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Thermostat temp for Chrysler 318 engine

On my '89 Dodge B250 camper van with a 318 engine, I noticed on a long trip today that the temp gauge never got above about the 1/4 mark…definitely not close to halfway up the gauge. I’m wondering if the stat is stuck open. It looks easily accessible at the top front of the engine, and new stats are cheap, so I’m thinking of throwing a new one in there tomorrow.

Looking at parts online, I see that I can get a 160, 180, or 195 degree stat, all of which will fit my 318 engine. What is the correct temp for this application? (camper van with an extended body and fiberglass high top, so it’s heavier than stock, mostly summer driving, I expect…)

And, what are the consequences of installing a stat with an improper temp range?

I would go with the 195 degree thermostat. The temp rating of the thermosat is when it opens. Once the thermostat opens it’s up to the rest of the cooling system to keep the coolant temperature under contol. Also, with a higher temp thermostat, the engine comes up to operating temperature faster. And that saves fuel.

Tester

Thanks, Tester. You the best!

I had an '87 Dodge pickup and my mom had an '87 Diplomat, both with the 318, and the temp gauge always did the same thing in both vehicles: never past the quarter mark, so this is probably normal. If you want to change the thermostat, it’s not a bad idea and I would also use the 195 stat, but I would be surprised if you see a difference in the temp gauge.

A 195-degree thermostat is pretty much standard on any V8 engine and pretty much most gas auto and truck engines in general.

Mark, thanks for the data points… in that case, I’ll probably just leave it alone.

Here is a not too scientific way to test the thermostat: Warm the car up, turn the heater on and put your hands under the heater discharge. If the air coming out is hot, the thermostat is working. You may also want to open the hood and feel the inlet and outlet hoses for the heater. If they are hot, the thermostat is at least working.

A thermostat can be tested. Place the thermostat in a pot of water along with a thermometer. Heat up the water until the thermostat opens and observe the temperature at which the thermostat opens.

Tester

Also not too scientific. Tape a meat thermometer to one of the heater hoses.
The is a good chance the temperature is stamped somewhere on the old thermostat. Go with that.
If I had to guess I would go with the 180 for this vehicle. It will keep the engine oil and transmission fluid temperatures a little lower.

If your heater puts out sufficient heat all the time, your thermostat is probably OK. How’s the temp when you go uphill? It should go up on the gauge. The longer the hill, the higher the temp. Your van probably has a good radiator that’s also kind of large so it works better than the regular one. It’s good that you are checking things out.

Yeah, it’s a big radiator, and I haven’t needed heat yet, so haven’t tried the heater…but I’m guessing Mark is right, and the gauge normally reads low.

Don’t be fooled by the heat that comes out the vent system. If the temperature is at 140 degrees it feels pretty good. But the engine management system doesn’t go into the closed loop mode until the coolant temperature reaches 150 degrees or higher.

Tester

As others have noted, go with the 195 thermostat. The industry moved away from 160 degree thermostats years ago (1950s?), and away from the 180 degree thermostat (IIRC) somewhere in the 70s.

Stant says the oe temp is 195 as long as the van does not have ecu or ecm you can runa cooler t-state.

Don’t be fooled by the heat that comes out the vent system. If the temperature is at 140 degrees it feels pretty good.

+1.
I recently had an issue with my Camry where the CEL was lit indicating a low engine temp condition. The heat was fantastic & both heater core hoses hot. The temp gauge was reading slightly lower than normal and had always been slightly below half way. I figured it must be the temp sender so I changed it. The temp gauge came up slightly but the CEL soon reappeared. Changed the tstat and the gauge came right up to the middle position and CEL was gone for good.

There is absolutely no benefit and a good chance you may cause problems running a cooler temp tstat than the 195 OEM setting.

OK, thanks guys. If I do replace it I’ll go with the 195.

I would change the thermostat anyway if it’s over 5 years old. They get sticky.
My vote is 195.