David Moody is struggling to find the cause of an engine oil leak in his Volvo 2002. Stu Davies has the answer

I have a Volvo 2002 18hp engine which has developed a mysterious symptom, the cause of which I hope you can help diagnose.

The engine, new in 1995, powers my 34ft cruising yacht, so it’s not as if it has worked tremendously hard all its life.

Indeed with routine maintenance and a few odd replacements e.g. the starter motor and thermostat, it has been very reliable.

The last time it was used it involved a two-hour motor at 2,200rpm back to my mooring.

When I came to pack up and turn off the engine seacock I could see that the front of the engine bay was covered in oil and the same at the back of the engine – so almost everywhere.

This looked like a serious problem. I cleaned it all up and started the engine again to see if I could locate the source of this oil leak, but to no avail.

For some reason, with no logic, I removed the oil filler cap when the engine was stopped and surprise, surprise, I distinctly heard a quick hiss of escaping air.

I replaced the oil filler cap and repeated the experiment; sure enough, a quick hiss of escaping air was clearly apparent. Is this part of the problem?

What do you think is going on here and can you suggest a remedy?

David Moody

Stu Davies replies:

Several things can cause oil leaks. I have checked to see if there is an issue with something like this on this engine but I can’t find any documented issues nor have I first-hand knowledge of dramatic oil leaks on these particular motors.

An oil leak can come from anywhere and can be caused by all sorts of situations.

My first advice is to clean everything up, check the oil level and make sure it is good, also estimate from the dipstick how much has come out of the engine.

Then run it in gear and see if you can spot where it is coming from.

Continues below…

A hissing sound on the removal of the filler cap is not normal. If I recall correctly, these engines have a breather valve on them and this could have closed and stuck shut so is worth investigating.

A small amount of blow-by past the piston rings is quite normal, however, and the breather valve should deal with this to prevent pressurisation of the crankcase.

If the crankcase is being pressurised excessively then oil can be blown out of the dipstick tube and anywhere else it can get out.

Your running of the engine on the previous trip shouldn’t have caused major issues so careful checking as detailed above and then some investigation of the breather valve should reveal what has caused this problem.

Enjoyed reading How to find an engine oil leak in a Volvo 2002?

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