Military-Vehicles: [MV] Brake Cylinders - Rebuild vs. Replace?

[MV] Brake Cylinders - Rebuild vs. Replace?

Alan Bowes (
Thu, 30 Oct 1997 10:07:27 -0700

Hi List,

Several recent postings have discussed brake issues, often related to
the effects of corrosion. Here are a few opinions from various sources
regarding rebuilding vs. replacing brake cylinders. As always, please
feel free to comment or critique.

A light honing can remove minor surface corrosion problems, but you
can't remove more serious pitting without honing the cylinder too far,
which can cause leakage, seal failure, binding, etc.

Fred Puhn, in his Brake Handbook (HPBooks), talks about a phenomenon
called "heel drag" that occurs when there is too much piston-to-bore
clearance. This is where the seal gets forced into the gap between the
piston and the bore, and this pinching causes the piston to retract
slowly or stick. He recommends replacing a master cylinder if there is
.005 inch or more clearance between the piston and the bore.

To check the clearance, if a very narrow .006-inch feeler gauge can be
inserted between the piston and the cylinder bore, there is too much
clearance and you should replace the cylinder (or have it sleeved). Or,
if you happen to have a small inside micrometer (or telescoping gage)
and an outside micrometer, you can compare the diameter of the piston
and the bore. If there is .005 inch or more difference, replace (or
sleeve) the cylinder.

I've also seen warnings about over-zealous honing in various
manufacturers' documentation.

There are numerous companies that will bore and sleeve master cylinders
or wheel cylinders. This is not a cheap process, often costing more
than a new cylinder, but if you can't find a new or good used cylinder,
it may be the best alternative. In some ways, it may be superior to a
new cylinder, since they typically use brass, bronze, or stainless
steel sleeves that are more corrosion resistant than the original cast
iron or aluminum cylinder bodies.

Here are some prices that I was quoted by White Post Restorations. You
can visit their web site at

Master cylinder (less than 1.5-inch bore diameter): 150 dollars
Master cylinder (greater than 1.5-inch bore diameter): 200 dollars
Wheel cylinder (single bore size): 80 dollars
Wheel cylinder (stepped/dual bore): 120 dollars

Prices include bead blasting, boring, sleeving (with brass), sizing,
applying a baked-on epoxy finish to the exterior, replacing all
internal parts, and a lifetime warranty. Not real cheap, but I think
they'd be better than new.

Does anyone on the list have any recent experience having cylinders
Can you recommend a good shop?
Any price estimates?


(Salt Lake City, Utah)

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