Coltri - mch6 - to unseize?

[shil]

HI all,

A friend's Coltri MCH 6 , seized while it was being used to fill air.
Need advice to get back running. We have a good workshop and tools and mechanics and would like to tackle this ourselves,
Looked on the net for service manuals, but nothing except users manual and schematic of the unit.
Any guidance as to what to look for and do in such a case , is most welcome.

Shil

ps, posted this in the DS first, only swampdiver replied... so the above.

 

[CraigAClark]

I would look at the 4th stage piston. It is at the bottom of the block. If it is stuck in the cylinder, you may have to remove the back (fan side) cover plate to get at the wrist pin in order to remove the cylinder (with the frozen piston). BTW, have you verified that it isn't the driver that is siezed. Sometimes you have to cut the belt off to know for sure.

Craig

 

[shil]

That's just what we did this morning here. (prime mover was OK).
We opened the fan side and checked, proceed to check the 3rd stage,then the 1st, then it became obvious that was the 4th which had seized. took it out and found it burred and scored.
We will be ordering replacement set of the whole 4 stage, but meanwhile just curious to know if it can be repolished and put to work. Anyone done that on a Coltri ?

Shil

Thanks for the tips

 

[CraigAClark]

No problem. I have seen them lock up and snap the con rod, guess you were lucky. I used to repair them, but being in a business situation, I couldn't try polishing. Couldn't risk the customer coming back a week or so later with the same problem, so they got replaced with new parts.

Once you get it up and running, I would suggest you change the oil early and often and if in doubt change it again! LOL I say this because that piston is partially submerged in the oil sump and any metal that wears and drops into the oil can possibly cause this to happen again.

Craig

 

[shil]

does that happen , often ? a bit of metal falling inside ?
thanks.

Shil

 

[shil]

HI all.

A picture of the shot 4 stage.

 

[CraigAClark]

With that amount of scoring, how does the cylinder look? BTW, just for grins, slide one of the con-rods off the crank and see what the spot (on the crank) looks like where the needle bearing runs.

Craig

 

[shil]

Did not check the liner as we were in a rush to get parts ordered. And will check the crank where the need bearing rolls.

Shil

 

[rcontrera]

Just a quick note ... a couple of years ago Coltri began matching the 4th stage piston and cylinder because of the close tolerances. Since there are no rings, too much clearance would cause too much blow by. Make sure you get a matched set.

Oh, and Craig is right ... check under the bearing on the crank shaft. Seizing on a cylinder can cause damage to the shaft at that point as well since the crank isn't hardened at the bearing surfaces.

 

[shil]

Checked the crankshaft. it looks and feels Ok. But will check further. By the way I hope it was a matched set of 4 th stage piston and liner which was sent to Curt Degler a few days ago, that ''s his unit we are dealing with !

what is the recomended degreaser to clean off the old oil before reassembly for breathing air compressors /

Shil