Seat and shims MK10 ?

[buddhasummer]

I'm servicing a MK10, I couldn't get an ip reading before taking apart as it was non functioning, ip crept way past 160 and climbing so I turned air off.

I'm not sure best place to start, a shim above and below spring? What seat to use? -,=, +? Any pointers would be appreciated. I'm trying to avoid assembly, disassembly and reassembly multiple times if possible, not sure if the crush washer can take it. Thank you.

 

[Couv]

Hi Simon,

If it had 2 shims on the spring then yes, put the 2 shims back; one on each side of the spring. With 2 shims on the spring, start with the HP seat marked -ll as that is the lowest IP seat, next is the -l, then the + If the IP is too low, replace with the appropriate seat. Each seat grade is worth about 4-7 psi. If the IP is too high with the -ll remove one of the spring shims. I would prefer to leave the one between the body and spring.

VDH sells shims Store - Vintage Double Hose that come in different shim thicknesses (0.01 & 0.015 inches) so if you can "fine tune" the IP by adding and removing different thickness shims-but now you're really getting into the geeky aspect of DIY.

Awap's idea to aim for the low end of the IP specs because over time the IP tends to rise rather than fall is a good one and well worth considering.

BTW the crush washer is reusable for many times-even if it fails, it can be replaced with a properly seated -013 seat.

Good luck and let us know how it turns out.

 

[buddhasummer]

Ok, one shim and II seat gave me 120, locked solid, swapped out seat for the +, by the way Robert your trick of using the tank to blow out seat worked a treat, with + seat ip locks solid at just over 130. A massive thank you to Herman for his awesome tools and to you, Robert and Matt for putting up with and answering my many emails. I owe you all many many beers. TJ too.

You guys and others who have given advice and pointers have helped me immensely on my DIY journey, there is no way I'd be where I am without you.

I've now successfully serviced a MK10, a MK11, 5 G250s, 2 D300s and a conshelf. I'm super stoked, the self reliance and knowledge is priceless.

Have a great weekend guys, I promise to leave Herman, Robert and Matt in peace, for a whie at least.

 

[Couv]

Ok, one shim and ....+ seat ip locks solid at just over 130...

Glad to help and well done! 130 at low tank pressure, right?

That is beautiful specimen you have.

 

[buddhasummer]

Thanks Robert.

No, 130 at high tank pressure. I thought pistons were set at high tank pressure and diaphragms at low tank pressure? Have I misunderstood?

 

[buddhasummer]

Ah, penny's dropped, pun unintended, so when the tank pressure drops so will the ip, so at low tank pressure it could be out of spec. So I'd need a ip higher at high tank pressure assuming a greater than 5 psi drop at low tank pressure. Assuming I've got it right, I think I do, then I'll need to add a shim I guess. Bummer, didn't want to mess with the piston. I'll put a second shim under the spring. Oops...

 

[buddhasummer]

Or am I likely to need to add two shims?

 

[buddhasummer]

I'll turn off air and bleed down to 300 psi and check reading.

 

[buddhasummer]

It dropped by just over 8psi at 300psi. Guess I'll need to add two shims.

 

[redacted]

I would leave it. But I tend to set IP at the low end of the spec. After the initial set, IP changes tend to increase over time.