Fleetwoodfloyd

About three months ago, I was going to drive out of the garage after many months of the car sitting idle. Brake pedal went almost to the floor with little stopping effect. Long story short, after replacing the master cylinder (new oem), power booster (new aftermarket), and both rear calipers (rebuilt), I still have the same condition. Master cylinder and brakes were power bled.
I checked the brakes with car on jack, and I have no rear brakes. There are no signs of leaks. My thought would be that the master cylinder rear brake piston is not sealing and fluid is blowing by, which is what I thought the problem was originally. That would mean the new MC has the same issue as the old one- not likely.

Any thoughts are greatly appreciated.

Charlie

Max Blast

If the old MCs issue was that it was dry when you stepped on the pedal and irreparably scored the inside of it, that means you have a leak somewhere.

so in that sense you still have the root cause issue. Fluid is going somewhere, find it.

ygmn

yes replacement parts canbe bad.

remove lines fromMC
INstall plugs
Try pumping pedeal slowly.
Should be hard to press very quickly.... if not get another one.
if hard.
Reconnect lines and jack car up and remove all 4 wheels.
Bleed brakes starting from furthest LH rear, RH rear, LH Front finally LH front.

Does pedal get hard aftr last one?
if not check for weapage/leaks at each wheel and all brake lines.

Did you prime and fill MC before installing?

Fleetwoodfloyd

To re-hash and touch on the two replies received-
The MC bore was in quite good shape on the original, except for some light corrosion on the forward (front brakes) section. Given the symptoms of not pedal and no leaks, I assumed the seal(s) were bad and installed a new MC. I also installed rebuilt rear calipers as the originals showed the seals breaking down and I didn't want to mess with rebuilding them myself. Still had the same problem. I didn't think it would be the booster, but I went ahead and replaced that as well, but am back to square one. I did manual bleeding with my wife on the pedal and then went to power bleeder. MC was bled by loosening the line fittings under pressure. I have gone through three quarts of fluid doing bleeding.
As I stated, I have no rear brakes, and cannot for the life of me find a leak. I will try to test the MC by plugging the outlets.
I have worked on older car brakes for years and this should not be rocket surgery, but this is beyond aggravating.

Thanks again.

ygmn

could be clogged or collapsed rubber line near calipers...

When you bleed are you getting fluid out?

Fleetwoodfloyd

All calipers bled fine with the pressure bleeder. Maybe I can do a manual bleed and see if I can tell a difference between how the fluid pushes front versus rear.
If I have no rear brakes with the pedal to the floor, maybe the flow will be weak compared to the front.

Max Blast

What brand master and calipers did you buy?

ygmn

can you post pics of each corner caliper and brake pads from side, quartering view and looking at rotor edge showing pads against rotor so one can tell how much pad material is left.

IF you can pressure bleed but the pedal is still soft.
No ABS on this car.

Issue is fluid is bypassing somewhere.
possible causes:
- Master cylinder is junk
- Re-built calipers junk.

You have some place in circuit where fluid is leaking (outside circuit or back to low pressure side)


Are you finding you have to continue to add oil after stomping on pedal and it nevers gets hard? Like the oil is streaming out somewhere and does not return to MC?
External leak somewhere.

or nope fluid level is fine and never really changes in MC reservoir -
MC has bypass leakage

Nothing fancy here

Fleetwoodfloyd

New ATE master and rebuilt ATE calipers

ygmn

new parts can be junk from start...
so do not dismiss any new part for being cause

Fleetwoodfloyd

I plugged the outlet to the rear brakes at the MC and the pedal was high and hard. I plugged the line the right rear brake and the pedal was high and hard. When I put the right rear caliper back on, the pedal was soft and went down to near the floor. Power bled between, then removed bleeder before each test. I just returned the right rear caliper; will see what happens with the replacement.

ygmn

sounds like a good troubleshoot.

any signs of brake fluid around or near this RR caliper?

Max Blast

but the only thing I can think of here is that both rear calipers somehow were installed upside down, or that you got two left side calipers and when you put the one on the right side, it went in upside down - and that you have a huge air pocket and one or both of them which would allow the pedal to go soft without any fluid loss.

easy way to tell is that the bleeder nipple always points up. I actually managed to do that once.

ygmn

YEs that is another possibility I did not thing of - probably because it has Never happened to me yet neither -
Good post and another thing I will check when changing calipers.

When he gets it right I do want to know what was cause and fix.

Fleetwoodfloyd

Well, I now have brakes after replacing the first rebuilt right rear caliper.

I think I likely did have them reversed.
Now the right-side caliper has the line entering at an upward angle, with bleeder on top.
The left side has the line entering at a downward angle, with bleeder on bottom, so it is wrong I assume.
However, apparently it is bled, as I have good pedal and the brake is holding.
I think I will get the correct one on though.

Thanks for all the help on this.

Max Blast

glad you figured it out, you’ll never get air bubbles out of the system with the bleeder nipple below the inlet.