Making a head gasket for an air compressor By glavey (Read 1,817 times)

[glavey]

I just bought a very old sears/craftsman air compressor from my local flea market for $15. I've been wanting some form of compressed air for general in-the-garage DIY type stuff for a while now and I thought that $15 isn't too much to lose if it doesn't work.





It was worse before I took these pictures, the entire base and some of the pump and reservoir had 1/16" to1/8" of oily-dusty... stuff on it.

I removed all of the pieces from the base board and cleaned them as best I could. While the pump was off of the base, I noticed that the crankshaft was slightly bent; when the pulley was installed on it, it would wobble about 1/4 inch off-center. Then I noticed that on the seals on both ends of the crank shaft were leaking oil. That explains the mess all over the base board.

Now to get to the point of this thread. I want to partially disassemble the pump and make new gaskets around the crank seals (they are bushings, actually) and inspect the top end of the pump; there are 4 cylinders, but only 3 are working.

Since this pump is nearly an antique, original gaskets are impossible to get. I need to know what, if anything, I can use to make a new head gasket. I first thought of form-a-gasket, went to their website and found this. Under applications it lists compressors and diesel head gaskets. It seems like it might work.

Does anybody else have any other ideas on what I could use? Preferably something that is available at a hardware store or some place like tractor supply co.

I should also mention that I will be running up to about 100 psi and it will only be used for about 30 minutes every... month or less, so very light duty.

[trashtruck12172]

the permatex product you mention is meant for valve covers, not heads. i use it to seal the carb to manifold on my moped but i don't believe it will withstand engine compression. you may be able to fabricate a head gasket out of copper sheeting.

[cyborg]

Oreilly sells sheet gasket material,, that should do the trick,,, as far as the machine goes,,, that thing is the coolest of the cool!!!!!!!!!!! Moses used that thing!!!! Got to get a receiver tank now,,, super cheap at harbor freight ,, is the crank bent or just the flywheel pulley on crooked?

[cyborg]

And also I forgot to mention one cylinder is out,,, one of the reed valves may be stuck closed from nonuse or the reed may be cracked,,,,

[glavey]

I have a little 10 gallon portable tank I plan on using. Not much, but I don't plan on using anything that consumes too much air. As far as the reed valves go, that is another reason I want to remove the head. The valves themselves have an, I think, 9mm hex head. As luck would have it, I have an 8mm and a 10mm.

I'll look into the gasket material at o'reilly's.

It is the crank itself that is bent. When the pulley is on and the motor is turning, you can see that the pulley and the end of the crankshaft are wobbling. I think "portable" (it weights about 90lbs) nature of it has caused it to fall down and land on the pulley, thus bending the crankshaft.

Because of that, I am quite sure I'll never be able to get the pump to completely stop leaking oil from the crank seal/bushing near the pulley.

[jct842]

for what you have in it you could just put a block of sturdy wood on the crank and smack it with a sledge hammer. Measure before hand so you know if it is helping it. worst case is -$15 and scrap iron worth a few bucks less.

[glavey]

I was thinking about doing something like that, but it is down on my list. I'm trying to get away from the mentality of, "fix something broken by breaking it the opposite way." Plus, I don't have a sledge hammer. If I really wanted to I could put the pulley back on, mount the pulley firmly to some surface and then grab the pump block and try and unbend the crank. I have a feeling that if I went the sledge hammer route the pump casing might crack from the impact.

[glavey]

After a little searching, I found a few gasket materials that might work, through none of them explicitly say they are for use as a head gasket:

Fel-Pro Pro-ramic
Listed for use as an exhaust gasket
Mr Gasket compressed gasket material
Again, exhaust gasket
Dead soft copper sheet
Throughout many threads on many different forums, I've found many mentions of using dead soft copper as a head gasket.

[glavey]

Back from the hardware store; got a hex wrench that fits the reed valves.

First I took off the intake valve on the cylinder that wasn't working. Apart from being a little dirty, the valve itself and the spring looked in decent condition. It had a little mound of what I think was paint on the exposed part of the valve, but all of the other valves had some paint there as well, so I just scraped it off and reinstalled it.

Before I had taken the valve out, I tested the whole motor/pump/micro-reservoir assembly:


As you can see, pressure wouldn't build above about 15 psi. The intake reed valve was letting air out. After I took it out, cleaned it, and re-installed it the pressure held up to about 45 psi (that is as high as I want to take this thing until I've done a more thorough inspection of the internals of the pump.

Next I took the exhaust reed valve off:



(In the words of Jamie Hyneman and Adam Savage) Well there's your problem! There's no "real" valve there, just what someone put in there, hoping it would work. It almost looks like a piece of gasket material (how ironic). Without that valve there, the pump will still work, but it will be down a cylinder and will leak (more than it would) air out of the intake reed valve.

I tested that by holding my finger over the air outlet on the reservoir, getting the pressure up to about 45 and shutting the motor off. The pressure dropped rather quickly. If I put a finger over the air outlet AND the bad cylinder's intake valve, the pressure drops slower, but still drops.

I MIGHT be able to make something that can be used as a reed valve out of a small piece of sheet metal, since that is what all the other valves are; springs and a piece of metal.

Even if I get that cylinder working again, I'll probably need a check valve between the air outlet on the micro-reservoir and whatever tank I use.

EDIT:

Oh, and I also took a video demonstrating the crank wobble:

[glavey]

Well, after screwing around with the pump for a few days, I've found out that the pressure limit is about 60 psi. That might have been good for back-in-the-day tools, but useless for anything except inflating tires today.

The only thing I would have used this compressor with would have been an impact gun for occasional scooter and car-related garage work (yes, I know that the pump wouldn't have been able to provide the cfm to use the tool continuously. I'm talking about removing, at most, lug nuts from a wheel; I can wait for the pressure to build back up after taking off one to two nuts.).

I'm now wondering if buying an electric impact gun would be a better choice... I can get one with a 1/2 in drive for $50-$100, and a small assortment of impact sockets from the local flea market for $25.

[richardv]

An electric impact wrench is definitely the best choice. I have an AC model that is better than my air impact ever was. I plan on getting a battery powered to carry in my truck to. An air impact will need at least 80lbs. pressure to take of lug nuts.