Cold Runner

Ive had an issue with the temperature of my 1987 MM 2.6 4x4 ever since I bought it. Its never gotten up to temperature (between cold and hot) even on hot days. my thermostat is good. I do have a bad heater core but that shouldn't affect the rest of the coolant system. It recently snowed here in north Carolina so I decided to go out and tinker with it. I took cardboard and put it in front of the radiator and low and behold, the truck got up to temp ( had to dog it though) anyone have any idea why it runs cold constantly? btw it doesn't have anything for a/c. previous owner took everything off except whats under the dash the compressor (removed it myself to free up space)

It might be running a summer thermostat. Or the temp sender unit isn't right. Other than the low reading, is it running o.k? I wouldn't obsess about a low temp unless it is getting so cold it is stalling out. I had an engine temp problem with a hatchback I did an engine swap on. In winter it would get so cold on the highway it would cause the choke to go back on! I would have to pull over and sit for a few minutes while it warmed up. I had to resort to cardboard on those days but in summer it ran hard and happy lol

It runs fine. It's got a standard thermo in it and the sending unit must be working if I was able to get it up to temp. I do need to pull the motor out and rebuild it though. Luckily I work for a trucking company and have access to a shop. But anyways. It runs fine just never got it up to temp like it shold be until I blocked the air flow.

Check to see if the fan clutch is locked up

If the engine compartment has a radiator cowling, you may try taking that off to allow the engine to gain more heat.

What your describing also makes me feel like your gauge or sensor might be tweaked, giving false readings possibly. If your thermostat is opening to allow water into the engine, then the engine is reaching the temp that the thermostat is set to open on. I myself run a 180 with an electric thermo set fan, though others have their own choices like a 190.
You could try putting a temp gauge into radiator and this could give you a more detailed idea what your temps actually are. One thing about a thermostat that works correctly is that it will not open until it has reach a specific temp. If your motor isn't getting to temp via the thermostat blocking cooler water from entering, then your thermostat is probably staying open and defective. This is the only device that I can imagine that could cause an engine to not get to normal operating temps. Being located in Spokane where cold weather seems to arrive every year, I have never put a restriction in front of my radiator to keep the engine warm.

My gauge has done some strange things before also. It recently finally took a dive and shows that it's pegged. Though before that it was reading way low also. I installed an aftermarket gauge and it reads perfect. I think the fuel gauge may be on its way also because it reads a tick lower then normal on a full tank. 29 years is a long time for any car part to work correctly, so expect stranger things to happen in coming years.

Strangely these trucks can be sort of a self destruction when they over heat, having a truck unable to reach proper temp is a very rare thing to see in this forum.

thanks for the replies everyone. my best bet before going into the cluster again I guess will be just tearing down the motor and rebuilding it. eventually I will replace the motor with maybe a 350 or bigger and just keep the 2.6 as a backup. anyone know where I can get motor mounts that will secure a 350 to my truck?

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Originally Posted by stem860

thanks for the replies everyone. my best bet before going into the cluster again I guess will be just tearing down the motor and rebuilding it. eventually I will replace the motor with maybe a 350 or bigger and just keep the 2.6 as a backup. anyone know where I can get motor mounts that will secure a 350 to my truck?

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That is a big project. They don't just drop in.
You will need to build your own mounts with a welder.

Luckily I know a guy near me that builds custom mounts