Air shooting through holes on HP seat retainer of MK7

[halocline]

I'm not so sure that a 70 would work better than a 90, I think the important thing is fit, and there is a tiny variance in size between specific o-rings. If the 90 has a slightly smaller cross-section, which one might equate with being denser material, then sure, it's going to leak. I would agree that on average, a 90 might be more difficult to seat correctly in the first place. But, SP's 'solution' was to ditch the o-ring altogether and use a semi-rigid bushing. I try to use 90s for this spot because of the high pressure differential and extrusion potential.

 

[Reefer]

Will try to get SP's latest MK5 kit but will take long to get one to here in New Zealand. I have only 3 kinds of 013 on hands. V90, used old puple original one and one from VDH which I have no idea which hardness it has but will try all of them.
Don't like hard spring touching soft brass. i found some 1st's have some rust where those two different materials meet too. But will take the shim out if IP is more than 135 once I managed to have it work properly.
Actually used same method Awap using to seat the o-ring in the place. I could push the socket pretty hard down to bottom. Could feel and see it was in the groove evenly before I start to assemble the retainer.
I was not aware retiners for MK5,7 & 10 are actually same one. Defiantly will borrow one from working MK10 for testing. I attached retainer from the MK7. Can actually see scratches on top.


All seats seemed had same hight position for orifice but I thought that -013 O-ring seats on top edge of the seat. unfortunately 1st flat seat already had marking on both sides when I got it.
Thank you all. Guess I know what to try now. Will let you know once I got news.

 

[redacted]

Will try to get SP's latest MK5 kit but will take long to get one to here in New Zealand. I have only 3 kinds of 013 on hands. V90, used old puple original one and one from VDH which I have no idea which hardness it has but will try all of them.
Don't like hard spring touching soft brass. i found some 1st's have some rust where those two different materials meet too. But will take the shim out if IP is more than 135 once I managed to have it work properly.
Actually used same method Awap using to seat the o-ring in the place. I could push the socket pretty hard down to bottom. Could feel and see it was in the groove evenly before I start to assemble the retainer.
I was not aware retiners for MK5,7 & 10 are actually same one. Defiantly will borrow one from working MK10 for testing. I attached retainer from the MK7. Can actually see scratches on top.

View attachment 215921
All seats seemed had same hight position for orifice but I thought that -013 O-ring seats on top edge of the seat. unfortunately 1st flat seat already had marking on both sides when I got it.
Thank you all. Guess I know what to try now. Will let you know once I got news.

While those flaws look bad, but I don't think that is the problem. If that were the problem, it would leak before the "pop". That pop is the sound of the o-ring dislodging and the only way that happens is it gets blown from the outside, inwards. And that would be casued by HP gas leaking into the outside of the o-ring. I'm fairly sure the VDH o-ring is duro 70 or 75 depending on the material. Both a duro 70 and a duro 90 would work fine sealing the small gap between the retainer and the HP seat. The duro 70 wouod do better sealing (flowing into) any defects in the metal surfaces. Then duro 90 should resist beomg blown out of place, but the fix is to eliminate the leak that is causing the o-ring to be blown out of place to begin with.

If the leak occurs without the o-ring being dislodged first, that would suggest those defects on the retaiier are not being sealed by then o-ring. If the old purple o-ring looks good, I would not hesitate to give it a try.

 

[Reefer]

I finally had some time to deal with the problem.
first, I tried a retainer from another MK7 and it still leaked at HP side like before. But I found that if I changed to other HP seats (all used), IP crept but there was no shooting air. So I put new HP seat and tried. IP locked at 157 PSI with no creeping and No Shooting air. Inspect HP seat with magnifying glass and there was very fine crack on top edge of the seat. I'm not sure that if you can see that crack.


So I assume it was the Bad HP seat that I never thought it was.
Thanks for the all comments I learned a lot. Now I just need to figure out how to sort out High IP problem.

 

[halocline]

The way to get the IP lower is to ditch the shims (maybe you've done that) and use the highest profile seat you can find; as I mentioned before the kits come with three seats. I've never owned a MK5 that needed the highest seat; I'm always using the lowest ones. It might be that your main spring is either the wrong one or just really old and stiff. I've heard that happens!

I have never seen a cracked HP seat before, how about that. Glad you figured it out.