sub150

I have had my 02Z for about 3 months. Coolant temp has been right around 220 the whole time (live in Phoenix so always over 70 in the morning, over 90 on the way home).

Coming home from work today though the coolant temp was around 240 about 5 minutes into my drive home. It usually takes around 20 minutes for it to climb from 90 to 220. Wasn't sure what was going on so I hopped on the highway, got up to 80 mph, and the coolant temp dropped to 220 and stayed there, which includes 15 minutes of driving under 50 mph.

Going to the driving range though the temp was once again at 240 and bouncing around. Lowering when I stopped and raising when I gained speed (opposite of what you would think).

Doesn't seem like a broken temp gauge since its not pinned against the max, just weird for the coolant temp to fluctuate so much and be so hot. Worried that I could be doing damage.

Nothing blocking the condenser. Oil temp is fine. Stock radiator...and up until now it hasn't gone above 235 (sitting in traffic on 100+ days, but stays there..drops when I start moving).

Anyone had something similar where the coolant temp was bouncing around or abnormally high?

silvzo6

The pros will chime in soon I'm sure but I can tell you the fan turns off at a certain mph which is around 35mph I think and when you fall beneath that speed it cuts back on which explains why it cools when you slow down , hope that helps somewhat

sub150

This morning, it gradually moved from 70 to 178 like it normally would (took about 5 minutes for it to reach 178), then it just lurched forward to 246 where it stayed. Took like 15 seconds to go from 178 to 240. Had the AC on and I checked last night and saw the AC/Passenger radiator fan was moving fine. You can't even see the driver side radiator fan but I did verify with my hand that I could move it easily this morning before I left.

Coolant temp stayed between 243 and 246 the whole time, speeds ranging from 0 to 70 mph. Air temp was 75 degrees.

I need to check the 3 fuses for the fans. Maybe the driver side fan isn't kicking on? Could that provide 20+ degrees of cooling? On a morning like this I would expect the coolant temp to be 220 max. Unfortunately it was raining this morning so not gonna be able to spot leaks most likely on the ground.

Also, this may need to be in the C5 tech section...may get better responses there.

baggerjohn

Possibly a wacky coolant temp sensor ?

sub150

Had a small crack in the surge coolant tank where the hoses come in from the bottom. New tank and I was in business.

If I drove long enough on the highway the temp normalized for the rest of the drive. Happened today on the way to the chevy shop.

bob guzzy

You might have a problem with the thermostat sticking, or you might have a piece of junk sucked up between the condenser and the radiator.

Check for the junk between the radiators blow out the leaves grass and whatever collected there first before moving on to the thermostat.

You can do the c5 fan trick, until you find the real problem, with that you will have air moving all the time.

Moto One

Sounds like the thermostat is stuck open, or a low temp thermostat was installed with out changing out to a larger capacity radiator allowing it to heat soak... (Coolant is flowing thru the radiator to fast and not cooling)

Also check the condition of the front spoiler, if it's damaged, it may not be trapping air for the radiator.

Mark

Vette_Fan

Not to steel the thread, but something similar is happening to my car too. I haven't driven it for 3-4 months. Just drove it today, and the temp keep hopping from 220 - 240+ I needed smog. The smog guy said check your coolant.

Well the level is fine. But I figured it's old coolant, which I flushed 6-7 years ago. So it's time to flush it again.

1) I have 2 opened cans of coolant (the Orange kind). They have both been opened for 3-5 years (can't remember). Both have 1/2 - 3/4 new coolant in them. Can I still use these cans?

2) And to drain, I guess, take off the lower hose, right? Kind of forgot it...

Thanks!

JrRifleCoach

Check the front spoiler and replace the t-stat with factory temp.

T-stats will go bad and can be checked with a IR temp gun. Just point the light at both sides of the housing as the temp starts to climb. The actual temp is irrelevant. However watching the differential temps will signal when the stat opens or doesn't.

FASTFATBOY

Clean your radiator, these cars are GIANT vacuum cleaners.

Read my thread here

https://www.corvetteforum.com/forums...t-go-well.html

Paul 75 L82

Take this as you like. If my car hit 240 it would be on the back of a drive on wrecker taking it back home. I don't care what anyone says that's to hot. So here's what I would do if it was my car. First you have to think that your cooling system is your insurance to keep you from spending 7K on a new motor. I would replace the radiator, replace the water pump with the 04 type along with a new stat. I would get my compressed air hose and blow out the A/C condenser to make sure all the air can get thur. A 50/50 mix of coolant, instructions on how to burp the system and then you will be good to go. I live in south Florida and it's always hot here, my crammed Z runs no more than 204 at anytime. It really stays around 198 but bad traffic can take it to 204. Find a tuner and pay him to lower your fan on temp, that's also helps. If my Z hit 240 I would flip out.

FASTFATBOY

Guys track there cars at or near 240, the system is pressurized for a reason....it raises the boiling point. I ran mine to 250-260 when the radiator was clogged, didn't hurt a thing. I fixed it after that. Car now runs 220-230 on track, beating it up......and most do.

I would clean the fins on the radiator first, not replace it.

Lowering fan on temp doesn't help unless you have a lower temp thermostat.

Ultra_Miner

I had similar issues with my 03 Z. Everything seemed fine, coolant level, thermostat, etc. One day I was detailing the engine and found the lower radiator hose was collapsed. Replaced hose and all was well. The hose actually looked ok from the top, but the backside was collapsed. Worth a check.