Yes the endoscope thing was good but fiddly, and as you will see from the video a bit Blair Witch shakey jakey. I took out the pair of pushrod tubes from 1 & 4 and filmed the bores to see if I could spot any real difference between them, which may explain the leak. Now I thought I had cleaned the bores really well but he endoscope says otherwise! The first one was remnants of previous black gunk on the edge of the bore and a bit of orange silicone. Also the bore wasn’t exactly perfect, but I guess they are all like that (non genuine heads). Also the edges going into the bore were quite sharp. So I have cleaned and then used wet and dry and finally polished with the dremel using a felt mop. I have also smoothed the sharp outer edges of the bores. Ran out of light and then bad weather so no further progress.
Hmm, those grooves worn into the heads are not normal, the tubes are meant to float on the seals - are they really that tight? No.1 has a nasty nick. I would definitely use sealant. Have a good look at the tubes too, the o-rings have to seal against those as well as the heads.
If my dad were still alive, he would have said that’s as rough as a badgers arse, I don’t know how rough a badgers arse is but those grooves, scratches, burrs and old sealant will definitely give the O-ring a hard time to seal. Clean it squeaky clean and smooth out the grooves and it should seal – I wouldn’t use sealant.
All so much easier if you have the head in your hand and not grovelling under the bus on a built up and installed engine though? I'm not really sure why you are so dead set against using some sealant in these circumstances - maybe you would remove and dismantle the top end and start from scratch? but to be sure - I wouldn't just for a pesky leak like this. No amount of effort on my own heads would have solved the corrosion pitting for example other than machining the bores, so, again, it's horses for courses/how far you are prepared to go to stick to your no sealant philosophy. After I removed my head and inspected the bores before cleaning, the sealant used had most definitely worked - it had literally bonded the o-rings to the head! I guess we could argue whether that's a good thing or not, but I'm pretty sure they did not leak at this joint though it did not help with any leak potential between the o-ring and tubes and by 'eck it made getting the tubes out difficult!
I have no objection to anyone using sealant, if it works fine, I’m just saying what I would do. Even the maestro Jake Raby used sealant, until he decided not to. And it’s very easy for me to say it needs to be squeaky clean because I’m not the one cleaning it, but then I wouldn’t have assembled it like that in the first place. He has cleaned, used wet and dry, polished with felt mop in a Dremel and smoothed the sharp outer edges of the bores. The O-ring should seal but those heads are a mess and the he might not get them leak free, sealant or no sealant. I hope he does and sealant does the trick; I don’t mind at all being proved wrong.
The engine was only 5 years old (heritage one) when I got the bus 8 years ago and my first type 4. I can’t compare the heads with genuine but I was quite surprised with the bores. The PO used silicone and genuine tubes, but they leaked from the day I got it. I changed to viton rings but still leaked. Even with silicone it minimised the leak but it was always there. Perhaps I should have asked at the start what the bores should be like - smooth polished? I can try and get them as smooth as possible and retry but am I being optimistic? Plus doing it laid down on a concrete drive isn’t fun
If the bore is clean of burrs, grooves and scratches the O-ring should seal but as soon as there is a lump of sealant or an axial scratch there is a leak path for the oil. Radial grooves are not so serious as long as they are no too deep or rough. Burrs will cut the O-ring but I think you have cleaned those. As zed says the tubes need to be as good as the heads. Normal O-rings in the kits should be fine, usually black at the crankcase and green in the heads but I wouldn’t worry whether they are Viton or Silicone. Is there any pressure or fumes from the crankcase when you remove the oil filler cap with the engine running?
All three of my type 4 engines have original heads and they are lovely and smooth . The new heads I skimmed from stateside were really rough .. perhaps using a brake hone tool may help to clean /smooth out and keep everything round and square
Not been able to do anything due to being unwell, but today honed the bores using this tool and am happy to report that using just oil to lubricate the tubes to relocate and having run up the engine, the tubes are leak free! Thanks for all the advice and suggestions, all appreciated! Cheers Jon
It didn’t last long before the tubes leaked, so all out, cleaned and reinstalled with rtv silicone. Got the engine hot and revved up and still fine but leak from rocker cover gasket. I did notice pressure when removing the oil filler cap when running.
