Question about pressure and level in coolant

[particlewave]

It’s normal for the tank to have pressure, but it’s possible that you have a faulty tank vent/bleeder valve. Remove the tray directly under the coolant and oil fill caps and you’ll see it.


Also, make sure that you have the most recent coolant cap.

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[KuaiThunder]

Thx for the reply.

I changed both the cap and bleed valve few months back when I have moisture issue which solved the moisture problem.

I can understand the pressure build up in the system but I can't understand why pressure pushed down the coolant level. I suppose coolant is not compressible so it has to go some where. I am thinking maybe I have a fail thermostat so the pressure pushed the valve open.

[blue62]

Originally Posted by KuaiThunder

Thx for the reply.

I changed both the cap and bleed valve few months back when I have moisture issue which solved the moisture problem.

I can understand the pressure build up in the system but I can't understand why pressure pushed down the coolant level. I suppose coolant is not compressible so it has to go some where. I am thinking maybe I have a fail thermostat so the pressure pushed the valve open.

Full is full and liquid is not compressible so I don't think thermostat open or closed or failed would be the issue.
Sounds like you have air trapped in the system or older coolant hoses that are expanding as pressure in the system rises.

[KuaiThunder]

Thx for the input the old coolant hose expanded under pressure is something I not consider but it does make sense. Geez I suppose I have lot of hoses to check now and some of them are not easy to access.

[blue62]

Originally Posted by KuaiThunder

Thx for the input the old coolant hose expanded under pressure is something I not consider but it does make sense. Geez I suppose I have lot of hoses to check now and some of them are not easy to access.

Yes and if you don't replicate the conditions a bad hose may be hard to locate.
It May not show it's self as swollen if not fully warmed up and under pressure.
Sometimes you can feel a soft spot in the hose when you squeeze them but that is rare.

[JFP in PA]

Originally Posted by blue62

Yes and if you don't replicate the conditions a bad hose may be hard to locate.
It May not show it's self as swollen if not fully warmed up and under pressure.
Sometimes you can feel a soft spot in the hose when you squeeze them but that is rare.

Actually, this is very easy to replicate, even with the system cold. You need a coolant system pressure tester, pump the system up to 18 PSIG and start looking at the components.

[blue62]

Originally Posted by JFP in PA

Actually, this is very easy to replicate, even with the system cold. You need a coolant system pressure tester, pump the system up to 18 PSIG and start looking at the components.

I had thought about that but the OP being in Hong Kong I didn't know if he would have access to something like that as a DIY.

JFP glad you added to this post your feedback is always no nonsense to the point and on target. Thank you