Cleaning Up the Air Pack & Rebuild

[dabtl]

I took an air pack apart today. Lots of crud in it. The slave cylinder tube has surface rust. I have worked on it with a brass brush. Now, I need to lightly sand it down.

Any good ideas on how to sand the piston tube?

 

[Stretch44875]

brake hone. Same as rebuilding wheel cylinders. If your talking about the air side piston, then 400 grit sandpaper sounds good.

 

[dabtl]

I fell back on my misspent youth. I ported and polished Chevy heads for one of the truly great engine builders in the 1960's.

So, I got a wooden dowel, cut it off to about 8 inches, taped a strip of 400 emery on it, rolled it like you would a paper towel and put it into a drill.

Took a couple of minutes. I thought about the brake hone but this cost $2.19

 

[jasonjc]

You know I had to do this.....

 

[poppop]

I just did one yesterday and used the brake cylinder hone on the slave. The air side had one rough spot I cound not sand out by hand so I used an engine cylinder hone on it. that cut it right out but left the finish a little rough. I polished it by hand with some 200 grit paper. It was still a little rough but maybe it will hold. It was either try or junk it and get another, so I tried. I won't know if it works until I have time to rebuild all wheel cylinders.

 

[dabtl]

I am going to post pics of the rebuild along side another core that I have. I will put the rebuild next to the disassembled core for a comparison.

I really think the brake cylinder hone does a good job, but I was just using what I grabbed at the hardware store.

One item you will want to get in advance is a pair of soft jaws for the vice. They are about $10 delivered from eBay.

 

[Steaminjim]

Forgot about the dowel trick. The hone I used on my master cylinder left it too rough. Thanks! will use it tomorrow.
Steaminjim

 

[dabtl]

Another hot tip: The air piston is two parts, not screwed together and not connected one to the other. Mine had what appeared to be a leather gasket, replaced with a rubber gasket, which had been compressed against the two parts so long that until I got a probe into the base it would not release the two parts. The TM is not very helpful here at all.

 

[jatonka]

This is a very worthwhile thread in my opinion and I Thank You Dabtl and others with info like this. I have several air pac rebuild kits and secveral air pacs that need to be rebuilt, so keep it coming men, I need all the help I can get . JT out

 

[combat32]

who has the rebuild kits right now? I have several cores and would like to redo a couple.

 

[dabtl]

Here are a few pics to help.

The core I used is fairly typical from what I have seen. I plugged the holes with brass plugs from Ace Hardware to sandblast the exterior.

The next few shows the disassembled tower on the top of the cylinder and the pump, completely replaced.

The next shows the piston assembly lower and with the replacement gasket on it. The original was some kind of rubberized material which over the years had hardened and become much less flexible than needed. The upper and lower parts are not screwed together and do not have some form of attaching device to one another. They are held in place by the nut on top of the piston shaft. The last pic shows the two parts, the gasket and expander installed. All that is left is to add the felt gasket at the front of the piston.

Because the piston shaft is highly polished you need soft jaws for your vice to hold it. They are at Sears for about $12. I cleaned the shaft and put masking tape around it to give the jaws traction. A little wipe down with paint thinner cleans off any left over sticky.

When you begin assembling the air tank and piston, you will quickly find the gasket for the end cap is TOO SMALL. I do not know if it has shrunk in the package or just a defect. I kind of hope the one I managed to get on works. We shall see, however. This is true for two rebuild kits I opened. One was packed in 1983 and the other 1985.

I have found a source for rubber o-rings, one round and the other square that may fit. I have ordered them and will wait till they arrive for my next re-build.

 

[steelandcanvas]

Great thread Dabtl. I, like JT, need all the help I can get. This is one of those projects I've been putting off too long. Thanks again!

 

[roger-wilco-66]

Did the same thing on mine, the piston was stuck in the top position and it was blowing brake fluid out of the breather tube. The cleanup worked well, it's OK now!

 

[dabtl]

I have opened the second air pack I have. Took the end off of the air piston chamber.

Piston in pristine condition. Stuck. No lubricant. This one has sat a long time. I will clean the chamber and lube it. So far no need for any rebuild parts. Don't forget the lube in the air pack is put in through the small square plug. It is apparent the gasket was not working well.

Also, the gasket needed is 4.5 inches inside diameter. I have ordered rubber round and square o-rings to see if they will work.

 

[dabtl]

The first pic shows the piston. It was in pristine new condition with a little nasty stuff that wipes off easily.

The second is the top of the piston.

The Third shows the interior of the cylinder with the crud and some rust.

The final pic shows the crud and some rust around the perimeter where the paper gasket had failed. Note the leftover Permatex type gasket sealer that someone attempted to repair the gasket with around the bolts.

 

[Monkeyboyarmy]

I think that I have found a source for new rebuild kits for these.If we can get enough interest,I could probably get them cheaper.Right now they are about $35.00 each plus shipping.I am going to buy one and make sure it is correct.

 

[dabtl]

My guess is the paper gasket for the piston cylinder will be too small. Mine are all NOS.

But, keep us posted.

 

[dabtl]

As an update, TM9-2320-209-34-2-1 on page 12-12 shows an o-ring (4) on the slave cylinder body. NO O-RING is included in the rebuild kits. It is a 7/8 o-ring available at the hardware store. I do not know that it is needed. The first unit I repaired did not have the o-ring. It appears it may not be needed because of the way the gasket seals everything off.

This second unit showed leaking around the fifth hole on the slave body,which is where the o-ring was supposed to be. Whoever tried to repair this unit used a lot, and I mean a LOT, of Permatex type gasket sealer on this.

 

[dabtl]

A few more pics.

The first shows the end cap as removed. Notice all the gasket sealer present on the first two pics. Also note the ill fitting paper replacement gasket. Close, just no cigar. I am going to see if a square o-ring gasket will work better.

The next three pics show the hydraulic cylinder plug being removed and the rusted condition of the spring. Actually the spring is not too rusted but as I had to have gaskets from one of the rebuild kits, I replaced the spring also.

The last pic shows the interior of the hydraulic cylinder and the spring cap. The interior is covered in some surface rust.

 

[dabtl]

After removing the air piston can, you can see the rear of the hydraulic cylinder with the spring cap and spring poking out in the first two pics. In the second pic you can see the 7/8 o-ring which is not included in the rebuild kits. Frankly, the way the gasket fits over the breathing hole, I do not think the o-ring is necessary. The first unit I rebuilt did not have the o-ring and I could not figure out the TM until I opened this one.

The second pic also shows the breathing hole completely obstructed by the gasket sealer. It is no wonder that the unit did not work.

The third pic show the surface after I cleaned the gasket material away. The large hole holds the piston shaft in place with the part shown in the fourth pic. It cleaned up easily with paint thinner.