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Runs too cool?

H

hh65flyer

NAXJA Forum User
Location
Kalispell, MT
1998, 4.0, auto.

Just replaced the t-stat with a 195 as the heat barely worked. PO replaced rad, waterpump, etc.

I noticed the old t-stat was also 195 but had two extra holes drilled in the body. I drilled one hole in the new one then put it all back together.

According to the scan gauge, I'm running 160. If I run any of the 'cool' settings (defrost, etc), the fan kicks on and the engine runs even cooler.

Should I put another t-stat in without drilling and/or block the rad for winter ops? Or are we thinking heater core? (please say no). :tears:

Thanks!
 
hh65flyer said:
1998, 4.0, auto.

Just replaced the t-stat with a 195 as the heat barely worked. PO replaced rad, waterpump, etc.

I noticed the old t-stat was also 195 but had two extra holes drilled in the body. I drilled one hole in the new one then put it all back together.

According to the scan gauge, I'm running 160. If I run any of the 'cool' settings (defrost, etc), the fan kicks on and the engine runs even cooler.

Should I put another t-stat in without drilling and/or block the rad for winter ops? Or are we thinking heater core? (please say no). :tears:

Thanks!
Click to expand...

Did you install one of those "fail-safe" thermostats? Those generally get stuck open and cause your jeep to run cold. Depending on the size of the hole, it shouldn't cause it to run cold, most people drill a hole thinking it helps purge the air out of the cooling system when they are filling it. But these vehicles came from the factory with no holes in the thermostat and that's worked fine for the past 200k+ thousand miles, why change it?

As for the heater not working I'd remove the heater hoses and flush some fresh water through the heater core to clean it out.
 
Going to try the HC flush today. Got a bunch of junk out of my Toyota that way but it had other issues. Did the trick though...

Does the OEM t-stat have one of those 'jigglers' to help with the purge? My replacement from CarQuest did not. I have always drilled my t-stats if they don't have the jiggler. Even with the jiggler, I usually take that out, lol.
 
No, however the past stat I bought did have one. I always buy the best one available as the cheap ones are garbage. You might also verify temp at the housing with an ir temp gun to verify sensor accuracy
 
I made the same mistake once of drilling my t-stat. This was many years ago on my '88 when I lived in Seattle. I drilled 3 1/8" holes and the thing would never warm up. So I installed another and drilled a single 1/8" hole and installed it at the 12-o'clock position (as a way to help purge air). On cold mornings it took a long time to get up to operating temp.

Lesson - do not modify the thermostat.
 
My recommendation is to get a thermostat from the Chrysler dealer with the check valve/ball and install it with no further modifications. In the past, I have tried many of the discount parts store offerings. Only the dealer part made me happy. With a good thermostat the engine will get to the proper temperature and so will the air in the cabin.
 
A single hole in the 12 o'clock position can help with burping air from the engine but it does take longer for the engine to warm up. You shouldn't be running at 160 though. I'd get an infrared temperature gun and verify against the thermostat housing at 5 min intervals. Could be the temperature sensor in the housing is damaged somehow while you were removing stuff
 
Thanks for all the feedback guys.

I reverse-flushed the t-stat earlier this afternoon. Nothing significant came out. I have also verified the temp with my hand-held IR temp gun and it's nearly identical to the OBD reading. I aimed it at the the t-stat housing. While running down the road I'm in the high 150's. If I let it idle it will go to about 165 tops.

I guess the next step is to get a good quality t-stat, no drilling this time!! Thanks again, I'll update once I get that all done.
 
I did block off a large portion of the rad (as a test) last night. Temps were low 30's this AM. Only gained about 5 deg. I'm heading to the Jeep dealer today to pick up a 'proper' thermostat. Will update again soon (hopefully).
 
**Resolved**

Well the solution appears to be the fact that I am a moron (partially). LOL.

The new T-stat that I put in was a 165...the parts store gave me the wrong one. I almost always check my thermostats in a pot of hot water before installing and just didn't do it this time because I'm apprently too lazy to do the job right and I was in a hurry.

What's the old expression about always having time to do the job 'right' a second time...?

I have a 195 in there now with no extra holes drilled and the heat works fine (but not great) now. Thanks to everyone that tried to help.
 
Interesting to note that I checked the original 195 T-stat and it worked just fine. Apparently the addition of the two holes in the T-stat body was enough to make it run cold though. It's pretty cold outside now (5 deg F yesterday AM) and the new allum rad is prob very efficient...
 
You can try flushing it with something. I have heard of some people using CLR and other chemicals. I did it last weekend with some white vinegar and it worked awesome. I was getting little to no heat for 10+ miles in mine when the outside temp was below 50 degrees.

I set up a very small pond pump in a 5 gallon bucket with a gallon of vinegar and half gallon of hot water and hooked it up to the heater core by itself. Let it sit and cycle through for about 30 hours and then flushed it gently with the hose. Not too much crap showed up in the bucket but oh my the colors that came out with the hose flushing. Now the fan stays on setting 1 or 2 and its t-shirt weather in my jeep while on the road.
 
I was nervous of this as well. That is why I chose to do plain white vinegar. Seems to work just fine. In fact we were roasting this evening while running errands. Had the temp turned down to half.
 
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