I don't often drive my Montero down to the city...but when I do I run into a strange problem. I am dropping from 9200 feet to 5200 feet in about 25 miles. Thus, almost the entire trip is down hill.

Yesterday the temp was 30-36 deg F.

The truck won't stay warm. The temps can get so low that I don't even get heat from the heater. At idle it will enter the cold loop where it keeps the idle higher than normal.

Before it gets really cold, anyone have any ideas on how to keep the truck warm? I could simply block part of the radiator for the drive down and pull it out for the drive up. Anyone have any better ideas?

First thing I'd do is replace the stat.

Try placing cardboard in front of the radiator (as you've clearly stated).
However, a higher degree t-stat, and a block heater might help.

+1

If that doesn't do it I'd look at the clutch on the clutch fan. If it's frozen fully locked then it won't be disengaging when the ambient temperatures change. Had this problem on my 'Bird twice before changing to electric and my Sport fan clutch was starting to do this, too, before I changed that to electric a couple years ago. PITA I understand.

Edward

I am stopping on the way home to pick up a new stat. Going electric on the fan was something I wanted to do.

I didn't even think about the thermostat because I was not having any overheating problems. If that is opening at lower temps then it would cause this problem. Thanks for the idea!

Make sure you get the correct temperature thermostat. The aftermarket ones are not all created equal and they may or may not start to open and come to full open at the temperatures that they're supposed to irrespective of what they say. A thermostat that doesn't open when the ECM/PCM expects it to will hork up your fuel control and can result in random codes and CEL.

Read my posts ...
Montero Sport thread - thermostats

Edward

I've never had a "Stant" fail. I recently installed their "SuperStat" in all my vehicles. It is much more robust than standard stats and claims to eliminate large fluctuations in open/close temps, keeping engine at a more even temp. So far so good.

Personally, with the consistently low quality I've seen in all brands and styles of thermostats, I'd recommend testing any thermostat before you install it. Suspend it in a pot of water on the stove to make sure that it opens at the correct temperature and that it opens and closes completely. It's far easier to detect and return a defective thermostat when you haven't installed it on the vehicle.

This isn't new problem. I've been dealing with crappy thermostats since the beginnings of the '80s. The effects have just gotten worse with computer controlled vehicles. You could get away with a thermostat that didn't open quite when it should or wasn't full open quite when it should be 30 years ago. Not any more. EVERYTHING is tied into ECT even A/T trans shifting.



OR, you could not waste $20 of your time and just buy one from the dealership. Never had a bad/inaccurate Mitsu thermostat and they last.



Good marketing on their part. Stupid, but good. So, they managed to charge a premium for a product to do what a normal thermostat should just do in the first place.

In other words, they'll sell you the broken part for n $$s but if you want one that WORKS, well, that's extra. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Like I said. Buy a Mitsu thermostat and be done with it. Sigh.

Edward

Could never tell the difference from the OEM stat, so not sure of your snide, broken part comment. Have you done temp testing you could post of Stant versus OEM so we might all see how the "broken" one differs so much?