Air Compressor Update........... Pulled The Head

[JoeLee]

A week ago or so I started a post about my old Campbell Hausfeld compressor pushing oil out of the crank case breather vent. This morning I pulled the head.

I found that the inside piston or fly wheel side was slightly wet. The cylinder walls look good, no scratches etc. didn't measure them but did try to wiggle the pistons and I don't detect any play.
Pretty tight still.



The reeds on the piston side of the head look good, (no missing screws) but when I tap lightly trap on each one with my finger I can hear that they are not firmly seated against the hole.
That may or may not be a problem as I don't remember how they were when I put them in. I doubt the reeds are bend but am more inclined to think either the mating surface is worn or there are some carbon deposits under them preventing them from completely sealing.

I checked my old head and those reeds are firmly seated, no ticking sound when I tap on them with my finger.



Here's the flip side. These two reeds are carboned up pretty good but are sealing. The three voids in the head were full of oil as you can see.
So I'm going to take the reeds out and clean everything up and see what happens.
You can see the carbon buildup through the four holes. that may be why the flip side reeds aren't sealing properly.



JL....................

[CalM]

It would seem to me that carbon on the valves would be a symptom of piston ring failure and blow by. Just as oil out the case breather is a symptom of piston ring failure and blow by.

[rdfeil]

If it were me at this point I would figure out a way to do a leak down test. The easiest way, with what I see, would be to make a simple adapter for the intake on the head to allow a leak down gauge to be connected there. Plug the discharge port and you are off and running. All you need is a source of air. Do you have a second compressor? Even a small one would work...

[JoeLee]

It would seem to me that carbon on the valves would be a symptom of piston ring failure and blow by. Just as oil out the case breather is a symptom of piston ring failure and blow by.

The carbon build up was the worst on the two reeds that sit on the top side of the head. Those are the ones that seal off the air from going back into the cylinder when it's being pumped to the tank. They were like that when I first rebuilt the pump back in 2007.

While I had the head off I measured both cylinder bores at BDC as close to the top of the piston as I could get and about 3/4" from the top of the cyl. I measured them both ways. What I got was 3.001. Actually I was surprised that they were both exactly the same all the way around. I was expecting sloppy bores.

I did find one reed that wasn't sealing 100%. It was the one on the left side just behind the brass fittings. The raised ring that seals against the reed was slightly lower on one end preventing the reed from closing flat against it.
I took a small 1/4" ground parallel, put a piece of stick it sand paper on the edge and carefully ran it over the top of the ring making it flat. I lucked out.

If that valve doesn't seal it'll allow compressed air from the right cylinder to push into the left cylinder etc. etc. Basically killing the efficiency of the pump.

I don't know if that has anything to do with oil coming out of the crank case breather or not but I compressor repair guy told me it could. We'll see soon enough.

The tank fills a little faster now than it did before and it even sounds different when it's running.




JL.................

[JoeLee]

If it were me at this point I would figure out a way to do a leak down test. The easiest way, with what I see, would be to make a simple adapter for the intake on the head to allow a leak down gauge to be connected there. Plug the discharge port and you are off and running. All you need is a source of air. Do you have a second compressor? Even a small one would work...

I had thought of drilling and tapping like a 1/8" pipe thread in some inconspicuous place so I could couple my compression gauge to each cyl. and get a reading, even if it's for comparison between the two cylinders but the valves would have to seal properly and if they don't seal 100% I wouldn't be able to tell if it's rings or valves.

The pistons are both firmly fitted, no side wiggle or movement and the walls are smooth so no broken rings. I measured them both as I mentioned in my previous thread.
It's possible that the rings are washed out but I would have to pull everything apart to measure the end gap, and I don't even know what that's supposed to be as there are no specs for it.
I can only guess and compare it to a lawnmower piston of the same dia.

JL.................

[CalM]

If I were doing it.

New rings , and a ball hone to prep the cylinders.
That burned oil on the valves has to be coming past the rings.

It would take a full day. But then it's done.

I did the full rebuild on my shop Kellog- American many years ago. It was worth it!
It's on a VFD to minimize inrush. A nice addition.

eta

The compressor must have an unloader valve... The head reeds don't hold the air when the pump is not running.

[nickel-city-fab]

If you really want to see where the leakage is, on a small budget, borrow a trick from the old-time NASCAR engine builders.
Get some rubbing alcohol and some red food coloring (dye) nix together until you have red alcohol.
Pour some in on top of the piston, put a plate of glass over the top of the cylinder (to keep evaporation down)
Then wait a while to see how much, how fast it leaks out.
They used a similar trick for the valves.

[I make chips]

I have the same cheapo CH compressor which had the same problem. Throw in a new set of rings and the problem will diminish. Won't stop it but will diminish the blowby.

[JoeLee]

If I were doing it.

New rings , and a ball hone to prep the cylinders.
That burned oil on the valves has to be coming past the rings.

It would take a full day. But then it's done.

I did the full rebuild on my shop Kellog- American many years ago. It was worth it!
It's on a VFD to minimize inrush. A nice addition.

eta

The compressor must have an unloader valve... The head reeds don't hold the air when the pump is not running.

I'm not sure if any parts are available for it any longer. But anyway......
I think I solved the problem. It was that one reed on the top left side of the head behind the two brass fitting that was leaking. Not quite sure how that cured the problem but it did.
I ran this thing hard all day sanding a couple steel stands for my sheet metal equipment and at the end of the day I couldn't find a drop of oil anywhere.

And yes, it does have an unloader valve. If it didn't the motor probably wouldn't be able to start.

JL.............

[JoeLee]

If you really want to see where the leakage is, on a small budget, borrow a trick from the old-time NASCAR engine builders.
Get some rubbing alcohol and some red food coloring (dye) nix together until you have red alcohol.
Pour some in on top of the piston, put a plate of glass over the top of the cylinder (to keep evaporation down)
Then wait a while to see how much, how fast it leaks out.
They used a similar trick for the valves.

I don't quite see how that would be an accurate way of testing where the leakage is. Any thin fluid will seep past the en gap of the rings and out the bottom. I tried that trick years ago when I rebuilt a 16 HP Briggs. new cyl. sleeve, piston and rings. the WD slipped right past everything. Took about a full day.
What the purpose of the red food coloring ??

JL.........

[nickel-city-fab]

I don't quite see how that would be an accurate way of testing where the leakage is. Any thin fluid will seep past the en gap of the rings and out the bottom. I tried that trick years ago when I rebuilt a 16 HP Briggs. new cyl. sleeve, piston and rings. the WD slipped right past everything. Took about a full day.
What the purpose of the red food coloring ??

JL.........

The food coloring just so you can see where. The literature I have from one of their most-winning builders says they would re-grind until there was no more leakage. Of course that was way back in the day before CNC. I imagine that some leakage past the ring end gap is understandable, but anywhere else was a no-no.

[wierdscience]

If one or both of the discharge reeds was leaking and the intank check valve was leaking a bit too, that would give you some blow by and poor efficency.

Jacks Small engine carries some CH compressor parts- https://www.jackssmallengines.com/ja...hocdwgqavd_bwe