Attempting to change the head gasket on a W202

[Nasco12]

More progress. The sprockets are now off largely due to the generosity of a neighbour who lent me his socket set:

Flickr

The Haynes manual had a bit how you had to have a flanged nut in order to withdraw the two main parts of the inlet cam sprocket separately. Well, I disassembled it anyway and I didn't hear any graunches or twangs so guess that was all right.

The timing chain guide rail pin is out. Here is a shot of it succumbing without much of a fuss to a slide hammer:

 

[gurpz]

Some progress to report. The inlet manifold is off. As are the cam cover, thermostat housing, front cover and timing chain tensioner.

The inlet manifold was a bit of chore due to inaccessible bolts. But we got there in the end.

Should the cam cover be that dirty? Would it benefit from a clean?

From Flickr

Signs of an oil leak. I was expecting to find an O-ring when I removed the (variable valve timing control?) but there was nothing there. Should there have been? Also, the Haynes manual talks about recovering an O-ring when the front cover is removed. There was none to be found.

The cam cover shoud not have that sludge stuck to it, lack of frequent oil changes would cause that build up in the past. Soak it in petrol and a soft brush will get that clean.

The cam adjusters are known to leak and have no O ring just a very thin smear of sealant but usually when they start leaking you need to replace them as they also internally leak causing oil to seap through the connector travelling up the harness. They are vailable from the dealer.

Dont forget to change the spark plug seals in the cam cover also they are common to harden and leak also.

 

[219]

This thread has reassured me that I did the right thing with my 190E when it started to show signs of head gasket failure .

Although I did one decades ago on an Audi 100LS , I didn't fancy doing another , and decided that an engine swap , at the same time upgrading from 1.8 to 2.3L , was the way to go .

Obtaining a known good engine , at a good price , from a fellow club member , made it a no brainer .

 

[Nasco12]

The heart of darkness

on Flickr

The gasket itself does not appear to be in particularly bad condition. There’s no rust and - to my untrained eye - no wear. Which makes me think that the real culprit is a warped head.

In fact the gasket doesn’t seem very old at all. It certainly doesn’t look like something that has been there for 20 years. And I don’t think it’s a Mercedes original. There’s no star or part number present.

And then there’s the way most of the bolts have come off really easily. Maybe I am getting ahead of myself here but I think someone’s had a go at this before.

Anyway, it’s off for inspection and - if necessary and if possible - a skim.

Talking of culprits look what I found lurking by the rear coolant inlet (outlet?):

A couple of years ago I was driving along when the coolant light came up on my dash. Then steam started to appear. The hose at the back of the engine had fallen off. There was no jubilee clip to be seen. I assumed it had fallen off the car. Not so. Now, this is not the sole cause of my problems. There was already a coolant leak. But I can’t imagine it did any good.

But why did the hose come loose? Could it be that whoever previously had a go at the gasket forgot to tighten it up properly or not at all?

That’s enough playing Sherlock Holmes.

At least the head bolts are within the tolerance:

 

[grober]

Try to use a new pukka MERCEDES cylinder head gasket or failing that one by REINZ [OEM to MB at one time]when rebuilding.

 

[Nasco12]

Yes, I've had that hammered in to me.

 

[horatio]

Interesting. The usual problem is oil leaking which is what mine has and my 190 suffered a few years ago.

Have you managed to find the head torque sequence & figures? Maybe I'm being a bit thick but the Haynes manual isn't very clear.

You can get an Elring gasket set, stem seals and head bolt set for about £60 with the discount code at Euro's. I'm going to call the dealer to see how much extra genuine parts are.

 

[Nasco12]

Well, the cylinder head people have taken a look at it and the news is not good. While I was expecting the head to need a skim it would appear that there is also substantial valve damage and substantial valve damage means a substantial bill.

While I was prepared to marry my handiwork to £100-worth of work £400-worth is another matter. Even if I had complete confidence in my abilities it would make little sense.

It's a real shame because I was rather looking forward to the rebuild.

Anyway, next question: do I want 6 cylinders in my life?

 

[a111r]

Any second hand heads on ebay?
Shame to pull it, this far in...

 

[Nasco12]

They do exist. They are not particularly cheap and there is no guarantee they don't have the same problems mine has.

 

[brucemillar]

Well, the cylinder head people have taken a look at it and the news is not good. While I was expecting the head to need a skim it would appear that there is also substantial valve damage and substantial valve damage means a substantial bill.

While I was prepared to marry my handiwork to £100-worth of work £400-worth is another matter. Even if I had complete confidence in my abilities it would make little sense.

