Brake bleeding poor results

[Bob H.]

Re: Brake bleeding poor results

It can make all the difference in the world. They certainly can the cause of your problem. If you don't want to change the rubber hoses due to age and getting them loose, it is likely all the more reason to change them. How old are they? They are a bit of a pain but should not be all that bad. Just make sure you use a flare wrench. It sounds like you had the problem with the original m/c and also after changing it. If it's not air in the system and no leaks, it pretty much has to be a hose that is expanding internally.

[Ted K.]

Re: Brake bleeding poor results

I have never experienced a brake hose expanding internally, actually never heard of it, but I will give it a try. Both front hoses have been on there a long time. I'm going to be out of town for a week so I will let you know when I get them changed out.
Thanks

[Patrick C.]

Re: Brake bleeding poor results

I changed all the hoses and wheel cylinders on my 64. Not that bad a job. Use some penetrant the night before on the joints and a flare wrench as mentioned by Bob.

Just a note, my drum brakes can easily be locked up, the pedal remains hard and has minimal travel. Consider those speed bleeder, it will make this job easier.

[Ted K.]

Re: Brake bleeding poor results

Started the job yesterday and as expected twisted the ends off of both steel lines, even though they were soaked in penetrant for two days. Oh well, ordered new lines and will continue when received. Probably needed to be done anyway.

[Bob H.]

Re: Brake bleeding poor results

The joy of owning an old corvette. Hopefully, once done your problem will be gone. You will certainly be much safer. By the way I just did mine so I can relate. Not much more important then the brakes.

[Duke W.]

Re: Brake bleeding poor results

The master cylinder has been on the car for at least 7 years. I guess it is possible that with a leaking caliper, in the car's history, the fluid level in the MC could have gone below zero and let air into the MC??? Can a MC be bleed while still on the car?? It is a power brake car.
Would a pressure bleeder get the air out of the Master Cylinder if there was air in it while bleeding the calipers??
Thanks
Ted

Yesterday I helped a neighbor install rebuilt front calipers and new hoses on his '77 coupe. The old front calipers were leaking and the fluid reservoir was dry. When we removed the calipers/hoses a couple of weeks ago I attached clear vinyl tubing to the brake pipes, looped it up to the top of the wheel well, then filled the m/c reservoir and within a couple of minutes the system had gravity bleed and all the air was gone. Then we installed the res. cap, removed the vinyl tubing, and installed rubber caps over the pipes while we waited for the calipers to be overhauled.

The installation sequence was caliper, hose to caliper, hose to brake pipe (both with tubing wrenches, of course) pads, and bleed. The system bled quickly using the manual method (one guy working the bleed valve, one guy working the brake pedal), and we also flushed out the rear for a complete brake fluid flush with DOT 4.

My recommendation is to always install new hoses when overhauled calipers are installed. Lack of fluid flow can be an internally disintegrating hose or a pinched brake pipe, due to damage from kicked up road debris, so brake pipes should be carefully inspected anytime fluid flow to the caliper seems poor.

There seemed to be less fluid flow per bleed cycle at the rear than front. I'm not sure why because I believe both front and rear m/c pistons are the same diameter and stroke, so fluid displacement per bleed stroke should be the same at both ends. In any event the job went pretty smoothly.

On another note, we also changed the coolant (Zerex G-05 HOAT). It's been about ten years, and I recall the last time when I removed the block drain plugs, nothing came out. I had to dig out debris with a dental curette to get the coolant to drain. I figured they had never been removed. Upon installation I liberally applied pipe joint compound, but they were tough to remove. (Used a SIX-POINT SOCKET, of course.) Once I got the damned things off the coolant flowed freely.

Upon inspection the threads were damaged... I have no idea why, so we deemed they needed replacement, but had a hard time finding 1/4 NPT steel or brass plugs with a HEX. Most were internal hex, Torx, or square. We finally found some brass hex head plugs at Fair Lady hardware in Torrance, CA, which has always been a great place to find a piece of hardware that's hard to find.


Duke