Bertie Wooster said:

Hello, many thanks for those ideas. I have tested for combustion gasses, and the coolant is contaminated with them. So there's a leak somewhere. A spot of corrosion was found on the head and this was welded to repair it. After a skim and pressure test it was replaced but there was no improvement so I'm wondering if there is a crack in the block, or perhaps a warped block, and I'm reluctant to spend more time and money chasing the problem. A replacement engine may be cheaper and easier ...... so, thanks for the contact details for Discpvery2parts. I tried ringing today but no answer, I'll try again tomorrow. Cheers.

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BTW Paul is away until 19th October, if you need to contact him.

Hellastony said:

VERY unlikely the block is warped, heads do get warped and need skimming, although LR say this is forbidden, as the surface of the head, although aluminum has been "hardened" somehow. Rather than skimmed, I suggest it should be "resurfaced" to remove any twist, but ONLY if it is warped. If not warped don't touch it other than clean it. I am about to do exactly this.

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And JM was one here a few weeks or was it months back giving, i think, details of how much one could/should skim/resurface a head. He also talked about how to measure warp as I was unsure if in this newfangled world there was a new way of doing it. but, no, straight edge and feeler gauges is still what you use apparently.

Hello Stanleysteamer and Hellastony, many thanks for your comments and help. I've been shielding since March and trying to get this engine sorted has had many challenges!! I've been relying on a friend of mine who has a much better workshop than my outdoor gravel. The second time he took the head off he, and another mechanic friend of hes, spent quite some time with a straight edge trying to find any kind or warp or twist, but they found nothing. He also checked the block and found nothing wrong. The company which originally checked the head found a small amount of corrosion which it thought could have been the cause of the problem. This was welded up and they assured me that a very light skim would not damage the head. They did this and pressure tested it, found nothing wrong, and returned it.
I realise that LR say the head can't be skimmed at all but I was really in the hands of the head repair company. Unless the corrosion was repaired they said the head was no good, and that a weld and one skim would be fine. The head was no good without that so I asked them to go ahead.
When this failed to cure the engine the head was removed again, checked by my friend and no problems found. The head company were happy to pressure test it again but advised against a second skim. So I couldn't see much point in that route and asked for the head to be replaced with a genuine LR head gasket and head bolts in the hope that the first gasket (not genuine) was duff. But exhaust gasses are still being blown into the coolant.
I may be able to free up a suitable building later in the year and. if I can find a suitable replacement engine, would swap i myself. And then, as you say Stanleysteamer, I could look at the original engine without pressure. The first thing I would do is take the head to a different firm to check.
Since these problems another mechanic from a local garage has told me that he would never have an alloy head welded, thet distortion would be inevitable, but it was no good as it was so why not give it a go? And yet another local mechanic has said that he's come across the odd TD5 engine which always seems to have head gasket problems,no matter what's done to sort it. Who knows? I certainly don't.

Ah, that's why I can't contact Paul - I'll try again after the 19th. Thanks for that.

Right!
So you've now told us a lot more about what has been done and yse you have had it checked for warp and haad it skimmed.

In that case I too cannot think what it can be. Maybe there is an internal crack that does not show up under traditional pressure testing but I cannot imagine how that could be. It certainly is a puzzling case and I totally understand why you are now thinking along the lines you are thinking.
I was wondering if @jamesmartin has ever come across this before. as he does a lot of this stuff.
Anyway, the very best of luck with it all.
Stan

gases in coolant ,can only be head, block or gasket crack or porosity, cracks in the head with such would normally be visible,harder with the cylinder and both usually only show up when engine gets hot so pressure test not necessarily an indication,we used to heat blocks or heads n a hot wash prior to testing ,cracks in a block often show s a faint rusty line, any passing of gases through the gasket because heads warped will show as staining across the shiny fire ring,if a heads been too hot it warps obviously you get them skimmed but if its been hot enough previous it may warp again either straight away or very shortly proof is with a straight edge

Hi Stan and Jamesmartin, once again, thanks for your suggestions. There's obviously a problem somewhere and I feel that if I continue looking for it a lot more time and money will have to be spent. And if I find something then it's likely it won't be repairable at a reasonable cost. So a replacement engine could be the best answer if one could be found. I'm favouring a rusty chassis, MOT failure, spares or repair Disco, because I could see the engine running, but certainly I'll be in touch with Paul at Discovery2parts when he returns.
Or perhaps it wouldn't be that much more expensive to buy another Discovery 2 - and I can keep this for spares? But that could mean buying someone else's problems. Mmmm, I'm thinking .....

