EDIT: Submitted the thread before finishing the title. Should amend "over-cooling issue" to the title.



Hi there,

Just picked up a 98 Ram from a car lot. I noticed the heat was weak so the sent me up to their shop they work with, who were sure it was a t-stat. Anyway, that changed the t-stat and problem not fixed.

I'm pretty sure the truck is overcooling. I don't think it's a heater core issue as the temp gauge is reading around 130-140 when driving. If I let it sit and run for a while I can get some heat and some travel on the temp gauge. Also, the hoses to the core are warm on both sides of the core.

The shop also replaced the radiator cap. No change.

Can someone give me a direction to look on this?

Thx!

 

First things first: Confirm with a thermometer that the engine isn't coming up to the temperature of the thermostat. You can dip a mercury thermometer in the radiator, or point an IR thermometer at the base of the thermostat housing (and add about ten degrees to the reading). It'd be really very surprising to find out that the thing's not warming up.

If the engine is coming up to normal temp, it's probably the temperature sensor and a plugged heater core ganging up on you.

 

It's definitely undercooling. Sorry I should have mentioned it was confirmed with a thermometer.

 

They may have put in a bad stat.... wouldn't be the first time I saw a bad part, new out of the box....

 

+1 on the bad stat - pretty common when using budget thermostats - I try to combat that by using a quality Stant Superstat - also, be sure that the cooling system has been purged of air bubbles, which can cause heating problems.

 

I'll pull the t-stat when I can and test it/replace if necessary. They put a NAPA t-stat in. If it tests good, and assuming all air was purged properly, what would be the next thing to check on would you think?

 

It's pretty much got to be a bad thermostat. If it tests good, you need to go have a long talk with the unicorn hiding under the seat.

 

Do you have a laser non-contact thermometer (for an example of one, see this link - http://www.harborfreight.com/non-con...ing-61894.html)? I'd use it to check the temperature readings at the inlet and outlet hoses of the heater core. Also, check to ensure that the damper doors are closed, so cold outside air doesn't defeat the heater.

 

Checked various hoses, t-stat housing, inlet/outlet, etc with a laser. Highest reading at the time was about 180F

 

And what did your temp gauge have to say about engine temp?