It's a real shame because I was rather looking forward to the rebuild.

Anyway, next question: do I want 6 cylinders in my life?

With 'substantial valve damage' you have to consider what else may have been damaged but remains un-seen. Spending out on refurbishing the head only to discover later that the crank/bottom end, may be damaged, would be my fear now.

I have been here with an engine that started off needing some minor work and ended up requiring a complete re-build. Sadly with that engine I had reached the point financially, where I had to carry on. A very painful lesson for me. Good luck.

 

[horatio]

That's a bummer

If the bottom end was damaged, chances are it have been knocking or have visible damage to the bores?

 

[neilrr]

Well, the cylinder head people have taken a look at it and the news is not good. While I was expecting the head to need a skim it would appear that there is also substantial valve damage and substantial valve damage means a substantial bill.

While I was prepared to marry my handiwork to £100-worth of work £400-worth is another matter. Even if I had complete confidence in my abilities it would make little sense.

It's a real shame because I was rather looking forward to the rebuild.

Anyway, next question: do I want 6 cylinders in my life?

Would this work?

It's being scrapped Monday.

https://www.mbclub.co.uk/forums/classifieds-mercedes-parts/222395-mercedes-w202-estate.html

 

[DrNick]

Just to add, based on the comment that the bolts didn't seem tight. Many years ago I had a Pug 405 that had a head gasket problem. After much messing about it was determined that there was a lot of crap down the head bolt holes that was not allowing the bolts to do up properly. If you do decide to go ahead, check that this isn't the case here!

 

[Will]

What's the damage to the valves and a who's the engineering shop you've taken it to?

I only ask as although I would expect the valves/guides/seats to be in less than optimum condition you have to be realistic as to how far you go when you're doing this on a budget. Perhaps they're looking for work and/or have different expectations as to the vehicle/your budget.

If it's an old car/not worth much and the only reason you're doing this is to get it running again I'd consider lapping the valves in if needed, cleaning up and have it lightly skimmed if required and get it back together.

Unless the valves are cracked I doubt they're damaged, probably a little coked up/worn on the edges. This isn't unusual on an older engine with high mileage etc. Re-seating/lapping the valves back in will probably do the job for now.

A skim would probably cost £30/40 and you can clean the head up yourself if you're keen

 

[horatio]

What is the mileage out of interest?

Mine is on 140k and seems to be very clean inside. It's had a light skim but apparently nothing else needed. Don't want to speak too soon though

 

[Nasco12]

Answers to questions and responses to points raised:

I sent the head to a company called Cylinder Head Services in Wellingborough. They have yet to send me a report but they have sent me a quotation. So, maybe I was hasty in using the word "substantial". They also haven't mentioned what happens to the cylinder head. I imagine that it's only real value is as scrap. I should probably get back to them.

Mileage = 87,000

The engine was not making any unusual noises once it had settled down.

There was some detritus in some of the bolt holes but not all of them.

Digging into a soon-to-be-scrapped C200 for the head is tempting especially as I now know exactly how to go about it. Unfortunately, I don't really have the time.

 

[Nasco12]

And so it goes on…

They have discovered that some welding has taken place in the past and that the welded material now has holes in it.

on Flickr

 

[Nasco12]

Right, the head is back so I can start to think about putting it all back together.

I notice the Haynes manual recommends using "sealant" on both the guide rail pin and the the timing chain cover. Is this necessary? and, if so, what sort of sealant should I use?

 

[Nasco12]

Update

Some of you may have begun to think that I have seen the error of my ways and abandoned this crazy project. Not so. Unfortunately, I have been rather slowed down by the death of a close family member but even so progress is being made:

1. The head is now on. Unfortunately, I managed to drop a bolt (not a head bolt) into the gap between the timing chain guide and the head. I have not been able to retrieve it.
2. The sprockets are now on. The inlet camshaft sprocket proved especially difficult.
3. The timing chain tensioner is in. This proved very easy. So easy that I wonder if I did it right.
4. The cam cover is on - not that you get any points for that.
5. The exhaust manifold is proving very difficult. My cunning plan was to remove the studs rather than unbolt the manifold from the exhaust. Having removed them I now find that I can't get all of them back in.
6. The timing chain cover is on but I seem to missing some of the bolts. And there I was thinking how careful I'd been to put them all in plastic bags with labels. Hopefully, they will re-appear as other bits of the job get done.

My current plan is to put everything back together and see if the engine will start. If so, I will get the professionals in to sort out the exhaust manifold.