1965 L76 Non Power Brake Car - Brake Bleeding Issue

[Ted F.]

I've searched the archives extensively and can't find anyone that had a similar issue and then a possible solution. I've owned this car over 20 years. DOT 3 brake fluid was changed two years ago. Run the car a couple of hundred miles a year. Brakes on the car have always been rock solid. Drove the car the other day ran perfect. Went back out to move it, brake pedal went to the floor. Checked master cylinder, obviously low. Put the car on my lift. Right rear caliper leaking badly. Two lip seals failed. Pulled all all four wheels and have rebuild all four calipers with lip seals, pistons and dust boots. Didn't rebuild MC yet. I've been bleeding brakes for the last couple of days. Can't get a hard pedal, really soft. Using DOT 3 fluid. Gravity and pedal. With gravity bleed, clear hose into jar, I'm getting good flow from all calipers except the right rear inner half. With pedal bleeding, on the press and hold pedal, crack bleeder screws, I'm getting good flow no bubbles from all calipers but the same right rear inner half. With pedal press and hold, fluid starts to move into hose then stops. So, obviously this is at lesst one of my issues. I've tried tapping the inner right rear caliper with a small rubber mallet to remove air. When rebuilding that caliper (actually all calipers), I blew air thru them and didn"t find any blockage. I"m not finding any leaks anywhere. I don't want to use a pressure bleeder because I'm working in a confined/small space with other cars and don"t want to take a chance of spraying brake fluid. I"ve never had a problem bleeding corvette brakes using gravity or pedal method before. I'm not saying it wasn't time consuming, just always got flow out of bleeders when opening them. Looking for some ideas and/or suggestions. Thanks in advance. Ted

[Leif A.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Possible plugged bleeder. I'd ask how old the rubber brake hoses are, but you say you're getting good flow from one of the two bleeders, so that is possibly not the issue. I would remove the bleeder that's giving you issues and depress the brake pedal and see what kind of flow you get. Hopefully, it turns out to be something that simple.
BTW, just noticed this is your first post in 15 years...welcome

[Edward J.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Ted,
try cracking the steel line loose before the caliper hose and see if you can get fluid flow, if you do then you may have a bad hose as Leif said. I myself prefer the gravity method when bleeding, rear calipers I start with the inner bleeder.

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Appreciate the replies. Thank you. I need to get this solved so I can move the car. This really has be baffled! I did switch out the bleeder to a known good bleeder. No change. The flow out of every other bleeder on the car is great, no bubbles and clean fluid. The rear line to the caliper flows great. I'm getting good flow to the outer half of that same caliper. Pedal is really soft. No leaks anywhere. Using the pedal push and hold method for bleeding, I'll get brake fluid to start to flow then stop. Then nothing. All other calipers gravity bleed perfectly. This caliper half won't gravity bleed. I was wondering about the master cylinder? With the cap off the MC, pumping, holding and releasing the brake pedal, I don't see any movement of brake fluid in the MC reservoir. Obviously, bleeding the calipers drops the brake fluid level in the resevoir. With air in the one caliper half, I would except to see bubbles or movement of brake fluid in the MC when pumping the brakes?

[Duke W.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

I doubt if it's the m/c because the problem only appears with the one inner caliper half. You need to remove that caliper, separate the halves, and disassemble the bad half... could be something as simple as a piece of debris. If you find something obvious and the 0-rings and dust boots are okay, you should be able to reassemble and install without any new parts.

Duke

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Duke thanks for your reply. I'm going to pull the caliper and see what I have. I used Zip lip seals, pistons and dust boots. Pistons looked okay, but rubber products weren't really impressive. Is there a preferred source for lip seals and dust boots? Caliper is a sleeved 545 casting number caliper. What's a good source for a 546 casting number caliper? Might just be easier to get a caliper that is correct for the car while I'm at it since the other three calipers are correct. Thanks Ted.

[Bob W.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Ted call Ken at Lone star caliper in Texas He may have what you need.

[Bob W.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Ted call Ken at Lone star caliper in Texas He may have what you need.

[Joe L.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Duke thanks for your reply. I'm going to pull the caliper and see what I have. I used Zip lip seals, pistons and dust boots. Pistons looked okay, but rubber products weren't really impressive. Is there a preferred source for lip seals and dust boots? Caliper is a sleeved 545 casting number caliper. What's a good source for a 546 casting number caliper? Might just be easier to get a caliper that is correct for the car while I'm at it since the other three calipers are correct. Thanks Ted.

Ted------

There should be no difference between '545' and '546' caliper casting as far as the problem you're describing is concerned. "546" calipers (i.e. 1st design) have internal piston guides whereas '545' (i.e. 2nd design) do not. Of course, many 1st design calipers have had the piston guides machined out, effectively converting them to 2nd design. Either way, the caliper halves are essentially interchangeable and could not cause the problem you are having.

