Advise - Am I being taken for a ride

[Robbys89]

Why would a head need skimming?
Original problem was chain, likely sprockets and guides,
a lack of experience is shown already when they weren't aware that this lot is at the back, of what I'm assuming to be a 251 lump.

But the car was running well before the known issue regarding the timing chain occured.
No overheating, I assume, as it stopped and refused to restart.

My take is the chain, guides, sprockets in whater ever order went bye bye.
Garage removes head to replace faulty kit,
but for what ever reason the head gasket didn't seal.

I see no reason for the head to be warped, but always willing to learn.

Regardless of overheating or not it's good practice to skim the head after removal, any reputable engine builder will tell you this, there is a fine tolerance of warpage a head gasket can take and after many many heat cycles and the unloading of the headbolts chances are there is some uneven surface across the head even if in the tolerance range it's a 50/50 gamble if the new gasket will take... Where as a fresh truly flat surfaced head and new gasket will perfectly mate.
But then there's always the question on the surface prep, block and head been fully clean and all old HG material removed etc etc

 

[stephenmercedes]

Eventually, you'll need to make a tough decision. To keep the car, or not. I have an ageing Celica GT4 which has cost me literally £1000s in repairs the last few years. However, just before Christmas my handbrake failed. Thought it just needed adjusting, but on a ramp, there was clearly issues with the braking system including seized brake calipers. (on a GT4 a refurbed caliper is over £200!). Also, both sills now need remedial welding to pass a future MOT. And the suspension has started to squeak indication more money. This was the straw that broke... The car is now up for sale as I really am tired just pouring money into a car that no longer gives me any pleasure because it's just one bill after another, and I'm just an ordinary 'Joe', not rich! LOL Breaks my heart as I've had her 15 years and imported her personally from Japan.

However, on reading your post, I know my experience is nothing to do with the faults you have, but the emotion of running a car that is constantly giving issues is heartbreaking - I feel for you buddy...

 

[Bellow]

Regardless of overheating or not it's good practice to skim the head after removal, any reputable engine builder will tell you this,

Beg to differ.
Unless there is warpage, there's no reason to skim and reasons not to. Skimming affects the length of slack run on the timing chain, affects the valve timing, alters the compression ratio (on a petrol). It isn't clear to me that the OP's engine isn't a diesel - or clear to me that a diesel head with valves flush (or very nearly flush) to the head mating surface can actually be skimmed. Can it?

 

[Bellow]

This thread has 'assumption and lack of forward thinking' writ large throughout.
The radiator failure may well be mere coincidence - or possibly weak (or weakened by mechanic damaging it) which then failed due to higher pressure caused by whatever issue is currently present. (You could ask for the old rad back to investigate further).
At the early stage, someone in the process should have envisaged the (very high) probability of valve and piston clash. If it hadn't occurred during chain failure then the attempted restart would have likely brought them in contact. Unless the engine is known to be a 'non-interference' engine (and they are rare these days), valve damage should have been suspected. That this was missed is deplorable.
To the current problem. Many of the assumptions in the thread as to the cause may well be true. Equally, I couldn't discount the possibility of more serious head damage due to the impacting of the pistons into the valves such as a crack in the head. Nor is it entirely unknown for pistons to be damaged when they make contact with valves (though that wont cause coolant leaks).
I view this as a failure on the garage's part to not inform you in advance of the possibility and high probability of the damage subsequently found which if they had would have given you other options eg, engine replacement or scrapping. Had they done so, you could have then decided whether committing £2.5k to repair the damage was your preferred option given the possibility of further (hard to identify) damage. It is on this basis I would go back to the garage and have a frank discussion on just how they imagined timing chain failure could cause no internal damage, strongly suggesting they did actually know but enticed you into the large repair bill with the lower initial cost. I suspect you are barking at the moon pushing the 'skimming' issue as unless warpage has occurred (and is invariably a cause of overheating) or corrosion/erosion damage (due to already failed head gasket) is present, absolutely there is no reason to skim.

