I found a very interesting article about Subarus in the US having a product fault on cars made between 1999-2002 that resulted in "external coolant leaks". See:

http://66.249.93.104/search?q=cache:p4TxfZ...uk&ct=clnk&cd=7

They brought out a "Cooling System Conditioner" which seemingly looked suspiciously like Holts Radweld...

So thoughts on my head gasket problem...

The Subaru problem was external, which I guess means it is from the cooling system into the outside world - into the engine compartment. This is the same pressure as the radiator so you can see how it is a cinch of a solution.. Also, the pressure in the cooling system would force water through the leak enabling a deposit of Radweld material (call it gunk!) to build up and seal the leak, which is how I assume Radweld works.

My problem is gases getting through from the high pressure of the cylinders into the cooling system - an "internal coolant leak". So, at least at present, there is no leakage from the coolant cylinder into the cylinders (although my garage tells me this is eventually what happens). So using Radweld would maybe not work because gases blowing through the leak would blow any coolant with Radweld out of the leak channel. So a thought..

I could use Radweld, run the engine for a while to stir it around into the cooling system and then just leave the car without running for a few weeks to allow capiliary action to carry the Radweld into the internal leak channel and solidify. OK, the Radweld is designed for sealing low pressure systems, but my leak is very small - I put about 1CM of water into the tank this morning after a journey of 140 miles yesterday. Also, the ability of the Radweld to seal will be dependent upon the size of the cross-section of the leak channel (measuring the pressure) and the length of the plug of Radweld filling the channel (measuring its adhesion to the inside of the channel). And if I leave it a few weeks, capiliary action may take the Radweld quite a long way down the leak channel. It may even be worth using a more diluted solution of Radweld so capiliary action can carry a small amount of Radweld gunk further before it sets (it does set does it?). With the replacement XM I could pretty much leave it as long as I like.

Any comments would be much appreciated, I'd be particularly interested in anyone who has used Radweld and knows what it does!

Sorry, I should add that the Subaru external coolant leaks were from the cylinder head gasket.

I just spoke to Holts' technical department and they said I would be better off with "Wonderweld" which is designed for this:

http://www.motortraders.com/xcart/catalog/...weld_250ml.html

"Permanently seals cracks in cylinder block, internal and external leaks in water jacket

Suitable for steel, iron and aluminium engines

Prevents the need for engine rebuild"

is what it says!

I'll give it a go!

Regards

Andrew

It seems to work, I found this link:

http://66.249.93.104/search?q=cache:3mbqeE...k&ct=clnk&cd=30

Hi Andrew, all this sounds interesting but I'll leave it to others as I have no own experience of those products. However I wanted to ask you: how do you explain that your engine cracked or your gasket failed? Are you watching the water temperature on your car? How does it behave? Do your fans work properly? Most of the times such problems are the result of something wrong with the engine temperature (overheating).
George

PS the XM u r looking at looks nice!

ah Jorgy I noticed when I killed my head the temp didnt rise but still it left me with an expensive bill for parts and now a scrap car. I would believe after meet Andy that the way my head gasket failed was for totaly diffrent reasons to his lol god it was fast that christmas

Hi George and Craig,

Well, I think 95 is a pretty sensible max for motorways...!

I do keep an eye on the water temp and it is usually about 80 degrees, nevers strays above 90 that I noticed. The car had a prang last summer and demolished half of the front bodywork and Craig sold me the bits to repair it (hence he knows what a sensible chap I am!). Not a scratch on the other car remarkably! I was a bit concerned that I didn't hear the fan cutting in after the bodywork repair, but I had the garage check it about 6 weeks ago and they assured me it was working. I must say, I never seem to hear it though and I recall it being fairly loud! Not a mechanical noise but the sound of it cutting through the air. Still, they've assured me it is working and certainly the temperature suggests it is.

Regards

Andrew

ouch Andy cut me deep with that one lol it was almost empty when I did my high speed run and I can now tell you how fast 2ltr turbo auto can go

oh and if anyone is intrested the 2ltr turbo manual will out run a volvo T5 too

Well, Craig, I was rather amazed (and thrilled) that a speed where the digits add up to 5 was possible in an XM!

So the feds drive Volvo T5's?

no fools in polo necks drive t5s but also the local police have a bule un-marked T5

Actually Craig, the I only mentioned the 95 max because I wouldn't want people to get the impression I'm an old duffer who drives around at 45 mph in 2nd gear the whole time! It wasn't just intended as a cutting comment to you!

best one so far has been a friend who also has an MR2 Turbo just clocked in belgium at 168mph

Im sorry if my comment would have made people think that you were I would like to change it to after meeting Andrew I can reasure that he is a more careful driver when it comes to speed however he is no old duffer is that any better ?