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Greg, Technician
Category: Mercedes
Satisfied Customers: 7273
Experience:  Automotive diagnostic tech
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Hi, just completed cylinder head gasket change as the coolant

Customer Question

Hi, just completed cylinder head gasket change as the coolant was being pressurised with combustion gasses. Now I have a problem with blue smoke when cruising along, the engine runs rough and blue smoke comes out of exhaust. When I put my foot down it stops and the engine performs normally. No blue smoke when idling, no blue smoke on start up. What could cause this. These symptoms were not present before the engine rebuild.
Submitted: 4 years ago.
Category: Mercedes
Expert:  Greg replied 4 years ago.
Hi .

Thank you for using justanswer for your automotive problem .

What i suspect has happened here is that you have O/H the head and not replaced the valve stem seals or they where incorrectly installed .

Also remember when an engine overheats the oil crystallizers in the oil rings ,if this is not taken care of then the engine will burn oil past the oil rings and burn oil causing blue exhaust .

What i suggest you do IF the valve stem seals where replaced then this leaves only the piston oil rings , so do the following .

loosen off the glow plugs to make sure they are lose then retighten start up the engine and let engine get to operating temp.
switch OFF engine and pour 2oz of brake fluid into the cylinders all 4.

then let soak for 4-6 hrs ,crank over engine to exspell brake fluid ,replace the glow plugs and start the engine ,Now you will have a cloud of white smoke don't worry let the engine idle for two minutes then rev up to 1800 rpm and hold for 10 minutes or until it stops smoking white . then do a good drive and check that you are not burning oil .

What this does is the brake Fluid will seep past the compression rings and also the oil rings and clean out any hard carbon deposits and loosen them back up .

If all this does not work then you will have to open the engine and repair replace the rings .

Need further assistance with this issue then please get back to me .

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Rgds Greg