Re: Coltri diagnostic, (summary to "lurking" thread)

PAGES 10-20


Originally posted by cngtennessee View Post
This is what my wrist pin looked like when I had my issue. Also...these are the service intervals that were sent to me by Nuvair pertaining to the MCH5.

As stated earlier (from Carl from L&M) the weak link on the mch5 is the 2nd stage wrist pin.
Don't know about you guys but I am going to replace the second stage wrist pin and bearing every 2000 hours from now on



Got the pin from L.F. sourced the bearing locally for 6.50$....nuvair wanted 55$

Second stage wrist pin/ bearing and rings replaced, still getting 1.5 cfm above 3000 psi....The Mystery remains...

Going to replace 1st stage rings tonight, that's the only thing left

I was asked about the method for removing/installing old/new needle bearings for the second stage while the rod is still attached to the crank

Credit goes to steve for walking me through this

As you tighten the bolt the 12 mm socket pushes against the race and pushes the needle bearing out of the connecting rod and into the 19mm socket, this is done after the wrist pin is removed (i just put the old one on there for reference)


This is what is used to press the new bearing (evenly) onto the connecting rod, you may need to use more then one bolt for this.

If the threads do not reach all the way down the shaft, i have one bolt that lets the bearing go about halfway on and another to fully seat the bearing


i am using grade 8 bolts for this not sure if this is necessary but they were only a little bit more and im not sure how much stress it actually takes to remove these things


Thought there was an off chance that my meter could be maxed out so I turned on every gas appliance including fireplace and outdoor fire pit to see if my cfm would remain constant or jump (as it should) with everything on it was flowing 7 cfm. ...with just the compressor running it's the meter is working properly

Also with everything running I was still getting a solid 2 psi on my intake pressure gauge (that's good)

I want that newly designed 3rd stage piston and head assembly ASAP



These are the current pressures, the intake pressure gauge is off by 1 psi (I need to recalibrate it)


I'm curious,

Brit, if you vent the discharge to atmosphere and you don't compress anything what is your cfm draw from your meter?

If it's like mine it will be pulling about 3.25 cfm...let me know


Originally posted by rcontrera View Post
Oil is actually fed into the compressor through the first stage as well as the third stage. On the first stage, there is a line that goes from the sump to the suction of the first stage. This top lubricates the rings and that lubrication carries on to the second stage. On the third stage, the pusher piston splashes oil into the third stage floating piston and excess drains back to the sump. However, there is always going to be some carryover. In an air system, there is a moisture separator that pulls off moisture and oil from the second and third stages before it hits the filter chemicals.

New parts arrived, got a 1st stage wrist pin and 2 sets of rings


Got the cylinder deglazed today, also pulled the 1st stage wrist pin, it has a slight gall but it's in great shape compared to the 2nd stage wrist pin.



Here's how I pressed the old 1st stage bearing out


This one (1st stage wrist pin needle bearing) is a Torrington HK2020B....5.99$ at my local bearing shop



Originally posted by rcontrera View Post
There is always going to be a little drop from low to high pressure. However, that really is excessive. My littlest air compressor is 3.5 CFM and at 4500 psi it drops to 3.1-3.2 CFM. The first suspects are valves. Rings are usually pretty easy to tell since it leaks into the sump and you can tell when pressure has increased by just holding your hand over the oil tube while it is pumping.

Originally posted by cngtennessee View Post
I have now pumped approx. 160 GGE's of CNG while using molecular sieve 13X in my prefilter(filter set up prior to NG going into MCH5) and the results are outstanding. In the past I would get 1-2 ounces of oil/moisture coming from the discharge filter attached to the compressor. I have not had any moisture/oil since using the 13X. I suggest after getting compressor fixed that you use the 13X.