Thank you Marshall. I will warm it up before I check it. Will removing the glow plugs while they are hot damage the threads? John I.
> Any advice on this procedure would be very much appreciated. Mercedes set acceptable pressures for NEW engines in the 24-30 bar range (350-435 psi). Most used engines in good conditions will meet or even exceed these numbers. The lower limit that Mercedes sets is 18 bar (260 psi) but in fact anything much below 20-21 bar (290-305 psi) will likely be VERY hard to start in cold weather. All of the cylinders within the engine must be within 3 bar (44 psi)! Before testing, valves MUST be checked to insure that none are tight. Tight valves of course lower compression. These measurements should be made with the engine at operating temperature. Cold compression tests will be MUCH more variable and much less useful in their diagnostic relevance. Marshall
