Coltri mch6 air leaking back through the air intake

[zider]

I haven't fixed it yet, but after pulling the 4th stage apart, the valve was in pieces and the spring was all rusty and horrible. The cylinder wall was fairly badly pitted so I think I've found my problem....
The third stage stage looked ok though.
It looks like I'll be replacing the 4th stage, any suggestions on where to purchase them at a reasonable price?

Do some searching related to the MCH-6 and you will find that water build up is common if the pump is left idle. It's really a design flaw as water will settle in the oil sump and corrode 4th stage components if its left idle for any extended period of time. I believe that Coltri has moved to a stainless steel MOC for the 4th stage to help combat this issue. Users recommend running these units regularly during downtime (i.e. through winter months) to prevent corrosion or doing an oil change before storing the unit away.

I agree with others that this isn't the best compressor, but it works well for folks like me who only do a few fills here and there. I follow the recommendation above and simply run the compressor up to pressure for about 5 minutes once a month. So far I've seen no issues. Good luck!

 

[lukejjon]

Thanks for all of the information on this. I've received a replacement 4th stage and you're correct, it is stainless steel. Just a note for anyone else, the springs in the valves on stages 2 and 3 were so rusted, they fell apart when I removed them - luckily the postons and cylinders were ok.

One more question, before reassembling, I'd feel better if I could "flush" the crank case just incase I inadvertently introduced any foregin material when I reassembled (I tried hard not to, but I suspect I may have transfered some - or maybe some was already in there as I could see some small non-metalic items). Would running the Coltri oil through a few times be the best or is there another oil or mineral I could use?

 

[Wallowa]

Thanks for all of the information on this. I've received a replacement 4th stage and you're correct, it is stainless steel. Just a note for anyone else, the springs in the valves on stages 2 and 3 were so rusted, they fell apart when I removed them - luckily the postons and cylinders were ok.

One more question, before reassembling, I'd feel better if I could "flush" the crank case just incase I inadvertently introduced any foregin material when I reassembled (I tried hard not to, but I suspect I may have transfered some - or maybe some was already in there as I could see some small non-metalic items). Would running the Coltri oil through a few times be the best or is there another oil or mineral I could use?

Curious about water accumulation and subsequent rusting.....that would take a very high humidity I assume? Lots of the MCH-6s in service and doubt if rusting internally is common, but I guess it could be if condensate drain is not purged frequently?

 

[Wallowa]

Also curious, I have no first hand knowledge, why "Do some searching related to the MCH-6 and you will find that water build up is common if the pump is left idle.' would sitting idle cause water to accumulate? Unless moisture is introduced, where does it come from to accumulate? Thanks.

 

[Agro]

Thanks for all of the information on this. I've received a replacement 4th stage and you're correct, it is stainless steel. Just a note for anyone else, the springs in the valves on stages 2 and 3 were so rusted, they fell apart when I removed them - luckily the postons and cylinders were ok.

One more question, before reassembling, I'd feel better if I could "flush" the crank case just incase I inadvertently introduced any foregin material when I reassembled (I tried hard not to, but I suspect I may have transfered some - or maybe some was already in there as I could see some small non-metalic items). Would running the Coltri oil through a few times be the best or is there another oil or mineral I could use?

I would not use oil to flush, it is to much viscous. I'd use gasoline, wash out all the oil and then blow out the crank case by air. Now surfaces are clean and you can easily inspect them.

 

[happy-diver]

Dont blow anything save you have particles in the bottom of your sump to be blown all over the place

It might all come from the same stuff underground but petrol stinks and permeates and leaves residue
and it shouldn't be anywhere near a BA compressor unless you are a farmer from a stupid country and

have no solvent, and a vacuum

 

[Agro]

Coltri crank case can easily be blown out, openings are very large. After blown out crank case is clean for sure.

Gasoline, solvent..... they all leave residues. Unless you blow them out, then they don't.

Vacuum might work as well if you have a tube by which you reach ever crank case corner.

 

[Wallowa]

Coltri crank case can easily be blown out, openings are very large. After blown out crank case is clean for sure.

Gasoline, solvent..... they all leave residues. Unless you blow them out, then they don't.

Vacuum might work as well if you have a tube by which you reach ever crank case corner.

Agree with Happy....gasoline is not a solvent it is first a fuel with additives......want residue? Use gasoline to wash parts. And all solvents do not leave residue....just my take.....

Never heard answer to "where does the water in the case come from"? Again, just my assumptions that it was there do to insufficient venting/draining of condensate tower or very high ambient humidity/water into intake...

 

[happy-diver]

Take your rebreather to a farmer for some welding and it comes back looking like a plough

 

[Wallowa]

Take your rebreather to a farmer for some welding and it comes back looking like a plough

I know that means something....but what?