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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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1990 Mercedes Benz 500SL what would cause low compression on

Customer Question

1990 Mercedes Benz 500SL
what would cause low compression on cylinder #2 & #4?
How would you recommend repairing this issue
Submitted: 1 year ago.
Category: Mercedes
Expert:  AZTechBrian replied 1 year ago.

Hi. the best way to diagnose the low compression is to do a cylinder leak down test to see where it's escaping. It may be escaping from one of the valves, or getting past the rings, head gasket, etc. The leak down test will tell us where its escaping.

Customer: replied 1 year ago.
Okay, do I need to take it to a mechanic to have the cylinder leak down test done or is this something I may be able to do on my own?
Expert:  AZTechBrian replied 1 year ago.

you could do it on your own if you have the equipment. they used to sell a cheap one at harbor freight, but I dont' know if they still do or not. Otherwise, it basically just entails adding compressed air to the cylinder while on the compression stroke and listening to hear where the air is escaping. Remove the oil filler cap and listen to see if you hear the air escaping into the crankcase, or out of the exhaust or out of the air intake.

Expert:  AZTechBrian replied 1 year ago.

Hi. Did you get it figured out?