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Engineering Pro
Engineering Pro, Automotive Engineer.
Category: UK Car
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Experience:  BEng, M-SAE, Qualified Mechanic.
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I discovered white smoke coming from my oil filler cap and

Resolved Question:

I discovered white smoke coming from my oil filler cap and when I took it off there was alot off smoke. I dropped it into a specialist today and they said that I needed a new engine breather filter which they fitted. however, i have just got home and the fumes are still in the cabin and the smopke is still billowing when i remove the oil fill cap! any ideas?
Submitted: 4 years ago.
Category: UK Car
Expert:  Engineering Pro replied 4 years ago.
Hello, well from the beginning... The oil system is obviously for lubrication, but it will always generate a certain amount of pressure, thats because its connected directly to the cylinders which when burning fuel will allow a small amount of the combustion to pass by the piston rings and hence put some exhaust gas and pressure into the oil system. This is normal and the crank case breather is how it deals with this pressure, it vents it back into the air intake. If there is excessive pressure being generated it indicates that potentially too much combustion is passing over the piston rings. The crankcase breather system is not designed to take vast amounts of oily gas, so the indication here that something is wrong is the air inlet system where the breather pipe meets will be covered in oil residue. You need to have a compression test performed to establish if the piston rings or valve seats have worn and are no longer sealing the cylinder when the fuel is burning. If you need any further information just get back to me... All the best... Jon
Customer: replied 4 years ago.

Hi Jon

 

I appreciate and thank you for your response, however, this is the sort of thing I have found on the web. Apparently you cannot do a traditional compression test on these new(ish) cars/engines.

 

Regards

 

Jon

Expert:  Engineering Pro replied 4 years ago.
That is not correct, compression tests are possible and it is the correct way to proceed to establish whether you have a lack of compression within your engine. Excessive blow by is the probable cause and if proven will require the cylinders to be honed (using an abrasive to remove the surface of the cylinder walls) and likely a new set of piston rings should they be worn. All the best... Jon
Customer: replied 4 years ago.

Jon

 

Thanks again, the specialists I took it to must be mistaken regarding a compression test (or they can't be bothered). Do you know how much this is likely to cost me? and in your opnion, do you think I should fix it or get rid? I believe a BMW525d with 125k on the clock is worth around £4.5k if this helps?

 

Cheers

 

J

Expert:  Engineering Pro replied 4 years ago.

J

Well a compression test itself is only a time based charge. An hour (two maximum) would be about right depending on how versed the mechanic is with the engine. So thats definitely worth doing. As for what it reveals then thats another story.

 

If all the compressions come back equal and within range then its probably worth re-examining the breather system replacement.

 

If it comes back to reveal a the cylinder/s are showing signs of wear then there are temporary fixes using various "'wonder sealing compounds" none of them work on a long term basis but they can tide you over until you make a decision.

 

The rebuild, cause dependent, will not cost a huge amount in parts, its the labour cost and future reliability that is whats at risk here.

 

Depends on how attached you are to the car and what you will replace it with.

If the sale cost will be what you purchase another car with, you run the risk of picking up something that could have exactly the same issue, only you dont know about it.

If you are getting something newer and are just using the sale price to add to the funds then you should probably consider getting rid of it.

 

Hope this helps

All the best

Jon

Customer: replied 4 years ago.

Jon

 

Thanks for the advice.

 

Regards

 

J

Expert:  Engineering Pro replied 4 years ago.

No problem, please dont forget to press the accept button...

 

All the best

Jon

Engineering Pro, Automotive Engineer.
Category: UK Car
Satisfied Customers: 1404
Experience: BEng, M-SAE, Qualified Mechanic.
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