Advise on my "new" MK5

[triggerman365]

Wow, I just bought a never used MK5 (2hp/5lp) for $75. The guy says he bought it many years ago and never used it. So, I am planning to test its ip but I'm wondering if I should just tear it down and service it since the o-rings are probably 20 years old. What do you all think.

 

[herman]

I would be more concerned about the condition of the oring lubrication than the orings themselves. Odds are it will work but with a reg that old it really needs to be dissambled, cleaned, new orings installed, relubed and tested. The old grease has to go, odds are it's getting a little stiff. Once your into the reg, it just does not make any sence not to replace a dollar or 2 worth of orings while you are in there.

 

[Fishpie]

Congrats.....I was tempted by that one myself.
Main thing is not to damage the finish when taking it apart......Seat cap, yoke nut and body split, you don't want some shiney gold gouges on a new reg.

 

[triggerman365]

I would be more concerned about the condition of the oring lubrication than the orings themselves. Odds are it will work but with a reg that old it really needs to be dissambled, cleaned, new orings installed, relubed and tested. The old grease has to go, odds are it's getting a little stiff. Once your into the reg, it just does not make any sence not to replace a dollar or 2 worth of orings while you are in there.

Great, I hadn't thought of the old grease, Thanks.

Congrats.....I was tempted by that one myself.
Main thing is not to damage the finish when taking it apart......Seat cap, yoke nut and body split, you don't want some shiney gold gouges on a new reg.

I held my my finger over the "commit to buy" button for a bit, knowing my Budget Director (my wife) won't see the value or need in this beautiful reg.

 

[elan]

Congrats thats a great reg and will serve well. I'm now using 2 pn my summer doubles serup and love them. They definitely look cooler than even MK25 in DIN config.
I would definitely tear it apart and put poliurethane orings on the piston and swivel turret a well as replacing the swivel bolt with staneless steel one if it has a brass bolt. If the saddle on the yoke is plastic chance are it is already an SS and it has the upgraded shouldered piston.
In any case this buy is a good one , you should have no regrets

 

[triggerman365]

Congrats thats a great reg and will serve well. I'm now using 2 pn my summer doubles serup and love them. They definitely look cooler than even MK25 in DIN config.
I would definitely tear it apart and put poliurethane orings on the piston and swivel turret a well as replacing the swivel bolt with staneless steel one if it has a brass bolt. If the saddle on the yoke is plastic chance are it is already an SS and it has the upgraded shouldered piston.
In any case this buy is a good one , you should have no regrets

Sorry it has taken me awhile to respond. I was on vacation in Kwajalein, got 16 dives in on my newly rebuilt 109!

The saddle is plastic or rubber, so hopefully the swivel bolt is SS. Did Scubapro switch to a SS bolt on late production MK5s? Or would the SS bolt have had to be changed by a SP tech, because the MK5 I bought is new and has not been to a tech. Same question applies to the shouldered piston?

Here's a picture of my MK5

 

[Couv]

Hello Triggerman,

Congratulations on a very nice find.

This regulator may have a brass swivel retainer; but it is not a concern. No one-day wonder has had a chance to over torque that bolt which is the real problem. So when you reinstall it, use a torque wrench. If you would feel more confident with the ss retainer, VDH has them Shop Online

The piston is probably a shouldered one, but if not I would not be concerned. If it were a real issue, ScubaPro would have had to recall all MK 5/6/7s with non-shouldered pistons.

 

[triggerman365]

So I got my MK5 and put an inflator hose on it with my IP gauge. The tank I have has about 1000psi. The IP is locking up at 125psi. Would tearing it down and re-lubricating it help the IP? I'd like the IP in the 135-140 range. And once its apart, I might as well put a shim in to boost the IP by 5. What do you think?

 

[ams511]

I don't think a tear down and a relube would help. What kind of seat are you using? How many shims are installed? In a MK-5 Scubapro only recommends 3 shims.

 

[halocline]

I usually leave mine at 125 PSI. IP is a little like blood pressure in that it rarely goes down with age. 125 provides plenty of flow, but you could add a shim or try the "+" seat, the shortest one, to raise it 5-7 PSI. If it really has never been rebuilt, it will have a white seat, maybe red, but the current MK5 kits come with three grey seats that have a slight conical profile. The seats are different heights; the shortest one raises IP the most, the tallest one marked "=" lowers it. I almost always use the shortest seat. Depending on the reg you can usually get some use out of two of the three seats and make up the difference in IP with shims.

So it's probably worth it to buy one NOS rebuild kit to get the three seats. I got lucky and a dive shop had a drawer full of "+" seats that it had not used and sold me several. Other than the seat, it's just o-rings.

For a few years I used polyurethane o-rings for the HP piston and piston head spot. They are supposed to be better for extrusion, which is a problem in the HP piston spot. This is what causes higher IP with a full tank in the MK5/10. I got a bad batch of those o-rings and they dried up. Now I have several viton ones and I'm using those. EPDM works fine too; the main thing is to use duro 90 o-rings for the HP piston spot.

Probably the biggest challenge in rebuilding the MK5 is removing the old HP piston o-ring cleanly without scratching the journal it sits in. I wonder how many MK5s were ruined by careless techs digging out that o-ring while answering the phone. I use the scubatools double hook o-ring pick for that; it works great. I just bury the point of the pick in the old o-ring so it never comes near the metal and ease it out.