How to stop MAF oil contamination (CLK 230K - W208)

[jamesmc]

It is believed that the info also applies to all W202 (C class) Kompressor engines.

History behind this.
There have been a few discussions in the Forum about MAF failure on the W208. This post covers the failure of the MAF - by oil contamination.

If your W208K has a mileage in excess of 90,00 miles
This is one job that you should carry out in the near future as a matter of preventive maintenance.
In excess of the above mileage even if your car is not suffering from this problem now it will, which is exactly why I did the job anyway.
The parts are cheap in comparison to replacing dead MAF sensors.
If you cannot do the job yourself approximately 4 hours labour should be allowed for a workshop to complete the job.

One Forum Member carried out a lot of research on the problem and, along the way, dispelled one particular myth quoted a few times in the past :

If your W208 (W202) has oil in the Air filter housing or any pipework leading, via the intercooler, to the MAF
then it will not be Kompressor (Supercharger) related failure causing the problem.​

The reason for this (as pointed out byjiminessex) is that, unlike a turbocharger, there is no oil feed from the engine to the Kompressor. The only oil the supercharger uses is held in a tiny inbuilt reservoir within the compressor body itself. This quantity of oil alone is insufficient to cause oil contamination to the point where it reach the MAF.


So, if it isn't a Kompressor (Supercharger) fault what causes the MAF oil contamination problem?
The research by jiminessex answers that:

The following applies specifically to my car, a 1999 CLK 230k Coupe with a 208347 chassis

no. and a 111975 engine, I believe the info applies to all 202 C class and 208 CLK class kompressor engines.
At 97,000 miles I became aware of oil in the air intake but it was then only a minor irritation, cleaning the MAF

sensor sorted it. By 140,000 miles the amount of oil in the pipework to the MAF sensor was becoming alarming

although it only caused a misfire and was solved again by cleaning.
Examination of the air filter housing showed the oil was entering the system from the Crankcase Breather System.

My understanding of the Crankcase Breather System:-
It operates in two modes, an upper partload to full load system and an idle to upper partload system.

The idle to upper partload system works directly off the crankcase and feeds into the cylinder head just before the inlet valves. The high load system from the cylinder head cover feeds into the air filter housing AFTER the the filter element.

The highload system is mounted on the cylinder head cover and consists of a black plastic oil separator and three hoses,it is very accessible and cheap to replace all components. Beware, get the parts first as the hoses are brittle with age and at least one will probably break. Changing all this did not solve my problem although it was clear that the oil was coming from here!

Conclusion - idle to upper partload system was blocked and forcing the highload system to accept the oil residue at low airflows.

The lower load system is hidden under the inlet manifold and consists of an oil separator built into the crankcase with a hose leading to a valve and tee-piece which in turn leads via two small bore hoses into two brass restricter nozzles in the cylinder head just before the inlet valves. The valve is spring loaded and NOT (in my case) the electric valve suggested in earlier replies. This system was blocked on my car and causing the problem.

After replacing all of it the problem seems, after a further 1000 miles, to be sorted.

Again the hoses were brittle with age so order before disturbing them.
The nozzles have a very small bore but are a press fit in the head so unless the head is off best to just poke them through. They are only 97p each so order them anyway in case.

I would strongly suggest the Kompressor outlet pipework and intercooler is cleaned as well as a lot of oil could be lying here and still cause problems even after the breather systems have been renewed.

Summary
The idle to upper partload oil breather system is blocked and forcing the highload oil breather system to accept the excess oil residue at low airflows.
The excess oil is then being dumped into the air filter housing then travels via the intercooler and associated pipework to the MAF.
The MAF dies!


The DIY repair. as carried out by jamesmc

Parts to be ordered prior to the work:-
1 x Main hose - MA111 018 15 82
1 x Valve/Tee-Piece complete - MA111 010 00 91
2 x Small bore hoses - MA 002 094 01 82 (supplied to me as one double length hose that I chopped in half)
2 x Nozzles - MA111 017 00 12 (These are brass)
1 Set (pair) of inlet manifold gaskets. Sorry no part numbers. These are more like silicone 'O' ring material rather than traditional flat manifold gaskets.

Tools required
A good DIY mechanics toolbox with Metric socket set will cover most of the work
Plus: Torque Wrench & Reverse Torx Sockets (for fuel rail/manifold bolts)

The Job
I haven't gone over every finite detail here but it stands to reason that any cables/connectors that hamper access along the way need to be disconnected.

