Ever hear of a truck running too cold???

[randy88k5]

My friend has a small Nissan pickup, late 80s, 4 cyl, Auto. I helped him replace the alternator cause it was a PITA to get to. He said when he drives it, the needle never goes above the C mark. This was happening in the end of summer too. I said it must be a stuck thermostat. I changed the thermostat and flushed the system.

I borrowed the truck yesterday to pick up some stuff since the Blazer is getting a lot of work done to it, and cant be moved right now. Since it was in the 20s here, I tried to use the heater, and suprise, no heat. The needle still read C. I guessed it must be a clogged heater core and a broken sending unit.

After a few hours of driving, I pulled into a parking lot and left the engine running. I popped the hood and grabbed the intake plenum with my bare hands , just a little warm. The radiator and the hoses were almost cold, and the exhaust manifold was just hot enough I couldnt touch it for more than a few seconds. And this is after a few hours of driving.

I have never seen or heard of such a thing. Everything in the engine compartment I could touch without getting burned in the slightest. Anyone got any ideas??? Thanks
-Randy

 

[low 84]

sounds like a stuck open thermo to me, but you said you just replaced it. could have got another faulty one, i've seen more bizzar things. i would take the thermo out and check it in a pot of water on the stove and verify its operating correctly.

does it have electric fans? mabey they are not kicking off

 

[sled_dog]

stuck open or far too cool thermostat sounds like. Probably not running its top like that either. Engines are meant to run in a certain temp range.

 

[randy88k5]

As for fans, no, just a single thermal fan clutch. When I changed the thermo, the clutch seemed fine.

And I used a brand new stant, 195 degree IIRC. Guess it could be defective, but this problem was why I changed the themostat in the first place. Didnt help a bit.

Thanks for the input.
-Randy

 

[MOABDADC22]

I would run a 160* or a 180* thermostat.

 

[ntsqd]

Engines usually warm up faster with a higher temp t-stat. Lowest I'd go is 180. 160 is for some sort of race engine. Otherwise the clearences are wrong for that temp and it will wear out quicker. If 195 was stock, and the engine's stock I'd put that back in it after checking that it opens at the right temp.

At those temps what happens if you block part of the rad with a piece of cardboard?