Well the engine has now been removed from the bus at long last ready for a gander at the possible reasons as to why she has been over pressurising. Removal was pretty painless, however, I am going to require a new exhaust as there were a couple of noticeable cracks once removed (to be fair it's a mild steel one which has been on there for about 9 years so it hasn't done too bad). Will be going the stainless route and put up a post in the wanted section shortly.
Unfortunately, I have completely mislaid my brand new compression tester so was not able to test the compression numbers prior to removal (I know I need a slap Paul!). I've posted up a couple of pictures of the ports on either side of the head - you can see slight discolouration on the first port on the right hand side compared to the other 3. This could possibly be leakage?
fingers crossed on the studs, heating the nuts helps and I recommend it even if it does bugger the plating its better than a snapped stud.
you want to be careful not to heat the valve springs, you can use a shield.
A cracked head is toast but don't assume its cracked, if you have a compression seal leak, when you stop the engine sometimes the valves will be open and steam will get into the inlet, an indication perhaps that this is the one with the leak?
This was a leaky compression seal, this is what you may find, you can see the discoloration at the top of the barrel sealing surface and the damage to the bore surface caused by water entering.
Seem to have located the source of the problem - the o ring seals on two of the barrels (one on each side) were not sealing properly due to poor condition and probably down to there being no anti freeze being used previously at some point in it's life:
So, at the moment its looks as though i need two barrels and all will then be honed at my mates workplace. Piston's will also be removed as i'm going to replace the rings whilst everything's off.
The bad sealing you have shown is not compression seals but when the green o rings fail it allows coolant to get to the compression seals and degrade them.
worth inspecting the barrel top sealing surface and the head sealing surface in detail
also worth lapping the barrels into the heads with fine grinding paste.
itchyfeet wrote:The bad sealing you have shown is not compression seals but when the green o rings fail it allows coolant to get to the compression seals and degrade them.
worth inspecting the barrel top sealing surface and the head sealing surface in detail
also worth lapping the barrels into the heads with fine grinding paste.
Cheers Paul - do you think that the o ring failure could have been the cause of the problem? The more I think about it, the more I reckon it’s worth going for a set of new barrels and so I’ve gone for it and purchased some
Untitled by Justin C, on Flickr
Untitled by Justin C, on Flickr
Untitled by Justin C, on Flickr
Untitled by Justin C, on Flickr
Untitled by Justin C, on Flickr
