I have changed the thermostat twice with no change. I have a 4"exhaust system and k&n filter, but stock otherwise. My exhaust guy says he hasn't had any other complaints with the 4" system causing my problem. I just can't seem to get it to come up to temperature. it warms up on the highway, but gets cold in town. It is like the stat is open and cooling too fast. The temp gauge is getting to about 65 sometimes, but the stat is an 80, and it takes a long time to get there. Any ideas?

 

What is your geographic location?

Are the engine temps really that cold, meaning is the gauge accurrate? Are you getting heat?

If it is really cold outside you may need a winter front, heck, some guys remove the fan completely for the winter months, or cardboard in between the intercooler and the radiator.

Might want to put a temporary mechanical gauge in to see for sure, but I would try the cardboard, unless you live in a warm climate. Kevin

 

My 98 does the same thing. It wont even get to 180

But, my 2001, it gets to 190deg, and stays there.

 

He talking in Celsius 65=149F, 80=180F
Sounds totally normal for a 12 valve in the winter to me. You're trying to fix something that isn't broken.

 

Yeah, mines about the same. I used to run a winter front, but a good headwind and a tall load on the trailer = PEGGED TEMP GAUGE!

I'm pretty sure I caught it before it did major damage, at least it doesn't leak any coolant, just oil . But advice from a friend going to school as a truck mechanic and that little event made me lose it forever. The truck is a little cold natured, but so am I (lots of "insulation )

Chris

 

i left my fan off after I killed my pin and it doesnt even get to 190. And im in wisconsin. I do have good cab heat though.

 

About what Palmetto said, I test drove a new truck and it did just that...right up to temp and held it nicely. Nice heat in the cab and a steady gauge. I find it hard to believe that in 1995 Dodge would be able to sell trucks that kinda made heat in the cab, and had a temp gauge that bounced up and down by 20 degrees. I watched mine get up to 85 on the highway (180) and the stat opened, then the gauge dropped like a hammer to about 60. I dont think this is normal behaviour. My fear is that the engine temp is fluctuating too spiraticly and could crack something or blow a gasket.

 

Actually, yes, it's perfectly normal behaviour for a 12v Cummins. Strange, yes, but normal. Apparently, the engine runs so cool, and the cooling system cools so well, that when the thermostat opens for just a second, it lets through enough coolant to drop the temp like that.

 

If you have an oil temp gauge you would see the temp holds steady, also egts stay steady while the coolant temp fluctuates. This indicates to me that the block temp is steady. If it's a problem it sure is taking it's time to show up, between my two trucks I'm pushing close to 500,000 miles with absolutely no engine problems.

What Cummins says,

THE COOLING SYSTEM USED ON THE CUMMINS DIESEL ENGINE EQUIPPED VEHICLES PROVIDES THE CAPACITY AND PROTECTION OF THE HIGHER GVWR AND GCWR RATINGS AVAILABLE ON THESE VEHICLES. OWNERS SHOULD BE ADVISED OF THE NORMAL SLOWER WARM UP AND LOWER ENGINE OPERATING TEMPERATURES ASSOCIATED WITH DIESEL ENGINES.
THE COOLANT TEMPERATURE GAUGE WILL FLUCTUATE ON DIESEL ENGINE EQUIPPED VEHICLES. IT IS INFLUENCED BY VEHICLE LOAD, OUTSIDE AMBIENT TEMPERATURE AND EXTENDED IDLE TIME. THIS FUNCTION IS CONSIDERED NORMAL

GAUGE FLUCTUATION WILL BE NOTICED MOST OFTEN UNDER STEADY STATE (HIGHWAY) DRIVING. PLEASE ENSURE THAT YOUR CUSTOMER IS AWARE OF THIS NOTE PRIOR TO RELEASING THE VEHICLE.

 

That is a very interesting quote from Cummins, Infidel! That addresses the issue directly, and pretty accuratly. So here is my next question....how did they correct it for the newer engines and trucks? Can it be retrofitted to the 12v engines? I'm up in Ontario and its cold here in the morning! I have 315 000 km on it now and would love to see it hit 500 000, but if it is going to frosty in there all the time, I may have to upgrade to a 24v truck!

 

Mine flucuates also. I was wondering if it was normal. I guess so. My question is how much do you cover the radiator and at what outside temp do you uncover it?

 

Your question is a good one, and perhaps often misunderstood. It is also unusual that my 1995 auto 4wd which I only owned for three months fluctuated as you indicate while driving on the highway, wereas the '96 2wd 5-speed is rock steady around town and then raises just slightly on the highway (and ever a bit more in hot weather.) In all of this, my '96 has yet to hit the 190F mark, in the hottest of weather on the freeway at 75, it manages to reach nearly 1/3 of the scale. That said, once warmed up in the winter, I never hurt for heat, but I'm not in artic conditions in Chicago. From the owner's manual itself on page 105 (you won't find this in the index in the back, by the way):

-----------
"Usually the coolant temperature indicated during operation will be to the left of center in the normal range (unlabled hash marks) of the gauge.

The coolant temperature gauge will fluctuate on diesel engine equipped vechiles. It is influenced by vechile load, outside ambient temperature, and extended idle time. this function is considered normal.

Gauge fluctuation will be noticeable most often when driving at steady highway speeds and stop and go city type driving."

To basically illistraute what the manual shows, here is an unloaded condition gauge on the left, and a loaded condition gauge on the right. The "exclamation points" are normal range. The "*" is the indicator tip. Never thought I would be drawing on a post!

[ !* ! ! ] [ ! ! * ! ]
140 190 230 140 190 230


Hope this helps!

 

Sounds like the T-stat is leaking around the seal. Did you replace the seal and stack the stat, seal and pull plate and align the stat with the notch in the housing? What size is the bypass hose?Should be a formed 1/4 in hose and have a restrictor fitting. I agree with what cummins says, but it should come up to temp and maintain temp.

 

my buddie's truck will sit and idle all day long and not even register on the guage, but as soon as you get on the road and romp on it, by the time you hit 100 mph, it is alredy at 140* (takes about 12 seconds) i dunno, havn't drove it much, but it seems like it goes back down pretty quick.

 

Where are u in ontario?