Do I repair, scrap or break my motor w203 C Class 2005 105k

[jpod]

My first Mercedes owned for a few years and it has been a great car - I am now a fan - I have done some repairs along the way and I understood these are prone to cam chain problems. MBClub forum buddies warned me about this and I can't complain - it has been a fantastic motor - so smooth. My GF has a 2003 one too!

Difficulty starting cold early this week. With my fisher price code reader I got:
P171
P201C
P2029

Wednesday morning from cold. Rough then ran fine when Warm.
Thursday - bit worse.
Friday worse this morning - had it diagnosed this afternoon and it barely made it out of the garage on to the local indi's forecourt! It stalled - start stalled.

The mech. star diagnostic got:

P0172 selfadaptation of mixture formation
Misfiring of cylinder 1 P0301
Misfiring of cylinder 3 P0303

Checked the hoses (they were renewed in recent past) - the ECU plug (oil free)

The car got harder to start and got code: P0010

Been told that it is most likely the chains which have stretched and jumped.
If it is by 3 teeth it can cause damage, if 1 or 2 in with a chance.
Estimated £800 for parts and labour - new kit
But there can be other damage. Cost could rise. Mentioned damage to cat...
First job was to take the top off and have a look at the position markers.

I am wondering if I can tinker with this on my drive.

Would I need new cogs and a camchain kit? Or just a cam chain kit?

The hardest mechanicing I have done was a cam belt and cylinder head on a VW golf - it would take me a while - I have a mobile mech mate who would help if I got stuck. I have a Haynes!

Any Pro advice appreciated.

 

[DSM10000]

Taking the cam covers off will show how much the chain has jumped and allow an inspection for wear on the sprockets. Why did your specialist not do / suggest this?

 

[jpod]

Taking the cam covers off will show how much the chain has jumped and allow an inspection for wear on the sprockets. Why did your specialist not do / suggest this?

Hi DSM, they sure did suggest it, may be I did not make that clear. "First job was to take the top off and have a look at the position markers."

Hasn't been done yet. I am thinking about it. What are your thoughts on it now?

 

[Knightrider2691]

Mate. Understand the price for an inspection before making a decision. It may end up within your budget. Without an inspection are we assuming things? Good luck anyway.

Sent from my H3113 using Tapatalk

 

[jpod]

Thanks Knighrider. I am thinking of towing it home and taking the top off myself - my mobile mate is the Pro - he is here Wednesday servicing 3 cars. If he is really unlucky he will have me as an assistant getting in the way.

 

[DSM10000]

Thanks Knighrider. I am thinking of towing it home and taking the top off myself - my mobile mate is the Pro - he is here Wednesday servicing 3 cars. If he is really unlucky he will have me as an assistant getting in the way.

Take a professional view and then decide. Good luck.

 

[markjay]

Assuming it's the M271 engine... and assuming that the inspection shows that a failed timing gear is indeed the issue... then £800 for parts and labour if quite cheap, I would have thought the cost to be between £1,200 and £1,700 depending on the parts used and the garage.

Keep in mind that at the very least (i.e. if there's no damage to the engine) you'll need a new timing chain, new tensioner and guides, and new camshaft sprocket wheels.

The reason is that the problem arises when the sprockets wear prematurely AND the chain stretches, so simply replacing the chain is a very short term solution.

Now if there's engine damage, then if you're lucky it will only be a few bent valves, but even so it's a head-off job. If you're unlucky, then the engine will also need one or more new pistols, and possibly also conrods, and that's a write-off.

Personally I would invest in diagnosis, and would only consider replacing the timing gear if the engine itself is fine.

Incidentally, I had a lucky escape myself... twice.

The first time was 30 years ago with a Vauxhall 1.8L OHC engine, the crankshaft pully separated while driving on the motorway and the pistons were being turned by the road wheels until the car glided to a halt (manual transmission) on the hard shoulder, while the camshaft was standing still... thanks God for non-interference engines of old. Pulley fixed back in position and timing adjusted at the roadside, and journey continued with no further events.

The second time was some 20 years ago, a Vauxhall V6 engine where the timing belt (not chain) jumped a tooth, engine sounded like a bag of nails but eventually only needed a new belt... and no engine damage. I was told that had the belt jumped another tooth it would have been a new engine. Phew. Plus I wrote to Vauxhall HQ in Luton and they covered 75% of the cost (car was just out of warranty). Result

Good luck...

 

[jpod]

Thanks DSM.

Markjay thank you for the comprehensive reply, and words of wisdom. I understand this is an interference engine! Dohh!

