Cooling system bubble?
 

I drained and flushed my cooling system yesterday, following the recommended procedure. All seemed to go fine. However, now the temp gauge runs around midrange at idle, and quickly creeps up to 2/3 or 3/4 of max while driving. It didn't overheat, but did come close to 7/8 of the way to 260.

When I was following the flushing procedure, fluid WAS streaming from the tube that dumps into the coolant surge tank... so I wasn't worried about a bubble in the system as some have reported. However, something is clearly not right, so where should I begin?

Re: Cooling system bubble?
 

What was the operating temperature range before you did the drain and flush?

Have you verified that the coolant system is full and the coolant over-flow bottle has water in it when the engine cooled down after running?

Jim

Re: Cooling system bubble?
 

When I drove the car home after buying it, the temp gauge was in the lower 1/2 the whole time (can't recall exactly where it sat), but it didn't jump out at me as being a problem.

Today it was definitely indicating much higher than before I touched it.

Re: Cooling system bubble?
 

you can use a little food thermometer to see what the water temp is . are your fans comming on ?how i fill my zs. is i take off the throttle body line on the passenger side. i hold it up with a coat hanger i bent for the purpose .i then slowly pour in as much as it will take with the motor off usually i can get in 21/2 to 3 gal oput the cap back on fill up the over flow totally full and start the car and idle till its totally warm.then shut her down and either ck the overflow in the morning or when i drive her next . i fill the overflow if needed. and shes done/jmho .thids has never failerd to work for me

Re: Cooling system bubble?
 

which T-stat did you buy? FWIW, the first time I went to order a stat from the local dealer they asked me "which one do you want? 180* or 195*?" I kind of didn't know, so I did my own search on the GM parts sites & found that it looked like, to me anyway, GM offers two. Looking thru all our stuff over at the netreg site, it seemed the car came with the 180* as OE.

Also, in the distant past Stant had a miss-box happen and people got a ford stat(?) in the LT5's stat box. The results were not very satisfying at all.

When you say "driving around" do you mean highway or secondary streets? I ask because the observed behavior of the gauge seems just like my gauge behaves if I'm doing the around town, 40 mph or less thing...no B to B traffic, but no above 50 stuff. If you are describing 50mph or better as in highway use, then yea something is wrong for sure as the gauge should be reading about 1/2, ya know around either side, but not toward the 3/4 mark. Only other reason I can think of is that the gauge's sensor picked that moment to go south on you, or it's air bound.

:cheers:
Tom

Re: Cooling system bubble?
 

Before the next time you drive, and when the engine is cold, check the level in the expansion tank and the overflow bottle. If you had an air bubble from the fill after the flush, that water can be added now.

Also I agree with Tom. My experience is that two of my ZR-1's will heat up way above "normal" when driving at a steady cruise speed at about 1600 rpm. For example 55 mph in 6th gear. Shifting down to 5th gear (2000 rpm) and the temperature drops rapidly back down to normal. Both these cars have brand new radiators.

Jim

Jim

Re: Cooling system bubble?
 

No thermostat swap yet -- but I have one on order, (the stant 180) so I'll be changing that, as well as what is presumably the original 20 year old radiator ( I think the coolant I drained out was the original coolant :jawdrop:).

The temp would creep up under load -- at steady cruise it would hang around 2/3 up, under heavier load more like 3/4. Idle was 1/2 way.

Re: Cooling system bubble?
 

TRY THIS AND SEE

http://www.zr1specialist.com/HAT%20W...%20coolant.htm

Re: Cooling system bubble?
 

Andrew, the gauge is not a linear representation of how hot things are getting. Go into the diagnostic mode on the AC controller by holding both fan speed up and down buttons for 5 seconds, release and -00- should show, use either the up and down button again ad go to -16-. Hit the auto buttun for fan speed. That will give you the coolant temp in C.

Re: Cooling system bubble?
 

I have the exact same problem and have had it since I purchased the car last month. Temp is fine on the freeway but climbs up to almost overheat on side streets or in traffic (although it never does go up further and actually overheat). My mechanic told me I need to have the rads cleaned as they have not been removed and cleaned in the 95k/18 years. I decided to replace the radiater with a new high capacity performance one as I was told it will make the car run approx. 20 degrees cooler. I figure the extra $500 is worth it if it will help to prolong the life of the engine. I am taking it in next week to have it done... I'll report back with the results.