clk55 oil on g box harness

[Tallsaj]

Hi guys I’m new to this forum. Interesting problem, my local mechanic who has a star diagnostic plugged in and it come with the following codes I will attach a picture after. Basically he took away the mat from the passenger-side floor the loom that was coming from the gearbox to the ECU and found some oil on the wiring loom, what he saying is that this oil must be coming from the gearbox loom to the connector into the wires and into the ECU. Chances are that the gearbox ECU will have a lot of oil inside and it he has come through, he said he can probably replace the ECU for the gearbox and clean the wiring harness but what is to say that it won’t happen again. I tried to upload the picture but it was saying the file is too large.

 

[andy27168]

Hi,
The gearbox ECU will be fine just clean/wash it out with lighter fuel, the oil is leaking from the gearbox because you need a new one of these
Plug Control Unit Automatic Gearbox with Seal for C E G M S-CLASS CLC 6971003562298 | eBay
Very common issue and has been subject to multiple part no. changes and revisions, Buy a new one from MB not expensive but you will be guaranteed to get the latest part version/revision.
Can be fitted without draining the gearbox oil just jacking up on the driver's side you will lose a bit of oil about half litre so remember to top up the gearbox oil after to replace this and any that has wicked its way up the loom into the car and the ECU.

 

[zipdip]

As above it is a well known problem a new plug normally fixes it and andy has even told you how to do it

 

[Tallsaj]

But how can the oil travel up because the gearbox is low and the ecu sits higher?

 

[Tallsaj]

All this messes up the gearbox gear change.

 

[Tallsaj]

And thanks for the quick reply.

 

[Tallsaj]

And thanks for the quick reply.

 

[Alps]

Andy is spot on, change the gearbox plug bushing and clean it up, common problem over the last few generations of mb`s.

 

[whitenemesis]

You may need to change the look from the box to the ECU as atf may continue to wick up. Some have success with flushing it out, some don't...

 

[Will]

I had this happen around 15 years ago on my old W202 230 Kompressor. Steve from Kent did the job for me at the time. Cleaned the loom, footwell and ECU, replaced the plug and adjusted ATF level - no problem ever since.

Regards how it gets up from the pilot bush (aka the electronic plug) to the loom and into the footwell area - I think the seals go, the ATF leaks past - possibly some pressure involved but even so the plug is one of the lowest points, the actual ATF level will be higher - a little capillary action/siphoning etc probably takes care of it, the outer wiring sheath is naturally well sealed so it will find it’s way up to where it can get out - eg the next connection/opening which is in the footwell.

Common fault on these 722.6 boxes.

 

[Tallsaj]

So chances are the loom and ecu will be no good? Mercedes should have had a recall for this. That’s one good thing about Bmw, does not matter how old the car is if there is a issue they will rectify it FOC

 

[Will]

Not sure I believe that last sentence!

As I and others have said, there’s a good chance the ECU and loom will be okay if you clean them properly. The pilot bush/plug is about a tenner to buy and easy to replace.

It’s not the end of the world

 

[Tallsaj]

So it has to
Be lighter fuel? Do I soak the bits for a length of time?

 

[andy27168]

All you need do is remove the ECU from the car remove its case rinse lighter fuel over it paying particular attention to the ECU connector, use a soft brush to agitate it slightly, allow to dry/evaporate.
You could use proper electrical switch cleaner (NOT WD 40!) as long as it evaporates.
The loom I would just wipe clean and use a bit of proper cloth looming tape to stop the original cloth tape coming unravelled.
When I had this on my AMG it was harder getting the oil out of the foam sound proofing under the carpet.
This is an extremely common problem on all MBs with the 722.6 GB, as the copious part.no. revisions and supersessions bares testament too.
To be fair the car must be 10 years old at least and if this the only GB problem there has been its not been to bad IMO

 

[Tallsaj]

All you need do is remove the ECU from the car remove its case rinse lighter fuel over it paying particular attention to the ECU connector, use a soft brush to agitate it slightly, allow to dry/evaporate.
You could use proper electrical switch cleaner (NOT WD 40!) as long as it evaporates.
The loom I would just wipe clean and use a bit of proper cloth looming tape to stop the original cloth tape coming unravelled.
When I had this on my AMG it was harder getting the oil out of the foam sound proofing under the carpet.
This is an extremely common problem on all MBs with the 722.6 GB, as the copious part.no. revisions and supersessions bares testament too.
To be fair the car must be 10 years old at least and if this the only GB problem there has been its not been to bad IMO

All you need do is remove the ECU from the car remove its case rinse lighter fuel over it paying particular attention to the ECU connector, use a soft brush to agitate it slightly, allow to dry/evaporate.
You could use proper electrical switch cleaner (NOT WD 40!) as long as it evaporates.
The loom I would just wipe clean and use a bit of proper cloth looming tape to stop the original cloth tape coming unravelled.
When I had this on my AMG it was harder getting the oil out of the foam sound proofing under the carpet.
This is an extremely common problem on all MBs with the 722.6 GB, as the copious part.no. revisions and supersessions bares testament too.
To be fair the car must be 10 years old at least and if this the only GB problem there has been its not been to bad IMO

Okay I took out the g box ecu there was no oil in the brain but I cleaned it out anyhow with isopropyl alcohol could not get large amount of non compressed lighter fuel put it all back together. Car drove okay for a couple of miles. Then guess what elm light same problem Back again, could this mean the ecu is toast?

 

[Tallsaj]

Also cleaned the connector to the ecu

 

[Tallsaj]

Changed the pressure switch on the gearbox

 

[Tallsaj]

Any idea guys?

 

[whitenemesis]

Get the codes read using STAR.

 

[DSM10000]

But how can the oil travel up because the gearbox is low and the ecu sits higher?

Capillary action (sometimes capillarity, capillary motion, capillary effect, or wicking) is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.