• Disconnect any necessary pipework... fuel lines etc. from the fuel rail.
• Remove all the inlet manifold bolts including the two extended reverse torx bolts which, as well as securing the fuel rail, also act as manifold securing bolts.
• Ease the fuel rail out of the way
• Ease the manifold off and away from the head to one side, but don't remove it completely.
  Pulling the manifold away from the head and to one side a little gave me enough access to do what was needed. I suspended the bulk of the weight from the bonnet using bungees so that (in effect) it was floating, almost weightless, to one side.
• Remove the two small bore hoses along with the 'T' piece and the main hose.
  Both of the small bore hoses (MA 002 094 01 82), which connect to the underside of the nozzles (MA111 017 00 12), were brittle as mentioned earlier in this thread, hence the need to ensure you have all the parts required before getting stuck into this job.

The brittle small bore hoses simply snapped off with very little effort.​

Look in the images below and you will see the original small bore hoses fitted with the 'T' piece in place​

• With a pair of small light duty side cutters snip off the rest of the brittle hose remaining on the underside of the nozzle tube connectors.

On inspection, and with a squirt of WD40 via a small tube up the disconnect nozzles, I noted that the forward brass breather nozzle was about 90% clogged and the rear nozzle 100%. So not a lot of breathing going on there!

This is the forward brass nozzle that was about 90% blocked​

You can also see the original small bore hoses and 'T' Piece in place​

Another shot of the forward brass nozzle that was about 90% blocked​

also showing the original small bore hoses and 'T' Piece in place before removal

Looking directky from above at the rear brass nozzle that was 100% blocked​

After inspecting the existing nozzles, even though I had two new replacements, I decided to leave them in situ. In my mind that was the safer option rather than trying to extract brass from aluminium that had resided (mated in that position) since they left the factory in 1999.

• Check the bore size of the new nozzles and select a drill bit that matches the bore size.
• Clean the existing nozzles out in situ using a small drill bit held by hand only. I also used tooth picks and WD40 to flush out the debris. End result? Two clear nozzles to original spec.

The Valve 'T' Piece (MA111 010 00 91) looked a bit choked up too when I investigated further. It could be cleaned I guess but the cost of a new one is minimal.

• Replace the inlet manifold gaskets with two new ones and reassemble.
• Intake Manifold Bolts are torqued to 20Nm as recommended by MB.

Additionally:

I would strongly suggest the Kompressor outlet pipework and intercooler is cleaned as well as a lot of oil could be lying here and still cause problems even after the breather systems have been renewed.

Extra DIY pointers: How to Clean your MAF by Parrot of Doom


For further reading check out thread Oil In Air Intake thread

 

[television]

Anyweb, please move this to the DIY section Sticky an excellent article

 

[Blobcat]

Anyweb, please move this to the DIY section Sticky an excellent article

Done .

 

[television]

Done .

Thank you young man

 

[jimsinessex]

Latest

As a follow up I would add that I have now covered another 55,000 miles since replacing the breather system under the inlet manifold without a single misfire or MAF problem.

Jim

 

[brandwooddixon]

I wonder if MAF problems with other vehicles are caused by breather problems?

 

[BlackC55]

I wonder if MAF problems with other vehicles are caused by breather problems?

Not generally.

It is not just the clk that is affected its all 111 Kompressor engines.

This repair has been around for a couple of years and works very well.

The cause of most air mass problems are dirty air filters and contamination sticking to the sensor. (they don't like silicone spray)

 

[jamesmc]

As a follow up I would add that I have now covered another 55,000 miles since replacing the breather system under the inlet manifold without a single misfire or MAF problem.

Jim

That's good to know Jim

I'm looking forward to the same long term results once I have cleaned out the air inlet pipes, intercooler & MAF. Actually it's running OK now, slight miss on tick-over sometimes, but as I had the oil breather/nozzle blockage problem then cleaning the rest of the system will be another job worth doing as a matter of course.

 

[Glenn Smith]

True the breathers should be clean, but i have my doubts that they cause the problems suggested, the valve used at low rpm uses vaccuum to draw the crankcase fumes into the inlet, this is because there is not enough airflow and very little crankcase pressure at low rpm, as the pressure increases the valve closes and the main system takes over. So, how does the low throttle system cause the contamination. my own view is that the oil contamination occurs over a period of time as a normal process, greatly affected as the engine wears and blow by increases, oil viscosity and dilution also contribute as does driving style, the Kompressor engine is particularly prone due to intercooler and pipework where the oil can separate and collect only to be blown in during hard driving thus causing said contamination of MAF.
However my advice would still be to clean the entire system if you are experiencing problems and you may aswell do the lower throttle system whilst you're at it, as the engine is set up to make allowances for the intake of crankcase fumes and keep the oil fresh with more oil changes than recomended.
Touch wood mine has had no problems so far despite 158000 miles, but it has had oil chnges every 6-7000 since i bought it and every 4-5 months before that (it was doing high mileage).

