[CNGBiFuel]

Yes, they'll often squeal or whine when the diaphragm is on the way out, bu t not always. This causes poor starting and lumpy running at low revs on petrol because the gas leaks making the mixture very rich. And usually hte gas side won't work at all or very poorly.

Hadn't heard of gas goingot pressure the cooling system. Not sure how that could happen. No real route I can think of unless the coolant going htru' the regualtor has bad seals too. Can't see it but possible. Never come across it.