So a while back, my dash brake light came on while driving. I know this is triggered by a switch between the front and back circuits, and is supposed to indicate a loss of pressure in one or the other.

Sure enough, the next time I was out I noticed a definite reduction in braking power, and the pedal has way more give than it used to.

Besides some minor cooling system issues, this will be the first real work I'll be doing to the Vette, and for the most part any car. My question is, where do I start?

I had the brake fluid reservoir open, and the front is a lot lower then the rear. So my guess is there is a leak in the front somewhere. I have the front of the car jacked up, but looking around under there I can't see any obvious leaks (brake anyway...). Any suggestions on where to go from here?

 

Keep the front end jacked up and apply brakes numerous times. You'll be able to locate easy if the car is not moved.

 

Check the inside of all the wheels, you might find that a caliper has been leaking, but not enough to produce a puddle. The most likely culprits are the calipers or master cylinder.

 

Same problem here but two times. Each ended being a caliper sucking in air. No visible dampness from leaking fluid. The culprit was rotors being ever so warped. Had to use a dial guage to find the real problem.

 

Thanks for the suggestions. Sorry for taking so long, but I'm only where my car is on the weekends.

I took the front left wheel off (figured if it was a front caliper, it'd be that one since the previous owner had the right one replaced) and still saw no signs of leaking, but while looking around under there I noticed that the jack stand on that side was damp, but it's well behind where the power steering is leaking (that will probably be another thread soon...).

So after working my way up, I found that the z-bar (is that what it's called? The clutch pivot between the engine and frame) had what appears to be brake fluid collecting underneath. Progressing to the logical conclusion at the top, must be the master cylinder. Seems like it's probably leaking between the M.C. and booster, then running down and dripping off the bottom of the booster.

I assume this warrants removal of the M.C. Is there a seal of some kind there that can be replaced, or will this be a more involved job?

Thanks for bearing with me.

 

yes.. seems like your MC leaking down .. they are pretty cheap... do a search here for how to replace.. bleeding is usually the hardest part..

don't drive the car...

 

So a leaking MC automatically means it needs to be replaced? I just don't want to be replacing a whole big part like that if a simple gasket or something could be replaced.

I cleaned off the areas where it looked to be leaking, so this weekend when I can get back to the car I'll see if there's fresh fluid there, and if so I guess I'll remove the MC and check it out. Anything I should keep in mind when removing it? Seems easy enough - just unscrew the two lines and remove the bolts in the booster?

 

Replacing a M/C is one of the few easy jobs on a Vette, the brake lines should be loosened with a flare wrench to make sure that you don't round off the flats. Get a good set from Craftsman or a good company, the ones I bought at the auto parts store are poor quality and you will need them again if you ever have to replace the rubber hoses or a caliper in the future.
Also make sure that the replacement M/C comes with a
'Bleed Kit' if it doesn't they are sold separately at the parts store for less than $10.00.
Lock the new M/C in a vise, connect the bleed tubes, fill the front and rear reservoir with brake fluid and push in on the piston until the fluid recirculates and there are no more air bubbles.
Then install the M/C and you should be good to go.

 

It needs to be repaired OR replaced. Depends on your abilities as a mechanic and the condition of the unit.

 

OK, checked it out again this evening and there doesn't seem to be any further leaking at the MC - no fluid on the z-bar. Also couldn't get any fluid to appear when pumping the brakes (actually observed that last weekend when I found the drips).

After thinking about it, I suspect that this actually isn't the leak. The weekend before last I had opened the MC to check the fluid levels again... I think with the added tilt from jacking it up, the rear reservoir (which is still quite full) must have spilled some over the back of the MC. The back of the MC is dark like it's wet with fluid.

So is it possible there's not a leak? That it's just air in the lines? I mean, if I can't get anything to leak by pumping the brakes...

I'm considering just bleeding the brakes all the way through with new fluid (what's in there isn't exactly clear) and seeing if that improves it.

 

If your pedal has gotten noticeably softer then you have air in the system. If your front rotor run-out is excessive on one or both sides, you are introducing air through the calipers.