Not easy is it? And I really do sympathise with you.
The obvs, but probably most expensive choice, would be a decent recon engine, but the cost of that you may well feel would be exorbitant.

jamesmartin said:

gases in coolant ,can only be head, block or gasket crack or porosity, cracks in the head with such would normally be visible,harder with the cylinder and both usually only show up when engine gets hot so pressure test not necessarily an indication,we used to heat blocks or heads n a hot wash prior to testing ,cracks in a block often show s a faint rusty line, any passing of gases through the gasket because heads warped will show as staining across the shiny fire ring,if a heads been too hot it warps obviously you get them skimmed but if its been hot enough previous it may warp again either straight away or very shortly proof is with a straight edge

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James, I seem to remember some sort of a test that used was it talc or french chalk to show the place where an otherwise invisible crack was located. Am I misremembering or was this some part of the hot wash thing you were mentioning? I had a feeling this was used to discover oil rather than water, but as I said it was ages ago and I cannot remember exactly what it was all about.
Is there any definitive test this chap could do to determine whether or not it is a block problem or a head problem? Apart from fitting a known good head and proceeding from there?

Stanleysteamer said:

Not easy is it? And I really do sympathise with you.
The obvs, but probably most expensive choice, would be a decent recon engine, but the cost of that you may well feel would be exorbitant.

James, I seem to remember some sort of a test that used was it talc or french chalk to show the place where an otherwise invisible crack was located. Am I misremembering or was this some part of the hot wash thing you were mentioning? I had a feeling this was used to discover oil rather than water, but as I said it was ages ago and I cannot remember exactly what it was all about.
Is there any definitive test this chap could do to determine whether or not it is a block problem or a head problem? Apart from fitting a known good head and proceeding from there?

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head should be visible blocks usually are too but can be tested by blocking all ports not easy in situ and built up, i often fit another engine and use the other for parts in situations as such, problems can be with skimming heads is when its cast a skin develops on the outside as it solidifies first then gradually the center this creates a tension and a hard outer surface,also if its an overhead cam when you skim a warped head you can distort the cam bearing alignment obviously in real life enough isnt usually skimmed off that this show up as issues

jamesmartin said:

head should be visible blocks usually are too but can be tested by blocking all ports not easy in situ and built up, i often fit another engine and use the other for parts in situations as such, problems can be with skimming heads is when its cast a skin develops on the outside as it solidifies first then gradually the center this creates a tension and a hard outer surface,also if its an overhead cam when you skim a warped head you can distort the cam bearing alignment obviously in real life enough isnt usually skimmed off that this show up as issues

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So the french chalk/talc thing was my memory playing tricks then?!

I might google it just for fun, but appreciate all you say.
At the end of the day, OP seems to be in between a rock and a hard place. Such a shame.
Had a lodger once who was an engineer, who was designing an aluminium rolling plant. He talked to me about ally cooling dendritically, fascinating stuff. But when you get down to the behaviour of the atoms when they are cast, and, as you say, how there is tension formed on the surface when they cool.....
Makes you wish they then reheated them and controlled the cooling to remove all tensions. But that would increase the costs astronomically. Maybe they do do this, I have no idea.

Aha! @jamesmartin
Found it!
https://www.garagejournal.com/forum/archive/index.php/t-163161.html
Also now remembered the name, Magnaflux.
The old grey matter does still function but the wheels turn slower than what they used to.

Getting of for 50 years ago, when in my teens, I helped a car mechanic/engineer (he had the equipment for skimming heads and regrinding cranks etc) and I remember him using a dye and white powder for finding cracks in heads and blocks. Seemed to work well.
Around that time my family had a twin cylinder Lister stationary engine for driving a fan which barn dried hay. The heads were separate and one developed a crack. This chap repaired the crack by brass stitching it. I've never come across anyone else who tried this but it worked well for this particular engine for many years afterwards.
You drill a hole at one end of the crack, thread it with a tap and screw in a threaded brass rod. Then drill the next hole part overlapping the original hole and part over the next bit of crack - until you get to the end. The brass heats faster than the cast iron and keeps things airtight. Bingo.
I think I shall go the route James suggests with my engine,and use this one for parts. But at some point I could well have the head tested again, just out of curiosity.

Magnsflux is NDT testing, using a red dye penetrant to go into a crack then a powder to then bring out the red dye by capillary action, red against the white shows up the crack , better would be Magnetic black light inspection as this is just about instant, as a new North and south form at the crack edge and the utlaviolat light used to carry out the inspection caused and build up of the flosesingfliud to glow brightly showing the crack position

Heyhey!
This is all coming out of the woodwork now!!!
There used to be a company near our place in the UK that specialised in repairing really old engines, and they did a lot of stitch repairs to cracked blocks. didn't have much choice really as there were no spares at all!