Brake Caliper Troubleshooting

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Oct 25, 2005 | 04:02 PM

shall36

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4th Gear

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Brake Caliper Troubleshooting

On vehicles with the non-lined brake calipers, it is possible to have a bleed-down problem (like a low brake pedal) without seeing fluid leaking on the outside of the caliper?

I just bought one of the Motion bleeder setups, so I'll see how that goes. Seems like I had this experience with a friends '74 C3...the pedal wouldn't hold after several days of driving, no matter how much we bled the system. We finally replaced the calipers and that solved the problem, but the old calipers were externally leaking fluid.

Oct 25, 2005 | 04:58 PM

Garys 68

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Funny you should ask. My pedal was continually getting soft and car started pulling to one side. Saw very little to no air when bled.
Last weekend, the caliper just started leaking. It is lined and I'm rebuilding with VBP O ring kits.
Gary

Oct 25, 2005 | 07:06 PM

Z-man

Race Director

Joined: Nov 1999

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From: Foxfield CO 1970 Convertible

Quote:

Originally Posted by shall36

On vehicles with the non-lined brake calipers, it is possible to have a bleed-down problem (like a low brake pedal) without seeing fluid leaking on the outside of the caliper?

In my experience, it doesn't take much of a leak to cause soft pedal. Only a few drops at one caliper will do it. Small leaks of fluid are hard to see. Stick your head under the car and look at the opposite side tire (with a flash light like CSI

) to see if you see a few wet streaks which would indicate a leak that has gotten on the outside of the caliper.
Also, as you mentioned, on stock calipers there are two "seals" that fluid has to get past before you can see it. The first is the rubber seal on the caliper piston itself. Then there is the piston "dust seal" that is pressed into the caliper and keeps junk from getting into the pistons. Theoretically, if the piston seals leak, you would have soft brakes even if the fluid didn't leak out past the dust seals.

Oct 25, 2005 | 07:14 PM

VBP

Safety Car

Joined: Jun 2002

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From: St Petersburg FL

St. Jude Donor '07,'13

shall36,
Be sure to check the rotors and bearings for any runout. Because the calipers are not floating mount, too much wobble will cause cavitation of the pistons in the bores and actually pump air into the system around the seals. This would happen gradually and you would not leak any fluid. If this is the case, O-ring brakes would fix the symptom, but not the cause. You might just need to have the rotors turned or some new bearings. Hope this helps.

Sincerely,
Alan G.
Vette Brakes & Products, Inc.
http://www.VBandP.com
alan@VBandP.com
800-237-9991

Oct 25, 2005 | 07:43 PM

shall36

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4th Gear

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WoW! All great advice. You guys are allright!

Actually, I plan to upgrade the calipers to the o-ring units offered by VBP. The car gets out once a week at most.

OK...sounds like this very well could be caliper problem, but I'll check the rotors, too!

Thanks!
Steve

Oct 26, 2005 | 07:08 AM

shall36

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By the way,

Alan, I see that VBP offers an o-ring conversion kit for the calipers. I assume that the '73 calipers are non-sleeved? Should the o-ring kit be considered for a non-sleeved caliper if a long-term solution is desired? Are sleeve kits also available? Does the o-ring conversion kit require any special fixtures/tools for installation, say beyond a brake hone and the like?

Thanks!
Steve

Oct 26, 2005 | 08:33 AM

mandm1200

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From: New Cumberland PA

Factory calibers did not have the stainless steel sleeve. I don't think putting in sleeves is a do-it-yourself project. The piston bore is enlarged to accept the sleeve and then pressed in.

The stainless steel sleeved bore will not corrode as the factory cast iron does. They will prolong the life between rebuilds. A visual inspection of the caliber piston bores will indeed show if sleeves are installed. No sleeves typically mean you might as well buy replacement calipers. If the sleeves are there, then seal kits are needed and possibly pistons.

Many members go with the O-rings. Its a matter of preference. I replacement calipers lasted 20 years without a leak. One of them started leaking after I had it off. Decided to rebuild all 4 with the standard lip seal.