1.9TD head replacement

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Post by CitroJim »

On the subject of head bolt tightening, I've heard reports of the 60 ft/lb initial + 220 degrees being very close to the point of the bolts snapping and/or stripping block threads. Admittedly on alloy blocked petrol XU blocks.

Furthermore, and again I stress for alloy XUs, opinions seem to indicate it is better to torque them to 80 ft/lbs and to leave it at that and disregard the angle-tightening instruction. I'd be interested in any thoughts on doing this on a diesel. What say 100 ft/lbs?

My personal experience on a petrol XU is that 60 + 220 seemed far too tight and I chickened out at 150 degrees as the bolts really felt like they wanted to let go. I know they stretch but even so.. Touch-wood, that has not caused a problem.

Added to the above, it is very wise to clean the threads in the block using a tap or an old head bolt with flutes cut into it and then thoroughly clearing any rubbish/swarf with an air-line. Then torque and angle-tighten in very gentle stages. Some say the bolts should be lightly oiled and others say dry. Any thoughts?
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Post by RichardW »

ISTR Haynes figure for the BX I did was inital torque + 120°. You need to get enough to stretch the bolts or they're in danger of not working. Once you get past the plastic limit, they do feel like they're going to snap - very odd (and worrying at the time!).

Yes clean the threads out, and yes a light oil - you want to make sure the torque is actually clamping the head and not just binding out in the bolt holes. Not too much oil though, or it can hydraulic in the bottom of the hole - and that really might spoil your day (or engine....)
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Post by CitroJim »

RichardW wrote:ISTR Haynes figure for the BX I did was inital torque + 120°.
Was that for the older-style Hex-headed bolts or the Torx bolts Richard? Something in the back of my mind tells me there was a difference in setting :?

You're right, getting to the end of the plastic-limit is scary, and even scarier when undoing them. they really feel they're going to let go. I find it best to apply torque from a long breaker-bar and let the bolt "follow around" whilst holding on the torque if you see what I mean. It feels like the bolt is made of rubber...
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Post by Xaccers »

BoL says 20ft/lbs first, then 60ft/lbs, then a further 220 degrees (maybe it should mention changing underwear at that point?)

It also mentions greasing the bolts and under their heads with a suitable high temperature grease.

But it is a Book of Lies after all.

Incase anyone is interested in why we're doing all of this, here's a photo:

Image


Now, the history is, about a year ago I was on my way to work in Staines along the M25 doing 40 in the roadworks when there was a thunk and I lost power.
The cam belt snapped.
Being seriously strapped for cash and not having yet found FCF and it's wonderful inhabitants, I had no option but to take advice from another forum on what to do, which was replace the cam, it's caps and belt.
This worked, and probably would have carried on working fine, had the nut from the cam belt tensioner not slipped off and caused the belt to jam between the pump sprocket and cam covers.
So the poor cam has had a fair bit of stress over the past year, not suprising it finally gave way.
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Post by CitroJim »

When we pulled the two halves of the cam out, we found the bearing carrier in the head nearest the cam sprocket was badly scored and damaged. It was so badly damaged that part of the carrier had splayed out as if it had melted which prevented the removal of No.8 cam follower and for the bearing cap to sit square on the carrier. There was also a lump of metal missing from the carrier :shock:

I have a suspicion that the initial cause of the problem may have been a lack of oil to the cam bearing, causing it to seize the cam and thus leading to the broken cam and cap :(

In a way, Xac was lucky, the cam broke between no.3 and No. 4 cylinders and it so happened that the cam lobes for cylinders 1, 2 and 3 came to rest in such a position that the majority of valves were either closed or very nearly so.

Rotating the engine with no cam indicated that all cylinders still seemed to have normal compression. Tough old beasts, these old XUDs, even when they turn themselves into twin-cam engines :D
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Post by jeremy »

A few points of which I'm sure you are aware come out of the above thread.

The cam bearings are line bored in the head and carriers. This means that the caps are only correct for the bearing to which they were fitted when they were bored - and so are not interchangeable from engine to engine - or even between bearings on the same engine. People do get away with fitting caps from another head but I think 'Get away' is the correct term.

I always clean a blind tapped hole (as in a cylinder block face) with a twist drill of the appropriate size hand held and twisted in the drilling direction. - put drill in hole, twist it and take it out and see what has come out. Keep going until the hole is clean. If the dirt is compacted an air line may fail to shift it - the drill will.

