The Stovebolt Site Forums The Parking Lot Big Bolts Wheel cylinder repair

I've a '52 6400 flatbed that I'm getting back on the road. I'm limited to the farm right now until I get my brakes fixed.

I have a new master cylinder, fully rebuilt hydro-vac brake booster, and new lines. I cleaned up and honed the cylinders and installed new seals and springs. The cylinders are leaking from the inside.

Is it within tolerance to minimally bore out the cylinder to rid it of the surface pits? Initially I thought the surface pits were too shallow and sparse to amount to anything.
I've researched the web extensively to find affordable replacements which a starting price of $70 is not (ChevysOfThe40s.com).

I am using this thread as a cross reference for my research: https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=587514

Thanks for your feedback.

Hy Snellen, pits are common in the center of the wheel cylinder and cause no problems as the cups (seals) do not travel over that area, pits toward the outside of the cylinder bore will cause the cups to wear and leak prematurely. You can hone the cylinders out, but not so much that the cups will go into the bore without folding in the lip of the cup, if you hone so far that your pistons are a sloppy fit in the bore you should have a machine shop make you up some new ones which are a tighter fit. Brakes are the most important system on any vehicle, not just for you but for those traveling the roads with you, so don't skimp on their repair. RockAuto lists Raybestos wheel cylinders for the rear of your truck under p/n WC14499 $63.79 and p/n WC14500 $74.79. Hope that helps.

Thanks for the post 3B.
The seal around the aluminum cups are certainly nice and snug to where I must spin my finger around perimeter to press the seal into the bore. The cups themselves have minimal clearance. I haven't mic'd them but they are not loose to cause initial concern.

I have honed pits out of hard-to-find wheel cylinders by going several thousandths oversize by mounting the wheel cylinder in a drill press vise and using a 3-stone hone with plenty of brake fluid as a lubricant. Then I machined new pistons to be a snug slip fit in the oversize bores. The rubber cups will accommodate a pretty generous oversize and still seal, as long as the pistons don't wobble in the bore. A big GMC I was reworking the front brakes on had two cylinders per drum, at a cost from NAPA of $96.00 each. Rubber wheel cylinder cups were about $3.00 each. That was several years ago, and the truck is still running and stopping with no leaks.
Jerry

Jerry, thanks, working great.

Ed

This looks to be the correct cylinder for the front:

https://www.summitracing.com/parts/dhb-w4358/applications

Nope- - - - -that cylinder is for a pickup with Huck brakes. This one's a big rig with a much larger brake system. A 6400 series is definitely not a pickup.
Jerry

That it isn't Jerry! haha. Thanks for the clarification. Was hoping I found a better priced piece.

Before you bite the bullet and buy those expensive cylinders, try honing yours. Is the cylinder you're looking for a double-ended one with two pistons? Those are fairly simple to hone, since the bore is the same size all the way through. The ones I was working on were blind holes with only one piston for each cylinder- - - -two cylinders per drum. Last resort- - - -send me the cylinders and I'll hone them out and make you some new, oversized pistons.
Jerry

My cylinders are the two piston style. Four in the rear (two on each side - front & back) and one each side for the front (top side). I honed them sometime last year which I was pleased with but had not calculated the magnitude of what minimal pitting would result in. When the brakes are bleed, we got firm pressure with no bleed through. However, two weeks later I return home to find out my pedal goes to the floor with no resistance Conclusion: a good lesson learned that the most minimal pitting will leak with brand new rubber seals.

I bought my '69 T50 two years ago with rusted hydraulics. I honed all 8 cylinders, 2 for each brake, enough to remove the surface rust but not enough to get absolutely all the pitting. When reassembling them I coated the rubbers and the cylinders with silicone grease, pistons still fit fine. One cylinder of the 8 leaks enough over the winter to drain the master. If I check it once a month no bleeding is needed. The point being that I really only needed to replace one of 8 instead of all 8, at $100 each.

Silicone is not brake fluid compatible. Use brake fluid.

Ed

Jerry,

I've tried to send you a direct message. Maybe it's the internet connection here but says "user not found".
E-mail please at James dot snellen at gmail dot com. Thank you!

Snellen, are you sure it's a wheel cylinder that's leaking, mine didn't clean up completely but the pedal has not dropped at all. I bypassed the hydrovac because it was leaking internally and no dripping outside the shell. So for now I have manual brakes and they are very dependable. When I rebuilt all the cylinders I soaked them in muriatic acid and washed them with detergent and HOT water, then honed them, they cleaned up good but not perfect.