Engine/Transmission (1998.5 - 2002) What about running without Thermostat?

[Morepower]

I just changed to a 180 degree thermostat and was wondering if anyone was running without a thermostat all together? Then just put it back in during the cold weather season.

 

[Bob Cochran]

Don't think this is a good idea. The water will move through radiator to fast to allow optimum cooling of it. You need to keep it in the radiator for a little while at least. I think you will see higher temperatures; maybe not when running empty but when loaded or towing. That is my thought on the subject.

 

[RCone]

Would mind sharing the part # of the 180 thermo? Is is a Cummins #3954194? I have been trying to figure that out.



Roger

 

[Morepower]

The 180 part number is 3954194 and sold for 18 bucks. It has a nice o-ring around the outside and is very easy to change, a 5/16 socket is all it takes.

 

[Mundgyver]

I had an oportunity to talk with a Cummins rep awhile back. Since I'm setting my truck up for towing and I did a trip to Utah and back with the temps in the 104 to 106 mark, I asked him if I needed to worry about overtemping the engine. He indicated that these motors with the current radiator package are designed to work continous duty in 120 deg heat. The highest I have seen is just a little over 195 on the water temp gage and my engin oil will run right at 205 if I'm pushing hard with a load on.

 

[Joe G.]

Bob is right. I've seen some cars that would heat up without a stat. However, these things have a BIG radiator and a LOT of water. I think it would run too cool. In that case MPG could be lousy. Best is to keep the stat in so it will run at the temp it's designed for.

 

[TPlasek]

Also, think about how long it would take for the engine to warm up to operational temp. Think of how long it would take the oil to warm up. I don't know the specifics off hand, but the motor and motor oil are designed to operate at a certain temp. IMHO around 180F.

 

[Sean Flanagan]

I was following a buddy when his 98. 5 kept over heating. We were both towing in the mountains on a hot day. His was overheating and mine wasn't so we figured it must be a stuck thermostat. We figured if we took it out it would be OK. The only problem is that the rubber seal around the outside of the thermostat is what seals everything. So you can't run it without the thermostat unless you glop everything with sealer. Instead he jammed the old thermostat open and re-installed it. The overheating problems went away. For that trip anyway.



IMHO the cooling systems in these trucks is bareley adequate for those who push it at high altitudes. The stock fan clutch stinks and so does the thermostat. I've been through three thermostats and have started carrying a spare.

 

[Sean Flanagan]

I think my post counter is stuck or screwed up or something...



It was over 300 a month or so ago...



Just testing...

 

[Deezul1]

I thought my temp gauge was broken when the needle never moved one day and it turned out to be the stat was stuck open. this was a 70 deg day around town. Mine wont get warm enough to cycle the fan clutch so the AC gets warm sitting at a light from no air movment and its 90 deg + here now and thats with the stat working.

 

[Bob Cochran]

Joe G. ~I did not think of it in that way. You probably right it would run cooler maybe.



Long time ago in a chevy dually with 454 had thermostat out and doing the winter heater would never warm up. I had a huge radiator.



Running to cold is not good either. I still need to change to a 180 thermostat!!!