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look what I found lurking in my 3rd stage head (MCH5)

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  • #16
    Re: look what I found lurking in my 3rd stage head (MCH5)

    Washer inside the head

    20150301_012427.jpg

    In a perfect world I would use a slightly larger O.D. and a slightly smaller I.D., but this should be close enough to help seal the oval port
    Last edited by trdscfjc; 03-01-2015, 02:58 AM.

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    • #17
      Re: look what I found lurking in my 3rd stage head (MCH5)

      I have tried everything I can think of.
      Still only getting 1.75 cfm...added the crush washer to the 3rd stage as well...sigh

      I'm sure I'm missing something but not sure what it is, I have changed every valve in this thing.

      This is the second stage
      20150301_235904.jpg
      20150301_235915.jpg

      This set to the right level, not sure if this would have anything to do with it (I'm running out of ideas)

      20150302_011940.jpg

      Back together again...

      20150302_015209.jpg

      Looks like I'm getting a slight bit of interference from the valve (likely due to the washer pushing the valve out ever so slightly, I do not see any marks on the piston itself or the valve so for now nothing is actually hitting

      20150302_021159.jpg
      Last edited by trdscfjc; 03-02-2015, 03:15 AM.

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      • #18
        Re: look what I found lurking in my 3rd stage head (MCH5)

        silly question. are your belts tight?

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        • #19
          Re: look what I found lurking in my 3rd stage head (MCH5)

          I feel for you, I have no idea what might be the issue, I was chasing my tale for ever with mine. I used the Bauer equiv. valve rather that the Coltri with the iffy green seal. Bauer 81409 will fit your old type head. Hope that helps you.
          Last edited by BritCNGUser; 03-02-2015, 05:38 AM.

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          • #20
            Re: look what I found lurking in my 3rd stage head (MCH5)

            Belt is tight

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            • #21
              Re: look what I found lurking in my 3rd stage head (MCH5)

              Because of the burnt stuff, I would take a harder look at the intercooling tubes. Maybe not all the way, but partially clogged. It'll be almost impossible to drag a cleaning brush or pipe cleaner through them, but you could soak them in Chem-dip carburetor cleaner and blow them out with compressed air.

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              • #22
                Re: look what I found lurking in my 3rd stage head (MCH5)

                Cleaned out the intercooler tube and it was actually pretty clean


                When I am not compressing any gas and I vent the discharge to atmosphere I'm getting 3.5-3.75 cfm (normal) but as soon as it starts compressing the flow comes to a crawl exponentially (higher the discharge pressure the slower it gets)
                All the valves have been replaced along with a new belt. This is a mystery.

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                • #23
                  Re: look what I found lurking in my 3rd stage head (MCH5)

                  Does your amp. draw look normal ? all bores and rings in spec, not just 3rd stage ?
                  Last edited by Lakewood90712; 03-02-2015, 08:52 PM.

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                  • #24
                    Re: look what I found lurking in my 3rd stage head (MCH5)

                    There's nothing left but to replace all the rings (that I can think of), not sure on amp draw it's worth a look

                    Open to suggestions before I order parts...

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                    • #25
                      Re: look what I found lurking in my 3rd stage head (MCH5)

                      Does your Coltri have a vacuum pump or at least a crankcase vent to keep a negative pressure in the crankcase? A positive pressure in the crankcase could cause a lot of blow by. The images I've seen of the MCH5 don't have pressure gauges on each stage. A pressure gauge on each stage would help a lot with troubleshooting. Something that's impossible with my Fuelmaker.

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                      • #26
                        Re: look what I found lurking in my 3rd stage head (MCH5)

                        you need gauges on each stage and a flow meter on the crankcase vent to make an accurate diagnosis.You may or may not have plugged intercooler tubes but it was certainly bad valve or valves , or excessive blowby that caused the initial overheating and carbon buildup.if you have 175 psi shop air available you can often tap in between the stages with the compressor off and find a leaking valve in a hurry.

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                        • #27
                          Re: look what I found lurking in my 3rd stage head (MCH5)

                          after another chat with steve i think we have it nailed down to blow by from the 2nd and 3rd stage with the 3rd stage being the likely candidate

                          I also spoke with Mike Casey from Lawrence Factor, I sent him and Ray Contreras the video about the new 4th stage valve and piston assembly for the mch 30 (similar to the 3rd stage on the mch5) and am awaiting pricing and more info on a possible retrofit, the mch30 may be slightly longer and wont fit in the mch5, will update when i have more info on this

                          i also spoke with Carl from L&M compressors who has experience with every major compressor on the market (Bauer,Coltri, Mako, GD etc...) and he also said that this sounds like a faulty ring issue.

                          A few other things that i found interesting about the MCH5 is that there is a weak link in the second stage piston wrist pin. We are unsure if coltri has done what bauer has done and beefed it up by using a needle bearing in the wrist pin but its something worth looking into.

                          Another thing that i wanted to share was that the newer compressors use a phenolic material for the piston rings as opposed to steel or chromoly. These being much more expensive (about 20$ each ring) but have very good wear properties and they do not conduct heat, this in turn seals better and minimize heat transfer to the gas. If i can run these rings i probably will and report back.
                          Last edited by trdscfjc; 03-03-2015, 11:15 PM.

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                          • #28
                            Re: look what I found lurking in my 3rd stage head (MCH5)

                            I thought this was the redesign of the 3rd stage. I believe Nuvair is selling these kits for around 600 bucks.
                            https://www.youtube.com/watch?featur...&v=ou6VMq-sDfk

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                            • #29
                              Re: look what I found lurking in my 3rd stage head (MCH5)

                              good call dave, i could only find the mch30 retrofit video, thanks for posting i will forward this to ray and mike

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                              • #30
                                Re: look what I found lurking in my 3rd stage head (MCH5)

                                http://www.filtertechs.info/products...pressor-parts/

                                wow all these look pretty much the same

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