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davemar

XU9J4 mysterious clunking and snapped head bolt

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davemar

When driving a couple of days ago in my Mi16-engined 205 the engine suddenly decided to sound like a bag of spanners when I was accelerating in 4th. The engine was still running, but something inside sounded horribly loose or broken. Even on idle it sounded like some loose metal was clunking away. Oil also appeared to have spurted out of the dip-stick hole too.

I then tried turning the engine slowly by hand (spark plugs removed) to identify and sound, and for about a 1/4 of the rotation there was a noticeable notchy resistance and a bit of knock coming from the bowels of the engine.

 

So I decided to whip the sump off, and nothing looked bad from underneath. I've now taken the head off, which looks looks fine, though the head gasket wasn't in the greatest condition. Turning the engine without the head still had the notchy feeling, so definitely a bottom end problem. I've now removed the pistons and liners, and the big-end bearings look ok (one pair is a bit discoloured, but not squished). The piston rings all look intact too. The crankshaft without the pistons rotates smoothly without any noises. So it does appear to be a piston/rod/liner thing, but nothing looks noticeably broken. So any ideas would be welcome.

 

Also, to make things worse one of the head bolts snapped when I was removing them. Annoyingly snapped below the surface of the block, so nothing to grab hold of. Suggestions welcome on how to deal with that too!

 

 

 

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DamirGTI

Hard to tell anything specifically or close enough without seeing the engine in real ... 

 

Anyhow , possibly piston slap , something with the piston rings/ring lands on the pistons , bearing shells or/and caps (big ends and mains) .. check visually for discoloration , blue , blackened etc.

Pull out measuring tools and do some measuring of the bottom end parts .

 

Make a few shots of those discoloured shells ... colour change on the bearings is never a good sign really .

 

Can also do some testing with each individual cylinder assembly  one by one , piston + liner + crank and spin it ... might identify/narrow down which of the 4 makes it bind .

 

 

As for the broken head bolt , i feel you're pain (had the same years ago) ... and it is really , an pain in the **** , when it snaps below the deck surface + likely it's "rust-welded" itself to the block too making things even worse to rectify on a DIY basis .

Myself personally wouldn't recommend even trying anything on a DIY basis , find an handy machinist he'll be able to fix it for sure .. even better , an machinist who has "tap burner/metal disintegrator" arc machine .

 

D

 

 

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davemar
Posted (edited)

Here's a picture of the big-end bearings. Not the greatest photo in a dim garage. The pair on the left have a bit of streaking, but the others seem to be reasonably evenly grey coloured. They still have a film of old oil on them. None of them appear to be measurably different from each other.

 

I've also measured the crankshaft big-end journals and those all measured 50.0mm on two axis, so don't appear to be worn.

 

I'll try and follow your tip of trying each cylinder one at a time to narrow it down. None of the pistons or liners look massively different from the others in terms of condition.

 

Given the engine went from running really nicely and quietly to instantly sounding very loud and broken did suggest something quite drastic, but nothing looks very broken.

 

I'm a bit stuck when it comes to taking anything to a machinist or anywhere as my other car is also in bits after the head-gasket failure the other day! So I'm trying to manage on my own at the moment.

20210831_210854_sm.jpg

Edited by davemar

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DamirGTI

Looks a little bit light "corrosion" damage on the shells ...

 

1. Acids in oil

2. Excessive operating temperature

3. Excessive blow-by

4. Coolant contamination of oil

5. Use of high sulfur fuel

6. Excessive oil change interval

 

... would blame that on 2 , 3 and 6 .

 

 

You'll struggle with the such broken bolt scenario by yourself , trust me .. best done by machinist with proper equipment/tools .

When it snaps below the deck surface it's really tricky , and as i said , the remains of the bolt are also likely rusted/welded/sized onto the block threads (galvanic corrosion) .

 

D

 

 

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opticaltrigger

Hi Dave,

Don't suppose you had an operating oil pressure reading in there at the time by any chance ? And have you managed to examine the oil pump etc yet ?

 

As to the bolt, agree with Damir totally. Very difficult DIY and best at a shop,,,, But, in your situation... One approach I might try, would be to hire a mag drill, and with the closest undersized cutter you can get, send that through. That would give you a very straight pilot to work with and remove most, if not all of the broken bolt.

And then,,,, get a re-thread coil kit and re-thread every single one. Just a thought really...

 

All the best,

O.T.

Edited by opticaltrigger
  • Like 1

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davemar

My oil pressure dial has always been a little bit temperamental, but it was generally in the 3/4 region as it has been for ages when the engine is running fully (i.e not idling). Although it did recently go to maximum on the dial on the odd occasion, but I assumed that was just an electrical thing; but maybe it was a sign of high oil pressure? 

 

I've removed the oil pump and it seems to be fine, spins freely and gurgling with the remains of oil in there when I spin it.

 

 

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davemar

Further testing to try and pin down the problem....

