Cummins NHC250 thermostat change

[bchauvette]

Disclaimer; not a liable prone how to, Just sharing my experience.

The radiator drain petcock is right above the glad hand, use a cut section of garden hose to direct the draining coolant into the bucket. (B.T.W. petcock end is hard to find in the dirt).

Used a 2" 3/4 drive socket for an install tool. Fits perfectly. There is no back lip where the seal seats. If it goes in crooked push it through then gently pulled it back out. It very much wants to be crooked.

I rough cut the gasket material then placed it on top of the housing then used a ball peen hammer gently taped the gasket around the areas to be removed to get an impression on where to cut and punch the holes. Insure old gasket is completely removed from both pieces. Applied a generous coating of red RTV. Don't use so much so that it oozes in to the inner works.

Run up to operation temp and insure thermostat is open and coolant is flowing then recheck coolant level. Monitor running temp, fan clutch and overflow frequently. Recheck fluid lever after running.

Technical makes a good work platform
Thermostat location
back side of housing, note thermostat orientation.
inner seal, note lip orientation
slide puller removing inner seal.
2" 3/4 drive socket makes a perfect seal and thermostat install tool

Stuff used that came with the M944: 1/2 drive socket set, Slide puller, 3/4 drive 2" socket and extension, gasket hole punch set, gasket material, Vise, Life is wonderful

 

[EMD567]

I must have gotten lucky- I didn't need the installation tool on M814- it came out and went in by hand.........

 

[bchauvette]

Seal was very very tight. Took numerous hits with the slide hammer to get the old one out. Using the 2" socket to get the new one in was not my first attempt it was like attempt number three or four. Trying different methods.

Was there a lip in the housing behind the seal preventing the seal from pushing through? It seems that if your seal was that easy to pull out it would push the seal through when you installed the thermostat with out that lip. My housing didn't have anything like that that would stop the seal from pushing through but was tight enough that it wouldn't move when installing the thermostat.

 

[162tcat]

Excellent write up! It's a good maintenance item that often gets neglected. Don't forget to switch to SCA coolant at the same time.

If anybody needs one, I have a few new 180 thermostats with gasket for the NHC 250, PM me.

 

[MyothersanM1]

When I did belts and hoses I decided it was a good time to change my thermostat. I got it all open up and taken out easy as pie. The darn thing was brand new looking. So, I put it back in. Done.