running too cold?

[lussenden]

my 1990 4.0 runs at about 160-170 on the freeway without the A/C on. my feeling is thats a little cold for a fuel injected engine to run at max efficiency. but when i stop at a stop light, itll go up to around 200, more normal. and in stop and go driving its around 210, and the electric fans go on and off properly. what could be the problem? could it just be the gague?

[Projectxj]

well, i have a 1990 4.0 4x4 laredo and it does the same thing i know my radiator has been changed in the past year so that could be a reason.has yours been changed recently as well?? i believe new parts tend to run better than some oem ones my engine usually always runs cool and ive had no problems and the engine still pulls hard....as for your jeep i wouldnt be to worried about it and from what i hear when there is somthing wrong with a cherokee it usually makes a noise....

[lussenden]

the radiator is the one from the factory, but the water pump and thermostat are new. but it runs fine so i guess ill be thankful its not running too hot!!

[AlohaBra]

Do you have the right thermostat? My 97 4.0 L runs at 210 all the time.

[lussenden]

yeah its a factory replacement, either 180 or 190.

[longfellow]

Suspect that the new thermostat is opening to soon. Run a heat open temp. test on themostat to see at what temp. thermostat does open.
If thermostat opens when it should as factory listed then I would suspect temp. guage on dash is reading a little under actual eng. temp..

longfellow

[lussenden]

i now realize for sure that its the gague. how i know for sure it that the electric fan comes on when the gague says its at like 180. but just to make sure, could it be the temp sending unit?

[longfellow]

When the temp. sending unit operates correctly' it sends a voltage to the motor coolant temp guage. Now rather this voltage varies in strength to effect guage readings' i,m not sure.
Need more imput from other readers on this question.
Another thought is if cooling fan kicked on you say at 210 deg,s I believe I read, isn,t this 2 early? Generally this motor runs at 210 Deg,s read. This would mean cooling fan would be running all the time?

[AlohaBra]

Easy quick check is to take wire off and gage should read cold all the way(100F).
Then ground the wire or yellow-violet I believe, and it should read 260F.
Spec according to 93 manual is 93.5 ohms at 220F(104C).
You could also remove it and put it in boiling water with a thermometer. At 212F-boiling it should read about 91 ohms(?).
A new one is about 30 bucks.