Engine Inspection, Head Off

[Pug_XUD_KeenAmateur]

Hi guys, pulled my blown HG XUD 1.9na apart a bit sooner than expected, largely for the 'head off' practice....

Not having pulled a head off before, I was a bit surprised to see no obvious issues with the HG itself; considerable oil fouling to No.1 (flywheel end) but the HG's intact. Can anyone point me in the direction of what to look for in terms of inspecting the the engine and how come the oil but no hole in the HG? Is this common?

What can I do to make an informed decision whether to keep it with a view to future use if need be?

NB: what a doddle it was to have the head off, had expected hard to turn head bolts, sheered exhaust studs, etc, but none of it; are they usually that easy or was I just lucky? Beggars belief to me now that I couldn't get the head bolts to budge on my 405, engine in situ, back in 2009. Maybe it was so easy coz its 'out'?

NB2: History...
One of two XUD9's I have, t'other one has 75k less on it but unlike this one haven't heard it run
Started easily from cold and ran sweet (lots of exhaust smoke first couple of mins)
Coolant came out brown, worst I've seen, but I've not seen many
Stored outside, covered up, six months & counting

[ekjdm14]

I don't know about the HG but I'd say that engine is ready for a rebore looking at the rust on one of the bores :/ you do get a bit of residual oil spillage when you lift the head, perhaps more so if the engine has been lying on it's side in storage so that may explain the oil in the bore.

If the damaged/rusted bore turns out to be superficial then I'd advise "fouling" the rest of them with some good thick oil to keep moisture away from them, a good (rough) gauge of if the damage is rebuild worthy is if, after cleaning (I've used WD40 and wire wool to clean corroded bores carefully before now), you can snag a fingernail in any of the pits or grooves.

[Pug_XUD_KeenAmateur]

ah, so that explains the oil then.... I'd omitted to remove a lifting eye from that side of the engine, so a couple of times I'd attempted to lift the head off & it had tilted that way. It's stored upright.

Thanks for the tip about the wear, it is a high miler; but not necessarily knackered, HG excepted. I had to 'waste' 1/2 a litre of oil to run it 10mins coz there was more oil in the coolant than in the sump.

Further question I thought of, to anyone... if the head's cracked, is that something I look for visually, or by feel? Is there a 'weak spot' where a crack's more likely than elsewhere?

[ekjdm14]

Sometimes a crack would be visible, but the only way to be really sure if there's any doubt is to have it pressure tested. I'd say if it were to crack anywhere it'd be around the pre-chamber, not that I've seen it on an XUD but other comet-style heads do seem to go in that area (usually resulting more in fountains of coolant than oil/water mixing though).

To be fair it's probably worth getting the head checked and maybe skimmed before it goes back near a block, just to eliminate any niggling doubts if you experienced a problem down the road. I'd agree that the bore visible in the photo looked largely the same as a 97k bore wear wise (I.e. very little wear) just potentially scored/rust damaged but a clean up and second look is required there and for the other 3 pots. I'd put money on the bottom end being serviceable as long as not too much crap ends up lodged round the pistons.

To that end I'd personally drop the pistons out (numbering them and the rods/caps prior to removal of course so it can go back as it was) and give everything a good clean up separately. Less chance of a bit of sh*t getting trapped and wrecking a bore that way. I know most folk would advocate having the bores glaze-busted (honed) and fitting new rings if going that far but to be perfectly honest I've often just been vey careful with the original rings while cleaning them and put them back exactly from whence they came and never had an issue with one. Depends how deep you want to go with it but if it was a good runner with decent compression and little oil use prior to the HG then I'd expect nothing to change as long as nothing gets damaged or moved to another cylinder while it's apart.

Sorry, bit of an essay but you know why that is lol

[Pug_XUD_KeenAmateur]

that's excellent. Thanks ekjdm really helpful.

A pressure test & check, maybe skim, it'll be .

I'm gonna 'fight shy' of dropping out the pistons, but I'll be pretty damn careful with the wire wool; cloth, vacuum cleaner that sort of thing to ensure zero / minimal debris

[CitroJim]

To be fair it's probably worth getting the head checked and maybe skimmed before it goes back near a block

Yes, definitely, even if the head measures flat within tolerance it's always a good idea to have a very light skim just to clean it up and definitely have it pressure tested...

Always use new head bolts on reassembly.. They're stretch bolts and should not be used a second time..

