Author Topic: Help!! Brake Failure!! (Read 6262 times)

88jetta350 · « **on:** March 17, 2009, 12:37:11 pm »

Ok, the search is being ghey again, and the Google Search didn't turn up anything useful, so I'll throw this out there.
'86 Golf Flair 1.3 carb
9.4 solid front brakes
drum rears.

Replaced sofar:
Master cylinder
Both rear brake cylinders

Symptoms:
No visible brake line leaks.

No braking force on right front & left rear brakes. Flushed the entire system, fluid was pretty gross.

Replaced both rear cylinders since they were leaking slightly.

Replaced master cylinder, since I had a known good one from a donor car.

Attempted to bleed brakes. Left front and Right rear bleed out normally, but right front and left rear will not.

When holding the brake pedal, and you open the bleeder valves on either of them, nothing comes out, brake pedal doesn't travel to the floor like it should, only as far down as it does with the bleeder closed.

When you pump the brake pedal with the valve open, fluid squirts out.

After bleeding, brake pedal has little resistance, with or without the car running, and there is ZERO braking force in the front right and rear left.

Jettagli16v · « **Reply #1 on:** March 17, 2009, 04:20:37 pm »

I know you said you changed it,
and I defer to the more experienced,
but my bet is on the master cylinder.

The reason I say this is: (to my knowledge)
the watercooled VWs run a dual circuit master,
with Right Front, and Left rear on one circuit, and the other 2 on the other.
I was told this was so if you had a master cylinder failure, you would be less likely to lose all brakes at once.
That should be the only common link on those two corners.
I know you put in a known good one, but they do not like to sit open (without fluid) for too long...

Just my guess.
-Brad

jtanguay · « **Reply #2 on:** March 17, 2009, 04:42:20 pm »

Quote from: "Jettagli16v"

I know you said you changed it,
and I defer to the more experienced,
but my bet is on the master cylinder.

The reason I say this is: (to my knowledge)
the watercooled VWs run a dual circuit master,
with Right Front, and Left rear on one circuit, and the other 2 on the other.
I was told this was so if you had a master cylinder failure, you would be less likely to lose all brakes at once.
That should be the only common link on those two corners.
I know you put in a known good one, but they do not like to sit open (without fluid) for too long...

Just my guess.
-Brad

yea brake fluid is VERY corrosive, especially old stuff. its hydroscopic meaning it will absorb a lot of moisture from the air, and the brake system is vented so yea... :roll: i would rather put a bag type system to let it breathe under heavy braking, and have a bunch of silica in there, but thats just me. the brake fluid would probably last 200% longer, or more.

if left open for even a short while, it might be just enough to ruin it (especially if the old fluid was bad enough)

88jetta350 · « **Reply #3 on:** March 18, 2009, 11:47:24 pm »

The MC was taken directly off of a car with working brakes.

Maybe the Proportioning valve?

Rabbit TD · « **Reply #4 on:** March 19, 2009, 12:06:19 am »

Quote from: "88jetta350"

The MC was taken directly off of a car with working brakes.

Maybe the Proportioning valve?

I think the proportioning valve just gives different pessures front and back to keep the ass end from locking,up. The discs need more pressure and you don't want that much on the back but I also considered that. But I am betting on the M/S too and possibly wrong bleeding procedure. Did you actualy bleed the master cylinder first with no lines hooked to it other then bleeder lines going back in the reservoir pumping till the fluid is bubble free. If you don't get it cleared of air first the air pocket just goes back and forth not building pressure in the lines. Replacement M/S's usualy come with these hoses with fittings.

jtanguay · « **Reply #5 on:** March 19, 2009, 07:23:03 am »

the proportioning valve only affects the two rear wheel brakes whether they are drum or disc. if you didn't have a proportioning valve, the rear wheels would tend to lock up under serious braking and the ass end would break loose and you would lose control.

that being said, you need to position the arm on the proportioning valve to properly bleed the system.

CODE4LS1 · « **Reply #6 on:** March 19, 2009, 08:53:19 am »

I had this problem when I restored my Caddy. It took my and a buddy about 2 hours on and off to finally get the brakes bled. We had the same symptoms as you did, we just kept bleeding them they way they were supposed to and finally had pressure to the RF and LR corners.

Don't know why it took so long, but it finally worked and all is well.

FWIW, All brake parts were replaced with new except for hard lines, so all the new parts were installed dry.

