Hi,

My truck will not come up to temp. The needle never moves from the white line(140). The oil pressure also stays a little higher than normal. It has gotten cold here and have only noticed this since the cold weather. I have heat. Could it be the thermostat?

Thanks!

 

Yes, and I'd replace it w/ a 195* t-stat ASAP. Engine wear accelerates running cold.

 

Thanks! Where is the thermostat located on 02?

 

I would only replace it with a cummins thermostat. I've ran a parts store cheapie, and a parts store high end t-stat. The high end stat worked but cycled open and closed real bad so the temp would not stay consistent. The cheapie, stuck closed and over heated my engine, taking out a week old head gasket. The cummins stat work's much better, it still cycles a little, but it holds temp much better.

 

Follow the upper radiator hose to the engine. It's under the housing, which is held down with three bolts. Be sure to pay attention to the direction it's sitting. New one will point in the same direction. BTW, if you have a few miles on the coolant, maybe do a coolant system flush. I'll find out the torque specs on the bolts.

 

89 in/lbs or 10 Nm

 

I had to replace mine this year makes a huge difference I can have heat now going to work.

Robert

 

Thanks guys. I'll tackle it today.

 

Well I just now got around to changing the t-stat.

I have a couple questions.
The new t-stat looks different than the old one.
The new one has the numbers 3946849. On the
box. Nothing on the t-stat itself.

The old one has 3937171.
02 down 190 degrees. On the
t-stat.

Are these the same? I got the new one from Cummins.
They said the new one was 88 celsius which is 190F.

Thanks!

 

Can't vouch for the part numbers. The 190* sounds right though.

I stopped by a Cummins NW shop about a month ago to get a replacement 'stat for my '98.5. They looked it up and gave me a 180* model. That's what was in it.

I remember when these engines first came out that the thermostats' temperature ratings were increased to 190* after a year or two of production. I think it was an emmissions related thing.

Here are a couple of pics of my 98.5's thermostat port. After about 80k miles and 8 years, the seal on the thermostat was starting to get tired. There was a bit of bi-metallic corrosion on the flange areas too. The internal coolant passages are nice and clean though. That was Fleetguard coolant in there. Well worth the $$.

 

That's the current #!

RJ

 

Thanks!

I put it in and everything seems to be normal.

 

Just curious.. IF i go to a Dodge dealer and get a MOPAR thermostat, is it the same as the Cummins??

I dont have a cummins dealer near me.. I found an online place that was selling the mopar t-stat for around $58 ($75 retail).. the gas enginers t-stats ran around $15dollars, so there seems to be something special about the diesel one.

thanks

Brian

 

Yes it is...

 

The diesel stat is different, I priced one at the local cummins shop it was 123$ Canadian !!!!!!!! So I went with a Stant for around 30$ so far it seems to work as good as my old stock one did (before it went bad)