Engine/Transmission (1994 - 1998) Engine won't warm up

[CFast]

History: 1 ton Dodge Ram 12V 1996 5 speed, company parts truck, bone stock. I was told by my service manager to "adjust the clutch", he doesn't know anything about these trucks, we sell CASE equipment. I checked the clutch fluid, it was full. While doing this I noticed the coolant overflow tank was dark. I looked inside and it looked like engine oil. So I stuck a long screwdriver in there and sure enough it had oil in it. Took the oil cooler off and found the gasket was torn, the bolts were loose for I don't know how long. I installed new gaskets and put in a new thermostat (a 180 unit from NAPA). I added some cascade to the cooling system to flush the oil from it, filled it with water and drove up and down the highway for 20 minutes. The temp gauge would go to 190 the fall immediately to 165 or so. It did this constantly. I used my heat gun to check the temps, the t-stat housing never got over 175 and the radiator never got over 100. I drove up and down the highway agian as hard and fast as this 180HP truck would let me. It never warmed up. It was at least 50 outside temp today, not that cold. What the heck did I do wrong? I've been a mechanic for 7 years and I've yet to run into this problem. This is also an EGR engine if that matters. I have a 24 valve that goes to 190 and sits there all day, it doesn't flucuate. Is this common on a 96 12V? I'm thinking I just go a junk T-stat from NAPA, it happens sometimes. Anyone have any other suggestions? This truck is making me feel stupid.

 

[Fordiesel69]

As frustrating as this sounds, you juts simply cannot use aftermarket t-stats. Before I knew better I put in 4 t-stats from autozone in my 6. 9L ford diesel. For what I hear cummins has a different tstat that does not allow the huge fluctuation like the oem one.

 

[DCreed]

yup, second the t-stat.

 

[GAmes]

I have found that the fluctuation thing is the luck of the draw. Some T-stats (from Cummins, of course) do it, some don't. The fluctuation is normal and won't hurt anything. The heater temp stays constant. You need a lot higher outside temps than 50 and a big trailer hooked up while climbing a steep hill to get over 190.

 

[QWaller]

Yup. . My napastat went in the trash as well. Cummins part now.

 

[ZBrown]

mine fluctuates just as described with the OEM T-stat... . thought it was the sender... . guess not

 

[Loren]

The temp gauge would go to 190 the fall immediately to 165 or so. It did this constantly.

CFast,



That's normal. My 1995 truck has done it since it was new. The thermostat has never been changed and it has 120,000 miles on it.



This situation was reported in the TDR magazine a loooong time ago, maybe in 1997 or so.



The engine is warming up, but with no trailer to pull or mountains to climb, it's not producing enough heat to heat the radiator. The thermostat closes until the water reaches 190 degrees, then it opens. Once the water gets down to 150 degrees or so the thermostat opens and the cycle repeats. The temperature drops rapidly because the radiator is full of relatively cool water.



I ran my 1995 truck one entire winter (in southern Indiana) with a piece of cardboard behind the air conditioning condenser. Another winter, I removed the fan. Neither of these actions made any difference in the cycling of the temperature gauge.



The cooling system is just overdesigned for running in our trucks with light loads.



Don't worry. Be happy.



Loren

 

[surfbeetle]

This is normal and if I remember correctly there was a tsb about it. I have 175000 miles and my original t-stat is still in and it has had fluctuated in the same manner since new when the truck is empty. I just keep an eye on it. When I am towing, it doesn't do it as bad.

 

[bmoeller]

I went from a 190 t-stat to a 180 at the last flush, and I noticed the 180 does it even more, with lower hp. Since I've cranked up the fuel, it is more steady, but still does it.

 

[tgordon]

The heater temp stays constant.

Mine the heater temp fluctuates with the gauge, a little annoying, but I live with it.



One spring I left my radiator covered and forgot about it till I was driving down the road, about 80 degrees out and the A/C wouldn't work worth a turd. Then I remembered I never pulled out the cardboard, temp gauge was constant though.



This would be why those guys in AZ could plug off that one ton and get away with it, but I have yet to hear of anybody having overheating problems with these trucks like they did the duramax, unless there were other issues.

 

[Dr.Bob]

Sounds right to me, put your heat gun on your heater vent see what you read.