 

[RGRA]

In no way and expert but did you experience any serious overheating during the coolant loss phase? Suggest you take it to another garage to have the cylinder head checked. Cracking or warping could explain the gasket seating issue. You do need independent eyes on this issue. WRT who is culpable, as previously mentioned your current garage should have warranty for their repairs, so if they are at fault in the way they have repaired/addressed this then you may have some recourse.

 

[Robbys89]

Beg to differ.
Unless there is warpage, there's no reason to skim and reasons not to. Skimming affects the length of slack run on the timing chain, affects the valve timing, alters the compression ratio (on a petrol). It isn't clear to me that the OP's engine isn't a diesel - or clear to me that a diesel head with valves flush (or very nearly flush) to the head mating surface can actually be skimmed. Can it?

When there's no warpage outside the tolerance specs a skim can take only tenths of a mm, less than the thickness of a sheet of paper ensuring a fresh clean surface for the new gasket to seal too, now giving chain and belt tensioners making up for any extra slack it's not really going to effect anything, along with the ECU adjusting for any change via timing sensors, carbon buildup withing the cylinders would have a bigger impact on CP ratio then a skim, but I do see your view on it, I'd certainly be skeptical of skimming if it did have a previous skim

 

[400ixl]

Skimming should only be done if the head is out of tolerance, you don't want to remove the hardened surface if you don't have to. You can only skim a certain amount from a head as well.

If the car was driven with a coolant leak and being topped up on that regular a basis, it could well have cooked the head, resulting in warping post the head gasket replacement.

 

[219]

I think they meant skimming the head. They probably used a pattern part head gasket- not a good idea.
TAKE YOUR CAR TO SOMEONE WHO KNOWS WHAT THEY ARE DOING.

Indeed - the fact that they initially said it was a timing BELT issue shows that they don't know much about Mercs .

Unless some very recent ones differ , Mercs use timing chains .

 

[219]

OP - I see you're in London . There are plenty of independent Merc specialists down there - take it to one of them for an assessment . Some of the members on here will be able to recommend a good place .

If this other garage has messed up your car and charged you so much , you need proper evidence so that you can take them to small claims court to claim the cost of fixing the car properly somewhere else . The other garage should pay since they charged you so much but failed to do the job properly ( otherwise you wouldn't be having this trouble now ) , but it is unlikely they will cheerfully do this when you ask .

Do you have legal assistance cover with your insurance or bank account ?

 

[livingthedream]

Many thanks for all your comments, some very detailed feedback which helps, I feel my hands are tied somewhat, I can't really do anything other than put things right, they have already indicated that it takes days for this overall so the inconvenience is a major issue (but again they are giving me a courtesy car)

I appreciate I have very little grounds on the Rad repair, just seems extremely odd, as I only returned the car back to them after the coolant warning, as I located many comments about being possible head related, which they say no it wasn't and now yes it is, possible coincidence? I don't know and what can I prove

The sad thing is the timing belt went a week I was going to upgrade the car, couldn't be more badly timed! excuse the pun!

I just want a working car! and after £2.5k worth of repairs I think I should have one really!

 

[Bellow]

The arrangement that saw you place the car with them for (full) repair should be honoured. That is, what has already been done (valves, etc) and with a sound, leak free union of cylinder head and block. If/when they achieve that, then you have what you paid for.

Radiators fail - on their own whim, timescale. I've not heard of one failing due to headgasket failure but not impossible if pressure level elevated sufficiently. You could ask for a refund on that basis but if it's found the coolant is leaking to anywhere but a cylinder - then they're off the hook. I'd concentrate on getting to the situation outlined in my first paragraph.

 

[QUTSELL]

Technically if the head had to be removed because of a valve train problem the head should not have warped [ no localised overheating] if it was removed and replaced using the approved technique---were the head bolts renewed for example? --- often these are of the "stretch type" designed to be deformed once only ---tightening by use of a torque wrench setting followed by an angular torque final adjustment. Coolant loss on those OM 651 engines is often due to the plastic water pump leakage.
As previously advised make sure the head gasket is the true cause coolant loss. Sounds as if the garage are trying to solve this problem by throwing your money at it!

Correct head bolts need replacing, and torqued in sequence, possible cause of head problem ?.