Question: Brakes Pressure Gone!

[Vette79]

Really :eek What did VB&P give as the reason for the delay?

Just got off the phone with them and it appears as though they are out of stock with this little part called "Dust Covers" which play an important role in building calipers. So, I'll gladly wait and let them do a good job. My parts will probably ship next week sometime they are saying...

 

[Mr. Chuck]

Special order / builds

Just got off the phone with them and it appears as though they are out of stock with this little part called "Dust Covers" which play an important role in building calipers. So, I'll gladly wait and let them do a good job. My parts will probably ship next week sometime they are saying...

When you order parts for out of production vettes, a one unit work order is issued and a stock clerk starts pulling component parts, often many are no longer on-hand. You are lucky they only are waiting for just one part, most likey there were others, but this is the last one still pending receipt. My experience is that part of the wait time (delay) is due to sub-contractors having to make the part and then ship it to Delco. Hopefully a senior assemblier builds your order and knows the model well.
I spent 28 yrs as a Quality Eng / mgr (Computer systems mfg), there are always small details of any product build that doesn't get documented fully; i.e. the benefit of having a senior assembler do the job and a through quality test.
A wise choice to not wanting them to rush the build!

 

[Evolution1980]

So, I'll gladly wait and let them do a good job.

Good call. I've learned, unfortunately, more than once that having someone rush a job usually doesn't work out in my best interests.

(If I had to learn "more than once", did I really learn? :L )

 

[Vette79]

Good call. I've learned, unfortunately, more than once that having someone rush a job usually doesn't work out in my best interests.

(If I had to learn "more than once", did I really learn? :L )

Parts came in yesterday from VB&P. Nice quality parts. Can't wait to install them. They look better then anything I have seen.

 

[Vette79]

The murky brake fluid spells contamination, which leads to rust / pitted sleve walls, i.e worn / leaking brake piston seals,. Going the stainless route, either w/ sleves or stainless calipers which don't rust, greatly increaand ses their service life and reliability. Did this on my 81 some 40 - 50K miles ago, and no sign of leak or other malfunction. SS calipers are worth the extra cost. I did the front and rear at different mileage, got fronts from Mid-America and rear from Auto Zone. Both have limted life time warranty, can't really say or tell which calipers (brand) are better since nether have given any problems. Hope this helps support your choice in going with SS calipers.

Calipers and hardware installed with DOT 5 brake fluid. Pressure bled them with a Power Bleeder. Pedal still goes to the floor. No leaks and bled them 3 times. When the motor is off and when you pump the brake it gets hard as a rock but when running it goes to the floor. Thinking ?Master Cylinder issue now.

 

[Mr. Chuck]

Power Bleeding, Comments

Calipers and hardware installed with DOT 5 brake fluid. Pressure bled them with a Power Bleeder. Pedal still goes to the floor. No leaks and bled them 3 times. When the motor is off and when you pump the brake it gets hard as a rock but when running it goes to the floor. Thinking ?Master Cylinder issue now.

Not sure how your 79 brake system compares with my 81 brake system configuration; my 81 shop manual details the following pressure bleeding procedure / cautions:
1. Pressure bleeder air source must be kept isolated from the brake system with a gasket (part of the adapter assy); otherwise more air will be introduced into the system, defeating your efforts to bleed air from the brake system.
2. Also noted is the need to bleed the pressure ball after each time you add brake fluid to the ball, otherwise air can be introduced back into the car brake system from the pressure ball.
3. Assuming the 79 wheel brake calipers have dual bleed points (inner & outer) like my 81; you need to work from inner to outer bleed points, left rear, then right rear, them left front and then right front in that order.
4. I remember from my caliper replacement activities, it took me, with my wife pumping, at least 3 - 4 trips around the four wheels, repeated bleedings and making sure the master cylinder fluid levels never got below 1/2 full, just to be sure no more air got in.
5. I also removed any old dis-colored fluid from the two M. C. reservoirs chambers, once fluid was removed, I wiped out any residue build-up with a lint free cloth. I preformed extended bleeding at each caliper, until clear fluid was seen as well as any air bubbles.
6. One thought regarding hard peddle with engine off and peddle to the floor with it running; with the engine running brake boost comes into play, greater amount of braking pressure is applied causing remaining air to compress / peddle on floor. Manual (engine off) braking applies a lot less pressure, especially after vac boost is depleted giving the hard peddle feel & less peddle travel.
7. Q, with engine running and when brake peddle goes to the floor are you getting "Brake System" failure warning light? Did you check master cyclinder fluid level? Where both reservoirs levels equal?

I hope this makes sense and you find it helpful!

