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2.7 Glow Plug change in situ ---- just not worth the grief ??
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onthecut   
Wed Mar 06 2019, 10:07am
Joined: Sep 20 2016
Member No: #2793
Location: West Mids
 When I first acquired the C6 I dutifully did the cambelt, thermostat housing etc., but not the glowplugs. I susequently kind of regretted not having done it all, so when recently the 'stat housing started weeping past its rear O ring (aaargh !), decided to get stuck in and change them.

Bought the replacements in advance and noticed they are quite long and pretty thin, so force not the order of the day. For reasonable access to the plugs you need to remove the air intake Y piece, oil filter top and breather box assembly (adjacent to the back of the fuel pump) On mine atleast, the breather basically just prises up and off. Two legs into seals in the valley and two legs into a hose assembly.

My initial feel of the plugs suggested three averagely stiff, two very stiff and one not stiff at all. In reality it turned nto a sod of a job. Gave them all a good and repeated dousing with Plus Gas, then the fun started. On all bar the free one it was a case of very small to and fro turns, listening to the horrible squeaking of tight threads. Essentially, even when the threads were clear of the head, the plugs were still significantly tight in their bores and required hours of manipulation to satisfactorily extract.

Then -- third plug, still in its thread, snapped. No warning, applying minimal force, socket suddenly just going round and round. Decided to get an extraction kit. Looked at the £30 Chinese stuff but decided on a proper Sykes set. They work on the premise that you extract the centre electrode, use a special dual size bit to drill part way down the plug, tap a LH thread, fit a supplied bolt and then slide hammer the thing out. All a great idea --- except on mine, the electrode sheared at the top, not the bottom. This is a drilling nightmare ( to me at least).
The electrode is about 2.5mm inside the (approx) 5mm bore of the plug. Had a sleeve machined to hold it central, but even so, drilling seemed to cease making any progress about half way down. Enough to start using the Sykes tool, but nowhere near enough to use it correctly. Totally fed up by now, decided on the 'easy' job of refitting the remainng five new ones. Dream on. They are almost as big a pain to refit as remove. Using the excellent 8mm tap in the kit, well greased to catch any nasties, cleaned the threads. It then took further hours of
offering them in and out, countless times, well lubed with plus gas, WD or a thin spray grease -- tried them all --- until they would screw down their threads with minimal force. Each time I pulled them back to wipe them clean they fetched out another smear of carbon based gunk.

With them all back in and as the broken one had only moved a fraction of a turn, decide to refit any crucial bits and fire up the engine to listen for any blow by on any of the plugs. Didn't fit the connector rails to the plugs. Fired up on the button, sweet as can be.

So -- all that grief and it doesn't even need them to start cold. What a waste of time. Yes, I know they also play a part in the early minutes running, but quite frankly I'd take a chance on missing out on whatever supposed benefit that offers, as the hassle of the job just doesn't seem worth the end result. I do wonder whether perhaps my plugs had been previously changed and not refitted quite correctly, allowing a degree of blow by up the edge of the body, causing deposits that then make them tight in their bores.

In the end, decide to leave the broken one as is. If it happens to blow out the core then will press on with the tool. If not, it doesn't appear to make a jot of difference to the starting or running. Would I do the job in situ again ? Absolutely not. Would I change them if the head was off ? Yes -- being able to access the lower end would make a massive difference, plus any machining detritus can be readily removed.

Mike.






e3steve   
Fri Mar 15 2019, 02:20pm
Joined: Jan 21 2013
Member No: #1163
Location: Warsash, Hants & Palma de Mallorca, Spain
 I had the same experience! I decided to change mine on the 2.7, back in 2014 and “while I was in there” doing another job in the vee. Jeez, what a faff!

The answer is: go in and do just the glowplugs! They will unscrew successfully, but only if the engine is hot, so you need to gear up to carry out the task after an hour’s driving or so.

Thanks to Speedfix for the “get it hot” heads-up!!
 

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