300tdi engine rebuild (with pics)

Chr1s · Mar 1, 2014

Well, after the catastrophic failure (http://www.landyzone.co.uk/lz/f7/runaway-300tdi-248004.html) of my the engine in my Defender, I've finally found time to start stripping down the engine to see whether or not it can be saved.

The first challenge, after a bit of a battle getting the engine off the hoist and onto the engine stand, was removing the siezed head bolts, but I discovered this unfortunately named but surprisingly good product to help loosen them up a little:

Super Crack Ultra 400ml | Euro Car Parts UK?s No.1 Retailer

With the head off, I discovered that the head gasket looks as though it has melted!?

But, to my very untrained eye, the head itself looks ok (I have cleaned the oil off and there are no signs of cracks or corrosion):

And all looks ok under the head gasket:

The engine turns freely by hand and there are no signs of damage in the bores, which is promising, I think.

The question is, could the head gasket damage be the reason why the engine would not turn over after the 'incident', or should I expect to find something more serious my very slow rebuild progresses?

jamesmartin · Mar 1, 2014

have you any pics of bores and front end of gasket, do all pistons protrude above block face equally

Chr1s · Mar 1, 2014

jamesmartin said:
have you any pics of bores and front end of gasket, do all pistons protrude above block face equally

Will take some pics of the bores in the morning.

Here are some more pics of the gasket (warning: they are quite large!) - Did you mean this view, or side on?

http://oi59.tinypic.com/2s8o6tt.jpg

http://oi62.tinypic.com/imi4np.jpg

I've just been out to double-check and all pistons protrude equally. From that, I assume it's reasonably safe to assume that nothing is bent/distorted?

jamesmartin · Mar 1, 2014

its a good sign for the rods

Brown · Mar 2, 2014

I'd be very surprised if a blown head gasket would stop an engine rotating. I'd be inclined to look for something else seized. If you're able to check the piston protrusion it suggests that the crank will go round and the pistons will slide up and down in the bores. Could anything else be stuck? Cam, valve gear etc.? As a youth I succeeded in welding the valve stems to their guides in my mother's Morris Oxford as a result of over enthusiastic use of the loud pedal. That seized it up pretty solidly.

Brown · Mar 2, 2014

Everything looks nice and oily which is a hopeful sign. Rather than just burnt, or that ominous bluish colour of overheated metal which I've seen inside defunct engines once or twice.

Chr1s · Mar 2, 2014

Well, despite my initial enthusiasm, it seems that all is not well. After a good clean, I have spotted that piston no.1 appears to have melted:

And the waterways don't look right to me:

There is also a scorch mark on the head face next to piston no.4, under where the head gasket had melted, but possibly not enough to be of concern?

Chr1s · Mar 2, 2014

Oh and a mark in the bore of piston no.1 (top centre):

jamesmartin · Mar 2, 2014

waterways are ok nothing unusual ,i wouldnt use those injectors again,and you may get away with new pistons and a good hone but you would need to measure to find out

Chr1s · Mar 2, 2014

jamesmartin said:
you would need to measure to find out

Is it likely to be worth investing in a set of internal bore gauges, or do you think ring gap measurements will be ok?

Come to think of it, if I have to take the block to the machine shop anyway, would it be cheaper to just go straight for a rebore and save myself the expense of bore gauges?

p.s. Thanks James. Your advice is very much appreciated!

Brown · Mar 3, 2014

I don't have James's extensive experience but I've had apart a few engines that have been over-revved and overheated, and I'm surprised how normal everything looks. That scoring on the cylinder bore and the erosion on the top of the piston could have been going on for years without anybody noticing. I'm more used to seeing pistons burned right through, fragments of piston ring welded to the inside of the cylinder bore and scoring the piston as it goes up and down, or pistons burned round the edge into the ring grooves.

Personally, I think if you're taking an engine apart like this, and it's intended as a repair rather than just a post mortem, you might as well make sure it'll last as long as possible once it goes back together. So I'd be tempted to rebore, regrind, skim, reface and renew wherever feasible.

jamesmartin · Mar 3, 2014

Chr1s said:
Is it likely to be worth investing in a set of internal bore gauges, or do you think ring gap measurements will be ok?