Don't oil the holes - wipe a little oil on the threads and the bolt won't 'Hydraulic'. Under heat the oil/grease will decompose leaving soot which can jam a bolt or impede heat transfer which can be important - as with a sparking plug. Most bolts requiring accurate torquing should be lightly oiled to prevent binding and the torquing should be done in reasonably big steps as if the steps are too small its possible that some bolts will not start to turn - and so defeat the purpose of the operation.
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Post by Xaccers »

Right, got the air intake hose off, 406's cam and caps out, injector pipes off, then it started raining so I went in for dinner.

So, tomorrow it's off to the scrappy hopefully to remove the head of the 406 which the cam came from.
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Post by CitroJim »

Xac wrote:Right, got the air intake hose off, 406's cam and caps out, injector pipes off, then it started raining so I went in for dinner.
Excellent :D
Xac wrote:So, tomorrow it's off to the scrappy hopefully to remove the head of the 406 which the cam came from.
Hopefully the Monday morning tornado that hit Northampton did not rearrange the cars in the scrapyard too much :lol:

See you tomorrow morning Andy :)

[/quote]
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Post by Xaccers »

TehAgent said he'll meet us there.
He needs another filter housing... are they going out of fashion or something? :D
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Post by AndersDK »

On the bolts tensioning issue :

I have found in the past, that the correct figures are to be found on the packaging of the new h/g.
The torque needs to fit the h/g material, thus the h/g manufacturer sets the correct bolt torque. Not Haynes.

The Citroen manuals states torque figures that matches the Citroen specified h/g manufacturers figures. This h/g may very well be of a different make than you source yourself from the aftermarket...

Headbolts should always be oiled these days. The only thinkable restrictions in headbolts lubing is because of hydraulic damages to the block when winding down the bolt in the thread.
There is no sense in adding the torque needed to overcome by the friction of dry metal cutting into dry metal ...
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Post by Xaccers »

Well, that was an experience today.
Took us 2 hours to take the head off, only to discover it was no good.

There were chunks missing between some of the pistons and valves!

Unfortunately, there were no other identical engines so we could go no further.

Did find a 2.1TD van with a mechanical pump, which we might go back for :D

So I've re-taxed Dex for now.
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Post by CitroJim »

As Xac said, not a successful trip :( Still, looking on the bright side, we learned exactly how to remove a head :wink:

I'd love to know what happened to make the head look so moth-eaten :shock: Cylindrs 1 and 4 were OK but 2 and 3 really looked as if something had bitten lumps out of it between the valves and pre-combustion chambers. It was so bad that the valve seats could be seen where the alloy had been eaten from around them, leaving almost a skeletal form; a bit like how termites eat wood in hot, far-away places. In fact, the holes ran right into the water passages :shock:

I guess the head had been very hot and parts of it had melted.

The strange thing was that the head gasket looked OK; no tell-tale signs of blowing or anything. In fact it looked very shiny.

If it were a petrol engine, I'd have said it had suffered very bad pre-ignition but the pistons looked relatively undamaged, as were the pre-combustion chambers and injectors. The exhaust manifold contained white deposits, suggesting the molton alloy had gone out of the exhaust.

So, is this the normal damage that these heads suffer when badly overheated or is it something unusual caused by something other than a catastrophic cooling failure coupled with driving it until it died big-time?

Needless to say really; Xac is on the look-out for a good head :lol:
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Post by Xaccers »

Talking of heads, does anyone know of any differences between the heads from engines with different engine codes even if they are all 1.9TD's?
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Post by jeremy »

My guess is that the head erosion is caused by water getting into the combustion chambers and reacting with the alloy at the hottest points.
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Post by CitroJim »

jeremy wrote:My guess is that the head erosion is caused by water getting into the combustion chambers and reacting with the alloy at the hottest points.
Thanks Jeremy :D

Cavitation perhaps as a root cause?

Just pulled this from Wikipedia:
Some bigger diesel engines suffer from cavitation due to high compression and undersized cylinder walls. Vibrations of the cylinder wall induce alternating low and high pressure in the coolant against the cylinder wall. The result is pitting of the cylinder wall that will eventually let cooling fluid leak into the cylinder and combustion gases to leak into the coolant.
Maybe another reason to ensure an XUD always has its coolant in top condition.. The engine in question had no sign of having had anti-freeze in it for some time.
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