C2 1966 Brake Bleeder Valve leaking

[John R.]

Hello all. I have a February '66 with a brake bleeder valve that leaks. It is on the inboard side of the passenger rear. The casting number is 5452281, with the outer casting being 5452284 so I believe them to be original. My father sleeved them with stainless steel back in the late 80's, and I rebuild the caliper about five years ago. This problem may have been around for a long time as I've always had to bleed the system every so often, but never took the time to trace the issue down. It is without a doubt leaking from the tip of the valve. The valve has exposed thread so I know it is long enough.

I will go over to Long Island Corvette and pick up a new bleeder with wishful thinking, but my question is this. If the seat is slightly damaged or corroded, is it possible to have the seat machined to restore the seal? If these weren't original I'd just replace the caliper, but these original cars come with added responsibility.

Thanks guys,

John

[Joe L.]

Re: C2 1966 Brake Bleeder Valve leaking

Hello all. I have a February '66 with a brake bleeder valve that leaks. It is on the inboard side of the passenger rear. The casting number is 5452281, with the outer casting being 5452284 so I believe them to be original. My father sleeved them with stainless steel back in the late 80's, and I rebuild the caliper about five years ago. This problem may have been around for a long time as I've always had to bleed the system every so often, but never took the time to trace the issue down. It is without a doubt leaking from the tip of the valve. The valve has exposed thread so I know it is long enough.

I will go over to Long Island Corvette and pick up a new bleeder with wishful thinking, but my question is this. If the seat is slightly damaged or corroded, is it possible to have the seat machined to restore the seal? If these weren't original I'd just replace the caliper, but these original cars come with added responsibility.

Thanks guys,

John

John-------


The most likely root of the problem is a damaged seat, as you surmise. I really don't know, for sure, if these can be repaired. However, your best bet would be to call someone like Lonestar Caliper and ask them. I'm sure they've come across this many times and will know if it can be repaired. And, if it can be repaired, they'll likely be the ones that will be able to do it. Let us know what you find out.

[Patrick B.]

Re: C2 1966 Brake Bleeder Valve leaking

Original bleeder screws are not plated, but the new ones used by Lone Star and maybe others are plated. If this plating gets scratched or starts to peal off at the contact point, the bleeder screw won't seal. If the leaky bleeder screw is plated that could be your problem. Replace it with an unplated original type bleeder screw before you give up on it. Grainger also sells copper gaskets for flare fittings. I don't know if there is a size that would fit into the bleeder hole, but that could be a solution if the bleeder screw is not the problem. If you have to get a rebuilt caliber from Lone Star ask them to use GM bleeder screws , even used ones, rather than the plated screws.

[Joe L.]

Re: C2 1966 Brake Bleeder Valve leaking

Original bleeder screws are not plated, but the new ones used by Lone Star and maybe others are plated. If this plating gets scratched or starts to peal off at the contact point, the bleeder screw won't seal. If the leaky bleeder screw is plated that could be your problem. Replace it with an unplated original type bleeder screw before you give up on it. Grainger also sells copper gaskets for flare fittings. I don't know if there is a size that would fit into the bleeder hole, but that could be a solution if the bleeder screw is not the problem. If you have to get a rebuilt caliber from Lone Star ask them to use GM bleeder screws , even used ones, rather than the plated screws.

Patrick-------

While original bleeder valves (screws) were usually natural steel, all GM SERVICE bleeder valves I am aware of (I have NOS examples of every one ever offered for Corvettes) were zinc plated. None are currently available from GM. If desired, plating can easily be removed from any plated bleeder valve, GM or otherwise, by short immersion in a mild acidic solution. However, I've never had any problem with plated valves.

I do not recommend the use of used bleeder valves. If one looks closely at a used valve, one will often note a slight circular, depressed "ring" on the tapered sealing surface. The valve may seal properly in the original caliper seat that created the "ring" but will usually not seal properly if transferred to another caliper.

[Patrick B.]

Re: C2 1966 Brake Bleeder Valve leaking

Joe --- I certainly agree that a used bleeder screw with a visible wear ring on the mating surface is a poor prospect for sealing a caliper other than the one from which it was removed. My experience with the plated bleeder screws on the Lone Star calipers is very recent. I don't know who made the plated bleeder screws in my Lone Star calipers, but they seem like a very bad idea. At the end of the initial bleed of a new brake system, it could not get the right rear inner bleeder screw to seal. I suppose I had opened and closed it more that the others since it was the starting point. Still, after fewer than 10 tightenings, the plating was starting to flake at the contact point, and it would not seal. I removed an original bleeder screw from an old caliper, and it sealed perfectly. Maybe I have been lucky, but I have never had a problem with original bleeder screws, and I had never experienced plated one before. Maybe the originals are a harder material. The old ones I have do not have wear rings.

I will use your idea to remove the plating from the faulty bleeder screw. I am curious whether it also has a wear ring from so little use. Plating on a soft material is really a bad idea for bleeder screws.

[John R.]

Re: C2 1966 Brake Bleeder Valve leaking

Thank you all for the ideas and suggestions. I went over to Long Island Corvette and picked up a few bleeders. When I removed the old one, as seen in the picture, there was quite a mark on it. In the last picture you can see that the mating surface has a slight curve in it. Looking into hole at the seat, it looks like it has seen better days as well. The new valve I installed was much worse with the fluid visibly dripping. The old valve sealed well enough to drive hundreds of miles. So I followed the advice given here, packed it up and sent it off to Lone Star. I spoke to Brad over there and he said they could fix it without drilling it out and placing a sleeve inside it, which would leave me with one bleeder valve being a different size that the other five. I'll post back when it returns and let you guys know how it turned out.

[Joe L.]

Re: C2 1966 Brake Bleeder Valve leaking

Thank you all for the ideas and suggestions. I went over to Long Island Corvette and picked up a few bleeders. When I removed the old one, as seen in the picture, there was quite a mark on it. In the last picture you can see that the mating surface has a slight curve in it. Looking into hole at the seat, it looks like it has seen better days as well. The new valve I installed was much worse with the fluid visibly dripping. The old valve sealed well enough to drive hundreds of miles. So I followed the advice given here, packed it up and sent it off to Lone Star. I spoke to Brad over there and he said they could fix it without drilling it out and placing a sleeve inside it, which would leave me with one bleeder valve being a different size that the other five. I'll post back when it returns and let you guys know how it turned out.

John------


Your photos perfectly illustrate the exact problem I described in my previous response.