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Hi Derek

The head bolts, so far as i understand should be lightly lubricated.
Hi Derek

I agree that you are right with the theory but if the bolt is unchanged as a result of use why should Citroen bar reuse?


I can be specific and say that the head bolts on the XM 2.5TD have to be lubricated before fitting, then tightened by angular measurement to the required limits, but this can only be done after the bolts have been measured and chrecked against Citroen's published specification to ensure that they have not lost their elasticity.
If they have lost it and thereby lengthened beyond the limit, then they MUST be renewed.
I would suggest that the same parameters should be applied to any modern Citroen/Peugeot engine when using genuine head bolts.
Hi Techmanagain

Thanks, that is very interesting and helps me a lot.
Can you expand on a couple of points please:
Which of the Citroen publications is the bolt length data published in?
You mention genuine head bolts, is this a particular use where 3rd world copies are known to exist and be substandard?
If so is there any way of checking before reuse that the existing bolts are genuine?


Well, the machine's up and running once more. To add to this whole angle gauge caper,
I must mention how much of a real git it was to do!! The first x2 steps were a real doddle
and despatched in short shrift using my trusty Torque Wrench but proceedings were halted
once the confounded gauge from past spannering wasn't found!! rolleyes.gif

I got one from Machine Mart for half the cost of a dubious Laser one from Halfords and
immediately found a flaw in it's use.

The 2.0i head bolts use the torq T55 head which has to be 1/2" drive but when used with
the angular gauge on the rear head bolts it fouled the head as this is deeper to the rear.
With a 4" extention to lift the gauge clear the pulling bar fouled the bulkhead, requiring
another trip out shopping to buy a 1 1/2" mini extention!! rolleyes.gif

As my memory recall of past Xm gasket changes is hazy, consulatation of all the manuals
prompted me to apply grease the bolt's thread and the underside of the head of the bolt.
After all the setting up side of my toolkit was actually done, the 170˚ bit was done with
some fiddling about to tie the support leg of the gauge to stop it all turning...

Hi all

I replaced the head bolts regardless of their condition, they are about £20 for the set from Citroen, so its not worth chancing it.
Glad your up and running again Andrew, hope your next catastrophe is a long time coming biggrin.gif
Hi all.

One line of XMExc last response raises an interesting issue --- that of third world items.

We have just completed an engine rebuild where the customer supplied plainly aftermarket pistons and barrels. (Subcontinental !) Within two hours running, liquid oil being emitted from the exhaust. After much head scratching, we stripped it all again. Result ? More wear in a couple of hours than the previous 30 years. Very, very clearly incorrect spec. materials. I've also noticed with some imported 'brass' screws, a huge difference between them and quality products.
I think we have moved here to a ridiculously overpriced economy, which is what primarily drives people to cheap imports. If the goods are just not up to it though, there is no saving. Maybe we should move to having engineering items properly labelled regarding their specification. If quality suppliers then went some way to easing back on price, we may have a happier situation all round. I recently had to buy in an engine maunfacturer's alternator belt, in their own packing, at nearly £19; same item in the maker's packing around £4.75. Other than a 'gotcha' mentality, there is absolutely no justification for so huge a disparity.

Hi Onthecut

Sadly the one bit of spec they usually perfect first is the product markings followed by any compliance paperwork.


Hello readers

Back in my CX Safari 2.5 turbo diesel days I had a lot of fun?? with a cracked cylinder head / valve seat which caused antifreeze to be lost into the exhaust system causing some fairly spectacular cloud formations on cold winter days!
I chose, unwisely, to have the head repaired by a cowboy outfit who welded up the crack successfully but in doing so removed all the temper from the alloy eventually causing a steel valve seat to fall out and cause mayhem in one cylinder( but that's another story).

I thus became quite adept at swopping this particular head which was tightened down using the angular method and I can tell you that the bolts (even with greased threads and heads) were really creaking when finally tightened (in fact I split an Elora 14mm socket doing this). I recall there was also a requirement to tighten the bolts a bit further after a few hundred miles. The point I am getting to is that the stretch bolts could be re-used provided that the length did not exceed a certain value specified in the manual I was using at the time. I suppose that as the bolt shank gradually elongates then then eventually there will be some tendency for the steel to 'neck' before finally yielding and snapping. The maximum stretched length is probably specified so that this limit is never approached.

Any metallurgists out there with a better explanation?

Regards, Ken Hall
Hi Ken

I can only comment from experience of dealing with many failures in various steels and bolts. Our high tensile bolts were much larger than XM head bolts but the broken ones were generally charecterised by sudden failure from a much smaller fatigue crack than you would expect in lower grade steels. The crack initiation point was usually from the first thread or occasionally the change of section at the head. I suspect that it is the torsional loading that would initiate a head bolt to break and failure would be in the threads just above the cylinder block. This would make it very difficult to remove the remains. I guess Citroens rules are to try to avoid such failures with the attendant difficulty over who should pay.


Hi all
I sheared a head bolt once on a K series rover lump when i was trying to get it out, and it snapped right at the beginning of the thread.....near flush with the mating surface of block mad.gif sad.gif ohmy.gif mad.gif .
The head gasket had gone, but it apparently had been done 6ish months before i got the car, So not only did they obviously not do the job right, they must have re-used the old head bolts as the others that i did manage to get out had not been greased and were stretched several mm beyond their specified limit.
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