Serious siezed glow plug removal problems on a merc... your thoughts please.

[chizzel89]

No 4 glow plug was sheared off when I bought the car. The hex just spun round, wobbled side to side but the plug wouldn't unscrew. However it still worked, so I left it be.
I decided to tackle this and booked it in with a Merc specialist who said he'd removed plenty of sheared plugs.
This is the chain of events:
Top of glow plug outer removed along with a good chunk of the electrode, creating a drilling guide. Original thread largely preserved.
Mechanic then tapped a thread in the glow plug body/casing and screwed in an M8 bolt. I was hoping he'd then attach a slide hammer to this and knock the plug out, but instead he tried to dislodge the end of the plug by tightening the bolt, and levering against the head with pry bars in an effort to pull it out.
On tightening the bolt again trying to twist the end of the plug out, it sheared off in the end of the glow plug.
He then tried to drill into the end of the sheared bolt to use an extractor on it, and the drill bit broke off in the end of the bolt too.

I suppose the only hope now is to continue to try and get another m8 bolt in there and use the slide hammer which should've been used in the first place?

Can the pre-chamber be removed with the glow plug still in?

He's told me now that the head needs to come off.... probably near a £500 total bill. Nightmare. I just don't have that much money. I will have to release some savings bonds prematurely.

Can the glow plug definitely be extracted with the head off anyway? Or may I need to find another head with less unfortunate attempts in removing stuck glow plugs?

What is more annoying still is that there's a £917 bill from 8 years ago, for removing two stuck glow plugs, one of which is THIS VERY SAME ONE!!!

I noticed a crash damaged C250 TD saloon on ebay with 70,000 miles on it. I'm wondering if I'd be better off trans planting the engine and box out of that into my car (the box on mine is making some slight mechanical noise)...

I have a car lift and tools, and did the head gasket succesfully on a 1.9 Peugeot TD engine last week. SO I think I could do the job, but at the same time I need the car to get around and I'm not sure how much of this glow plug fiasco is my fault (shearing bolts and drills in the end of the plug etc).

It's all a bit confusing really... I don't know which way to go!

Any thoughts much appreciated.

 

[Dieselman]

You can't get the pre-chamber out with a plug in it as it needs to turn.

Just keep drilling.

 

[martyz]

Your idea of an engine swap would seem to be the quickest perhaps cheapest route,and resolve your gearbox issues at the same time,and 70k is baby mileage too!

 

[EasyManHugo]

Don't know where you're based but had a couple of glow plugs removed by these. Was very pleased with the service. They have alot of experience with mercedes vehicles where this problem seems to be common.

Contact Price Bros

 

[chizzel89]

Cheers for that recommendation EasyManHugo. Will bear them in mind next time! I actually spoke to them on the phone. Very helpful.

On a positive note, the broken drill and the sheared bolt have been removed but the other extraction techniques have been tried to no avail.
The plug just will not come out. I'm glad I have confidence in the mechanic again though!!
Lots of slide hammering actually stripped the thread which had been cut in the glow plug it was that stuck. So the glow plug was helicoiled and a stud screwed in again. A puller was improvised using a socket and bracing against the head, and after a lot of cranking a big chunk of the glow plug tore off, helicoil and all.

The drilling is still perfectly on course, so the next thing is to drill all the glow plug away apart from the last few mm so as not to damage the tapered sealing face.

The suspicion is though that when the head came off 8 years ago to remove two stuck plugs (including this one), the machine shop who did the work damaged the sealing face for this plug and semi glued it in with loctite or similar. The is further supported by the fact that although monumentally siezed, the remains of the plug are not gas tight. If you spray easing fluid into the GP hole with the engine running, it immediately starts sucking in the fluid and spluttering and knocking.
So maybe they mangled the seat, covered the sealing end of the plug in some compound or other and then torqued it in so hard that it sheared.
The other plug they extracted was a bad job as well, though the head still accepts a glow plug ok but the head is extremely traumatised around where the plug was- lots of punch marks. Looks like they lost a lot of meat from the head whilst drilling and punched the soft alu from around back in to cut the thread into again. Shocking.
Will post tomorrow once the remains of this plug have been drilled away.

