Quote:
Originally Posted by embee
How is the compression test being done? Normally the figures are quoted for a hot engine, all plugs out, cranking with wide open throttle and a decent battery charge (maybe 200rpm+).
If you do it with a closed throttle you'll get very low figures, when you say "40% of what they should be" it makes me suspicious.
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When I said "40% of what they should" take that with a pinch of salt. I need to find the exact figures, but I left my Haynes in car, which is at the mechanics doing the test. I'm waiting on a merc forum for the correct values and tolerances. I was just trying to ascertain whether the values I have been given are reasonable given that the car runs, or whether the mechanic is trying to pull a fast one! I have a feeling he is hamming things up more than is actually the case to try and convince my girlfriend get the engine rebuilt.
As for how it is being done, I'm afraid I don't know because I'm not doing it!
FWIW Test results are
CYL# 1 2 3 4 5 6
PSI 135 90 130 130 90 110
Just trying to figure out whether it is just 2 & 5 which are low or the whole lot is and 2 & 5 just happen to be the worst. Searching a Merc forum came up with a thread that quoted a Max of 350 PSI and Min of 220 PSI, but since there were 3 engines (with different no. of cyl and petrol/diesel) available for this model, I can't tell from the posts which one they are talking about which is why you should take a big pinch of salt with the 40% thing!
EDIT: They are talking about a diesel - must be which would explain the high compression. Doh!