Discussion:
gas pressure in cooling system
DBA Forum (B) - Martin Phillips
2014-08-26 21:26:00 UTC
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I had a similar sounding problem with the original BMC 1.8 on my nb. Checked head gasket, replaced head, fiddled with header tanks, it still pressurised. Most likely cause was a cracked cylinder liner or "porous block". It was however definitely exhaust-type gas getting in judging by the smell, and there were very small traces of oil getting into the coolant (small amounts will emulsify / disperse in the coolant mix so might not be visible). It got slowly worse over ten years. Gas built up at the top of the skin tank forcing coolant out of the "radiator" cap on the engine.

The only way I could think of checking it was to connect a compressor to a glow plug or injector port and see if I could get air into the coolant side. Never tried it though...

We never established the cause for sure as the engine died a few years ago and it seemed easier to replace it.

Martin/

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