 

[Evolution1980]

Jeff, I just did a quick search for some "bleed brake" threads in the C3 section. Take a look at this thread. There may be some relative info there.
I was pretty sure that Hib had a procedural write up for bleeding brakes on the C3's, but I didn't immediately find what I was looking for. (or maybe I did and I just remember it differently)

 

[Vette79]

Jeff, I just did a quick search for some "bleed brake" threads in the C3 section. Take a look at this thread. There may be some relative info there.
I was pretty sure that Hib had a procedural write up for bleeding brakes on the C3's, but I didn't immediately find what I was looking for. (or maybe I did and I just remember it differently)

Yea, Hib provided some good info which we read. VB&P suggested taking off the master cylinder cover and pump the brakes to see if there is any activity and when my wife pumps the pedal hard there is fluid that pumps up from both reservoirs which leads me to think there is no problem with the master cylinder and maybe the proportioning valve. Just don't know. I will call VB&P back tomorrow. I'm thinking of ordering both parts and whatever I don't use just send back for a refund. Such a PITA with this car sometimes......ad

 

[Vette79]

Not sure how your 79 brake system compares with my 81 brake system configuration; my 81 shop manual details the following pressure bleeding procedure / cautions:
1. Pressure bleeder air source must be kept isolated from the brake system with a gasket (part of the adapter assy); otherwise more air will be introduced into the system, defeating your efforts to bleed air from the brake system.
2. Also noted is the need to bleed the pressure ball after each time you add brake fluid to the ball, otherwise air can be introduced back into the car brake system from the pressure ball.
3. Assuming the 79 wheel brake calipers have dual bleed points (inner & outer) like my 81; you need to work from inner to outer bleed points, left rear, then right rear, them left front and then right front in that order.
4. I remember from my caliper replacement activities, it took me, with my wife pumping, at least 3 - 4 trips around the four wheels, repeated bleedings and making sure the master cylinder fluid levels never got below 1/2 full, just to be sure no more air got in.
5. I also removed any old dis-colored fluid from the two M. C. reservoirs chambers, once fluid was removed, I wiped out any residue build-up with a lint free cloth. I preformed extended bleeding at each caliper, until clear fluid was seen as well as any air bubbles.
6. One thought regarding hard peddle with engine off and peddle to the floor with it running; with the engine running brake boost comes into play, greater amount of braking pressure is applied causing remaining air to compress / peddle on floor. Manual (engine off) braking applies a lot less pressure, especially after vac boost is depleted giving the hard peddle feel & less peddle travel.
7. Q, with engine running and when brake peddle goes to the floor are you getting "Brake System" failure warning light? Did you check master cyclinder fluid level? Where both reservoirs levels equal?

I hope this makes sense and you find it helpful!

Hi chuck, yep we did all of that. Initially, before the caliper install I did get the brake light a couple of times when the pedal went to the floor during braking. No leaks. All levels good. No air in system after power bleeding three times with inner bleeders first.

 

[minifridge1138]

I would get a new master cylinder.

Mine gave out (started leaking fluid out the back where it mounts to the booster).

I bought a replacement MC. Installed it. Bled everything. Pedal was hard with engine off. Started it, and the pedal sank to the floor. Turned the car off, pedal was still soft. Pumped it and let it sit a few minutes and the pedal got hard again.

Returned that MC for another one and everything was normal.

 

[White75]

I had the exact same problem and solution. my replacement MC ended up being bad and got it replaced.

 

[Vette79]

Having the correct Master Cylinder installed usually helps!!! Check out the difference.....ad

 

[minifridge1138]

Having the correct Master Cylinder installed usually helps!!! Check out the difference.....ad

Other than age, what's the difference?

 

[Vette79]

Other than age, what's the difference?

Look at it a little more closely. See the plunger in the bore? The brake booster's little piston pushes in on the plunger. With the new correct master cylinder there is more area for the plunger to travel in the bore of the master cylinder. I have never been able to lock up my brakes and now I can. The brake pedal is not hard as a rock as I thought it would be and goes further to the floor then what I thought it would but my brakes are much better then before.

 

[JohnZ]

Other than age, what's the difference?

The old master cylinder (on the right in the photo) is made for MANUAL brakes, with a "deep" hole in the rear piston for the pushrod from the pedal (so the end of the pushrod can't fall out). The correct master cylinder (on the left), for POWER brakes, has a "shallow" hole in the rear piston, for the short pushrod from the booster (which is captured between the booster and the master cylinder and can't fall out). If you use a master cylinder for manual brakes on a power brake booster, the rear piston won't stroke fully, and you'll have little or no brakes.

Many rebuilt master cylinders are incorrectly identified as to their usage; if it has a "deep" hole in the rear piston, it's for non-power brakes.

 

[Vette79]

The old master cylinder (on the right in the photo) is made for MANUAL brakes, with a "deep" hole in the rear piston for the pushrod from the pedal (so the end of the pushrod can't fall out). The correct master cylinder (on the left), for POWER brakes, has a "shallow" hole in the rear piston, for the short pushrod from the booster (which is captured between the booster and the master cylinder and can't fall out). If you use a master cylinder for manual brakes on a power brake booster, the rear piston won't stroke fully, and you'll have little or no brakes.

Many rebuilt master cylinders are incorrectly identified as to their usage; if it has a "deep" hole in the rear piston, it's for non-power brakes.

Thanks John. I was hoping someone would respond to the pic and explain the differences between the two.