Ask The Expert- TJ with Mishimoto Radiator operating temp

[SethG]

Hi there, I have a 97 TJ I6 with a Mishimoto radiator. The operating temperature doesn't climb to 210 on the gauge like I would expect. It stays on the hash mark just to the left of 210. It sometimes climbs about half way between the hash mark on the left and 210 when driving for a while on the highway but drops right back down when I slow down. I think that may be from the trans fluid pumping through the internal trans cooler at the higher speed. I know that the gauges are necessary accurate but the heat is not that strong either.

Do these Mishimoto radiators cool that well or do you think the thermostat is stuck open?

As a side note, I didn't install this radiator, it was in the rig when I bought it. The PO gave me a new Mishimoto thermostat in the box in a collection of parts he had to give with the jeep. I wonder if these radiators need a certain thermostat and he left the old one in. I plan to change the thermostat out but didn't know if anyone had experience with these radiators and whether I may have the same "cool temp" situation either way.

 

[timatoe]

Is it possible the PO already put a Mishimoto t-stat in it? A real quick check shows that being a 180* t-stat, a lot of times people do that even with basic Stant t-stats trying to correct some other issue. It should be a 195* stock. I'd change it to a stock t-stat myself.

 

[SethG]

Yup. I just looked at the Mishimoto replacement stat in the box and it's a 182 degree stat. I'll put a 195 in. Thanks for the heads up. That never crossed my mind.

 

[Brian]

Wait...Wait... I have dealt with too many motor that you have no clue why someone did certain things. In this case, might there be a tune in the engine or something that calls for a cooler thermostat? IMHO, a 182 to a 195 is not much, unless you feel you are getting poor fuel mileage due to the engine trying to warm itself. If it is running great, I would not change it. Beyond that, NEVER trust your factory gauge to be 100 percent accurate.

 

[SethG]

I don't think there is a tune on the engine. It runs fine but cool with valve tick. I changed the plugs, rotor, and dist cap and the plugs showed some signs of not operating at the proper temp. I figured the cool temp may be gunking up the valves and the lifters. The mileage stinks (12-15) but I think that's due to 35's and hundreds of pounds of bumpers, skid plates, fenders, etc.

 

[lindel]

A tune on a TJ engine, especially an older one, wouldn't make much difference...the PCM isn't sophisticated enough to notice. The T-stat should be a 195, as noted, and the engine temp should be a fairly consistent 210, or nearly straight up on the gauge.