Please Help Running Very Hot

Chad91gt

Member
Mar 2, 2017
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1991 mustang gt. Was running 1-2 notches below red line on temperature.. which is still high.. flushed radiator now runs way above red line.and stays there. But when I start it when car is cold shows it at normal temp. And rises fast. But when use infared on water pump and neck shows 160-170-180.. am I checking the right area with infared? Could it be my thermostat? Or my coolant sensor? No water in oil..No coolant is spilling out of radiator ..
 
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Go buy a cheep manuel temp gauge and install it. Zip tie it to your wiper arm and watch the gauge.
Report back your temp readings,
Just a thought, you said cold temp gauge is at normal? Where is the needle when key is off?
 
Go buy a cheep manuel temp gauge and install it. Zip tie it to your wiper arm and watch the gauge.
Report back your temp readings,
Just a thought, you said cold temp gauge is at normal? Where is the needle when key is off?
Thanks I'll purchase a cheap guage and see what happens. I meant when I give a little time to cool Then start it the needle will drop.. and if the next day it will be at the bottom like normal. But goes up pretty fast.
 
So I took out the thermistat.. took forever with the bottom bolt. And I boiled water .once boiling I out thermistat in there for 20-25 seconds. And does not open. This means thermistat is no good. And probably was the problem? Also I ran It hot for 5-10 mins over red line. Wht should I look for if I did any damage to my engine.? I check the oil and there is no coolant in it and no white smoke. No ticking. Engine still sounds good
 
the 5.0 wasn't as bad as some other ford engines for getting vapor locked but still did,,oem ford thermostats had a small ball bearing valve on them to bleed out the air from the intake side,,I always drill a 1/8 inch hole in aftermarket ones so the air will bleed out ,,doesn't make a difference in warm up or operating temp,,you cant always count on the air bleeding out thru the bypass
 
So I took out the thermistat.. took forever with the bottom bolt. And I boiled water .once boiling I out thermistat in there for 20-25 seconds. And does not open. This means thermistat is no good. And probably was the problem? Also I ran It hot for 5-10 mins over red line. Wht should I look for if I did any damage to my engine.? I check the oil and there is no coolant in it and no white smoke. No ticking. Engine still sounds good
Put thermostat in andgo with it your likely ok.
 
Motorcraft thermostats are still available. I picked one up at O'Reilly auto parts recently. Think it was $12. It will only go in with the little ball vent at the top.
 
1991 mustang gt. Was running 1-2 notches below red line on temperature.. which is still high.. flushed radiator now runs way above red line.and stays there. But when I start it when car is cold shows it at normal temp. And rises fast. But when use infared on water pump and neck shows 160-170-180.. am I checking the right area with infared? Could it be my thermostat? Or my coolant sensor? No water in oil..No coolant is spilling out of radiator ..
Just a question you didnt change the serpentine belt if so is the waterpump turning the right direction. I had that problem with my car i had the pump goin the wrong direction.
 
1991 mustang gt. Was running 1-2 notches below red line on temperature.. which is still high.. flushed radiator now runs way above red line.and stays there. But when I start it when car is cold shows it at normal temp. And rises fast. But when use infared on water pump and neck shows 160-170-180.. am I checking the right area with infared? Could it be my thermostat? Or my coolant sensor? No water in oil..No coolant is spilling out of radiator ..
Just a question you didnt change the serpentine belt if so is the waterpump turning the right direction. I had that problem with my car i had the pump goin the wrong direction.
 
So I finally changed the thermistat. I put in a 180 tstat. And changed the two hoses that connect to the water pump. Bam...... problem fixed. Doesn't go above half way point when fully warm. Thanks everyone for the help
 
Wanted to be more on the safe side . Feel like a lower tstat would make me feel a little better. Dealing with over heating. And I did burp the system. Anyone recommend a specific type of coolant or additive like water wetter
 
ok. but a lower stat does not control the operating temperature.
dont use anything but coolant and distilled water. 50/50 works for most climates in the south you can use 70/30 water to coolant
you installed the stat with the spring facing the motor