Sorry tale of glow plug replacement - what next?

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Ian Donkin

Active Member
Joined
Dec 8, 2009
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566
Location
A Yorkshireman in Surrey
Car
'57 plate ML420CDI
I needed the glow plugs changing on our E-class (mines the OM642 V6 variant) and out of convenience entrusted the work to a mechanic in my local village as opposed to travelling out. I’ve previously seen him rebuild a customer’s Merc 3.0 V6 petrol when the bearings failed and he’s always working on expensive cars, so I believe(d) him to be highly competent.

Long story short with my job, one of the glowplugs had taken a permanent fancy to the surrounding cylinder head that necessitated the removal of the left bank and subsequent machining to remove all the debris - not exactly the sort of costs anyone would wish to incur to change a £10 part, but I was assured that everything had come apart without difficulty and all the components (turbo, timing chain, cams, cylinder bores, pistons, injectors, valves, inlet manifold and flaps, etc.) were perfect so at least I felt happy that everything was otherwise good.

Almost three weeks later my car was ready and now had a sound at tickover rather like a family of crickets having a party around the aux belt area. Once the aircon was turned back on however the sound disappeared, so this noise was attributed to the compressor and I was dispatched on my way (it must be all of 800 yards back to my house).

I turned on to our private road and gave the throttle a prod only to be met with the sound of a boost leak so back to the mechanic we go. I should also note that the pipe from the turbo to the intercooler didn’t look right as there’s now a ‘shiny’ section where the turbo and pipe join together and it looks out of place with the patina on the rest of the aluminium in that area. I suggested that this couldn’t be right and the mechanic agreed, but pointed out that as everything could only fit in one place (fixed bolt holes etc.), it must be correct.

Two days later I get my car back again with a new seal fitted in the aluminium pipe from the turbo to intercooler, but it still felt both laggy and a little flat when accelerating, plus I now could hear a turbo whistle for the first time as it started to produce boost. There’s still a section of exposed shiny metal and the plastic air intake from the filter housings is now broken at the turbo end, so a part of the seal is visible between the jubilee clip and body of the turbo.

Breakages aside, the mechanic had already suggested it didn’t feel right, but to drive it and see what I thought. Fortunately I’d recently had a Surrey rolling road session so went back and sure enough, the car was around 50ftlb down on torque and the plot lagged the previous runs by around 400rpm – boost leak came back the observation from Charlie.

Back to the mechanic for another day and the leak (found where the aluminium pipe connects to the plastic / composite pre intercooler, that hadn’t been seated correctly) is now rectified and I finally have a lively car. However, driving the same 800 or so yards home I experienced a new noise that transpired to be the undertray scraping along the road with three of the four securing bolts missing. To say I’m starting to lose my patience at this point would be an understatement.

A quick fix later and an uneventful commute to work and back the following day I had managed 50 or so miles with the car since the rebuild however it’s back with the mechanic as the mother of all metallic rattles that can be heard over everything else has suddenly started around the fuel pump / timing chain area. He’s offered to pull the fuel pump, investigate with a camera and report back.

His bill included 15 hours labour by the way and I understand the book time for a cylinder head removal / refit is 10 hours so I don’t think he’s been short of sufficient paid time to do the job properly.

Looking to the positives (!) the O2 sensor replacement also carried out (all MB parts were used throughout the job) has removed the dip in the torque curve after peak that my first rolling road session highlighted and the exhaust is less sooty (so much as it can be after 50 miles).

I’m pretty sure this saga isn’t over yet, but what are the collectives thoughts here. Are there lots of specialist tools needed to complete this job that I can ask him to show me (as proof he was correctly geared up to the task), or specific alignment procedures for the timing chain / tensioners / cam sprocket, etc. that he could have got wrong?

I’ve already paid (on the one day it seemed good) and by bank transfer so I can’t leverage a s.75 claim with my credit card, but what is the likelihood that having given him a car that he acknowledged was in such rude health on handover, I should now have problems that I can only believe are related to the work he has done in the same area of the car?

Any appropriately qualified input would be appreciated.
 