 

[jimsinessex]

True the breathers should be clean, but i have my doubts that they cause the problems suggested, the valve used at low rpm uses vaccuum to draw the crankcase fumes into the inlet, this is because there is not enough airflow and very little crankcase pressure at low rpm, as the pressure increases the valve closes and the main system takes over. So, how does the low throttle system cause the contamination. my own view is that the oil contamination occurs over a period of time as a normal process, greatly affected as the engine wears and blow by increases, oil viscosity and dilution also contribute as does driving style, the Kompressor engine is particularly prone due to intercooler and pipework where the oil can separate and collect only to be blown in during hard driving thus causing said contamination of MAF.
However my advice would still be to clean the entire system if you are experiencing problems and you may aswell do the lower throttle system whilst you're at it, as the engine is set up to make allowances for the intake of crankcase fumes and keep the oil fresh with more oil changes than recomended.
Touch wood mine has had no problems so far despite 158000 miles, but it has had oil chnges every 6-7000 since i bought it and every 4-5 months before that (it was doing high mileage).

The low load breather failure IS the primary cause of MAF sensor contamination precisely because it then causes the crankcase to ventilate through the high load system but at low air velocities, so oil will more easily deposit out and accumulate in the air inlet system. If the low load breather system is maintained in good working order contamination will not occur unless engine wear gets to a point where the crankcase is pressurised beyond the capacity of the low load breather system to handle it. The nozzles are very small restricters after all.

Of course serious engine wear will eventually overwhelm the breather system and force oil into the air intake and at various points throughout this saga I have suggested doing an engine compression test early in the investigation to eliminate engine wear as the cause.

I am interested to see you have reached such a high mileage without needing any attention to the low load breather. What was the mileage when you acquired the car and can you be certain the previous owner(s) did nothing to the breather or clean the air inlet system. Have MAF sensors needed to be replaced or cleaned at any time? The hoses in the breathers become very brittle by about seven years in my experience. Check the easily accessible hose from the camshaft cover to the high load oil separator and if it doesn't break when you pull it off it has probably already been renewed at some point.

Jim

 

[Glenn Smith]

Yes i can see, your point on the breathing through the main breather at low velocities, but there would be very little oil and the separator should catch it. The car had around 100k when purchased and was 4yrs old (but had stood on forcourt for 9 months), so the car had been getting around 4 oil changes a year, service records don't show evidence of any work on breather or replacement MAF, the only parts on the motor i have replace are the belts and a crank oil seal (about 2yrs ago as it was weaping slightly) when i last checked for oil contamination there was a tiny amount which had collected around the ridge created by one of the air intake joints and the throttle body looked like new. In my experience blocked low load breathers (or engines without them) tend to cause excessive condensation in the breather leading to a build up of snot causing blockage, usually ending up with oil pumping out of every orifice. And excessive oil in the intake usually caused by excessive crankcase compression due to worn rings/bores or blown head gaskets, or by overfilling with engine oil, (very common).
However, i am very tempted to clean my breather system and air intake, just in case.

 

[jimsinessex]

Yes i can see, your point on the breathing through the main breather at low velocities, but there would be very little oil and the separator should catch it.

The high load breather oil separator will not catch oil at low velocities. It will only work when there is a decent air flow through it, at low air flows the oil will not be separated out. There is a small pipe connected from the kompressor outlet port which has an angled connection through a plastic nozzle into the hose to the air cleaner which increases the air velocity through the high load separator in order to increase the separator effectiveness. This has little effect at low load when the kompressor output is low.

Thus oil accumulates in the pipework after the separator at low loads and then at higher loads is carried forward to contaminate the rest of the air intake system.

Jim

 

[jamesmc]

........However, i am very tempted to clean my breather system and air intake, just in case.

Just caught up on this thread whilst on the move.. in Canada at the moment (not with the car or the bike I might add).

Cleaning the system will not do any harm for sure. I would be interested to read on what you find with regards to the state of the nozzles and hoses.

