# Rear brake weird problem bleeding



## MYK (Nov 24, 1999)

So I was having an issue where my brake pedal would suddenly lose pressure while driving so I decided to take a look. I just got the car back on the road after charging up the ac and then this problem started. I decided to bleed the brakes and get some fresh fluid in it since the stuff in the car was old and dirty as hell. Had some issued trying to vacuum bleed the brakes. Made a pressure bleeder but it didnt work very well either. I wasnt getting much flow. So I just did it the old fashioned way. Ran some tubing into a jar, submerged the end so air wouldnt flow back and starting bleeding. Right rear went fine, got clean fluid coming out, ok. Then when I went to left rear I cracked open the bleeder and nothing came out, hit the pedal and its firm like the bleeder isnt open. Pulled the bleeder valve all teh way out and its pretty much dry. But it is open, I blew air through it and its not rusted shut. Tried hitting the brake pedal with the bleeder valve out and nothing, pedal stiff firm, nothing coming out of the caliper. Thought the caliper was rusted shut so I disconnect the line going to the caliper and there is fluid in the caliper. Line open not attached to the caliper and it still wont flow. I figure its blocked somewhere so I look to disconnect one of the rear lines where it meets a hardline to see if I get any flow. Most of the flare nuts are already kinda buggered from whoever installed the ss lines on the car originally so I dont mess with it. I tried as a last ditch effort to start the car, hit the pedal and it goes soft, pumped it a couple times and fluid came out of the line, then all of a sudden it firmed up again like the valve was closed. So I figure the line isnt blocked anywhere, I traced it all the way to the front, no rust, not kinked anywhere. Do I have air or a blockage maybe in the pump? I am totally stumped on this and cant find anything while searching that is similar to my problem. Can I just disconnect that line and let it gravity bleed through the pump and maybe blow some air through the line to make sure its open all the way to the back?


----------



## germancarnut51 (Mar 23, 2008)

The maser cylinder is probably worn out, but it sounds like you also have a problem with some gunk in the brake lines.

Removing the hose from the caliper and stomping on the brake pedal is an effective way to clear a blockage. You should also visually check the brake lines all the way from the master cylinder to the calipers to check for damaged/crushed brake lines.

You can't tell 100% for sure if the master cylinder is good without getting rid of all of the air in the system first.

When you bled the rear brakes, did you have the rear of the car lifted? If so, how did you lift the car? If you let the rear wheels droop, then the proportioning valve will retard fluid flow to the rear brakes, and you will not be able to bleed the rear brakes effectively. When you're going to be bleeding the rear brakes, and you're going to put the car on jackstands, place the rear stands under the axle beam so the wheels stay where they are located when the car is on the ground. Then, you will be able to bleed the rear brakes.

If the brake pedal never comes up high and firm, and the rear parking brake is adjusted properly and is working, then the master cylinder is defective. Buy a Meyle Brand replacement master cylinder for about $45. The Meyle master cylinder is a very well made alloy bodied part (as opposed to the OE part which is cast iron and rusts like crazy), and much less than a replacement will cost you from a VW Dealer.


----------



## MYK (Nov 24, 1999)

thanks man, your advice on the ac system helped me get it charged up great. 

my issue with the brakes is weird because my car has no rear proportioning valve, its all regulated by the abs module and pump assembly because the lines come straight off the abs pump and to the rear calipers. I checked the line all the way to the front and there are no kinks or rust on the outside anyway but I have some sort of blockage because I did pull the line of the caliper and press the pedal and got nothing out of the line. Its like the bleeder is closed. The pedal is firm and high like normal. I think either the line has gunk in it or the pump has air caught in it that is holding the valves shut or something. at one point I fired the car up and it did bleed some fluid from the line and then it firmed up again and no more came out. This is with the line completely disconnected from the caliper mind you.

Do you know if the abs pump has valves that open and close to go to the rear calipers? Os does it have a bypass through the pump? I have all four wheels off with the car on jack stands and the rear stands are under the beam so it's not drooping. It doesnt droop far anyway because of the coilovers. But like I said no rear proportioning valve on the rear beam. Is there something integral to the pump that senses the angle of the beam or the car?


----------



## germancarnut51 (Mar 23, 2008)

I didn't catch that your car has ABS.

Sorry, while the problem could be a bad master cylinder, or air trapped in the line between the master cylinder or in the ABS Brain, your problem is probably the ABS Pump/Brain. You can try taking the car to the VW Dealer to see if they can purge the ABS Pump for you, and if that's helps. But, you will probably end up replacing it (big bucks).

That's the price of having ABS.


----------



## MYK (Nov 24, 1999)

I've got a few friends with vag-com and one that works at the dealer that has replaced a pump/module before. I was going to pull it this weekend, make sure that brake line is patent and go from there. I've found a couple places that rebuild the modules for a great price. Whats funny is I dont get an ABS light at all, but I do think there's an issue with the module keeping a valve shut or air trapped in the valve or something.


----------



## MYK (Nov 24, 1999)

update: i pulled the lines off the pump and the one line to left rear didnt leak any fluid. All the other lines did. I think I have a blockage in the pump block somewhere. Anyone ever take one of these things apart. I should probably jump find a good used one.


----------



## germancarnut51 (Mar 23, 2008)

MYK said:


> update: i pulled the lines off the pump and the one line to left rear didnt leak any fluid. All the other lines did. I think I have a blockage in the pump block somewhere. Anyone ever take one of these things apart. I should probably jump find a good used one.


You could have an air bubble. And no, you can't gravity bleed the ABS pump. How about trying to get your friend with the vag.com to come over and try to use it to turn on the ABS pump, and bleed the ABS pump and lines? 

You might get lucky.


----------



## MYK (Nov 24, 1999)

update: Friend of mine had an extra pump in his garage and let me try it. It flowed through the block fine when pushing fluid through it. Put it in this afternoon after it stopped raining, sucked fluid through the block, connected all my lines and bled all four calipers with no problems. Still have some air in there I think as the pedal is slightly spongy but I'll bleed them again tomorrow and get it over to another friends house to purge the pump of air with vag com and re-bleed it again. So I'll get it on the ground probably tomorrow and see how it does. But my problem was definately a clogged up abs pump manifold. I read on some other places and a porsche forum about people having trouble with clogged pump manifolds and sending them off to a place that rebuilds them. I think they shoot pressurized brake fluid and other stuff through there to clean out the corrosion or crud or whatever. Anyway did a full flush of fluid, all the stuff that came out looked about as dark as beer, very brown and had a lot of crud coming out at first. PO definately neglected the brake fluid. And I neglected to check it when I bought it.


----------

