Engine/Transmission (1998.5 - 2002) Heater doesnt get hot!

[STPdieselhp]

The heater is my truck works and will get semi warm but it just wont get hot. I was kinda leaning toward t-stat but my temp on my truck stays pretty consistent. If I kinda play with it a little around town then I can get the truck to heat up to about 210 so do you think that it is a possibility that the thermostat is bad?

 

[LDPetersen]

My 95' has had almost no heat the last 2 times I have used it. I only use it weekends to pull a large trailer. Should heat up plenty but only gets to 140 deg. with the front covered up. And it was about 0 or 10 deg. outside. I called the closest Cummins truck dealer today and had him ship a thermostat and gaskets. Will know Thursday nite if that does the trick. It has always had pretty good heat in the past even when it was -20 deg.

 

[Cummins724]

The heater is my truck works and will get semi warm but it just wont get hot. I was kinda leaning toward t-stat but my temp on my truck stays pretty consistent. If I kinda play with it a little around town then I can get the truck to heat up to about 210 so do you think that it is a possibility that the thermostat is bad?

The thermostat is bad..... would be my first guess. This is why you are getting temps up, but not getting warmth into the heater core.

 

[jkalchik]

Just to throw another data point on this... ...



I replaced my tstat (failed open) last fall with a stock replacement from the local Cummins service counter (gotta love counters open 'til midnight!) As the temp drops, the heater just doesn't keep up, yet the coolant temp gauge stays rock solid around 170-180. Yes, I've got a piece of cardboard between the intercooler and the radiator, cut out for the fan hub.



I suspect that I've got some crud built up in the heater core that needs to be flushed out. I'm not about to tackle that at 10 degrees F.

 

[getblown5.9]

i partially fixed my heater by insticker the blend door on my 02... but its still not hot... and i noticed my truck takes 15-20 minutes idling to move the needle off of 140 when its only about 30 degrees out. and when driving, the needle will fluctuate between 160 and 190 but never higher.

im wondering if maybe the t-stat is stuck open.

 

[LDPetersen]

I think you are right. That is how mine has been all fall. I am quite sure mine is stuck wide open.

 

[Cummins724]

I think you are right. That is how mine has been all fall. I am quite sure mine is stuck wide open.

Sounds like it is stuck open..... I would do a coolant flush & change the thermostat.

 

[TJSHOTROD]

If he is making engine temp then the thermostat is not bad. My truck was doing the same thing and I tried to flush the system but that did not work. It ended up being the heater core was blocked up and needed replaced.



TJ

 

[Ragain]

Maybe the shut-off valve to heatercore is partially open?

 

[Thomas]

Maybe the shut-off valve to heatercore is partially open?

There is no OEM shut-off valve.

 

[Cummins724]

If he is making engine temp then the thermostat is not bad. My truck was doing the same thing and I tried to flush the system but that did not work. It ended up being the heater core was blocked up and needed replaced.



TJ

You've never seen a sticking thermostat? It is possible that it is sticking or only opening part way..... he said that engine temps get up to 210. It probably is in need of a good flush.

 

[LDPetersen]

We put in the new thermostat yesterday and that did the trick. The rubber ring around the body of the thermostat was sucked down inside holding it open. Back to normal again. Larry

 

[Cummins724]

We put in the new thermostat yesterday and that did the trick. The rubber ring around the body of the thermostat was sucked down inside holding it open. Back to normal again. Larry

Those thermostats can do some tricky things..... Glad it worked.

 

[GCULP]

just an FYI, I had a similar problem, and low and behold it was because I was low on radiator fluid, there was enough to cyle through the engine and cool it, but not enough to get through to the heater core.

 

[TJSHOTROD]

You've never seen a sticking thermostat? It is possible that it is sticking or only opening part way..... he said that engine temps get up to 210. It probably is in need of a good flush.

Yes and it makes it where it will not heat up like in LDP trucks the original poster STP said his truck makes temp 210 that is what I was refering to.



TJ

 

[Cummins724]

Yes and it makes it where it will not heat up like in LDP trucks the original poster STP said his truck makes temp 210 that is what I was refering to.



TJ

A thermostat can also not pop off at the correct pressure If it is sticking. I would still do a good coolant flush, but I still think it is a thermostat for him as well. The thermostat doesn't open..... whats it doing? It holds the coolant back & it doesn't circulate to the heater core & most of what does go through can get sent to the overflow jug to cool... ... or it can create a vapor lock.

 

[TJSHOTROD]

If it is not opening he would have high temps correct.

 

[Cummins724]

If it is not opening he would have high temps correct.

It could be a corroded or bad spring that is stuck or only opening sometimes..... or only partway. I've seen these things happen too many times & not saying that it is definately the thermostat, but If I were a betting man... . thats where I'd put my money.

 

[TJSHOTROD]

STP lets us know I have my money on it not being a t-stat.

 

[Cummins724]

I guess we'll have to see, but like I said..... I'm not a betting man no more & you are from Reno..... odds are against me on this one, but I'm sticking to my post... . thermostat.