Dieselman- is the tapered sealing face for the glow plug in the head or in the pre-chamber?

thanks

 

[chizzel89]

Your idea of an engine swap would seem to be the quickest perhaps cheapest route,and resolve your gearbox issues at the same time,and 70k is baby mileage too!

The drag is that the car has no MOT and isnt really driveable, and is 170 miles away! So even if I got it for say £400, I'd still have to trailer it back which would cost near £200 probably.

I've since found another good candidate with 124k miles, but with an MOT. It has MOTs to back that mileage up. Will do my best to get that one. Although I can't really afford to invest in a donor car right now, I think it's nearing the point where I can't afford not to get one! I really like these C250 Sports... really nice cars, when they aren't spitting K2 gearbox bushings and refusing to give up their glow plugs. Its done over 20k miles on mostly 100% WVO and it has never missed a beat. The engine is sweet. So with the huge fuel saving I don't mind sorting its issues out even if they are a hassle.

 

[chizzel89]

Update. SUCCESS!!!

IT IS SORTED!!!!

After drilling down to about 5mm away from the combustion chamber, another thread was cut in it, this time really really deep. Another high tensile stud screwed in, slide hammer on the end. Initially it sounded solid, like we were trying to knock off the cylinder head. Then after 3 or 4 good hurls of the slide it suddenly sounded hollow and came out!

The seat in the head looks ok. No gouges. So we quickly reamed it out, sprayed the new plug in some kind of coating he had, and screwed it in and threw it all back together.
I'll be rebuilding the lift pump in a week or two so I'll have it out again and check the seating more thoroughly and ream it more (to get rid of any carbon) if need be. Is copper slip ok to use? My theory is that if the plug has an enormously thick coating of copperslip, there won't be room enough for the carbon to pack in there should it not be seating perfectly.
Anyway... glow plug issues sorted

 

[Dieselman]

Copperslip is Ok. The reason the plugs stick is because they don't seat properly due to either inadequate torque or dirty seat.

Always ream the threads AND seat when installing new plugs.

 

[chizzel89]

Well, the car nearly caught fire yesterday. This was because he supplied inadequate spec hose for the injector leak off pipes. Over 25 miles, this hose softened and plasticised and popped off no5 injector (the end cap one). This filled up all the injector recesses in the head with hot diesel/veg oil mix which then slopped over onto the hot exhaust manifold when I went round a sharp corner. LOADS of white smoke. How it didn't catch fire I don't know.
So I managed to patch it up at the road side somehow and limped home with smoke coming from under the bonnet, pulling over every 3 minutes to check the injector pots werent filling up again (I happened to have a vetinary syringer in the car so I was able to suck most of the fuel out of them).

Fuel all over the engine, underside of the bonnet, inner wings etc etc. A tiny drop even found its way past the cap on the end of the trans dip stick. Gearbox seems fine though. I doubt a couple of ml of 70% derv 30%WVO will do it any harm, I hope.

I've wiped off all the rubber coolant hoses as I thought they'd be the most vulnerable to damage. Anything else I should do? It seems to be drying up now, but the car still stinks of Derv from about 10 feet away.

So, it seems I owe this specialist Mechanic £320 for extracting the glow plug in a long winded manner (he dropped it out that his initial use of twist-in extractors spread the stub of the glow plug a bit, making it tighter still in the head) and nearly causing my car to burn down. Just goes to show that paying an experienced and recommended mechanic £50 an hr doesn't guarrantee a professional service

 

[Dieselman]

Oil onto a hot manifold CAN catch fire, but it's very difficult to ignite diesel without either atomising or a wick.

You say you are running veg oil, in which case i would be concerned for the gearbox, as I doubt the seals and lockup clutch adhesive will like vegetable ester.