 

[4xxxx]

hi

hi i have that problem with my car
i am not mechanically minded at all and this work is way beyond my scope
how much would it cost to have this work done?

 

[jimsinessex]

hi i have that problem with my car
i am not mechanically minded at all and this work is way beyond my scope
how much would it cost to have this work done?

£20 approx for parts but 4 hrs worth of labour. Definitely one for an indie and not an MB Dealer.

Jim

 

[nitro1471]

Hi hope someone can advise me.
I have a 2001 C230k Coupe with the 111981 engine with 64000 miles, 2 months ago the engine warning light came on and local indie said it was the MAF unit which they replaced, then 3 weeks ago light came on again they sent someone out with a star machine and he said it was oil in the wiring harness, i booked car in and they replace the front magnet and fitted new modified MB short harness, 5 days after getting car back from them light came on again, they sent same guy out again and it now has oil in MAF unit and trunking and he says its a common problem and engine is breathing too hard so needs new engine :cry: or just clean out MAF for short term fix.
So to my question, do the above posts for the W208 also relate to a W203 or is he right.
I have to say that this is the worst car I have owned, in the past 6 months the following have failed.

1. Command no longer reads CD's or Nav disc - tried cleaning but no good.
2. Heater flap motor noisey behind dash - Indie quoting at least a days labour
+ parts.
3. EC rest light on permantly - advised it needs AC regas and poss new
condensor.
4. Maf failure - cost to fix at indie £470
5. Short engine wiring harness and magnet - cost to fix £270
6. Bas light on - replaced brake light switch

What next, and coupled to that I wanted to sell car and without any faults its worth about £4500-4800, all because Gordon Brown has gone green and raised Road Tax

 

[BlackC55]

Change your indie.

Yes it can relate to your engine.

A proper inspection is needed. I probably think that the oil in engine loom may have reached your lambda sensor and buggerd it up.

It needs some time spent on it with a Star.

 

[television]

Hi hope someone can advise me.
I have a 2001 C230k Coupe with the 111981 engine with 64000 miles, 2 months ago the engine warning light came on and local indie said it was the MAF unit which they replaced, then 3 weeks ago light came on again they sent someone out with a star machine and he said it was oil in the wiring harness, i booked car in and they replace the front magnet and fitted new modified MB short harness, 5 days after getting car back from them light came on again, they sent same guy out again and it now has oil in MAF unit and trunking and he says its a common problem and engine is breathing too hard so needs new engine :cry: or just clean out MAF for short term fix.
So to my question, do the above posts for the W208 also relate to a W203 or is he right.
I have to say that this is the worst car I have owned, in the past 6 months the following have failed.

1. Command no longer reads CD's or Nav disc - tried cleaning but no good.
2. Heater flap motor noisey behind dash - Indie quoting at least a days labour
+ parts.
3. EC rest light on permantly - advised it needs AC regas and poss new
condensor.
4. Maf failure - cost to fix at indie £470
5. Short engine wiring harness and magnet - cost to fix £270
6. Bas light on - replaced brake light switch

What next, and coupled to that I wanted to sell car and without any faults its worth about £4500-4800, all because Gordon Brown has gone green and raised Road Tax

You are being had - cheated. there will be nothing wrong with the engine only the breathing pipes as mentioned above.


The MAF will not put the engine lamp on, but the oil from the breather above will as the oil gets onto the O2 sensor, and it is this sensor that has moved from its stored settings and this puts the light on.

A new MAF if needed cost £145 from Bosch and takes all of 5 mins to put on.

OK the laser has gone down on the Sat Nav and firms on Ebay fix them for £225

The Air con may just want a charge,, go to quick fit and they will charge it up,,£40 if it works and free if it does not work

The wiring harness and new plug is quick to fit and this could be your only engine problems.

Where do you live in the UK

 

[dragon]

Not everytime is MAF problem. While I was around Camberley/Farnborough/Fleet area last year, the engine light of my 2001 W170 came on. I sent it to Merc Basingstoke they robbed me £260 by changing two inlet valves.

They said it choked with dusts. They even frightened me they might not even be able to remove it without breaking the other part(? attached to by the inlet valves).

 

[dragon]

Not everytime is MAF problem. While I was around Camberley/Farnborough/Fleet area last year, the engine light of my 2001 W170 came on. I sent it to Merc Basingstoke they robbed me £260 by changing two inlet valves.

They said it choked with dusts. They even frightened me they might not even be able to remove it without breaking the other part(? attached to by the inlet valves).