Hey guys. It’s Kevin here and today I will be talking about how to replace the thermostat on a Cummins 12-valve.
This here is a 1994 Cummins Dodge 2500. We’re replacing the thermostat, so couple little thoughts that might be able to give you here. First off the alternator has to come out in order to get it out of your way. Might be able to do it like slide it by the alternator but it’s not likely and I decided to pull it loose.
There’s a little bracket that’s on the top of the alternator that comes off and then the alternator kind of flops down this direction. I still couldn’t clear it well so I went ahead and removed it completely.
Parts you’re going to need, the part numbers actually This is the actual gasket, a Felpro Engine Water Pump Gasket, part number 35633 and this is a Murray Temperature Control Plus, thermostat from O’Reilly and the part number is 4248.
Here is the old thermostat I pulled out of there. The new ones already buttoned up inside but this one’s been in there a while and its definitely is not working, I think it’s allowing water to come through and not heat up through the heater core. So I’m not getting full heat through the heater core, I’m hoping this is what the issue was.
Anyway its kind of a weird design if you’ve done a thermostat on any other car this is gonna be different. Right here is basically a latch point for pulling the engine. It happens to be right in between the thermostat housing and the block. Makes no sense to me that they did it that way but that’s the way it’s done.
This is your little bypass hose right here. What I did is I took off the screw here, took out these three 10mm bolts right here for which you’ll need a 10mm socket for and then to get the alternator loose you need a 13mm, a 10mm and a 15mm, the nut on the back of the 13mm head is a 15mm nut, which makes perfect sense. I love when they do stuff like that.
The 10mm nut is welded in so that ones a slam dunk and its right on top and then lastly there’s one more bolt thats a 13mm that’s also welded in there all part of this upper bracket right here. It should be pretty simple and easy to get out. I scraped down both, well all 4 surfaces in this case, inner and outer, left and right, and then basically just reconnected everything back together again.
Make sure the bypass line is back on. I’ve got my upper radiator hose tucked back down underneath the drain. I’ll attach that here with a hose clamp which I cleaned this off really well with the brush grinder.
One last thing, the serpentine belts need to come off before the alternator. You might be able to see my socket ratchet in there. Its a half-inch that gets plugged into the tensioner right there and then you can go ahead and release the tension on the thing.
Anyway I just wanted to give you a heads up on this so you don’t struggle and this video has helped you out. If you have any questions, or comments, please don’t hesitate to contact us.
We are building an Overland vehicle out of a 1994 Dodge Cummins here. Basically utility bed and camper and stuff like that. If you would like to see more progress on this project, subscribe to our youtube video channel.