W203 2002 oil in coolant and spark plug

[MaltaMerc]

Hi all, Help wanted, I got a 2002 C180K I have a misfire on P0301. I took the coil off and swapped it with number 2, I was going to replace all spark plugs when I removed cylinder 1 there was oil below so I just deoxidized the old one and put it back still misfires, then I checked the coolant and found black oil in it and very low coolant level still not overheating, what is your best guess valve gasket, or oil cooler seal or both, anyone else had a similar problem? I only just got the car and had also added fuel system cleaner.

 

[markjay]

Well clearly you have oil mixing with coolant... so the issue is either leaking head gasket, or leaking heat exchanger (as you said yourself). A compression test should help pinpoint a leaking head gasket.

 

[MaltaMerc]

Well clearly you have oil mixing with coolant... so the issue is either leaking head gasket, or leaking heat exchanger (as you said yourself). A compression test should help pinpoint a leaking head gasket.

Thanks for your reply, Have a great day

 

[markjay]

A compression test might not show a leak between an oilway and a coolant passage, so having normal/equal compression in all cylinders isn't definite proof that the head gasket is indeed intact.

However, a leak directly between an oilway and a coolant passage will typically occur when the head becomes corroded (due to poor quality coolant, for example), so it's quite rare. The most common head gasket failures occur around one of the cylinder bores, due to the high pressure during the combustion phase, and this will be detected by a compression test (i.e. one cylinder, or two adjacent cylinders, will have significantly lower compression than the others).

One other thing you could do is pour a teaspoon of engine oil into the cylinder with the lower compression - if this causes the compression to go up, than the issue is with the compression rings and not with the head gasket, but if the compression remains low then the issue is not with the compression rings (i.e. it's faulty head gasket of a leaking/bent valve).

 

[MaltaMerc]

A compression test might not show a leak between an oilway and a coolant passage, so having normal/equal compression in all cylinders isn't definite proof that the head gasket is indeed intact.

However, a leak directly between an oilway and a coolant passage will typically occur when the head becomes corroded (due to poor quality coolant, for example), so it's quite rare. The most common head gasket failures occur around one of the cylinder bores, due to the high pressure during the combustion phase, and this will be detected by a compression test (i.e. one cylinder, or two adjacent cylinders, will have significantly lower compression than the others).

One other thing you could do is pour a teaspoon of engine oil into the cylinder with the lower compression - if this causes the compression to go up, than the issue is with the compression rings and not with the head gasket, but if the compression remains low then the issue is not with the compression rings (i.e. it's faulty head gasket of a leaking/bent valve).

Thanks for your reply appreciated

 

[Justintyme]

The tea spoon full of engine oil down the low compression cylinder is a good tip.

 

[Petrol Pete]

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MaltaMerc , it's been 2 months now . How you getting on with this ?