Replaced tstat. No change. But i had higher engine temps this time. However it doesnt appear to reflect on temp guage. AND...... When i unplug temp sensor. Fans then kick on. Any other time. I cant get it to kick on. Cuz it wont apparently come up to temp. I am at a loss here. Any ideas?

 

my cherk will only come up to temp when the ambient temp is above 14F...i have a (2 week old) 210 stat (yes 210), new coolant, pressure bottle...and a factory crap rad. i think its a case of inefficiency in the rad. today it was -36F with the wind, and it would not go much past the first line after an hour of driving. and no its not a defective stat cause i can hear it open with my stethescope in the shop... 'click whoosh"

 

air pocket in the system?????

 

Well i did run it low in res tank??? O.o

 

Updated: '91 4.0 - Recent (5 months ago) rad, cap, tstat, watr pmp, hose replacement and flush. Just replaced heater core valve (after this all started). But it is running VERY COOL according to temp guage. Started after it got cold here. Will not get to normal op temps at all according to temp guage. Ambient temp today around 50*. Should get warm. Temp needle drops when i hit the gas. Shot housing with a temp gun and shows between 200-215*, which is good. The elec fan doesnt kick on though. Upper rad hose gets hot. But no fan. Now when i implug temp sensor on housing, fan fires right up. Prob failsafe to keep temps down in case of failure? Any ideas guys? I am at a loss! New temp sensor? What else can i replace? I also swapped my bendix brakes recently. Dont think i unplugged something related to cooling system???

Oh and i ran it low on coolant. It had been leaking from the htr core valve. I didnt realize. So maybe air in system?

I know dj......... Have a look! -

 

How well, or not, does your heater work?

 

Gets warm. Just like always seemingly. Dont think its core. Though ive been wrong once or twice.

 

"Gets warm"....does that mean hot enough to be comfortable? If yes, then actual coolant temp is probably getting higher than what the gauge indicates.

 

If the t-stat opens at 210F (click whoosh), wonder why the gauge would be at about 100F (1st line)? Does your heater get warm/hot enough to be comfortable?

 

Im suspecting your coolant sensor now since you say heat is warm but guage is showing 100* or so.

 

Yeah dj its comfy n there. Temp guage needle bounces around too. Not like a bad speedo. But still quite a bit. Dumps low quick when i hit gas. It will get up to 210 on guage but fan never kicks on.

 

Check the temp sender connection and verify you've got a good ground from the back of the head to the firewall. Sometimes you need to scrape the paint off under the firewall attaching point.

 

I checked it in my shop...not gonna stand outside and do that in this weather...hardly any heat on the highway, 45-50 mph.

 

If the t-stat is actually opening at 210, there should be plenty of really hot coolant flowing to/thru the heater core well before the t-stat opens.

 

today it idled for about 10min. had it plugged in all nite...my needle was right between middle and first quarter mark...got on to freeway and it never moved. it was also -47 F with the wind this morning. it still put warm air into the cabin, but i freezed my *** off!

side note: it was cold enough this morning that when i started the heep in nuetral, it actually moved forward a bit. fluid in the tranny must be super stiff!