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Joe, thanks for replying. Car is extremely original. I've owned it for over 20 years and it didn't have a lot of prior owners. Since, the other three calipers are 546 castings, I figure that as long as I'm at it, I might as well get the correct casting # caliper. Looking for a second design modified 546 caliper so that they all match. Other than my known problem. There is something about this caliper that doesn't seem right to me other than it is a 545 caliper. When I took this caliper apart, it was a mess. Gunk, etc,... Other calipers were clean. Car brakes were always great, so it was working before. I know that there are a lot of issues with brake lines. Before I tear everything apart again, I want to make sure that I have as many bases covered as possible and have parts coming. Clock is ticking and I need to get this car moved before weather stops me. If I had a semi plugged brake line, not enough flow to handle both caliper halves, wouldn't I get flow to the inner caliper and not the outer. Is my thinking wrong? I'm thinking like Duke advised, that I have a plugged inner caliper half. Thanks for any comments.

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Ted call Ken at Lone star caliper in Texas He may have what you need.

Just a follow-up. Got ahold of Lone Star on Monday. Received my 546 casting caliper and other misc. brake parts yesterday afternoon. Caliper is beautiful and rubber products are definitely high quality. They did exactly what they said they would do. Very refreshing! I know there are lots of threads praising Lone Star, just thought I would give them kudos. I don't know if this new caliper will solve my problem? However, seeing that this was the only incorrect caliper on the car and I was going to have to dissassemble the incorrect one again anyways, this option made sense to me. We'll know shortly if this solves my brake problem. Appreciate everyones' advice and comments, so far.

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Still battling these brakes. Looking for some more advice. Lonestar did a great with a caliper and parts. Installed new caliper. All calipers halves bleed now. I'm bleeding thru clear tubes into a jar that is half full of new brake fluid. Using the push and hold, I get a solid 5" flow of brake fluid out each caliper half, close to bleeder. Repeat same thing. No air bubbles. I can't get more than 5" of solid fluid flow close to bleeder. Can't get a solid flow of fluid into the jar. With the cap off the master cylinder, I don't see any movement of fluid in the resevoir when pushing and releasing brake pedal. Going thru lots of brake fluid! Almost, sounds like master cylinder is sucking air. I can still push pads off rotors with my fingers when brake pedal is released. Harder to do now, but still can do. Still soft brake pedal. I'm now thinking maybe something not right with master cylinder? Any ideas? Thanks in advance.

[Duke W.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

I don't understand your post... suggest you edit for clarity or repost if the edit function is not available. It sound's like the original problem may still be there, but it's not clear.

Also, it's a good idea to make liberal use of paragraph spacing. When faced with a dozen or more lines of single spaced test, I usually don't bother to try and read it.

Duke

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

Changed settings in my editor. Now, it is not eliminating my paragraphs.

I can get brake fluid to start to flow out of each caliper half bleeder into a plastic tube into catch bottle. It is not a full flow into the catch bottle.

Pump and hold, open bleeder, I get a flow of about 5 inches of brake fluid out and the rest is air space in the tube into the catch bottle. Close bleeder, press and hold pedal, open bleeder, five inches of brake fluid flows into tube. Can't get fluid to flow freely thru tube into catch bottle.

Using this same procedure, before I replaced the blocked caliper. I could get a tube full of brake fluid (no bubbles) out of each caliper half into the catch bottle, except from the one inner rear bleeder, apparently blocked caliper half.

Nothing has changed other than I removed the old caliper and replaced it with a new rebuilt one.

Have been careful to not press brake pedal to far to cause damage to the MC seals. MC has never gone dry. Brake pedal is still soft.

In the past, I've never really paid much attention to sounds from MC when bleeding brakes (sounds like MC is sucking air when brake pedal is depressed) and or looked at MC resevoir when pumping brakes. Cap off MC, pumping brakes, there is no apparent movement of brake fluid in the resevoir. I've always been lucky over the years, I guess. Replaced calipers, lines or MC (bench bled MC) and bleed all four corners of car a couple of times and had hard pedal. I'm thinking now something has failed with the MC?

This is a nonpower brake car, single resevoir and no proportioning valve, basic system. However, it seems to be really figthing me. Before the seals let go on the right rear caliper, IMHO, the brakes on this car were as good as any older corvette I've ever owned or driven.

Thoughts - Thanks.

[Ted F.]

Re: 1965 L76 Non Power Brake Car - Brake Bleeding Issue

3 days on and off bleeding, still spongy pedal! A couple of questions. I like to identify a problem before I just start rebuilding and replacing components. I'm thinking that I'm going to rebuild the master cylinder and replace the rubber hoses to the calipers. That's about all that is left to do.

Questions:

When the brake pedal is pressed and released or just pumped, should there be visible movement of fluid in the MC reservoir (cap off)?

Using push and hold of brake pedal for bleeding. Clear tube on bleeder into vented jar. Only get a couple of inched of brake fluid flow in tube at bleeder. If I leave bleeder open and pedal is pushed again, nothing comes out of any bleeder on any caliper. I'm thinking MC isn't holding pressure. On other cars I've bleed, I could fill the jar with fluid using this method. Of course, I would close bleeder once the flow of brake fluid into the jar was clean and clear.

This is an extremely original car! I don't like to just start taking things apart w/o identifying the problem first. Would appreciate comments on what I'm finding. Thanks.