[saab_praab]

Greetings everyone.

Brief history of my braking woes:

I had a bad brake line over a month ago that ruptured under hard braking. I replaced the bad line and bled the caliper (rear left). The brakes worked after this, but the pedal was lower than usual. I drove like this for awhile until the grinding noise started. Time for new pads. I ordered pads and saw (should have known!) it was new rotors time as well. Ordered and installed. Was able to retract front driver's side caliper piston to receive new pads (although even with piston fully retracted, I can't fit a new outer pad, so I put one of the older, less worn ones in--wondering if this is due to bad e-brake calibration, don't know).

Then to the really big issue at hand.

My right front caliper piston was seized (which I think explains why the pads were worn down to nothing on that side and not on the other) so I ordered a reman and proceeded to install it. When I went to bleed at the bleed screw, absolutely nothing came out (except a super small amount of air) with helper pumping the brake pedal (open screw, depress and hold pedal; close screw, release pedal). We spent a great deal of time doing this with nothing to show for it. I checked bleed order in the Bentley manual, and it says to start with front right anyway.

I'd heard a collapsed rubber flex line was the likely culprit since I was getting no brake fluid to the caliper, so I removed it and blew air through it successfully. It seems to be fine. I then tried bleeding at where the metal brake line connects to the flex; we obtained a slight trickle and a very small amount of air. Using a homemade vacuum bleeder, we were able to extract some pretty clean looking fluid, but that section of line is so long I suspect it was all fluid just sitting in the line already. The level in the reservoir did not go down noticeably.

I wondered if I was dealing with a collapsed line elsewhere.

I then opened the line at the junction near the reservoir where front and rear brake lines meet. No fluid once again after several pedal pumps.

Finally, I opened the line where it terminates at the master cylinder and got just a small amount of fluid followed by a small amount of air. I plugged the inlet with my thumb while my helper retracted the pedal, and uncovered it as the pedal went down. This was repeated several times and no more fluid. I could feel slight suction on my thumb as helper retracted pedal, but it seems like it should be more than that.

So now I'm convinced none of the lines are bad. Am I dealing with a problem in the vacuum booster, or just a bad master cylinder? I've never let the reservoir run dry, even after the brake line rupture over a month ago.

 

[Sipes216]

were you twisting the caliper pistons as you were retracting them?

these cars don't have "traditional" hydraulic pressure-only calipers on the front, like every other car in the world.

rather, they have the style that most european cars have on their REAR.

this was a large surprise to me when i did my first bit of work :lol:

they act seized when applying inward direct only presusre.

get the caliper piston-srew tool. that should help.

after that, if it's screwed, you can get calipers locally at a parts store. surprisingly they still stock them, somewhere, a day away...

 

[saab_praab]

Thanks for your thoughts, Sipes. I did a lot of homework prior to this undertaking, including searching out the pre-1988, screwy "twisty-piston" design.

Yes, I believe the piston won't even retract with just inward force. Only when twisted. I used a nice pair of bent-end needle nose pliers to accomplish the piston reset (special thanks to user "jetman" who posited this idea here). Thankfully, the replacement for the other side was already retracted and ready to go.

Any idea about my pressure issue? Why would I not be able to bleed at any point all the way up to the master cylinder? I am bad news ready, so lay it on me.

 

[saab_praab]

This is my third time posting this. Seems like it keeps getting deleted. What's up with that?

I had said,

"Thanks for the advice, Sipes. Yes, I was aware of the piston needing to be twisted as well as pushed. I used a pair of bent-end needle nose pliers, advice courtesy of an older post by user "jetman" on these forums.

Thankfully, the replacement caliper I ordered for the truly seized right side was already fully retracted and ready to go.

What of my pressure issue? Why would I have so little pressure all the way up to the master cylinder so that I cannot bleed at all? I'm almost certain an MC replacement is in my very near future, but I want to rule out the vacuum booster first (or anything else)."

 

[jetman]

Hard to guess without seeing, but there could be a blockage in there. To properly bleed the brakes you need to do it in an x pattern. Lf, rr, rf, lr.

 

[Sipes216]

This is my third time posting this. Seems like it keeps getting deleted. What's up with that?

I had said,

"Thanks for the advice, Sipes. Yes, I was aware of the piston needing to be twisted as well as pushed. I used a pair of bent-end needle nose pliers, advice courtesy of an older post by user "jetman" on these forums.

Thankfully, the replacement caliper I ordered for the truly seized right side was already fully retracted and ready to go.

What of my pressure issue? Why would I have so little pressure all the way up to the master cylinder so that I cannot bleed at all? I'm almost certain an MC replacement is in my very near future, but I want to rule out the vacuum booster first (or anything else)."

happy to help!

as for your no-pressure issue, make sure first that you have no air in the master cylinder. they are a ***** to bleed out if you get air in that part.
their symptom will be little to no pressure in the channel if there is air. it tends to be a lot more squishy than hydraulic fluid, go figure

 

[saab_praab]

What's the best method for bleeding the master?

It baffles me how I could have gotten that much air in it. I simply had the line open at the bad caliper for several days while waiting for the replacement to arrive. I understand every time the system is opened it needs bleeding, but I didn't pump the brakes while the line was open so no excessive air should have been drawn in.

 

[Sipes216]

You just described the best way. You're gonna need a 4 wheel flush after you re-bleed the mc.

If you have one channel left open for long it'll keep draining. Those "air trap loops" the system has, protects for short term, not days of draining.