[Paul-R]

Run a tap down the threads in the block for the head bolts to clear out any crud. You don't want the new bolts bottoming out and giving a false impression of correct torque. If not done, that way another HG failure lies.

[CitroJim]

Run a tap down the threads in the block for the head bolts to clear out any crud. You don't want the new bolts bottoming out and giving a false impression of correct torque. If not done, that way another HG failure lies.

That sir, is very, very good advice indeed...

Then blow each threaded hole out with an airline...

[ekjdm14]

Yes indeed, and make sure the holes are dry of any oil etc too since that can cause similar problems. Being careful cleaning the bores ought to be fine, I've just done the Escort head refresh that way with no issues. Enjoy

[Pug_XUD_KeenAmateur]

Thanks everyone

Perhaps surprisingly, the 'blowing out with an air line' is not possible, as my tooling doesn't run to a compressor*; as weird as it'd look, does anyone have a clue whether a rather puny forecourt pump [which often seem rather lacking oomph] would suffice - set it to 'flat tyre' and hold it over the hole? Or vacuum it?

Also, I don't have a 'tap' but am happy to buy one for the purpose. Does anyone know the size which I presume is metric?** I buy the vast majority of my stuff online so relevant detail to locate the correct size 'd be lovely. ...or can I get away with running an old bolt up & down?

Which brings me to my final question, about dry threads: some of the bolts that came out were far from dry, a real 'mix' which is perhaps the cause of the HG failure in the first place. See pic***. Views on how to get the threads 'clean' welcomed... I was thinking maybe throw a bit of petrol down the hole then tap or wind an old bolt til it comes out clean?

*my situation is probably a bit unusual in that I have only two 8ft x 6ft wooden sheds (no garage or driveway), which is part of the reason why. t'other is funding.

**I'm reminded of that recent Guy Martin programme, where he set out to average 150mph in a Transit and the prog' included the info that until a lot more recently than you'd think, UK and German built transits were different in that the UK ones were Imperial. If you didn't see it, its well worth watching if its still available on iplayer or the likes; I'm not into 'speed for speed's sake' but the preparation side of it was proper interesting

***I didn't note which was which, knowing I'd not be re-using 'em, but from memory, the oily ones were No.4 Cambelt end (ie the opposite end to the oily bore) and the dry, rusty one I do remember was in the middle at the front. Engine mostly stood upright, bar a month or two back when I had it on its back while I soaked diesel 'round the glowplugs and a day or two on its side while I did similarly with the bottom pulley.

[ekjdm14]

Another work around if you don't have the appropriate tool (a bottoming tap of, I *think*, it's M12 is whats needed) is since you'll be replacing head bolts anyway, you can cut vertical grooves into an old head bolt in much the same style as a proper tap, and use that for the purposes of chasing out the threads.

As for making sure they're dry, my mode of attack is usually an aerosol of brake cleaner to thoroughly blast out any other fluids since it evaporates readily with no residue & then a quick prod with either cotton buds or twisted up strips of kitchen roll or even better, blue roll.

Again, you often find oil on bolt threads due to the leakage when stripping down so those bolts ain't unusual looking IMO even if they've come from a diff. area to the major spill. Head gasket *could* obviously be a factor as it was duff but nothing majorly wrong I can see with them, you can even see the front centre bolt with the rust on it... Seems water get/sits in the threads of that one somehow... (lol just read the postscripts and it is indeed front centre)

Oh, and I wouldn't bother trying to blow anything anywhere with a forecourt compressor. They struggle/fail to even seat beads on motorbike tyres in my experience and you'd be much better served by a cheap double barrelled footpump & the kind of conical adaptor used to inflate paddling pools etc that commonly come with a new pump. the key is volume of air more than pressure and the pump method will suffice although it's not entirely necessary if you employ the thread-chase & brake cleaner routine.

I am also currently sans un compresseur due to funds being spent elsewhere. They are a jolly handy thing to have, especially when you're checking tyres on a small fleet of vehicles and/or have a rattle gun, but by no means essential if you apply a little lateral thinking to situations where others resort to "that big tin of wind in the corner"!

[Pug_XUD_KeenAmateur]

..."that big tin of wind in the corner"!

Thanks again ekdjm, another quality bit of advice. I better make sure the missus don't see the above else I'll have a new nickname!

[ekjdm14]

..."that big tin of wind in the corner"!

Thanks again ekdjm, another quality bit of advice. I better make sure the missus don't see the above else I'll have a new nickname!

Likewise myself, now you mention it... *parp* "was that you?"