Suspect Blow-by

[Voltan]

Hi, I am quite confused with local techies opinions regarding an issue in my W220 S320CDi. The car is with 78K miles now and is maintained by the book. 10 months ago I installed a Kleemann KD Box and was fine for 2 months except of quite heavy dark-grey exhaust smoke on hard accelerations.

On one high-speed long distant run I got the 1 litre top-up reminder on the dash, which I did. However after about 625 miles the same reminder flashed. Since then if I drive gently below 75 mph, I can stretch the top-ups to about 900 miles, otherwise 500-600 miles.

I notice that when opening the oil cap with the engine running, there is a fairly high air pressure which can be felt some 9 inches above the filler hole.

Without touching anything, a few techies suggested that I have worn piston rings and the pressure being the result of combustion blow-bys. But then the mileage is SO LOW, and worst, the expensive dollar signs are now flashing in my poor head. Could I get advise and suggestions from members before the naturally dollar seeking guys experiment around with my car. Thank you.

 

[BlackC55]

A compression test is what is needed.

I would be thinking along the lines of poor quality oil has been used or it has been run with very low oil level for this to happen.

 

[Voltan]

A compression test is what is needed.

I would be thinking along the lines of poor quality oil has been used or it has been run with very low oil level for this to happen.

When I purchased it a year ago from the previous owner it had clocked about 65,625 miles. I was informed it was serviced using a German engine oil and lubs, and I sighted the receipt and invoices. Within 1K miles after purchase, I sent it for a B service, using Mobil 1 5W50 MB229.3 approved oil.

At least since then, I have treated it like pampered baby...

For your info, just now I uninstalled the Kleemann KD Box and felt the car ran smoother and with much lesser smoke on hard acceleration.

I checked with a couple of workshops, none have the compression gauge for diesels. What can be done if the compression gauge is not available?

 

[BlackC55]

Buy one? They are not expensive. I am sure MB will have one in your country.

 

[Voltan]

Inspected the oil divider (a triangular black plastic box) which is located near the turbo; found it dripping with engine oil. As a precaution it was replaced with a new one.

The w'shop suggested that the car be ran for a while, while they source out for a diesel compression tester.

With the new oil divider, and a new MAF sensor (reported in another thread) in place the engine is smoother, quieter and seems more responsive.

What many of you may not realise, is that there aren't many diesel powered passenger cars in use in this part of the world. Thus tools and test equipment associated to light high speed diesels are very rare. Likewise technicians and engineers in the automotive industry have little hands on experience with the latest diesel technologies. Theories yes, they know a lot. In simple term it is far easier to get guys to handle the latest jumbo and long range executive jets than ones who can handle the humble CDis, TDis, TDs etc.

Therefore this forum is in a way a life-line like members like me.