You could have also gotten air in all the channels, so play safe and full flush when done.

 

[Sipes216]

Also, best way to avoid this would have been leaving the old caliper hooked up, not necessarily mounted. That will keep the system sealed, thus avoiding THAT.

 

[saab_praab]

So, to summarize what you're saying:

1) the reason I'm in this situation (can't bleed as normal at the caliper) is due to leaving the line open for that long.

and

2) the remedy is to continue bleeding the master using my thumb over the inlet and pumping brakes as described earlier. Is that what you meant when you said, "You just described the best way"?

Could you confirm points 1 and 2?

Planning for a full bleed...

 

[Sipes216]

So, to summarize what you're saying:

1) the reason I'm in this situation (can't bleed as normal at the caliper) is due to leaving the line open for that long.

and

2) the remedy is to continue bleeding the master using my thumb over the inlet and pumping brakes as described earlier. Is that what you meant when you said, "You just described the best way"?

Could you confirm points 1 and 2?

Planning for a full bleed...

sorry about that!

point one, you're in this predicament because the master cylinder resevoir and cylinder itself are above the brake caliper. that said, leaving it open so long. gravity is going to draw that fluid out of the system slowly, and replace it all with air.

point #2) what you will need to do is a master cylinder bleeding process.
https://www.youtube.com/watch?v=4oi3Y6HMCbc

"the best way" referred to how you got the air in there. leaving the caliper off for a long time "is the best way" to get into that situation

you're going to spill brake fluid in the car when you do this. use water or brake cleaner to wash it away thoroughly before it hurts paint.
it takes hours to hurt the paint, so do your work, clean the area, and you're fine.

 

[saab_praab]

Thanks very much for your help.

So basically do what the guy in the video is doing, except with the master still attached?

 

[saab_praab]

Never mind, the fellow in the video said it can be done on the car with a partner.

I'll give it a try and let you know how everything comes out.

 

[Sipes216]

It can be, but takes a bit more time and fluid, unless you recycle fresh from the bleeder, with a clean container.

A final step I recomen when you finish with the on-car bleed, is to just for 5-10 minutes step on and off the brake pedal repeatedly. This will vibrate any remaining air in the top of the cylinder back into the reservoir.

This is a FINAL step I do myself as a final security, once everything is closed and sealed, "just in case".
You won't find this in any book, its one of those " old shop guy" tricks I picked up along the way.

 

[saab_praab]

Wow, I can't believe it but I was able to "bench" bleed (in the car) the master cylinder using some leftover clear flex tubing and two of the stiff inner tube pieces from a couple ballpoint pens. Fit perfectly and kept vacuum.

Pumped the brakes slowly and evenly probably over 100 times; watching it go from large air pockets to tiny bubbles to only fluid was awesome. Quickly removed jury rigged apparatus and replaced flared tubes and nuts.

The pedal felt very hard after this which was encouraging.

Then to bleed at the caliper. Nothing but a slight air gurgling sound after a couple dozen pumps. Is this to be expected? I know I'm basically trying to fill an empty brake line and empty caliper, so I assumed there'd be some delay.

I've got the system completely closed up until I find out if I'm doing anything else wrong!

 

[saab_praab]

Today I checked for fluid expulsion from a connection point 12 inches or so from the master and, with pedal pump, I can't get anything beyond gurgling air sounds. (If I can't get flow there, of course that's why I can't get it at the caliper!) I'm making sure to entirely close the line prior to pedal release so as to not draw air in again. The system has remained closed ever since bleeding the master cylinder yesterday.

This has me baffled.

I'm willing to bench bleed the master again, but if it didn't help the first time, why do it a second time?

 

[saab_praab]

Well, I re-bled the master twice more today. The only way I could get some fluid and air flow at the caliper was through my crude vacuum bleeder (cattle syringe with a clear tube attached).

My question now is, is it possible there's so much air in the system that it's not possible to bleed with the pedal and the system needs to be vacuum bled?

 

[Sipes216]

what's probably happening at this point is that there is so much missing fluid between the caliper that air might have gone back up into the mc (again) if your process wasn't quick enough...

brake systems cane be a ***** like this sometimes....

 

[saab_praab]

Sipes,

So I finally got my car started (been sitting so long the battery went dead) and with every part of the brake system hooked up, the brakes feel completely soft with no resistance at all.

I wish I could figure out whether or not this is just stuck air or a failed master because I think I'd rather buy a new master cylinder and bench bleed it (knowing it was going to work) than mess around with my current setup.

What do you think? General troubleshooting tells me air in the lines and master cylinder failure will feel about the same at the pedal. The only thing that strikes me as strange is the master cylinder "happens" to fail when I've got my brakes torn apart.

 

[Sipes216]

anything can happen on old cars, i suppose... it is one of the risks we take by loving old things.

i really don't want to call the MC, dead just as of yet.

have you tried getting a second person and having them apply the brake then you open the bleeder valve?

in this method i do this -

tell them to apply brakes.
with pressure in system, i open bleeder valve, release pressure.
i close valve.
tell them to release the pedal.
lather, rinse, repeat.

in this manner, i am able to keep up a pretty good pace that keeps any problems from arising.

one other novel thing i do have is a "motive" brand power bleeder. it screws onto the resevior opening and you pump it to like 10 psi, then can open the bleeder and it forces the fluid down through while refilling it along the way.

are you local to dfw? if you're kind of close, i'd be willing to come out.