Hope this helps.

Rabbit TD · « **Reply #7 on:** March 19, 2009, 08:12:12 pm »

Since you don't have any pressure to the front either it sure points to the mastercylinder. If you are positive the cylinder is bled, which I doubt it is, then folow that line for the affected wheels to the next junction for the front and seeif it will squirt there and follow the trail to the front wheel. When you find where it is not getting pressure and fix that the back should be working by then too. After you can get fluid out of all four bleeders I would pump all the old fluid out till it clears up on each line. Just don't use DOT 5 fluid, just Dot 4.

jtanguay · « **Reply #8 on:** March 20, 2009, 05:47:20 am »

yea DOT 5 is a silicon based fluid, and apparently it will wreck the whole system. i wish we could use it though, because it lasts much longer, and isn't corrosive so brake parts last much much longer.

clbanman · « **Reply #9 on:** March 20, 2009, 09:24:32 am »

While this info comes from a H***a site, it has one of the better explanations of brake fluid ratings I have found: http://hondatuning.automotive.com/81116/htup-0807-honda-brake-bleeding-tutorial-guide-and-tips-with-pictures/dot-3-dot-4-dot-5-dot-51.html One other note is that one thing mentioned in this link as well as many others is that DOT 5 does not absorb moisture. This is true, but you can still get moisture into the system and the water can still cause rust, it will just sit in localized spots.

jtanguay · « **Reply #10 on:** March 20, 2009, 10:43:43 am »

Quote from: "clbanman"

While this info comes from a H***a site, it has one of the better explanations of brake fluid ratings I have found: http://hondatuning.automotive.com/81116/htup-0807-honda-brake-bleeding-tutorial-guide-and-tips-with-pictures/dot-3-dot-4-dot-5-dot-51.html One other note is that one thing mentioned in this link as well as many others is that DOT 5 does not absorb moisture. This is true, but you can still get moisture into the system and the water can still cause rust, it will just sit in localized spots.

true... the moisture mainly comes from the vented reservoir though, correct? so maybe putting a silica vent system would be superior? princess auto sells air drying stuff for air tools that could probably be modified some. might be a little overkill though...

Garrett · « **Reply #11 on:** March 20, 2009, 07:53:15 pm »

I'm having the same issue as the OP... I just replaced front and rear brakes; as well as one of the wheel cylinders. All wheels bleed perfect aside from the left rear.

Any insight?

Rabbit TD · « **Reply #12 on:** March 21, 2009, 05:48:45 pm »

Quote from: "Garrett"

I'm having the same issue as the OP... I just replaced front and rear brakes; as well as one of the wheel cylinders. All wheels bleed perfect aside from the left rear.

Any insight?

Did you take the bleeder screw out and see if it' not rusted shut inside, if you can't blow through it just get a small drill bit and twist it in and out and clear it out till it's open. They do fill up with the same junk you see in the dirty fluid. If that isn't it then crack the line at the wheel cyl. and see if it squirts, if it doesn't, go up to the rubber hose and check that, it might be collapsed inside. Probably just the bleeder screw though.

jtanguay · « **Reply #13 on:** March 21, 2009, 07:38:28 pm »

Quote from: "libbybapa"

It could be a blockage in the line from the master cylinder that leads to those two wheels. I had that on a van once and it took me a little while to figure out.

Andrew

can you still bleed the brakes when this happens? did you have to replace the rubber lines or the steel ones, or both?

Rabbit TD · « **Reply #14 on:** March 22, 2009, 07:36:34 pm »

Quote from: "Rabbit TD"

Quote from: "Garrett"
I'm having the same issue as the OP... I just replaced front and rear brakes; as well as one of the wheel cylinders. All wheels bleed perfect aside from the left rear.

Any insight?

Did you take the bleeder screw out and see if it' not rusted shut inside, if you can't blow through it just get a small drill bit and twist it in and out and clear it out till it's open. They do fill up with the same junk you see in the dirty fluid. If that isn't it then crack the line at the wheel cyl. and see if it squirts, if it doesn't, go up to the rubber hose and check that, it might be collapsed inside. Probably just the bleeder screw though.

Since you do have pessure to the right rear wheel the master cyl must be working OK. The problem almost has to be between the left rear bleeder screw and the t-fitting that separates the 2 rear wheels. Make sure those holes in the bleeder screw are not blocked first and it's the easiest thing to fix also.