wheel cylinder - again

[jakub]

Just finisching coffe, changing to dirty set of jeans and off to replace wheel cylinder, third time in six years.
All were new in 2005, in the meantime I replaced one front and one left rear back-back, now is left rear back-back again. In two previous cases it was slight inside corrosion at top part of cylinder so water condensation seem to be obvious suspect.
I do around 1000 miles with bit off roading per year. I do replace brake fluid (DOT4) every odd year.

I suspect there are two main reasons for this, not enough driveing so water once in brake fluid has time to separete and rust away metal and local climate with rather big differences in beetwen day and night temperatures which only adds to water condensation.

But perhaps there is way to avoid this in the future, any suggestions ??

[retro-roco]

Find a shop to sleeve your cylinders with stainless steel. much less likely to develop rust...

[dr deuce]

Stainless Steel sleeve and have a brass piston made. The brass will not corrode like the alu pistons

[jakub]

Thanks guys, stainless steel seems a very good option, however local shop asked pretty high money considering that I use wheel cyliders from old Polish star trucks (http://en.wikipedia.org/wiki/FSC_Star),

As it happened it was water corrosion again, however this time it was water getting from outside not from within, can't remember fording a river recently however driveing in heavy rain with snow I do remember.

I guess driveing more often would be also a option and very pleasent one as heat should help evaporate the water.

[dr deuce]

I put some wheel bearing grease between the pistin and the cover to keep the water out. No too much,

[Fort Susquehanna]

I'll qualify this by saying that I have only owned my CCKW for one year and only repaired one wheel cylinder so far. What I am writing here is based on information from other owners and some aviation experience I have.

A friend who has a lot of CCKW experience told me to get rid of the vacuum after you drive. You do this by tapping the brakes a few times after you shut down. If you leave vacuum in the chamber, it is eventually going to draw moisture into the system. That water is going to wind up somewhere, probably in spots between hard lines and soft lines, wheel cylinders, and at some point your master cylinder.

If you do rebuild a wheel cylinder, you really need to put anti-seize on the end caps. I was told that a single end cap seizure is a common issue with the CCKW and that is what happened to mine and two other owners I talked to around the time it happened. I pulled the cylinder off, honed it lightly because it was in such good shape, and rebuilt it with new cups only. When I re-assembled the end caps I used a product called E-Z Turn, also known as fuel lube. I chose it based on use in brake systems in a North American B-25J I work on once in a while. It is available at www.aircraftspruce.com. Fuel lube is impervious to hydraulic fluid, gasoline, oil, and water. We use it on the B-25 in the piston and o-rings on the brake packs. The piston is really a ring with a cross section of about 1-2 cm square, about as big in diameter as a pie plate. The o-ring is behind it and seals the fluid in the cylinder. The fuel lube prevents corrosion on the aluminum parts of the cylinder. Every B-25 brake pack I have disassembled after use of fuel lube has been in perfect condition, no evidence of water or corrosion on any of the parts; that's why I chose it for the CCKW job. CAUTION: Once you get fuel lube on your fingers, it is going to be there until you shed your next round of skin cells. Fuel lube has to be applied with a tool- a screw driver or small putty knife. If you don't do this, you will be tasting it in your food for weeks, and it is TOXIC. USE A TOOL!

When you bleed a rebuilt cylinder, I think it is wise to let the truck sit for a few days, then run it, and then bleed it again. I noticed some softness in my pedal after I put my new cylinder in, and I found some air when I bled the brakes again. I did ultimately have to replace my master cylinder, so it may have been that was an issue. But with all the volume in a CCKW brake system, a second bleed might be good insurance.

Like I said, I'm not the CCKW expert so more experience might bring some different ideas. But I am pretty sure about the fuel lube and getting rid of the vacuum after running as I have heard that elsewhere from a few different people.

[dr deuce]

There are 2 schools of thought on the releasing of vacuum. One is as Joel says to step on the pedal a couple times, the other says that iF you do, gasoline fumes may travel past the check valve into the hydrovac, which cannot stand gasoline and will do some damage...

[bobc]

Since every one here seems to have been into a wheel cylinder recently could some one please tell me what size cups they use, and are the chevy cylinder the same size, I have one cylinder leaking right now but I'm sure I'll have to go through them all once I start driving it. Thanks Bob.

[dr deuce]

from memory:

1 3/8 front

1 1/2 rear

ALWAYS replace the return spring. Jim Carter antique truck parts has them for ~$8 each.