Coolant temp rising fast only at idle

[laserjpb]

I've been so far unable to diagnose the following problem and would really appreciate some help-

Recently (past week or so) my temp gauge will read completely normal (at halfway or just under halfway) for 100% of driving, even racing/high speed highway runs, but as soon as I pull into my driveway and let it idle for more than 1- 2 minutes the temp gauge slowly creeps up to real hot. (Even close to red zone). However, no steam or coolant ever bubbles or does anything weird.
I have done all the checks for blown headgasket and do not get any tailpipe smoke ever, so I'm thinking it is something in the cooling sys. Thoughts?

(Also - The rad. fans turn on just fine, also the system pressurizes just fine and circulates well so I don't think it's the water pump...)

 

[ddavisaf]

Are you losing any coolant at all?

 

[laserjpb]

No coolant loss that I am aware of...

 

[ddavisaf]

Do a radiator flush and see if that fixes your problem. You said your thermostat works fine and your radiator cap is good, not leaking, not smoking, and the fan works fine which is everything minus a flush, to fix overheating problems.

If that doesn't work run a compression test.

 

[laserjpb]

Just went for a solid fun run and upon return, same thing. Coolant level is fine, and fans work as normal.

Couple other clues I noticed- If I rev it when the temp is rising, the temp will rapidly drop back to normal range real quick (leads me to believe not failed h2o pump), also I noticed the hose going into the coolant resevoir was super hot and has some light steam coming out of it....??

I am thinking maybe it is the temp sensor or maybe an imperceptable leak around the t-stat housing/cap. I'll do the flush and see what happens..

 

[K_Hill]

Yes try flushing it and see if that fixes the problem.

 

[StandBackImaPro]

It Is probably the water pump, since you said when you give it gas the temp drops, which means the water pump is speeding up, pushing more coolant through..

 

[Lordpaxin]

DO a compression check.

I had the same exact problem with a car i had.
though it would loose some coolant.

what was happening the sensor was getting bathed in water during higher rpm. but at idle, the water turbulance was low and the sensor was exposed and read 100%. rev it up, water splashes on it again. and temp lowers.

I replaced everthing, flushed, radiator, tstat, water pump, and did a compression check.
my compression was jack shitty. but the car ran good. my coolant had a odd smell to it also.

I replaced the engine, and the problem stopped.
when the engine was torn down the cyl walls looked like crap, pistons everything looked junk.

id do a comp check and go from there.
report back.

 

[Defiant]

Wash the bugs and dirt out of the radiator fins.

 

[laserjpb]

Did a compression check about a week ago (but before this started) and everything was 140s except for #2 which was 13x. I'll do another compression test when I have some time w/the car this weekend to flush coolant, do some more checks, etc...
Thanks all!

 

[tsunari]

have you looked at your accessory belt that drives the water pump? Perhaps it's loose and slipping @ idle, but when u rev it up, the rubber heats up and bites into the metal and turns it quicker . . .

 

[laserjpb]

Thanks to all-- did a coolant flush this past weekend and that took care of it. The temp problem that is.

 

[tsunari]

Thanks to all-- did a coolant flush this past weekend and that took care of it. The temp problem that is.

Awesome . . . just make sure to do that once a year from now-on and hopefully you'll never have that problem again

 

[laserjpb]

Yeyeah! Good call