Re: Car damaged by garage during service

watch the video here of a proper job in situ:

Oh wow! How would that take in real time Mr C?

That video is of the mercedes cdi engine which is well known for stuck glow plugs, hence the purpose made kit. If access is good then about half an hour per plug should be enough. But on some engines you need to remove the injection pump before you can get access, so every vehicle is different. The main point is that with the right equipment and skill, glow plugs can often be sorted out without removing the head and taking it to an engineering firm.

Even as a perfeshunal enjinear it took a while to work out exactly what was going on in that video. However having Googled to see what a complete glow plug for one of those ought to look like I assume that the one in the engine broke below the top thread leaving just the bottom part in situ and the thread in the head still ok. The sequence then seemed to be drill, tap, screw in impact puller, pull out broken remains, ream hole for new glowplug.

However if the old plug broke above the thread because it was rusted into place it would be an entirely different problem. So do they normally break below the thread or above it?

It also means that on many vehicles its actually far more cost effective to remove the head than strip away all the other ancillary bits to gain access .

By removing the head you also know that your drilling operation isnt going to bugger up anything else

Clearly not someone who knows anything about engines. Any ancilliary that had to be removed to get access for an in situ repair would obviously also need to be removed to get the head off, plus inlet manifolds, exhaust manifolds, cam belt and much other stuff, then you've got many many hours of head removal and refitting labour, new gaskets and head bolts, the chances that a bad mechanic won't clean everything up properly or screw the cam timing up when refitting and bend the valves. Compared to a 1/2 hour in situ repair it's a no brainer. No one in their right mind would remove the head on a modern FI or diesel engine if they didn't need to.

Different matter on an old A series Mini or a CVH or Pinto. Couple of hours tops to get the head off those if you need to helicoil a spark plug or summat.

glow plugs can seize on their threads, or on the taper seat or just where the hot bit pokes through Mostly the hex is snapped off before the thread, often by amateurs using manky spanners rather than a nice single hex socket and a T bar (which is what I use and so far have not had one break, touches wood)

the design of the plug is such that the size reduces after the thread, so accurate drilling can effectively release the thread on its own, the thread is easily removed as a thin tube (as for standard broken bolt removal), then removal of the rest of the plug is a pull out job after threading the inside where the heating element goes.

I have taken out a few broken ones by welding a nut on the remainder and turning that

Not so Dave in some cars and light commercials to get a drill in to bore out the offending plug you will possibly need to remove radiators , grills , air con , fans coolant pipes alternators , wiper motors fuse units et al , some you wont even get a drill into to do the job or you wont be in a position to judge the angle or depth .

When taking a head off whilst some components will need to be removed others only require one or to fixings to be removed .

Its horses for courses , most garages dont have the machinery to correctly remove and re seat rusted up plugs .

Most 'mechanics' now are fitters not mechanical engineers and wouldnt be able to perform small engineering tasks .

How many garages actually rebuild/ re engineer engines now , i dont know of any , the just parcel them off to a specialist

Yes I agree with you there. I've rebuilt two engines totally (both top and bottom ends) and had the blocks into a machine shop for rebore prior to fitting oversized pistons/rings. The first took me a month because I went very slowly, the second a week because I knew what I was doing. Similarly for gearboxes, strip down, remove the broken parts, refurbish and replace what's needed and rebuild.

Talking to modern car mechanics it's something they just don't do anymore, whereas the old timers of my age it's more bread and butter. Now it's drop the gearbox out, put in a refurb and ship old back to refurb.

Those are nearly always the ones that it's dead easy to get the drill in though.

Isn't that the case with most things these days? My father was a TV/video engineer before he retired, and even 10 years ago was one of the few left who could repair most faults, while other engineers just changed a whole panel.

Years before that, my grandfather, who was a skilled toolmaker, would look at what broke in his car, think it through, redesign it and machine up an improved part!

Purely as an idle question from a rank amateur - when drilling out a glowplug or spark plug without removing the head, how much risk is there of getting metal bits into the cylinder that causes damage as soon as the engine is started after the repair?

I well recall my father dropping a single small washer into the open throat of a carburetter while the engine was running, and the mess it made of a cylinder lining, piston and cylinder head.

I would have thought that a small bit of swarf that fell into the cylinder may well be practically impossible to spot and even less easy to remove.

Very high ...

even a speck, milligrams, could get stuck on the valve seat and lead to it burning ... as another poster suggested, when carrying out this procedure, it's a good idea to put the cylinder in question to TDC to close the valves and shield the cylinder wall ... but the risk still remains. Another trick is to smother the area in grease in the hope it will catch any swarf, but you now what sods law is like ....

I remember going to the garage with my father over 45 years ago and they had lathes and what looked like large drilling machines to a young lad , the engineers thier used to let me watch as they machined and milled parts up for some of the older cars

Went into citroen before Christmas just rows of toolboxes , ramps and a computer system , no pits or beam lifts

Was that airline (used several times) a blower or a sucker? It didn't seem like a sucker to me.

It would be wise to use a miniature inspection camera to check inside the cylinder, to see if any swarf and other crud was lying inside.

Finally, I would flood the top of the cylinder with thin oil, disable ignition (how, on a diesel?), put a rag over the open glowplug hole, and crank the engine for a few seconds. That should get rid of any remaining crud (via the valves or through the hole).

How much gap is there between a piston and the cylinder wall? ISTM that if a small metal filing were to get into that gap and sit on the top piston ring, it may well escape all the above methods, and become dislodged only with the detonation of the first power stroke.

The question really I suppose is whether the risk is low enough to be worth the saving (and risk) of removing the head. Head removal in the only cars I have ever worked on was a quick and easy job, but a look under the bonnet of a modern car suggests that it was designed by someone who was a master at both jigsaw puzzles and tetris ...

Depends how old the engine is!

It depends what sort of filing it is. Filings that are basically "dust" will not, in small doses, lead to any problems - certainly not in the short term, anyway - and are likely to be blown away in the normal operation of the engine. Larger filings (i.e. of the order of millimeter size or bigger) would be far more of a problem, but realistically there is no excuse for leaving these behind.

Lol. BMWs are a prime example.

The last operation seemed to use a vacuum hose as it was inserted in the hole formerly occupied by an injector; the tubing was also rather thicker than that of the airlines I use..

Could ants be trained to remove any swarf that got into the cylinder?

As I doubt that thin oil would wash out a bit of swarf stuck between the cylinder wall and the piston, might it not be a sensible precaution to add some thin oil via the injector hole before the process was started?

Of course, this would mean that the ants would also have to be trained to swim.

the only time that anything can get into the cylinder is after the removal of the remains of the glow plug, the only operation done then is to use a reamer to clean coke from the bore of the hole, some thick oil is put on the reamer first, even if some coke does get into the cylinder at this stage it would do no damage, bits of coke are in the cylinder in any case during normal running and fall off and go out through the exhaust on a regular basis.