it. Pretty straight forward process that is. I still get some weird temp fluctuations. Around town it runs a needle thickness below the 190 mark. Once I get on the highway it bumps up to the 190 mark. I pulled the same hill twice today and both times the needle goes past the 190 mark by the thickness of the needle and once I crest the top it goes back down. My egts were around 1000-1100 degrees both times. I rotated my fan today and there is some resistance there. Whats the best way to check the fan clutch? Also am I ok to drive the truck on my trip and back. There is not really and huge hills and the load I am taking is maybe 3000 pounds. Thanks for the help.

 

[CAPTPHIL]

You will get those changes in temp. as the thermostat opens and closes. That is normal and tells you it is working. From the sound of things everything is normal. I assume your egts are pre-turbo. If your fan is working properly,you will hear it kick in with an audible roar when your temps go up. Unless a fan clutch is in real bad shape turning it will still show some resistance.
CAPTPHIL

 

[twheat]

My egts are pre turbo yes. I cant hear the fan kick on so I am thinking the fan clutch is gone. I have had the truck for almost 2 months now and I have pulled steeper grades for longer amounts of time in 90+ degree weather and had the temp barely change that's whats sparking all my interest that's all.

 

[CAPTPHIL]

Did your old thermostat look like it broken, normally they will be trying to come apart. It sounds fan clutch to me. Last time mine went out, I was pulling 10000 lb. hit first steep grade on I77 and oil and water temp. took off. It took me a few min. to realize that I couldn`t hear fan. Changing the clutch isn`t bad, you just need the right tools.
CAPTPHIL

 

[twheat]

The thermostat that we pulled out was all together. Tonight just driving around town it was fine temp wise never went above the 190 mark so I will keep an eye on it tomorrow. I got plans now to have my buddy take his 3rd Gen CTD on the trip so mine will stay parked until I get back then I will replace the fan clutch. Any ideas on what brand is best to use when replacing the fan clutch? Napa sells a heavy duty one for the CTD thats like $130. Thanks for the help CAPTPHIL!

 

[CAPTPHIL]

I got my last one from Discount Auto, they were the only parts house that had one in stock and I had a trip the next day. NAPA did warranty the bad one. It was less than a year old, maybe 30k mi. . As far as whose product to buy its warranty and availability, in my experience none of them last any longer than the other. I would go with price and warranty. Remember, I drive a lot of miles mostly loaded from 7000lbs. to 12000lbs. with a lot of wind drag at 70mph. Keep me posted on your progress.
GOODLUCK CAPTPHIL

 

[twheat]

Well it looks like NAPA sells one for $130 bucks built for our trucks and it has a lifetime warranty, so thats the one I will be buying. All the others I have found only have a 10k to 30k warranty for the same price or more. I will be doing this once I get back from my trip so I will keep everyone posted! Thanks.

 

[twheat]

UPDATE: I ordered the Napa fan clutch today. It was $145 after tax and has a lifetime warranty. They told me as long as I own the vehicle if the fan clutch fails they will replace it no questions asked. I get it tomorrow and will put it in on Sunday. I'll update this thread once I am done.

 

[twheat]

Ok I put the new fan clutch on today. It still has its weird temp spikes. I took various pictures to show what I mean maybe that will help.

Here is what the temp needle looks like when I am at a stop light or in town at very slow speeds.
#ad


This is where it gets sometimes while driving at normal city speeds 30-45mph and also at stop lights.
#ad


Picture of the hill that makes the temp raise.
#ad


Another shot of the hill.
#ad


Heres some pics of where the temp needle gets during the hill.
#ad

#ad


Let me know what you guys think. This worries me because the truck has never had this type of temperature fluctuation before. Could I have gotten a bad thermostat? I know the fan clutch is good because it roars when its cold after I first start it. Thanks for the help.

 

[CAPTPHIL]

You are normal. That shows the thermostat is opening and closing as it is supposed too. It will also do that at highway speeds as your fan clutch turns on and off. Drive it like you stole it.

Good Luck CAPT PHIL

 

[twheat]

Ok cool. Is there a reason why I have never noticed this in the 2 months I have owned this truck? Maybe I am just being overly concerned! Thanks for the help.