200 TDi: rounded bolt on rocker shaft type disaster

Searching for some hints and tips here.

Finally got around to spending some time on my wife's ailing Disco 200TDi. Replaced the steering damper pretty easily. Feeling emboldened, I thought I ought to stop faffing around and remove the head.

Got as far as "progressively slackening the bolts securing the rocker shaft". They were all pretty tight but unfortunately two of them are 10mm heads and one absolutely refused to budge.

Having rounded it off nicely, I've tried every obviously sensible alternative (right through to hammering on a 3/8"th socket...which - erm - split!!).

I'm reluctant to try heat given the danger of wrecking the head or valve train and cannot see cutting a slot in this bolt and trying a big screw-driver is likely to work given how tight it is (although it will make a swarf-laden mess...).

Any other ideas? Do I need to remove the valve train before taking the head off (if the head was off the car I might be able to drill it out using a piller drill).

Oh, Happy Easter by the way..!

Malcolm

you could try a product like this, I have not tried any myself though.

http://www.screwfix.com/app/sfd/sea/searchresults.jsp?_dyncharset=UTF-8&howMany=5&searchText=96028

I'd go for hammering on a 3/8" airgun 6 sided socket and try again, also worth trying to tighten very slightly before trying to undo. I'd rather snap the bolt, get the head off then drill and re-tap hole rather than drilling in-situ.

Cheers guys...I'll take a trip to Halfrauds tomorrow and try and get myself a 3/8's air/impact socket. If that doesn't work I'll get the mini-drill out and slice the top off and drill it out later...

Has anyone tried those nut/bolt extractor things James pulled off the Screwfix website. Look promising in a way that things like "Gator-Grips" never did..?

Malcolm

Re the bolt/thread extractors, I linked this to the Rover forum I'm a regular on and asked there too:

See http://www.rovertech.net/forum/viewtopic.php?t=49726

Guess that makes them like those screw extractors which I've had nasty experiences with myself. I think I'll save my £20

Malcolm

The bolts will be fairly high tensile, so they probably twist 1/4 turn then ping out, unless they are 6mm or less thread then it will just snap, but drilling will definitely be a pillar drill job for re-tapping.

Got it out today. Was really successful with the mini-drill and mole-grips and did near enough a perfect job!!!

However, when I went to undo the cylinder head bolts I found (and I'm not a small bloke...) that some of them are almost completely immovable...even with my full weight.

Had my torque wrench (my biggest lever) set at 200lb/ft and although I managed to crack them all I couldn't actually unscrew a couple!!!

Given they have to come off in order (so the head de-stresses properly I guess) I'd better buy me a BIG breaker bar!!

Not missing a trick somewhere am I?

Malcolm

Have you tried an old fashioned impact driver? Failing that whack the bolt heads downwards with a steel hammer while turning them with a ring spanner.

Will try the impact driver (one of the bolts in question is by the rear lifting eye and the other one is front left corner inside the cam cover...so not exactly spanner-able).

All the outer bolts up the right side of the head by the manifolds creaked and cracked as I turned them through the first 45 degrees, so I know they won't exactly fall out...

My impact driver is slightly b@ggered and if it doesn't do the trick, I suddenly have an excuse to buy a air impact hammer...

Malcolm

If you do buy a air impact gun Dont buy the cheapest it is unlikely to have the power to shift stubborn head nuts. I would use a threefoot long breaker bar first Cheaper and will undo or break most nuts or bolts .

bonnybaggot said:

If you do buy a air impact gun Dont buy the cheapest it is unlikely to have the power to shift stubborn head nuts. I would use a threefoot long breaker bar first Cheaper and will undo or break most nuts or bolts .

Click to expand...

Good Impact air guns break very few bolts, but can undo so many things you can't easily undo with a 3 foot breaker bar, that said I've got and use both on mine

Please let me know what use your air impact gun is when you are stranded 20 miles from the nearest compressor.

bonnybaggot said:

Please let me know what use your air impact gun is when you are stranded 20 miles from the nearest compressor.

Click to expand...

You stand on the roadside and point it at the next passing ATS van like it's a gun, get him to pull over, hit him over the head with th air gun, then hi-jack his van and use his compressor

The cheapest 3 foot (1 metre) breaker bar I've seen looking on the web is about £50; several impact guns can be got for that price or less...with sockets.

Point taken about cheapies though and I've only been looking at 1/2inch drive ones with max torque capabilities of 220lb/ft or higher.

Strange but true...you can get a 2 foot breaker bar for about a tenner; however as my torque wrench is two foot and I couldn't shift the bolts using that I'm not going to bother with them. A length of scaffold pole is a possibility; don't know where (by the weekend and out of hours) to get a single random length though..!

Malcolm

any building site or the council tip. take a good hacksaw!

had to use a 6 ft section to remove the rear hub nuts off a vw beetle.
god knows how they tighten em that tight?

ormus said:

had to use a 6 ft section to remove the rear hub nuts off a vw beetle.
god knows how they tighten em that tight?

Click to expand...

They use a 10 ft length of scaffold pipe

Right - back again and I got the head off today. Boy was it fun (see "Question about air tools..." in "General Chat")!!!

Having had a careful look all over I can now see what the immediate problem was and have found something I don't know if I must deal with now or can leave for a few months (when I have more time & money).

What I saw was:

1. The head gasket was blowing...hot exhaust gases had eroded the gasket at the back of No.4 cylinder and there was clear evidence on the bulkhead of this too. Was also seeping betweeen cylinders 2 and 3. Loss of power and whoosing/tapping noises explained! No mixing of oil and water as all oil and water galleries were still sealed.

2. Piston No.2 has a 1-2cm crack on the crown. It's not by the edge, but is right on the rim of the deep "golfish bowl" shaped concave depression in the centre of the crown. Sliding a thin feeler gauge in doesn't indicate the crack goes right through (but I might be wrong as the crack is not very straight). In fact I'm confident it doesn't.

3. The new head gasket has restrictions in the waterways which may or may not have been present on the old gasket. Hard to see if they have rusted away to be honest; but the coolant was extremely weak so this is possible. I will have to give the whole system a thorough clean when I reassemble (ie those two stage cleaners/conditioners). Presume I leave these restrictors in place (92 200TDi)?

4. For 175,000miles, I was very surprised at the good condition of the bores. Honing marks are just visible and there is no scratching or wear lips at the top of the pistons travel. I tried jiggling the pistons in the bores and felt no slack so I think piston rings are okay. Haven't rotated engine as is still full of oil - but I do realise I should jiggle all pistons at tdc and half-way down to be sure(r).

5. The head itself seems in good condition - I'm about to strip it now but expect no nasties. Valve stem seals need replacing and a couple of valves clearly need lapping in again, but that's it.

So my question to the knowledgeable is; seeing as it seems feasible to extract the crank and pistons with the engine in-situ and without removing the head for a second time (ie. via the sump) should I ignore the crack in the No.2 piston and reassemble? If I still have problems surely I can strip the bottom of the engine this time (sump gasket is leaky anyway!!)?

Opinions welcomed!

Malcolm

Personally I wouldn't risk it, you are about to start running at higher compression ratio than you were before with those leaks, and if it goes and implodes then you are probably looking at a re-bore + associated damage from large lumps of metal circulating everywhere.

Too much of a gamble for my liking

it is always worth sorting problems out before they get any worse or the bill may be higher.

besdies the bother of taking the gearbox etc.. off to get the crank out in situ, i wanna come and watch, you get the pistons back in the bores again from underneath. (with the head on).

id take the block out now and do the job proper.
itll save no end of heartache.

just bite the bullet mate, ive never known a piston to mend itself yet.