If your pedal has not gotten softer you may have worn your pads and require increased pedal to give braking. Replacing the pads with new pads will require less fluid to apply brake pressure to the rotors. Your level in the front chamber of the master cylinder will rise due to the pad replacement.

I would check the condition of the front pads to see how much liner material is left, and replace if questionable. If you have a leak, then brake pressure application should be obvious. You are correct in the assumption that the indicated fluid leak at the z-bar could have been the removal of the master cylinder cap. Worth repeating; if you have an actual leak, it should be apparent.

When ready to operate the vehicle the brake warning light should be extinguished. If still illuminated your braking action will be compromised, until the combination/proportioning valve is re-centered.

 

Ah, thanks for that feedback. I will check the pads. How big a deal is it to do that? Not having worked on brakes before, I'm not sure what's involved. I assume the caliper needs to be removed?

The pedal is definitely what I'd call softer, although of course there is increased travel too as a result. I'm more and more thinking it's air. But whether it's only air... might as well check the pads while the wheel's off right?

Also, if the problem is fixed and normal line pressure is restored, should the valve re-center itself? Should the light be out immediately afterward upon starting the car, or maybe after giving the pedal a good press?

 

To check the condition of the pads, remove the wheel and have a visual inspection for the thickness of brake material left. You can see the pads without removing the calipers. The dash warning light will normally illuminate when the system pressure is too low in the front or rear system and stay illuminated until the valve is re-centered.

Is the brake warning light "on" or "off"?

Top up the fluid, re-cap the reservoirs and try rapid, solid brake pedal applications to re-center the valve. Do this until the light is extinguished. Re-check for leaks and determine the pedal feel at this time. If pedal pressure is good, your front pads may be worn but you should be good to go; and stop. Check how much pad thickness you have left and make a decision whether or not to replace the pads. If the light comes on after driving some distance then I would be looking at rotor run-out.

I haven't had any brake leaks that I couldn't locate with a fluid puddle or fluid coating on the vehicle.

 

The brake warning light is currently on.

Are you suggesting to top off the fluid without bleeding to see if that helps? Or should I bleed first to get any air out?

EDIT: Well, I went ahead and topped it off, I guess I'll see if that helps any. Now to wait for the battery charger to get it startable again... (it's always the little things that hang you up, huh).

EDIT2: As will happen, other priorities got in the way. All the wheels are off, and I have now bought more brake fluid, but I didn't get a chance to do the bleed. Hopefully I will get a chance to do it next week, and I will make a new post with my results.

 

Well, I found some time to pedal-bleed the brakes and I'm not sure how effective it was, being my first time doing a bleed and considering I had a loose-fitting hose to simply direct the fluid into a bottle. However, when I got to the front left caliper there was some noticeable air escaping, so I'm hoping that was the majority of the problem. That probably means that caliper is leaking (I think it's original) and should be rebuilt/replaced. Bleeding it should have at least remedied the situation for the time being anyway.

Unfortunately, when I was going around with a socket making sure the bleeders were tight, I broke one off. The outer right rear bleeder valve sheered off. To make matters worse, when I got a screw extractor in it, that broke off inside the bleeder!

So now I'm stuck with possibly needing to drill out a hardened chunk of steel from my caliper, but as long as it's not leaking (and it shouldn't be, since the valve is closed - not to mention the extractor plugging it) I'm thinking it should be OK to drive at least, right? I was thinking that I would like to just replace all the calipers with aluminum ones at some point, so as long as I don't need to bleed that particular caliper half any time soon, should it be OK to leave it?

 

OK, just an update. I pumped the brakes and satisfied myself that none of the bleeders were leaking (especially the broken one) and put the wheels back on.

Well, the brakes aren't perfect (pulls a little to the left on hard braking) but they seem to at least be where they were before the light came on, so I guess the problem was just air, most likely from that front left caliper.

As I mentioned previously, I hope to replace all the calipers at some point, so I think I can live with it for the time being.

Thanks to all who offered assistance, this car is going to be quite the learning experience.

 

If you ever replace the calipers be sure to get calipers that have stainless steel sleeves and o-rings. The original style lip seal calipers had problems with failures and leaks. VB&P still has their holiday deal going on right now.

 

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