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Engine Coolant Temp Fluctuating

WAIT, So just out of curiousity, my car runs like this currently(summer temps), cut car on and temp is low, drive for a while temp goes to the first big line on temp guage, stop at stoplight and temp goes up, accelerate from light and temp goes back down. thats normal right?
 


t-stat opens at 195 which is first big line.

when car isn't moving there isn't enough air moving to keep the coolant at that temp.

Thus it rises till the fans engage.

A/C preheats the air going into the rad thus making its job even more difficult.

As long as your temps never exceed the halfway mark you're good.
 
Mine exceeds the halfway mark and goes to the lower part of the 200 degree area when im stopped at a light for a little while, and seems to stay there until i start moving again. sound about normal right?
 
Could be the sender is off.

Unless you had something to scan what the PCM sees as your ECT i'd say you're probably fine.

225 is half IIRC.

Mine is in Celsius....
 


Question on this topic- I changed out the heater core and thermostat on my 99 Prix. I flushed the entire system. Started overheating like mad. Heater temp would fluctuate. Obviously an air bleed issue as stated here.

However, when running the motor with the heater on, the air bleed screw would just sit there and hiss for over 30 minutes! No water stream. Only steam. I checked for coolant leaks and I am good. The oil is clean of water. Car runs fine it just gets incredibly hot!

How long should it take before I see water from the bleed screw?

Thanks!
 
When I did it, only a couple minutes. What temp thermostat did you get? If you aren't getting any fluid to come to that part, probably means something wrong with the thermostat cause it should open up, and that's when you get the fluid to the bleed screw. Though there are other people that know alot more about this topic than i do...
 
195 sounds right, I think that's the stock temp thermostat rating. I'd wait till a few more people respond that know more than me, but I'd say that either the thermostat is bad, or somehow during the install something went wrong.
 
Pull the thermostat and it's housing. Fill LIM that way. If there's any air bubbles trapped. It'll fix ya right up. :th_peaceout:
 


The way I bled it out was by leaving the radiator cap open, bleeding it, and then filling it the rest of the way. Then filling the resevoir.
 
Ok, minor issue. After replacing the thermostat I can't seem to get the air out of the system. Ends up boiling out of the cap neck before the bleed screw ever has a constant flow of coolant. Any bright ideas for how else I could get the air out of the system without having to fill directly from the thermostat area. I put the RTV sealant around that housing, so I'd like to avoid taking that off and redoing that process if at all possible. Thanks for any pointers.
 
you are using the bleeder screw on top of the t-stat housing right?

i leave the rad cap off, let the car idle till the fans come on, that way you know the t-stat opened up, top off rad if needed, loosen the bleeder screw, keep open till a stream of coolant comes out, shut screw, top off rad, cap it.
 
That's pretty much what I did the first time i did it. Maybe I'm opening up the screw too early. I'll try it out tomorrow with keeping the screw tightened till the fans kick on. See how that works.
 


I tried everything mentioned here and this is what I wound up doing. I took the hose off where it connects to the thermostat housing. Filled water there. and reconnected. I ran the motor and loosened the bleeder screw. The air bubbled out then I got my steady stream of water. That is what worked for me in the end.
 
I apparently had air stuck in hard places. So i filled the radiator, capped it and left the cap unscrewed about 1/2 to 1 full turn. Let the air get pushed out both the cap and up to the resevoir. Also used the bleeder screw to get the air out of that part of the system. Seemed to work, engine temps stay where they should atleast. Gotta double check the resevoir to make sure it has enough fluid though once the system cools down.
 
I have worked recently on the UIM replacement, LIM gaskets, water pump and coolant elbows. buttoned everything up, no evident leaks, not burning coolant, no smell in exhaust. I have been having issues with fluctuating temps as listed above. i have also replaced the radiator cap with a murray locking cap, i think it may be my problem. it doesnt seem to seal as well as the stock, and i need to do a UV dye leak test to see if its pushing out from the ring. I do not hear hissing when i stop from driving that would normally come from a leak...i did the complete bleed steps, etc and somehow i still am low on coolant after about a week of driving. it may be time to replace my rad, it is 13 yrs old. every time i open up the rad cap, there is brown gunk on the gasket...did a flush a little while back, and this stuff is still present. any ideas?
 
Mine now goes from 180 to 210 then from 210 to like 230 ish and it fluctuates up and down when I drive it's scaring me. Lol
 
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