No compression one cylinder help

10 Dec 2016
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United Kingdom
Hello. new to the forum so apologies for any mistakes.
Vehicle is a 2004 megane 2. 1.9dci f9q engine.
A long story but the original fault was check injection showing on dash.
Plugged into diagnostics which showed glow plug fault.
Called mobile mechanic to replace glow plugs. found no2 glow plug to have the tip stuck in the block.
the mechanic has knocked the tip through in hope it will get broken up and out of the exhaust.
He's then turned over the engine and greeted with knocking from the engine. approx 10 seconds switched engine off.
Came back next day to take the head off and remove debris. no 2 piston showing signs of wear. no holes but scratched and metallic silver colour compared to others. he has told me this wasn't due to the glow plug going through but the damage it has already caused by overfueling in the cylinder .
Checked head for any damage and concluded no damage to valves etc. although was in the dark.
Started engine and seems fine. no knocking, idling fine etc.
He then spots oil loss and realises a seal has come off the turbo return pipe upon refitting. after replacing the pipe and oil he then starts engine again. it now has hardly any power. and low idling. taken to an injection specialist who has performed a compression test to find no compression on cylinder 4. or as I'm told no1 as French are reverse order. so no 2 (or 3 ) is where the glow plug went in and no 4 (or 1) is where there is no compression . I'm told the glow plug incident wouldn't cause no compression on another cylinder. so my question is.. what do you think could have happened to it.
Do I give up and scrap the car. or do I try and fix the problem? thank you in advance and please ask if you require any further information .
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Certainly its a bizarre thing to do - allowing metallic parts to enter the cylinder :eek:
I'd say there was a huge risk of damaging an exhaust valve, and if it passed through that there's the turbo next in the way to be destroyed.
However, this still doesn't explain why another cylinder has now lost compression so either something has entered by the EGR system or the engine has ingested some other metal part.
Is there any possibility of the timing belt being put on incorrectly, do you think?
Cylinder head off again I'm afraid......the oil leak does seem like another red herring as you mention the oil return which is a low pressure drain back into the sump - at the back of the engine.
John :)
Given that the "mechanic" has had the head off, and clearly knows geoff-all about mechanical sympathy, perhaps the head surface, head gasket or block surface have been damaged to such an extent that that cylinder won't hold compression. Though when you say "no compression" do you mean not enough to ignite the diesel, or None at all?

I imagine the engine really enjoyed the 10 seconds of knocking too :eek: The F9Q is a fairly tough traditional diesel, common rail.
Surely a job like this is well outside the scope of mobile work?
John :)
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Cant quite believe what I've just read, did the mechanic arrive on horseback? Had a Volvo truck at work a few years ago, the original FL6's had a preheat system on them for cold starting. Driver reported one morning pre heat lamp was still flashing and wouldn't go off, was told by the boss's son it'll be fine, just go. He got about a mile.... Appears glow plug got so hot, the tip fell off, piston hit it on the way up, and so something had to give.

Con rod snapped and went round a few times knocking holes in both sides of the block. New engine time.....
I'd guess a valve has dropped on that cylinder, unfortunately - unless the engine has inhaled something and punched a hole in the piston.
As its direct injection, the combustion space is machined out of the top of the piston itself.
Head off time!
John :)
I imagine the engine really enjoyed the 10 seconds of knocking too :eek: The F9Q is a fairly tough traditional diesel, common rail.
Surely a job like this is well outside the scope of mobile work?
John :)

If the scope of the mobile work is to turn over the engine in order to mash up pieces of glowplug, then I'm sure than can be done any where, any time!
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