Cooling system bubble?

[VetteMed]

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?

[QB93Z]

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

[VetteMed]

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.

[jonszr1]

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

[tomtom72]

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

[QB93Z]

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.


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

[VetteMed]

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

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.

[WB9MCW]

TRY THIS AND SEE

http://www.zr1specialist.com/HAT%20Web/articles/filling%20coolant.htm

[Jeffvette]

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.

[Pqtaces]

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.

[jonszr1]

do you have the stk prom still in your car if you do even with the new rad it will get hot when going slow as the factory setting for the fans to come on is around 223. unless you have the air conditioner on .

[Pqtaces]

I don't think the fans are a problem. The fan switch is bad so my guy bypasses the switch and connected the fans to the ignition to come on when started until we can replace the switch (having that done at the same time as the rad). He said the high temp is due to the lack of air flow.

Mind you, I know very little in the mechanical arena so I am putting a lot of faith in the shop. I am taking the car to Guldstrands exactly for this reason as they come highly recommended and are regarded as a top shop. From what I found there are only a handful of good shops here in SoCal and they are the closest to me (only about 3-4 miles from my office).

They have treated me well so far. I took the car in as soon as I bought it to be completely checked over and they only found a few minor things. Cleaning the rads was one of them (replacing the rad was actually my idea not theirs- so it doesn't seem as if they are trying to bleed me).

[HAWAIIZR-1]

TRY THIS AND SEE

http://www.zr1specialist.com/HAT%20Web/articles/filling%20coolant.htm

:thumbsup: I agree and Marc's method has never failed me too.

[WB9MCW]

"I am taking the car to Guldstrands exactly for this reason as they come highly recommended and are regarded as a top shop."

Yep they will get to the bottom of it all -- top shop indeed! :cheers:

[VetteMed]

I already tried Haibeck's approach... so maybe it's not a bubble after all.

[Ccmano]

Once the car is at operating temp, turn your HVAC system to full max heat (defrost will do it) If there's no or little heat inside the car you have an air bubble. If you get full heat you have a radiator/thermostat and/or fan issue. Did you remember to turn the heater on when you refilled the system and brought the car up to operating temp.
H
:cheers:

[WB9MCW]

do you have the stk prom still in your car if you do even with the new rad it will get hot when going slow as the factory setting for the fans to come on is around 223. unless you have the air conditioner on .

Good point here -- Mine used to get real hot with the factory chip and the silly high 223 fans on setting (for passing emissions by orig GM design) with my new mod chip the fans kick on at 180 and cool down to 160.

Best part is that even on a humid 95+ Chicago summer day my Z can sit at idle for long periods and never gets above 205 and back out on the road and with a bit of air flow and a mile or so and I am back down to 170.

This is why I never put the big mouth aid dam on -- really no need to -- stock stat as well for me and orig rad too.

Got rid of the dreaded cags too and the performance improvements were great as well.

best mod for the money the chip is indeed. :cheers:

[VetteMed]

Once the car is at operating temp, turn your HVAC system to full max heat (defrost will do it) If there's no or little heat inside the car you have an air bubble. If you get full heat you have a radiator/thermostat and/or fan issue. Did you remember to turn the heater on when you refilled the system and brought the car up to operating temp.
H
:cheers:

Plenty of heat... HOT heat. I did run the heater while flushing, BTW.

Thanks
Andrew

[WB9MCW]

Andy did you try what JeffVette said >>>

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.

Are you running a stock prom chip and dealing with 223 b4 the fans kick on?

[VetteMed]

Andy did you try what JeffVette said >>>

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.

Are you running a stock prom chip and dealing with 223 b4 the fans kick on?

I'm out of town this week so I can't check anything until next week. But I will look into that ASAP and report back with my findings. PROM is aftermarket (Z-industries). I haven't observed the fan-on temps yet.

[Ccmano]

Looks like a bubble is not your problem, having used Haibecks bleed method and getting full heat from the HVAC would pretty much count that out. As a final check, make sure the fans are coming on as they should. As you have probably seen running "hot" is both a common problem and to some degree normal. For emissions resasons these cars were set up to run on the hot side of what we are normally use to seeing. I had the same issue when I first bought mine. It would climb almost to max in hot weather around town. I found the radiator fins clogged with fine dirt and sand. Replaced the radiator with a new stock unit, a 180 degree thermostat and a Haibeck chip that turned the fans on at a lower temp. It now runs cool, half or under on the guage, under most conditions. BTW unless your racing or have a highly modified engine, an aftermarket high capacity radiator is a waste of money. IMO
H
:cheers:

[tomtom72]

Oh god, the sand in the fins! That drove me crazy trying to pick it all out of my rad. Never really got it all either and I'm sure it is affecting my system performance.

I put the "screen" on my car when I took delivery. Then about two yrs later I pulled the rad to clean up the cooling stack. I didn't find alot of leafs or candy wrappers, I believe the screen stopped that stuff. I did have a lot of sand/dirt stuck in the fins. I never got it all as I was going cross-eyed so I gave up after 4 hrs. I got most of it, but not all of it. In hind sight, I should have just bought a new rad from GM.:redface:

My point is that my Z was a G/Queen. Only had 7400 miles when I bought it from the O.O. I put the screen on and that for sure stopped the garbage from collecting up there. I'm not so sure it stopped all of the sand/dirt from getting up in there. I hate to tell you to take apart the stack, but if everything else is okay then Hans is proly correct in his diagnostics.

:cheers:
Tom

[VetteMed]

Success -- took out the old radiator, swapped in the new one tonight, new 180 degree thermostat, and we're running cool!

The climate control panel reads 87-89 degrees C when at operating temperature. Sounds about right.

Still have a little waver at idle from about 900-1100 rpm back and forth. Runs great otherwise!!

Thanks for the advice, everyone!

[WB9MCW]

Way to go Andy!

You may still want to go the chip route for all the other goodies and the + of the fans on early as well. Perf chip might help with idle too!

[tomtom72]

:thumbsup: Glad you got to the bottom of this! Whose rad did you go with, if you don't mind me asking?

:cheers:
Tom

[VetteMed]

:thumbsup: Glad you got to the bottom of this! Whose rad did you go with, if you don't mind me asking?

:cheers:
Tom

Used the stocker from the partsladi. Seems to work just fine!

[tomtom72]

Used the stocker from the partsladi. Seems to work just fine!

Thanks for the info!:thumbsup:

:cheers:
Tom