Quote:
Originally Posted by DRG-ler
As for the pressure drop test (25%)... I did that a while ago. I used this tester for that. The pointer stopped at 25%, in the clearly green area. This confirms that the piston rings and valves are properly tight. No reason to make any repairs.
I also asked myself this question, especially since the pressure loss test was only carried out when the development of the noise indicated a defect! But the answer is quite simple. The pressure loss test is only tested with 2 bar. The head gasket was still sealed at first. The pressures during compression / combustion are many times higher, even with low compression. That's why the error wasn't noticed there. If I had done a compression test, I would have noticed the defective seal sooner. But I didn't have that gauge back then.
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Andy, it appears your mind is already made up, ...which I am OK with whatever your decision is, -however for the benefit of all the other readers who will come along at a later date and likely obtain misinformation from reading this, I will post some thoughts;
To begin with, it appears you are using one of those cheap Chinese-manufactured gauges which have been proven to give erroneous readings. They are cheap for a reason.
Most professional engine rebuilders (-or mechanics) would never use use that poor quality level of a tester. Mine is a OTC brand with calibrated gauges that are certified. It does not have colors on the gauges as that feature is useless. It uses a scale of 0 - 100 only. The Green, Yellow, & Red colors on your gauge mean nothing as it is all about percentages which those numbers are different between types of engines and the usage of that engine.
Next, by you telling me you used 2 bars of air pressure to test with, therein lies the issue with your test. Your gauge is designed to be operated with EXACTLY 100 psi (-approx 6.9 bars) of line pressure. For proper (-i.e.: accurate) leakage readings, this psi number is crucial as that 100 psi number is the benchmark for determining 100% -or any percentage of that. Had you used the tester properly and introduced 100 psi into the cylinder, your percentage of leakage findings would have likely risen exponentially.