Hi Bob, When you say that low vacuum is very common, do you also mean that it's normal...or just caused by something else? I am expecting to find something like the cylinder to cylinder head flat gaskets bad, and I do burp the system occasionally with the pressure cap, but it pressurizes too quickly to be able to do that regularly. I like the idea of the small valve on one of the cloth hoses, I was thinking about an automatic pressure relief valve. About changing the intake valve adjustment to .006, do you do that with self adjusting lifters(where the adjustment is usually set snug plus i think 1 3/4 turn). You're backing off the adjustment to .006? Is this just for testing purposes, to see it's effect on the vacuum reading, or do you run the car with that adjustment? Thanks for the suggestions, John
----- Original Message ----- From: "ROBERT DONALDS" <donalds1@VERIZON.NET> To: <vanagon@GERRY.VANAGON.COM> Sent: Saturday, August 07, 2004 6:40 AM Subject: Re: Diagnosing a low (8-10 inches) vacuum gauge reading
this low vacuum is very common with the vanagon engines but I don't see it tied into a combustion gas leak into the coolant. If the engine was overheated and the inner gaskets received to much crush caused by the cast iron cylinder expansion then the that would be one explanation. The other possibility is a cracked cylinder head. you stated that the engine is only 10K old did the rebuilder use OEM heads they commonly crack and recrack when welded and are known to have uneven head gasket surfaces. I had a 85 that would seal the inner head gaskets once the engine would warm up and you could drive all day without problem but I did need to burp the system after the engine got up to temp. This can be dangerous I used a small valve tied into one of the cloth hoses to do this and dont recomend burping the coolant system with the pressure cap The compression could be 140 150 cold and 80 hot if you are reading the vacuum hot and the compression cold then I would consider adjusting the intake valves to .006ths cold and testing the vacuum again hot. Bob Donalds Boston Engine |
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