Cylinder head rebuild M271 - What else should I be doing?
 

Hey guys, first time poster here, did a quick search but probably not hard enough for you guys.

Anyway, we have a W203 C180K with the M271 supercharged motor.

It recently skipped a couple of teeth on both the inlet and outlet camshaft sprockets, consequently... smashed every valve into the top of the pistons!

I've consequently ordered a VRS kit, timing chain and tensioner kit, new valves, new head bolts and a new water pump (It looks like it comes off when removing the front timing cover)

I'm also a big fan of "While you're in there" so are there any suggestions for things I should be doing while the motor this far apart? So far on my list of things to do at the same time are
- Port and Polish, it's cheap when you can do it yourself, but it takes a LONG time. But then again, so does lapping the valves.
- Considering changing the breather hoses at the rear of the motor, it's just easier now but not too difficult once the engine is back together
- I've already deleted the EGR -> Intake hose and blocked it off as way too much oil was making it past
- Camshaft actuators will be replaced as our current ones leaked like a sieve
- I'm not going to get the head machined at all, the car has never overheated and I really don't see the point, convince me otherwise though! I do listen to others!

So, can you guys think of anything else I should be looking to swap out while I'm this far torn down? Anything to the compressor like an oil change? Bearings? Intake Sensors?

Many thanks in advance for anyones input.

So it locked up? Was it just idling or at a decent speed when it blew? I'd check pistons real well, how bad does the damage look?

IMHO while you're in there stuff might include the air pump at the rear of the head, and would definitely include all the plastic coolant fittings that seat into the head with rubber o-rings. All the plastic fittings tend to crack at the groove where the o-ring sits.

How many miles on it?
If it was me, and it's near or past 100K miles, and I had it all apart anyway, I think I'd throw in a new themostat, water pump,
Alternator brushes, starter brushes, fuel filter, fluids, hoses, just stuff to make it reliable to so you won't repairing stuff every 5-10K miles. And yeah, maybe a new or rebuilt supercharger. I replaced mine at 120K, found one on ebay new for 600 years ago, sold my old one for 250, 350 out of pocket. Now at 245K, still going. It wasn't bad, it was just that, if it went unexpectedly out of town I'd be stuck with huge repair (dealer cost on that repair $2K+) or towing bill, vs. just doing it advance for less than $400. I spoke to an Eaton rep and he stated the life expectancy is 100K miles though some people might go as long as 200K or more. Fix it so it's troublefree for the next 100K miles. Just an FYI, I got 200K miles out of original fuel pump and water pump. Starter went at ~140K.
I didn't wait for the alternator to fail, had it rebuilt around 130K. Brushes were down to nubs.

I just did a head R&R on my 03 1.8. Things to have are as follows: You will need all three coolant pipes that connect the the head (Should do a new thermostat while at it). You will need an extractor, or get creative with a long bolt/washer and nut that fits, for the timing chain guides. They must be removed to get the front head bolts out. This means you need new guide seals (which didn't come in my head set.). You will need a new timing tensioner seal since it will get destroyed also. The one that came in my headset was too large. Ordered all these seals separately. The Valve seals were the final thing that were incorrect and I got directly from Mercedes. The rest of the head set was all correct making it a good deal still at $80. If you want to avoid the headache, spend a little more on the head set I guess or go with dealer.

I'm really not a fan or "while you're in there" because you end up spending a fortune on repairs. What you should do is have access to specifications and if something "ain't broke" don't fix it. For example: The head bolts are torque to yield type and many consider this a necessity to replace every time the head comes off. I reused mine because after checking the stretch limits I found mine to be well within specification. In fact they were closer to brand new length than the stretch limit. I also inspected my chain before removing the tensioner and found almost no slack in it. So I reused my chain tensioner as many would advise against after removal. You don't have to replace everything just because you're in there.