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[amba]

Would a leak from a faulty HBV show up with a coolant pressure test ? or does the valve need a vacuum to operate the internal diaphram to show up a leak

[feeutfo]

It may not. Depends on what cc setting makes it leak.

Try engine running first, and play with the Differant temp settings, see if hbv leaks each time.

Or it may just leak on any setting, in which case it will show on a pressure test.


...if you see what I mean.

[amba]

Thought the HBV was either On or Off. Vacuum caused diaphram to move allowing water flow either to be blocked or allowed through.

[Andy H]

I cannot remember how close it is to the exhaust manifold. I would be tempted to wrap it in a bit of kitchen roll & tie it up in a plastic bag to preserve the evidence (assuming that it didn't cause a fire risk...............).

[amba]

Clever idea with the bag and tissue paper.

Just liked to understand how to identify if the HBV is causing a leak..or more importanly a "dump" of coolant only when a bit of  pressure has been aceived in system.

I know my coolant system is not maintaing correct presssure as when coolant resrvoir top is released very little "hissing" is heard