Any job that requires significant removal and work has an element of issues afterwards. It might be best to lend him the car for a week to shake it down.

It doesn't sound like He's done anything wrong, just not been careful enough on the rebuild.
 
Yup .......... sounds like he needs to have the car back for some "adjustments",
after such a strip down its wise to break in the new work done "onsite" rather than let the customer find any problems.

I'm sure there's similar stories from MB main dealer workshops similar to your present experience.
 
So the timing chain tensioner has failed... Even I can compress it with my weedy hands. An unhappy coincidence or is it possible to damage these during the removal / refit procedure that was necessary to allow the cylinder head to come off in the first place?

I only hope replacing this sees an end to my woes...
 
My first question has to be, why was the cylinder head removed?

We extract seized, sheared and bodged glow plugs in the OM642 in-car, with about an hour for each plug, although they can take less or more depending on access, but usually removing fuel rails is the worst of it.

Have a look on Youtube and you will see several vids detailing this procedure.
 
Just to close the loop on this one - the replacement chain tensioner did the trick as I've since done approaching 1,000 trouble free miles over the past fortnight and everything is back to how it should be. If only they'd given it back like this first time!

Having said that, I'd had my head turned by an amazing spec W212 whilst this was being repaired so it looks like someone else is going to benefit from my expenditure.
 
Hi

My 518 sprinter with the OM642 engine has 3 ( at the last count) faulty glow plugs

I would like to get these changed but worried about the extra costs / damaged should they snap

I read with interest that alexander patie reports :-

"We extract seized, sheared and bodged glow plugs in the OM642 in-car, with about an hour for each plug"

I would be interested to know more ( are these using heli coils ?) there are some tools on youtube that I have seen that remove the broken plugs with out damaging the original threads in the heads

alexander what do you use ?


my local MB commercial dealer told me not to bother changing them as it was too much of a risk in them snapping !


2008 model with 30k miles
 
just changed our 2001 cdi plugs with 400,000 on the clock no probs and last year our 2007 315 again with no probs, my advise take your time be ultra careful and get the engine hot before attempting. Our vans although high milage are on long distance work though it may not be as simple for vehicles that are on local top start work
 
in a moment of madness I attempted to remove my three faulty glow plugs (1,2 & 6) on my OM642 V6

after applying gasplus a few days previously & by getting engine upto operating temp plugs 1 & 2 came out ever so easily

Plug 6 didn't want to budge even with considerably more effort than 1&2 needed

Only using 1/4" drive 6" extension and a small Tbar & a deep 8mm socket as I don't want to snap them off

thought I would try one of the others ( ideally I would like to change them all out for new)

so had a go at no 3 which needed more effort than 1&2 but not as much as I had tried on 6 - it started to move & as it needed a bit more effort I applied more gasplus & gentle rotated it back & forth as it was sticking , when I got it out I could see that it had picked up some of the aluminium from the head on the 3rd & 4th threads down from top which could actually be the top two thread turns on the block . Fortunately the new plug went in though not quite as easily as 1&2

so now concerned about attempting no 6 again

can any one recommend any specialists near South Wales UK with the specialist extractor tools ?

found Extract Engineering who has some fancy high frequency vibrating tool (Vibropac M40) but he is in Carlise

has anyone experience of this type of tool ?
 
I would soak it in wd40 the night before and then get engine up to tempt and try #6 again might be lucky and it comes out if not and it breaks then source a guy with a tool to rectify the breakage. Never know you might just get it out without the expensive of using someone
 
Thanks guys for Your replies

From my experience with my no 3 plug picking up some of the aluminium head thread and that all the plug tips didn't appear sooted up I am guessing that my no 6 is also stuck at the threads and not due to carbon build up
Both 3 and 6 are at the back of the v6 so I wonder if there is a connection


I have already liberally applied gas plus , would wd40 be any better as a penetrating agent ?

That Sykes pickavant tool looks just like an air impact driver - is there anything special about it ?

Would it be worth me trying my bosch cordless impact drivers ?

I don't want to brake this off !
 
You obviously didn't watch or understand the video
 

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