Bottom end - partial strip rebuild/advice

Hi guys,

As some of you might reall a couple of weeks ago I discovered (if that's not too poor a pun) that our 200TDi Disco had a crack in one piston.

Not having much cash, spare manual labour or time, I'm looking to fix this properly in the easiest way. This obviously means renewing the piston, but without removing the engine/g'box if I can help it. Once I have the sump off, can I remove the piston and conrod without removing the crank (and therefore gearbox)?

The replacement piston will be standard (I know there are two types...I'll know what I need once I have the old one out) and I was planning to gently deglaze/hone the bore with a honing tool in an electric drill...yes I'll be very, very careful about damaging the crank and coating everything in swarf. Does this sound realistic?

If I hone one bore, should I do likewise for the rest of them (and are new standard rings okay to go in a honed bore or should I be buying oversize rings (I'm intending to reuse the other 3 pistons).

Am I being realistic hear and if so is there anything else I should be aware of or consider renewing?

Cheers!

Malcolm

pretty sure you can take the piston off through the top. youll need to take the head off.
i wouldnt do any work on it (in situ) that creates swarf etc.. probably do more damage than good.
i still think it makes sense to take the engine out. all the engine bits need to be inspected after an event like yours.

Heads already off - so thats a start!!!

Desperate to avoid the crank out scenario as frankly I can't afford what that entails and don't really have the time (or willing helpers available when I'd need 'em).

The piston has a small fracture on the crown so I'm comfortable nothing major's gone wrong elsewhere (he said looking dubious).

A bit of googling found this post on MIGweb where one of the contributers takes a "fag-packet mechanic" attitude to deglazing which I don't feel comfortable with, but others seems fairly comfortable doing as I propose (albeit on Astras)...

http://www.migweb.co.uk/forums/vauxhall/mechanical-electrical/47382-fitting-piston-rings.html

Guess I'll have to get that piston out and assess the situation from there..!

CHeers!

Malcolm

yes do that. its the cheapest and quickest solution. just replace the piston and try it. (if money is a problem).

but be aware, that you may have to strip it all down again sometime soon.
be prepared. with luck itll be just the piston and nowt else.

Right - update time:

1. Head removed few weeks ago (one injector still to be prised out)!! Head to be rebuilt finally this week. Might need to replace an exhaust valve (tbc).

2. Sump and ladder frame removed. Side play in big ends checked and found to be perfectly healthy.

3. Offending piston removed. Crack didn't got anywhere other than along the crown but scraping off carbon revealed it's actually 2.5-3.0 cm long (twice what I thought).

4. Piston is standard size for my engine (200 TDi with a 12L engine code) as I had it measured by the local engineering shop.

5. Big end bearing shells are okay but exhibit some signs of wear on this piston, so to play safe all will be renewed.

6. Therefore my shopping list is:
one standard piston.
a complete set of rings
complete set of big end bearing shells.

7. Bores will be gently honed just to remove the glaze.

Questions for y'all..!!

1. I've been warned that replacing a single piston could be problematic if the replacement is not identical...does anyone know if the pistons sold by Craddock, Paddocks et al are a good match (especially in weight) for the originals?

2. There are apparently two types of standard pistons ("X" and "Y") and I cannot see any particular reference on mine that tallies other than a code on the crown including an "X". Is my supposition that I have "X" pistons correct? If it helps, my gasket was the 3 hole variety.

3. I haven't really been trying yet, but best quotes I've seen for pistons are circa £40, ring sets are £12.50 per piston and bearing shells are about £40 for four pairs (last quote was from engineering shop who offered to relieve me of £120 for a new piston...). Anyone know if I can better those?

4. Bloke at the engineering shop suggested faulty (overfuelling) injector might be responsible for the pisiton cracking. Any comments?

Cheers guys!!

Malcolm

Got my new piston and it is definitely the same as the old one - all the dimensions match exactly.

However as it is a Britpart item rather than a Land Rover original it weighs something like 15-25 grams more than the original (the scales only measure in 10 gram steps over a kilo).

Do I need to get some machined off or is this an acceptable variation?

Cheers!

Malcolm

personally i would leave it. esp considering your budget.
as the engine is an old one and slow reving unit. doubt it will make that much difference.
if it was a mini cooper (eg) i would fit 4 new matching pistons.

there are too many variables for the cracked piston reasons.
too much local heat is the most likely/usual cause. or maybe just a faulty casting?
check your valves carefully and the hg.

It's done!!!!

So bl@@dy relieved I can't tell you...new piston, new big end shells all round, new rings all round and a new head-gasket topped off by a shiney clean cylinder head. Leaks from sump etc seem to have been cured too..!

Ended up shaving as much weight off the piston as I could but still have a 15gram variance between the old one and the new one.

Having given it a blast yesterday, even at 70mph I can't feel any untoward vibrations.

Going to drain the oil and the coolant off this weekend and replace with new (I put cheap oil in just for the first few days and the coolant went into a filthy system that needs a really thorough flushing and is rust coloured already!).

Fitted the front section of the exhaust properly onto the the cast iron downpipe from the turbo and it makes the engine so much quieter.

Never done anything quite this involved before and was shocked when it started on only the second chug of the starter!!

Yours in happiness and satisied mugness,

Malcolm