I6 thermostat

cajunmudder · 01-20-2005, 08:31 PM

What happens if you put a 160 degree thermostat in a 4 Liter?

Brian's 97 ZJ · 01-20-2005, 09:17 PM

Good question.

With a stock radiator, 180 degree thermostat, high flow water pump and a slightly higher compression ratio my engine temp never reaches 210. Not even during the summer with the A/C on. My engine temp comes up quickly but never gets higher than ~200. I've noticed this winter that my heater gets plenty warm to keep the windows clear but the air is certainly not hot.

I guess that doesn't really answer your question though.

- Brian

Note: Edited to correct the temps.

cajunmudder · 01-21-2005, 07:45 AM

Yeah it does thanks. Everytime they tell you to replace the stat they always say use a 195 like the stock one and I didn't knwo why. Thanks.

**Phil Gerard** · 01-21-2005, 07:56 AM

I also put a 180 T Stat in a few weeks ago so that I could install a Jet Stage2 chip. Everthing's working fine, plenty of heat, no detonation.
Not sure 'bout a 160 though - why a 160?
Curious

Phil

greasefingers · 01-21-2005, 08:11 AM

When an outcome or result is an unknown, changing a variable more than 10 % is considered drastic. The first thing that comes to mind is, incomplete combustion and hence producing more emissions. I know there is a coolant temperature input to the PCM, but I do not know how the PCM will handle such a low input. One possibility is that the PCM could stay in Closed Mode in which the PCM uses stored input valves instead of real voltage inputs. I am no expert in this area so don’t believe I word I say

jeepholic · 01-21-2005, 12:43 PM

Quote:

Originally Posted by greasefingers

When an outcome or result is an unknown, changing a variable more than 10 % is considered drastic. The first thing that comes to mind is, incomplete combustion and hence producing more emissions. I know there is a coolant temperature input to the PCM, but I do not know how the PCM will handle such a low input. One possibility is that the PCM could stay in Closed Mode in which the PCM uses stored input valves instead of real voltage inputs. I am no expert in this area so don’t believe I word I say

Way over my head, but if I understood that right, the computer won't turn on correctly or at all until it see's the right temp, that I believe and have seen first hand.

dougy147 · 01-21-2005, 04:53 PM

I put a 160 in my 95 once. It was fine over the summer, but once winter hit I was quite cold until I got a 195 in there. I think it ran better with the 195 anyway, my advice is to stick with the OE, or if your dead set on going lower a 180, but not 160.

midwest97gc · 01-22-2005, 07:42 AM

I had a 180 in my older 4.0 and it was cold in the winter, I sold that Jeep, and when I will have to replace my T-stat on my current GC, I will not go lower than 195

Cassius

Drew · 01-22-2005, 09:10 AM

A 160 will cause the pcm to stay in closed loop. Which is the warm up mode. It will inject more fuel unnecessarily causing crappy gas milage, carbon build up, and crappy emissions. I have seen some cases where it has ruined O2 sensors and fouling plugs. You might be able to get away with it if you don't have winters, but if you get any cold weather then I wouldn't do it. I'm not really a big fan of the 180's either, but that's just me. I'm on my 4th 4.0 Jeep and have run 195's with all of them and rarely see a temp above 210. Most times it hovers at just below around the 195-200 mark.
Some people thing the 160 stats are the solution to an overheating problem and that's not the case either.

Oh, anyone have any info on MotoRad thermostats?? They are supposed to have a safety feature where when they fail, they fail in the open position???? Most fail in the closed position...
Good Luck
Doug

Meerkat · 01-22-2005, 10:36 AM

The amount of electronic spark advance provided by the PCM is determined by five input factors: engine coolant temperature, engine rpm, intake manifold temperature, manifold absolute pressure, and throttle position.
With a cooler thermostat than required by the PCM (be it 180* or 160*), the engine timing will be altered. So fuel will be wasted (running rich), engine timing will be off (possible detonation issues), and emissions levels will increase (possible failure of O2 sensors, catalytic converter poisoning).

HTH

cajunmudder · 01-22-2005, 02:06 PM

Alright thanks a lot everybody. I almost made a costly mistake

OlllllllO Jeep1 · 02-20-2005, 01:58 PM

Latey I have noticed that my Jeep has been hitting the 210 temp mark. I believe it used to get around 200 tops. It never gets over 210. Although it is winter and I dont want o have probs this summer. It is a 4.0. Should I just try to change the stat and see what happens?

Drew · 02-20-2005, 04:17 PM

Quote:

Originally Posted by OlllllllO Jeep1

Latey I have noticed that my Jeep has been hitting the 210 temp mark. I believe it used to get around 200 tops. It never gets over 210. Although it is winter and I dont want o have probs this summer. It is a 4.0. Should I just try to change the stat and see what happens?

That's the first thing I would start with. I would also drain out as much coolant as you can and add fresh. I was suprised on my 01' at how nasty the coolant looked.
When I just did mine I used the "Motorad" thermostat. It is the safety one that fails open if it should happen to fail. I got it at the zone for about $10. So far things seem good.
Good Luck
Doug