I reinstalled only the 4th piston (furthest from the flywheel) to see if that would make the notchy rotation of the crank come back. And sure enough it did, with a noticeable three clunks for about 30 for 360 degrees of rotation. However, the clunks didn't really appear to be coming from the end where piston was, but the flywheel end. So I got my trusty assistant to press the clutch pedal while I turned the engine. This made the notchiness and clunking go away, and the rotation felt smooth. So the clunking was only when the clutch was release in neutral. 

 

So it appears to clunk when there's a piston installed at one end and the gearbox input shaft is engaged at the other end of the crankshaft. So I'm now thinking this is a main bearing failure that only shows itself when the crank is loaded up at each end. Does this sound plausible?

 

Obviously I'll have to go through the faff of removing the gearbox to remove the crank to really check them all.

 

BTW the engine was last stripped for bearing and HG change over 15 years ago (maybe 80k+ miles) including a recent 2 year 'rest', so the bearings aren't exactly the freshest. The head gasket certainly looked very tired when I removed it.

Edited by davemar

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DamirGTI

Thrust bearings .. take a look .

 

 

D

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wicked

Failing clutch cover? 

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Richard309Sri XU5JA 205GTi
On 8/31/2021 at 6:04 PM, davemar said:

Also, to make things worse one of the head bolts snapped when I was removing them. Annoyingly snapped below the surface of the block, so nothing to grab hold of. Suggestions welcome on how to deal with that too!

 

On 9/1/2021 at 11:00 AM, opticaltrigger said:

As to the bolt, agree with Damir totally. Very difficult DIY and best at a shop,,,, But, in your situation... One approach I might try, would be to hire a mag drill, and with the closest undersized cutter you can get, send that through. That would give you a very straight pilot to work with and remove most, if not all of the broken bolt.

And then,,,, get a re-thread coil kit and re-thread every single one. Just a thought really...

regarding the broken bolt had exactly the same failure mode; and kit/DIY repairs by hand drill only 

as per OT comments above and agree with OT & Damir, it looks hard to do, because you obviously cant really "precision engineer" using a hand drill, could easily go all over the place, yeah need a mag. drill min.   

 

I bought the kit as per the photos but never got around to install it. Yeah it's got to be keepin the drill bit vertical that's going to be the most important part,  need a steel high speed mag. drill agreed, some way to clamp a steel plate onto the top of the head adjacent to the bolt to be removed, maybe a MS plate drilled M11 also and then using other head bolts to hold down, mag clamp to keep it true vertical, very strong base so it doesnt move 

 

in the end I just bought another block on ebay- well that was for the XU injection engine for a 1.6 gti 205

 

might try it with more time, "V Coil" kit looks ok ish - as per photos,(b&!£&*ks I have lost one LOL) 

not that expensive 

 

Didn't realise you had to do all 10 head bolts though?  that makes it more like just buying another block would be much easier/well quicker and less work, as the cost and time for a mag drill well unless cheap mag drill hire or buy second hand good one   

 

obviously other option but I reckon bolt removers for this would also be impossible in practice as no one could get a key into the old bolt that would be strong enough given that the bolt snapped in torsion stress they must be pretty well stuck in there and its only M11 (?)

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20210902_152851.jpg

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SRDT

On the XU9J4 the rods are centered by the pistons and free on the crank pins so the crank must be moving quite a lot before pushing on the rods.

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petert

Those v-coils are too short. You need 2.5D helicoils.

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SweetBadger

Been there got the t-shirt:

 

 

agree 2.5d would be better than the 2d ones I used.

 

you should be able to get the broken bolt spark eroded fairly cheaply, then it’s not too difficult or costly to helicoil all 10. With a drill guide you could have a go at drilling it out, but that’s pretty risky - not something I’d try.

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Tom Fenton

I’ve drilled and helicoiled in situ. It’s awkward but possible with care. 

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davemar

Anyway, I've finally got round to getting back on the job to get things apart to see what's what. I removed the gearbox (such a faff!) and discovered the flywheel bolts where only finger tight! So I'm not entirely sure if that's what caused the horrible sound if it was knocking about. At least it something that I'm glad the strip-down has identified. I've removed what's left of the engine (block and crank), and will try and remove the crank when I have time and room to do so.

 

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petert

The flywheel bolts need Loctite as well, otherwise oil will seep past the threads and ruin your day.

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welshpug

have come across something like this this before with the bolts, happened during mapping on an 8v, got to 5k rpm and it started knocking..

 

flywheel bolts were not torqued up, and the pin had snapped allowing the flywheel to slap back and forth on the bolts!

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davemar

I did get round to getting the crank out in the end to check the main bearings. They all looked as good as new. So it seem seem the only fault was the flywheel, so the engine didn't really need to come apart in the end! But the headgasket looked very tired, so probably not a bad excuse to give the engine a bit of recon to get more years out of it.

 

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