Come to think of it, if I have to take the block to the machine shop anyway, would it be cheaper to just go straight for a rebore and save myself the expense of bore gauges?

p.s. Thanks James. Your advice is very much appreciated!

i would but buy the new pistons first so bores match pistons

Chr1s · Mar 3, 2014

Brown said:
I don't have James's extensive experience but I've had apart a few engines that have been over-revved and overheated, and I'm surprised how normal everything looks. That scoring on the cylinder bore and the erosion on the top of the piston could have been going on for years without anybody noticing. I'm more used to seeing pistons burned right through, fragments of piston ring welded to the inside of the cylinder bore and scoring the piston as it goes up and down, or pistons burned round the edge into the ring grooves.

Personally, I think if you're taking an engine apart like this, and it's intended as a repair rather than just a post mortem, you might as well make sure it'll last as long as possible once it goes back together. So I'd be tempted to rebore, regrind, skim, reface and renew wherever feasible.

As I'm sure is becoming painfully obvious, this is my first rebuild, so you've a vast amount more experience than I do, so your input is very much appreciated and welcome!

Whilst the head looks ok, it's clear that it has been taken off (badly) in the past, so I'm planning to invest in a replacement from Turner Engineering.

jamesmartin · Mar 3, 2014

Chr1s said:
As I'm sure is becoming painfully obvious, this is my first rebuild, so you've a vast amount more experience than I do, so your input is very much appreciated and welcome!

Whilst the head looks ok, it's clear that it has been taken off (badly) in the past, so I'm planning to invest in a replacement from Turner Engineering.

whatever you do dont refit injectors without a rebuild first

Chr1s · Mar 3, 2014

jamesmartin said:
i would but buy the new pistons first so bores match pistons

That's settled then!

Turner sell these with size 020 (which I guess is +20 thou?). Considering that there isn't any major damage, I assume there is no reason to go for larger than that?

300TDI engine parts from Turner Engineering, LDF500180 cylinder head

Chr1s · Mar 3, 2014

jamesmartin said:
whatever you do dont refit injectors without a rebuild first

Yep, new injectors are on the list! I picked up on your comment about not reusing them, did some reading, and discovered that they could be the cause of the problem, which I hope bodes well for the turbo!

jamesmartin · Mar 3, 2014

Chr1s said:
That's settled then! Turner sell these with size 020 (which I guess is +20 thou?). Considering that there isn't any major damage, I assume there is no reason to go for larger than that?

300TDI engine parts from Turner Engineering, LDF500180 cylinder head

youd need to get bores measured 20 thou is only 10 thou a side, usually enough to give a new bore ,but not allways , you must have piston though before rebore ,pistons though called +20 or +40 arent necessarily so its a nominal size and can vary 5 thou or so from it ,and piston clearance is only 1-2 thou

Chr1s · Mar 3, 2014

jamesmartin said:
youd need to get bores measured 20 thou is only 10 thou a side, usually enough to give a new bore ,but not allways , you must have piston though before rebore ,pistons though called +20 or +40 arent necessarily so its a nominal size and can vary 5 thou or so from it ,and piston clearance is only 1-2 thou

£50 is a lot to spend on a piston that might turn out to be no use so I will give my local(ish) machine shop a call tomorrow and see if they would be willing to take in the block, measure and then recommend a piston size before I order the new pistons. They are close enough to drive the new pistons over so it shouldn't cause too much of a delay... Unless they tell me to bugger off and measure my own bores!

Brown · Mar 3, 2014

Looking at your pictures, aside from the superficial vertical wear marks, you can still see the original crosshatching so I'd be surprised if it needed much taking off. I'm used to seeing a distinct 'step' you can click your fingernail over at the top and bottom of where the piston rings rub. As you can probably tell, most of the cars I've known intimately have been pretty near the end of their useful lives! There was a motor engineers near where I used to live in Somerset which would rebore and sell you a set of pistons to fit. We needed + 80 thou taking off our Series 2 bores. But that was a very comfortably worn in engine.

Brown · Mar 5, 2014

Any more news Chris?

300tdi engine rebuild (with pics)

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