Broken piston Coltri/Nautica MCH-6

[Fishpie]

I just picked up a little MCH-6 with a 5hp Honda for next to nothing.
It's looks like an older model at least 20 years old.

When I bought it I was told that it had seized because it had blown out the dipstick and run low on oil.

I would like to learn about compressors and this seemed it would be a good project as parts are readily available.
I would like to rebuild it more as a learning project than anything else.

I have completely disassembled it.....all pistons out and crank removed.
The reason it stopped running is because the 4th stage piston has snapped in two with the broken part jamming the con rod against the housing.
This makes me think that there was a hydrolock (probably oil lock) and the dipstick blew out as a consequence of the piston failure and not the other way around.

It will need a new 4th stage piston and con rod.....the cylinder looks good but it might be best to replace this too.
I probably should replace the rings and hone the cylinders since its all apart.
Valves?.....I know nothing about compressor valves.
The crank looks okay with some light scoring but since the big ends run on roller bearings I hope this will still be usable.
The cylinder walls, pistons and rods of the other stages look good.

Since I live in Ft Lauderdale I know there are allot of helpful folks down here.
I need advice on where I should buy parts and get a proper service manual. The Owners/Maintenance manuals are all over the web but can't find the workshop manual.

I'm pretty good with basic engine stuff but a novice with compressors.

I haven't looked at the filters yet...it came with 3, 2 on the frame (water trap and filter/water trap combo) and an added extra that fits on the fill whip the same size as the secondary filter on the frame.

Advice needed on what I should replace on this rebuild.
Where to buy parts?
Is there an overhaul kit (cylinder o rings, valves, rings etc}?
Where to get a workshop manual?

Thanks for any help.

 

[Fishpie]

Here's some pics:

 

[Fishpie]

How's the place on Old Griffin Rd?
I don't really want to order the parts until I have some feedback.
Is there any variation in prices? Or does everybody charge the standard retail price.
Thanks

 

[roastbeef]

Sell it off and get your self a nice Bauer Junior you'll save your self allot of head ackes.

 

[Fishpie]

I already have a SA6 that's working fine and an old Mako that needs an overhaul.
My thoughts were to learn more about compressors in general before starting in on the Mako.

 

[rcontrera]

The MCH6 is really an easy compressor to start learning on. Most likely, what happened to your 4th stage was that it sat for a long time without being run. The 4th stage sits in the bottom and is submerged in oil. If the compressor has been operated for a while without an oil change, ANY moisture in the oil will settle out and go to the lowest point ... the 4th stage. That little piston has oil grooves in it and I would guess that at least the first groove was in water and rusted.

You are going to need to replace both the cylinder and piston since they are actually a matched set now.

Since it is a 20 year old machine, I think you should also do the 500 hour valve kit as a minimum (has all four stages of valves, 1st stage and 4th stage heads). They have also changed the inlet filter housing so you will need to upgrade that as well.

 

[Fishpie]

Double post

---------- Post added April 11th, 2012 at 06:19 AM ----------

Thanks for the advice.
I got the compressor from the previous owner with the knowledge that it was "seized". He said it had been running well but left the compressor to go answer a phone and when he returned 2-3 minuted later he found it stopped with the dipstick blown out and oil on the floor.
I was happy to find a broken piston jammed between the crank and case and not a piston stuck in the cylinder.
Do you have a rough idea of the cost of the 500hr kit?

I still would like to know where to buy parts.....I have emailed and left messages to Coltri-Sub HQ here in Coral Springs but they haven't got back to me.

---------- Post added April 11th, 2012 at 06:38 AM ----------

One other thing I noticed on dis assembly was the 3rd stage piston wrist pin was loose and simply fell out.
Is this normally pressed in?

 

[rcontrera]

Do you have a rough idea of the cost of the 500hr kit?

About $300

I still would like to know where to buy parts.....I have emailed and left messages to Coltri-Sub HQ here in Coral Springs but they haven't got back to me.

HellOo!

If you buy from them, you can just drive up and pick up the parts. If you order from me, you will have to pay about $15-20 for shipping but I don't charge you sales tax. $20 shipping or $21 sales tax ... Kind of a wash.

One other thing I noticed on dis assembly was the 3rd stage piston wrist pin was loose and simply fell out.
Is this normally pressed in?

The wrist pins have Seeger rings on the ends to keep them from falling out. They are pretty thin steel so I would guess that the previous owner never changed the oil and let water build up to a point that the internals just rusted up.

 

[Fishpie]

I see clips on the other pistons but I think the wrist pin on No3 has got worn on the ends as I don't see any grooves to hold the clips.

 

[roastbeef]

I see clips on the other pistons but I think the wrist pin on No3 has got worn on the ends as I don't see any grooves to hold the clips.

Those little Italian made compressors have such a fast RPM you can expect them to last long that its rough on internal components.