Airpack hydraulic cylinder pitted

[jerseyjeep2003]

OK, so I tore down my air pack for rebuild and found the air side to be in decent shape, had some brake fluid in it, but no rust whatsoever. Now on the other hand, the hydraulic side has a fair amount of pitting. Starting at the end with the brake light switch extending about 2 inches in, the bottom (like it was sitting for a while with water laying on the down side of the cylinder) has a section of pits that look to be maybe .010 deep. My question is, will honing be ok? I know the rubber cups are pretty forgiving and will take up a fair amount of the cylinder being oversized. Or maybe send it out and have it bronze sleeved? I really looks as if the pits are past the travel of the piston (with properly adjusted brakes). I would replace the whole unit, but you don't know what you get with used and the new ones are way too pricey. I THINK I could get it sleeved for less than $100. Just have to find a shop that does that type of work.
Thoughts?

 

[hndrsonj]

You can get used takeouts pretty cheap for a core to rebuild.

 

[rlwm211]

Here is the deal.

The portion of the slave bore that does 90% of the work is the far end from the switch. If you collapse the spring as far as you can you will see that the piston will not get to the very end of the bore. What is critical is that the portion of the bore where the piston will travel is clean and smooth.

Now, I am not able to look at your slave cylinder bore and tell where the pitting stops but if it is in the area where the piston cannot travel to it is ok to rebuild that component. This is your judgement and I will add this:

If the pitting was a problem it would make it so the brakes fade away when you activate them. This is because the fluid can bypass the piston. The other issue is that the piston can get 'stuck' on the rough surface and also this can damage the piston seal.

As I said, you have to decide how far into the bore the pitting goes that the collapsed spring takes up which limits the piston travel. If it is in the area where the piston cannot get to you are good to rebuild this unit.

Don't forget to make sure the bore accross from the air valve where the hydraulic brake fluid comes in is nice and smooth too. This bore is a part of the compensator circuit and if it is not smooth it can create problems with varying levels of braking as you change your needs. It can slow down or stop the airpack from responding to your input with the master cylinder,

Just my two cents and contents do settle during shipping!!!!!!!!!!!!

 

[jerseyjeep2003]

I just gave it a light honing, maybe .003/side, and 90% of the pits came out. The only ones that didn't come out are about 1 inch from the brakelight switch end. The new cups have a decent "drag/compression to the cylinder wall. I feel pretty confident that it will be alright, but I will definitely take it slow and local on that first test run.