Cooling system expansion tank question

[Wigert]

Hello all

Could someone please help me understand if my cooling system is working as it should. More specifically if the termostat in the refill lid is working and the expansion tank doing its thing.

The reson why is that no matter if the car is warm or cold the level in the expansion tank seems to remain at cold. The temperature of the coolant there also seems to be cold. Also, sometimes I have needed to add a small amount of coolant in the main reservoir to top it of up to the exanpsion system hole. I tested and blew air into the expansion hole and it bubbled in the expansion tank so there is no restriction there.

Is there something I am not understanding here or do I have an issue? The thing that bothers me most is that I may need to top of the reservoir eventhough the level in the expansion tank is good... Also, there are no leaks that I have seen so far.

Thanks in advance guys!

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[Dynomite]

Radiator Cap on Reservoir in front of passenger firewall might be leaking and not holding 15 lbs pressure. During cool down Air is entering through the Radiator Cap as the Cooling System Retracts.

Time for New Radiator Cap :thumbsup:

[A26B]

Radiator Cap on Reservoir in front of passenger firewall might be leaking and not holding 15 lbs pressure. During cool down Air is entering through the Radiator Cap as the Cooling System Retracts.

Time for New Radiator Cap :thumbsup:

:cheers:

[Wigert]

Radiator Cap on Reservoir in front of passenger firewall might be leaking and not holding 15 lbs pressure. During cool down Air is entering through the Radiator Cap as the Cooling System Retracts.

Time for New Radiator Cap [emoji106]Thanks for the pointer, a new cap is a cheap thing to start with. Then I will also get a new thermostat at the same time.

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[A26B]

Thanks for the pointer, a new cap is a cheap thing to start with. Then I will also get a new thermostat at the same time.

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Correct thermostats are hard to come by these days. Many parts suppliers show some parts as being correct for the ZR-1 but the part is NOT for the ZR-1. This is particularly common for the thermostat.

Jerrys Gaskets does not have any in stock, but here is what it is supposed to look like.

https://cdn10.bigcommerce.com/s-nkg90o/products/623/images/1367/10135627__72538.1438825482.1280.1280.jpg?c=2

[secondchance]

My 94, even with working radiator cap, coolant level in the overflow tank typically settles at cold marking. As long as coolant stays even and not disappear on you, I wouldn't worry.
Also, if you are running silicone hoses, check and tighten all clamps. I was loosing coolant and turned out clamps were loose. Situation like this, seepage would occur only when the motor was hot and evaporate as it seeped making it next to impossible to notice.

[Wigert]

Correct thermostats are hard to come by these days. Many parts suppliers show some parts as being correct for the ZR-1 but the part is NOT for the ZR-1. This is particularly common for the thermostat.

Jerrys Gaskets does not have any in stock, but here is what it is supposed to look like.

https://cdn10.bigcommerce.com/s-nkg90o/products/623/images/1367/10135627__72538.1438825482.1280.1280.jpg?c=2I have already replaced the main thermostat but isnt there a thermostat in the cap? Looks like it but maybe I am mistaken...

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[Wigert]

My 94, even with working radiator cap, coolant level in the overflow tank typically settles at cold marking. As long as coolant stays even and not disappear on you, I wouldn't worry.
Also, if you are running silicone hoses, check and tighten all clamps. I was loosing coolant and turned out clamps were loose. Situation like this, seepage would occur only when the motor was hot and evaporate as it seeped making it next to impossible to notice.Good input! I have replaced some of the hoses with silicon ones and have already suffered the loose hose clamp leakage (significant)... I do not see any further leakage after tightening but as you stated it could be very small now and not showing. After a short drive there does not seem to be a need for top off but after a longer drive the level seems to be slightly decreasing in the main reservoir...

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[32valvZ]

If the leak is external, then you should be able to smell the coolant as it evaporates. I had the same issue and it was a loose clamp on a silicone hose. When completely cold, sometimes Id see a small spot on the garage floor... not always, but sometimes. Drove me crazy. One day, while cleaning under the car, I was able to spot a glint of coolant sitting where the hose slipped over the T Stat housing. Took maybe a 1/4 turn and the leak hasn't returned.

You can pressure test the cap as well as the system with a cooling system pressure tester. Pretty inexpensive tool really... nice to have though.

[Wigert]

If the leak is external, then you should be able to smell the coolant as it evaporates. I had the same issue and it was a loose clamp on a silicone hose. When completely cold, sometimes Id see a small spot on the garage floor... not always, but sometimes. Drove me crazy. One day, while cleaning under the car, I was able to spot a glint of coolant sitting where the hose slipped over the T Stat housing. Took maybe a 1/4 turn and the leak hasn't returned.

You can pressure test the cap as well as the system with a cooling system pressure tester. Pretty inexpensive tool really... nice to have though.Thanks for the input! I'll have to try and use my nose. A pressure tester would indeed be a good thing to use in this case. I'll see if I can find or borrow one here somewhere.

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[secondchance]

I have already replaced the main thermostat but isnt there a thermostat in the cap? Looks like it but maybe I am mistaken...

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There is no thermostat in the radiator cap. It's spring loaded set to release pressure at predetermined pressure. Caps for Corvettes of the era was 14-15 psi.

[Wigert]

There is no thermostat in the radiator cap. It's spring loaded set to release pressure at predetermined pressure. Caps for Corvettes of the era was 14-15 psi.My mistake, I very much appreciate you clearing that out. Okay so it's only a spring for pressure release.

If the engine is hot and running, should I in that case see a higher coolant level in the expansion reservoir up front at idle? If it has not leaked out elsewhere...

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[secondchance]

My mistake, I very much appreciate you clearing that out. Okay so it's only a spring for pressure release.

If the engine is hot and running, should I in that case see a higher coolant level in the expansion reservoir up front at idle? If it has not leaked out elsewhere...

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My guess is, if the overflow tank level is at its highest when the motor is at operating temp and at high rpm.