I understand that the test for bent valves is a compression test on each cylinder.

Note what you have both said about diagnosis. Thank you very much indeed for taking the time to post.

 

[markjay]

The tricky part is that you can't run a compression test until you sorted-out the timing. Chicken and egg......

 

[markjay]

You could try an engine leakdown test instead:

How to do a leakdown test | Mobil™ Motor Oils

 

[jpod]

The tricky part is that you can't run a compression test until you sorted-out the timing. Chicken and egg......

Thank you for deepening my understanding MJ. That is really interesting and I will have a read and let it wash over me. Thanks for the link.

 

[jpod]

An update

The mech looked inside – the chain had jumped on the NS by 3 teeth. In this image the crank pulley was at TDC.

It was tight.

He was not keen on a leak-down test but he told me what I needed to know and whether to continue with his service. He was a great help.

Looked in with a boroscope and suspected marks on top of pistons but very difficult to determine. Mech expected valve damage at the very least on the NS.

It has done 105k and is not worth a great deal. I am an amateur mechanic – a hobby I have had it recovered to my home.

Unfortunately, it looks like the recovery guy cranked the car because when it was delivered the bottom pulley was no longer top dead centre and the upper OS sprocket was not longer in alignment and my battery was goosed! It would not recharge – but I will try the repair setting on my charger.

I plan to have a go at a repair on my drive and have the cylinder head repaired - got nothing to lose - I will break it if I can't fix it.

It has only been cranked and has never been driven at speed with the obvious poor running so I hope there is no piston/con rod damage.

The mech said the upper sprockets were fine and did not need changing; it was the chain and the tensioners which let go.

I have been told lots of variations on what to do:

Change the chain and the tensioner on the OS only because it is easier.

Change the chain and all the tensioners – more work – I assume more things need to come off? Supercharger?

So the car is on the drive – it is going to be covered over and stored for a short while until I have had a read and researched and can set some time aside to tinker.

I would welcome your thoughts!

I guess I would change the water pump; oil, filter........

I will also post what I do with pics. My most difficult spannering to date has been a cylinder head and cam belts on a VW Golf – very hard – but rewarding – I am divining the Golf now my main vehicle is kaput.

Why did Mercedes use one chain? And make the chain out of tin? Can this be prevented by just changing the tensioners?

Thanks for those who have posted so far – it is appreciated.

 

[markjay]

Unfortunately a 2005 W203 with M271 engine suffering timing gear and valve damage is commercially beyond economic repair.

I say 'commercially' because if you can do the work yourself and have access to discounted parts you might just about be able to repair it.

Said that, it really depends on how many valves need replacing, and if there's piston (and potentially also conrod) damage.

With regards the timing gear, you do need to replace both camshaft sprocket wheels (even if the mechanic said they "look OK"), the timing chain, tensioner and guide. Not doing so is false economy as the issue is likely to recur.

You can of course take the view that you will carry-out the minimum required to get the engine to fire-up again, then flog the car to an unsuspecting buyer, or just trade it in, but I wouldn't suggest that you do that.

 

[markjay]

As for the single chain... yes it is a weak link (no pun intended), but it does reduce inertia weight, and ultimately there are other single chain engines that don't suffer catastrophic failure at 100k miles.

So the single chain itself doesn't fully explain the problem. The issue is a combination of stretched single chain and worn sprockets.

 

[a111r]

The sprockets look buggered to me, as they look well 'shark toothed'.
That dark residue abounding also tells a tale of the likely causation.

 

[jpod]

.............. then flog the car to an unsuspecting buyer, or just trade it in, but I wouldn't suggest that you do that.

I agree that would not be the gentlemanly thing to do. I have another 271, I am interested in learning about the cars - I like to work on them myself. Thanks for posting the info and always welcome your input.

 

[jpod]

dbl post

 

[jpod]

The sprockets look buggered to me, as they look well 'shark toothed'.
That dark residue abounding also tells a tale of the likely causation.

Will take some better pics of them.

What is the black stuff? It has had a regular oil change in my ownership since 70k.

 

[jpod]

Would the bottom sprocket need replacing?
Water pump?

 

[markjay]

The sprockets look buggered to me, as they look well 'shark toothed'.
That dark residue abounding also tells a tale of the likely causation.

As above.

When new the sprockets look lime tiny equilateral triangles.

When worn on one side they look like shark's teeth, or shark's dorsal fin.

With regards oil, has the engine been serviced with the correct MB-Spec oil (229.3 or 229.5) throughout its service life?