Xantia loose spark plug and slipped aux belt

hamster · Post by **hamster** » 27 Dec 2010, 14:03

Drove 250 miles from Southampton to Bolton yesterday and all seemed fine apart from a little rattling when we arrived which I thought was my exhaust brackets rattling a bit as drove like a dream as usual.

Just got in to pop out and started ok. After 200 yards put the air con on to demist. As pulled out of a junction at same time, there's no power And an awful rattling and blowing noise and smell and no power to pull away. Managed to hop put of junction onto pavement. Start to investigate an find a plug has worked loose which would explain the rattle and blowing noise. Just like James may's BMW on top gear las night. Put it back in although thread looked a bit knackered and started ok so drove 300 yards back home.

Pulled plugs out again to check them all and just about to replace them but at same time saw that the aux drive belt has slipped across a groove on the belt as well. So goin to change this as well.

What has causes this? Are the two related?

Car has run fine until now and has plenty of oil and antifreeze in it. Got to dive back down south on wednesday and don't want to do it on back of as truck.

Xantia 1.8 16v 99v reg

Post by **CitroJim** » 27 Dec 2010, 14:44

Nope, they won't be related but damaged plug threads in the head are not unknown. It's a relatively straightforward job for a good, competent engineering firm to helicoil the plug thread and often they can do it without removing the head.

The aux belt may be worn but more likely there is a misalignment on its run due to a bad tensioner or a collapsed bearing in the aircon compressor. have the belt off, check all tensioner jockeys and give the aircon compressor pulley a good tweak to make sure spins without noise and has no play in it.

Hope that's the only thing it's caught from James May and TG last night. Just be careful with tow-ropes...

The baby Stig bit at the end was brilliant

HDI · Post by **HDI** » 27 Dec 2010, 15:23

check the crank pulley also.

hamster · Post by **hamster** » 28 Dec 2010, 13:41

Upon changing the plugs I found that the plug that had come loose had totally stripped its thread from the head block meaning that the new plug won't go in

Obviously not the best time for this to happen on a double bank holiday with all garages etc clossed.

If its going to work again it'll need a new head block or the old one repaired with a helicoil or such like. Where do i start looking for places to do this when everything opens tomorrow? Local garage or somewhere a bit more specialist? Only got limited space and tools here so its going to be a garage that does it for me or a tow truck 250miles home so i can attempt it.

Also worried about what has happened to the old metal that was the thread. its no where insight so can only assume its gone into the cylinder and out throught the exhaust causing inknown dame somewhere along the way.

Any thoughts?

HDI · Post by **HDI** » 28 Dec 2010, 13:54

It is possible to helicoil a plug hole with the head in situ, I have done it with total success in the past. Care is needed but any decent garage should be capable.
My basic technique is to get the cylinder in question to TDC with valves closed, do the helicoil, then use a vacuum cleaner to suck out most of the swarf. Then before reinstalling the plug, run the engine for 10 or 20 seconds, this will blow out the remainder without it causing any harm.
Without and endoscope there is no way of knowing that all of the debris is removed but it is aluminium and any small amount of remnant will be blown out quickly when the engine is run.

dnsey · Post by **dnsey** » 28 Dec 2010, 13:59

You'll probably find the remains of the thread wrapped round the plug thread. It's often difficult to see, as it can form a tightly-coiled 'spring'. Be careful - it might be quite sharp, too.

A good old-fashioned garage (not a filling station, quick fit place or main dealer) should be able to helicoil the head. An automotive engineer would be ideal though - it's bread and butter work to them. Failing that, a small general engineering shop would be able to do the job, provided they have the correct size coils and fitting kit.

I'm curious to know how they temporarily fixed May's plug!

HDI · Post by **HDI** » 28 Dec 2010, 14:05

dnsey wrote:I'm curious to know how they temporarily fixed May's plug!

I know how I would have done it

andmcit · Post by **andmcit** » 28 Dec 2010, 14:25

Didn't they say the plug was glued in? Nothing would surprise me with their
irritating blatantly juvenile behaviour; sadly watching this laddish programme
seriously winds me up! A bit of men behaving badly/carnuts being stupid
that ought to know better.

Andrew

Post by **CitroJim** » 28 Dec 2010, 20:39

HDI wrote:
dnsey wrote:I'm curious to know how they temporarily fixed May's plug!
I know how I would have done it

Chemical Metal? That would count as glued in I guess Andrew.

Later on in the show it was most likely properly Helicoiled. Those places they visited may have looked a bit basic but in every town out that way there's always a very competent engineering outfit hiding away.

They did a good job of the Beemer's head gasket back in Iraq. That never failed again and it got some pretty thorough testing.

The secret to enjoying TG is to not take it seriously. James May's injury was real enough though.

I really enjoyed the Boxing Day episode..

Deanxm · Post by **Deanxm** » 28 Dec 2010, 21:07

I think they just stuck the plug in with plastic metal, ive done it a few times on outboards, motorbike engines and my Dad done it on his stag before the engine rebuild......they dont come out again

.
James may actualy sorted that head out himself, same as Hammond stayed up all night with one of the behind the scenes guys to strip his vauxhall after he drowned it in Africa.
Every time i see one of these episodes it gives me the urge to go off and do something like the mongal rally or somesuch event, might be doing the round britain endurance next year.

D

the_weaver · Post by **the_weaver** » 28 Dec 2010, 23:00

I had a spark plug thread go on a Peugeot 405 (petrol). I took it to a place that specialised in rebuilding/reconditioning engines. They did it without removing the head.

Paul

hamster · Post by **hamster** » 29 Dec 2010, 01:31

Ok so we're walking to the local garage in the morning to see what they say about getting me back on the road.
If they can help me out and fix things, how long can I expect it to last with a helicoil or such fix?
Is it a short term or long term fix?
Should I get them to check the other cylinders? It mist have happened for a reason and as said previously temp has constantly been on 85 and never higher.

If it's not looking good, replacement wheels have been sourcednon autotrader!

andmcit · Post by **andmcit** » 29 Dec 2010, 01:59

If done properly by a decent old school garage, a helicoil will last years
and many 1000's of miles. Just don't go so wild tightening the next plugs
up when they're changed!

Andrew

HDI · Post by **HDI** » 29 Dec 2010, 10:04

If done correctly a helicoiled thread is better than the original !
Many motorcycle racers helicoil plug threads as a matter of course due to the number of times they need to remove plugs.

The stripped thread on your car was probably caused by a ham fisted mechanic during a past service.

handyman · Post by **handyman** » 29 Dec 2010, 11:16

Wire thread inserts (the correct term) will last indefinitely if installed correctly. They can even be replaced easily if worn. They are used as standard in stressed alloy components in the aero industry.

The reason why the threads go on these heads is due to the type of aluminium alloy used in their manufacture, the grain structure and the size and shape of the thread form. I have found the problem is usually caused by the thread being over-tightened or crossed when being installed. Sometimes the thread seizes onto the plug and when removed, it is stripped from the head.

I have done quite a few thread inserts on Citroen and Peugeot cylinder heads, most with the head in situ. With a bit of care, any swarf that enters the combustion chamber does no harm and usually disappears out of the exhaust port PDQ. As the alloy is very soft, any contact with the valves or seats will not result in any damage.

PM me if you get stuck as I keep a whole range of wire thread inserts in stock, including some very weird ones.

Handyman