E320cdi piston removal/engine noise

[Transalpir]

Hi All
I'm new to forums and have a tricky problem try this with...
i have a 2000 facelift E320cdi while towing a 750kg trailer n load Ihear a strange rattling noise like metal shooting down the exaust? Engine seems unaffected apart from a knocking that seems to come from the top end.

I took out the injectors and stiped it down to the hydrolic lifters. found that no9 inlet had been scraping and had deep scores init put a new one in after testing the valve spring ( comparing force required to open it with the others). reasembled and took car for a drive...no change

I have now bitten the bullet and removed the head to see whats what. Iexpected valve seat issues but they seem fine on initial inspection, but will remove and regrind/stem seals while I can.

In the bottom end I found that no5 cylinder has some abnormal scoring to it so needs out, but how. the engine is in car and the sump has to come off!

Seems that the subframe may need to come out ? Anybody got any hints and tips please?

 

[GordonTarling]

If the cylinder is scored, then it seems to me that you're going to need a rebore. I know there are a few places that can do it in situ, but wouldn't it be simpler just to remove the engine?

 

[Transalpir]

Hi Gordon
The scoring is light but needs attention, i recon a quick spin of some cylinder honing stones should do the job.

However I still need to get the piston out to both do this and replace the ring set as its clearly not scraping oil properly from the cylinder. I also need to check the connecting rod bearings and the piston mounting bush, to understand what is going on here. Theres no point in not doing this considering how much more work it would be if I fail this basic step now. I was told that you need to take the auto box out with the engine, is this so or can they be easily split for engine only removal. I could get hold of an engine hoist if needs must!

I have a number of screw jacks and 2 trolley jacks aswell as standard and 6 ton axle stands to hand, should i have to drop the sub frame.

It's a bright day here and so have had my head under there again to plan what to do next.

Looks like I need to fabricate an engine support to sit on rhe fain frame rails with a lenght of box section across the engine with a bracket to fix it to the head mounting points between pots 2 and 3.

Then uncouple the steering linkage (not sure how this is done yet, looks like there maybe ajoint hiding in a heat shield on the lower end of the columb just up from the rack), torsion bar and droplinks, hang the brake calipers in wheel arch, loose a ball joint or 2, unbolt the steering pump from the block and remove its cooler hoses, upper shock mounts and the cables for the pad wear and abs. fit some spring compressors and then it should not be too far away from dropping the frame.

Any hints and tip would be greatfully recieved as 2 or more heads have to be better than just the one.

I have to say having had a number of mercs in the past I'm very surprised that a large diesel with 140,000mile (just run in) is showing these problems. I alsoa have a petrol 2ltr with the same miles and it runs like new. The MOT tester was shocked by its 0.01%co2 and just 5 parts per million hydrocarbons. I guess 1 of the previous owners failed to service properly.

 

[GordonTarling]

Sorry, I can't help much more, as I've never had cause to dismantle an MB engine in situ. The last engine I overhauled was in an Austin A40 - things were much simpler then!

 

[Dieselman]

If you really want to do this with the engine in situ, you will need to do as you say. The subframe can be lowered and the steering does have a clamp inside the aluminium cover, but I would have thought it was as easy to remove the engine having removed the radiator and slam panel.

 

[Transalpir]

Update...

I have fabricated a frame and fitted it to supprt the engine from the side rails. this then allowed me to remove the engine mounts and front sub frame/axle, which was a far easier than expected and less hastle than taking the engine out.

The sump is also off and the offending piston out. the piston has a severve case of indigestion... it has obviously tried to eat some metal pieces that have jammed the upper and lower piston rings in place, which in turn cased the piston skirts to drag in the bore. The piston is what you might call dead!!!

The problem is now finding out what and where it came from.I think its likely to be a componant from the inlet manifold as that would go with the "pebbles rattling down a pipe" sound that came from that area of the car just prior to the engine tapping noise starting.

Has any body experianced this before and or have any ideas as to to the origins of this problem...is there a likely hood of reoccurance after repairs of pot 5 are compleated.

You might guess I keen not have this strip down to do again as its turning out to be a rather costly self fix!(ok very cheap compaired to the local stealership!!!).

 

[E270 Owner]

Sorry to drag up an old thread

Seems like a common fault the more I have investigated this problem.

A inlet manifold swirl flap fails
engine sucks flap into cylinder
piston picks up the bore whilst munching the flap
flap passes out into exhaust leaving engine knocking with piston slap.

Replace engine.

I thought these engines were Alusil type and cannot be done with a honing tool but special compound and felt brushes.

Mercedes Benz Alusil Cylinder Conditioning - YouTube