Coolant Temperature

[Enchanter]

2007 Z06

The serpentine belt tensioner failed and resulted in overheating the motor (entered reduced power mode), and the coolant boiled over. The tensioner and belt have been replaced by the dealer but I now notice that the coolant temperature climbs at a much more rapid rate than before. The oil temperature behaves normally.

When I start the car the coolant temp indicates 50deg (ambient temp is 50), the coolant temperature will rapidly climb to 196deg within a half mile of driving (at 40mph or less). The temp will stay there while the car is in motion, and climb to 205 when stationary. The dealership confirms that the fans turn on when they should, and the car never overheats.

What could be causing this phenomenon? Is it possible that there is air trapped in the system? Where?

[c4c5specialist]

Hi there,

Most likely no, I wouldnt think air in the system.

I would be checking the thermostat but its possible that there is something else going on.

As long as it does NOT overheat, I really would not be that concerned.

Allthebest, c4c5

[Enchanter]

Thanks for the quick reply.

Why would the coolant temperature indicate a 100+ degree change in less than a mile when the outside temperature is below 40deg, and it did not do this prior?

[NORTY]

I'd look for differences/changes in equipment from before the tensioner failure to the present.

Specifically, I look for damage the belt caused when it was thrown. This includes sensors, wires to/from sensors. Actually, any wires at all that were molested by the belt.

I'd also check the type of coolant. I'd burp the coolant system also. next, I'd check for any obstruction (leaves, plastic bag, dead cat) that could be in between the A/C radiator and the engine radiator. Remember, the Z is a front breather (coolingwise.)

[c6vette]

I would never second guess Paul's wisdom (c5c6 Spec.) but I had the same thing happened to my 05 some years ago. There may be air in the system.
With a warm engine 196 or whatever, remove the overflow cap and rev the engine to 2000 RPM for 3 minutes. Hopefully any trapped air will be expelled. This is the easy way to get air out if there is any.

[Enchanter]

Update:

Got caught in some holiday shopping traffic this evening and the temperature got up to 221deg.

[c4c5specialist]

HI there,

All the information here is valuable and should be checked, no question.

Without the vehicle in front of me, I really can only theorize.

221, a bit high considering lower speeds of fan comes on at 208.

Inspection of the engine bay for damage as Norty suggested would be recommended.

Allthebest, c4c5

[LLC5]

Originally Posted by Enchanter

Thanks for the quick reply.

Why would the coolant temperature indicate a 100+ degree change in less than a mile when the outside temperature is below 40deg, and it did not do this prior?

I have seen this quite a few times in vehicles with a bad head gasket, not saying that you have one but it can be possible after over heating an engine. If after checking all electrical, and for any trapped air in the coolant, the problem still persists then you may want to have a cylinder leak down performed to check for any leakage. Good luck with it.