Master cylinder pitting - how much is too much??

[Robert B.]

I'm in the process of rebuilding the braking system on the '66 coupe, and when I opened and cleaned the dual master cylinder, I discovered some minor pitting about 2.5" in from the end of the bore. The area involved is about the size of a fingertip. I can't tell how deep it is - I can feel it, but it seems pretty minor. Should I try honing it, or re-sleeve it, or just install a rebuild kit and call it good?

Bob

[Paul J.]

Re: Master cylinder pitting - how much is too much??

Bob, hone it first and see if you can get it out. If you can get it smooth (or at least close) then rebuild it. If there is still appreciable pitting after honing then you might have to have it sleeved, but this should be a last resort.

Paul

[Edward J.]

Re: Master cylinder pitting - how much is too much??

Bob, I would say if you can take your fingernail and catch it on the rusted - pitted area send it out to be re-sleeved. Your talking safety of your corvette and yourself, for something that may cost about 150 .I am not sure if your 66 has a single or dual reservoir but they sell a pretty good reproduction of the dual reservoir and its priced great,

[Robert B.]

Re: Master cylinder pitting - how much is too much??

I can just barely feel the pitting, so I'll try honing the bore. Since it was working before I took it apart, and it was just seeping a small amount of fluid, I might get lucky.

And yes, it is an original dual reservoir MC.

Thanks,

Bob

[Joe L.]

Re: Master cylinder pitting - how much is too much??

I can just barely feel the pitting, so I'll try honing the bore. Since it was working before I took it apart, and it was just seeping a small amount of fluid, I might get lucky.

And yes, it is an original dual reservoir MC.

Thanks,

Bob

Bob------


I suppose it's worth a try to hone it. However, my experience is that honed master cylinders just do not work out. They just won't hold the pressure involved. Many "el cheapo" rebuilt master cylinder have honed bores. One might have to take 4 back to get one that works right (and even that one probably won't work exactly right).

Based upon what you describe, my guess is that it will take quite a bit of honing to get your bore cleaned up and the more honing you have to do, the less likely you'll be successful.

GM says that any bore corrosion/damage that can't be cleaned up with crocus cloth (i.e. like jeweler's rouge) requires a new master cylinder. I TOTALLY agree with them. However, when they made this instruction, sleeved master cylinders had not been invented. In the vast majority of cases, though, a sleeved master cylinder is equivalent to a new one.

Keep this in mind: if you hone the master cylinder and rebuild it with a kit, you then have to bleed the master cylinder and install it on the car. Then, you'll probably have to bleed the rest of the system. After all this work and hassle, if the master cylinder does not hold up, you'll have to have it sleeved and then start all over again from square one.

[Craig J.]

Re: Master cylinder pitting - how much is too much??

Why not send to White Post and get it sleeved? Then you're set for good.

[Kenneth B.]

Re: Master cylinder pitting - how much is too much??

Bob------I suppose it's worth a try to hone it. However, my experience is that honed master cylinders just do not work out. They just won't hold the pressure involved. Many "el cheapo" rebuilt master cylinder have honed bores. One might have to take 4 back to get one that works right (and even that one probably won't work exactly right).Based upon what you describe, my guess is that it will take quite a bit of honing to get your bore cleaned up and the more honing you have to do, the less likely you'll be successful.GM says that any bore corrosion/damage that can't be cleaned up with crocus cloth (i.e. like jeweler's rouge) requires a new master cylinder. I TOTALLY agree with them. However, when they made this instruction, sleeved master cylinders had not been invented. In the vast majority of cases, though, a sleeved master cylinder is equivalent to a new one.Keep this in mind: if you hone the master cylinder and rebuild it with a kit, you then have to bleed the master cylinder and install it on the car. Then, you'll probably have to bleed the rest of the system. After all this work and hassle, if the master cylinder does not hold up, you'll have to have it sleeved and then start all over again from square one.

VERY VERY good advice. Listen to this man as he knows with where he speaks.