MB stripdown and rebuild

[Alan Geraghty]

Having removed the clutch and flywheel, I have mounted the engine onto an engine stand.

Starting on the easy side first, removing all ancillaries including any sensors and the like.



This is what happens if you dont keep proper coolant in your engine...



Picked clean:



Now over to the slightly more congested side of things:



Exhaust came off easily enough thanks to stainless fasteners (are these standard?)

Got a bit of a shock when I noticed the controversial Dialynx manifold



Intake manifold mounting holes badly damaged at a few places, I'm not sure if this is a result of a gorilla over tightening the fixing screws, some form of warpage from the exhaust manifold, or typical wear and tear from age:



Intake manifold will not come off without first removing pipe between in and the head! (Just crossed my mind this morning.

[KIG1971]

Alan,

Nice pictures, I hope that you will post some pictures when the job is complete prior to putting the engine back in the engine bay.

Goodluck!

Ian

[Alan Geraghty]

Thanks Ian,
All going well I will make posts until its running again.

Got the intake manifold off:



Followed by the exhaust manifold complete with turbo and wastegate:



Then the oil filter/cooler mixing unit (is there a thermostat in here?):



The RHS engine mount fixings were really tight, and of course one of the stupid hex headed bolts wrung, meaning the drill was yet again required to persuade it to get out:



Camshaft pulley next, along with the water pump which also acts as the belt tensioner:



Getting much lighter now:



Head after removal, a quick visual shows no cracks or other apparent damage:



The block deck and the piston domes also seem free from any apparent damage such as detonation:



Looks like the exhaust manifold may have caused the stripped threads on the head:



And it also looks like someone has repaired this head before as this insert would suggest:



The crank and its attachments are next to come out and then I can measure the bores and the pistons.
I really am hoping that they are at or below the wear limits so that just a honing and a set of piston rings will be required, otherwise a custom set of pistons will have to be made (unless some really nice person has a set of oversize MB pistons under their desk!

[mikes2]

There is a thermostat inside the oil filter bracket housing.

It's rated at 100 degrees

[Alan Geraghty]

Thanks Mike.
I saw a spring in there and guessed at it being so.

I took off the camshaft today and there is scoring on the journals and on the cam itself:



I then removed all the tappets and replaced the cam to allow it spin freely without pressure from a valve spring.
I dont have plastiguage so I placed an indicator on the cam and rocked it up and down in the head.
The movement is about 0.25mm so given that this is usually max 0.1mm I may be in trouble here, so I may be looking for a head (or 2 given that the wife reckons I loose mine frequently!)
I will have to get some professional advice here.

Moving down to the block, I removed each piston one at a time and reassembled them marking the cylinder number on each one.
I then measured each piston shirt and bore to see if a rebore and new pistons were required.
The pistons are just under the factory wear specs, but only by about 0.015mm on average, so I feel a new set of rings will be ok here.
The bores are mostly smack in the middle of the tolerance, with the exception of no. 5 which is 0.02mm oversize, again I feel that this is fine for a car that is not going to cover huge miles from now on, but I will ask the experts.

The surface finish is mostly good, the exception being a fine layer of corrosion in places, most likely a result of being idle for a year or more.
I will probably hone the bores first to ensure there will be no issues with pitting before getting any work done.
There are some slight vertical lines showing too, but again I am unsure if this makes any difference at the moment.

[Alan Geraghty]

Time to remove the crankshaft next, and I am sure some are wondering how I am going to hold the engine whilst trying to loosen the pulley bolt.
Rather than the law of the lever, I decided to use a different kind of mechanical advantage,
Namely this bad boy here (Thanks Tom)


1900 lb/ft torque if required.

To stop the crank from moving I simply placed a piece of wood between it and the block.



Easy for once...

Oil pump and and bearing carrier off next.
Pump well scored, fit only for bin.



Block with crank out, the oil squirters are visible in the cylinders:



Having contacted a machine shop today, I am sending off the block, crank, pistons and head complete for inspection and I will review what course of action to take then based on an expert opinion.

[Martin Kennedy]

Nice thread. Enjoy reading it.

[omigod]

I agree with martin, this is a great thread. I was wondering though Alan what history do you know of the engine? ie how many miles, what service history and how was it running before the stripdown?

[Alan Geraghty]

Thanks guys, hopefully it will be of use to others.
With regard to the history, there is only 110,000 miles on the car, and to be fair to its previous owner(s) it was genneraly well cared for, with the usual fortune of reciepts kept.
When I got the car it was really tight, no smoke, pulled well and never used oil.
Where I feel it all went wrong was over the course of a few weeks I was doing some small repairs like issues with the electric windows, mirrors, that sort of thing.
This meant turning on and off the ignition without actually starting the car, and this primes the fuel system (correct me if I am wrong here) and if one of the injectors is leaking it sprays fuel into the cylinder. (the oil in my sump stank of petrol).
Not a huge issue if the car is started and driven to burn off the petrol, but if its not being burnt up it simply thins out the oil to the point where is little more effective than water as a lubricant.
Then the car was put on the road and the wife (she is competent, really!) was using it for a few weeks while hers was off the road.
One day I noticed the oil light flashing at tickover when hot and also smoke.
I then stuck a pressure gauge on and started to get worried.
And here we are!
The bottom line is check your injectors (WR and MB owners the RR has electronic injectors) and make sure they are not leaking.
It may also be wise to fit a proper oil pressure gauge, by the time the red light comes on its game over.
It may also be worth pulling the fuse on the fuel pump whilst doing repairs like I was, then there is no way that petrol is going to get into the engine.

[JimH]

The fuel pump does (should) not run until the engine is turning over at more than (something like) 450rpm. But if you had a leaking injector, enough to make the oil smell strongly of fuel, yours is certainly not the first engine damaged in this way.
I think what normally happens is the oil is gradually thinned out by the fuel, and the excess is burnt off. You carry out regular oil level checks which appear fine (although an increasing % of the volume is fuel, not oil).
I think the fuel leak is more a drip or weep than a spray, so the issue develops gradually over time. It'll drip fuel into a cylinder after shutting down the engine. This can also cause problems with hot starting, as the system will struggle to hold pressure after shut down.

This obviously results in greatly increased engine wear as you suggest.