I swear I'm not nearly as inexperience as this question probably makes me seem --- but --- I'm replacing the thermostat on my 95 and I've confused myself. I didn't pay any attention to how the entire thermostat housing came apart (housing, inner seal, and lift bracket) --- I have the Dodge manual. Now that I'm ready to put it back together it seems like the manual is telling me to put the inner seal in backwards. The manual shows in going in with the shoulder toward the thermostat. It seems to me like it should go with the shoulder toward the lift bracket --- with the shoulder inside the lift bracket and sealing against the block.

If it put in together like the picture shows, it seems like I will have a leak between the lift bracket and the block.

Can someone please straighten me out?

 

I've had the rubber seal come loose and hold several stats open. On all of the them I just removed the seal and tossed it. Don't think it makes any difference if it's in forwards, backwards or not at all.

 

Thanks for the info.

 

Sorry to hijack this thread, but I am doing a coolant change this summer and my normal practice is to change the thermostat at the same time.

Anyone have any opinions on using a genuine Cummins thermostat vs. a Napa or Carquest replacement part?

 

The newest part number for the cummins dealer is 3934373 some have stated it helps with the fluctuation, I have yet to try one, as far as the napa I would assume it will fluctuate. Goodluck,,Rick

 

Can't answer the NAPA vs. Cummins question yet but give me a week. T-stat is stuck open now and waiting to be changed. The shoulder is towards the T-stat (away from the flange) fortunately the new seal is even marked with a directional arrow.

Paul

 

From what I have read here the other brands are problem prone. Cummins is $20 or so well worth it.

 

I'm about to replace my thermostat, it's stuck open, i like most people have changed them a dozen times on cars and trucks with gas engines. But I was wondering about this O-RING should I toss it or put it in? If I install it does it go in before the stat or after it?

 

My experience is with the 1st gen CTD. Last year when I replaced my radiator, even though the thermostat was OK, I replaced it as well. The one in there was the NAPA type that only has the one bleed hole, and when running, I found the engine temperature would hunt. The thermostat I took out had also been installed with gasket cement.

The new Cummins thermostat is of a different type than the NAPA one, it has three bleed holes and fails closed, which prevents the coolant from by-passing the radiator. The NAPA thermostat fails open which allows the by-passing of coolant, and is the opposite to what the Cummins wants. I cleaned all of the gasket cement off the faces, and installed the rubber ring dry. The order of installation is block, rubber ring with shoulder towards the thermostat, thermostat, then the housing. It does not require gasket cement.

I have put 12,000 miles on the engine since then, and have no leaks, and the temperature hunting stopped. The Cummins thermostat cost me $42. The Dodge part was priced at $50.

I'd say use the right thermostat and the rubber ring.

John

edited 10.40pm to add order of assembly.

 

thanks John

 

the napa t-stat is a peice of junk. I have had problems more that once.

 

I installed one from Autozone. It's a piece of junk too. The temperature fluctuation is crazy. It's is almost constantly bouncing around over 2/3rd of the range of the guage. I didn't mind the normal fluctuation of the orginal thermostat, but this one worries me. I'm going to change it as soon as I get can get one from Cummins.

 

I picked one up from Cummins yesterday and installed it, it looked just like the one that came out only newer I could see where the old one had failed. There is a wide black rubber band around the stat that got wedged in the opening preventing it from closing.

 

 

That's a great pic, it would have come in real handy before I change the stat not after I managed to limp through it anyway, it wasn't rocket science.