What's Wrong With My Brakes?

[Caerbannog]

So it started when I got a leak in my left rear wheel cylinder last week. The cold weather and perhaps 6 years service probably had something to do with it, but one morning the brake pedal went to the floor. A quick inspection found the wet wheel, that was verified by pulling the drum -- it was the cylinder and not the brakeline.

I got some brake fluid, temporarily crimped the line in that corner, and bled the master cylinder and I had a high firm pedal.(We'll skip the part about how I drove around that way for a while! ) Deciding to be thorough, I got both rear cylinders and some brakeline, intending to replace both sides.

So I replaced both cylinders, all the lines between the proportioning(?) valve and the wheels. (Removing the flexlines took a lot more effort than should be legal! ) I freed up the sticky parking brake lever and even replaced a brake cable.

But at the end of everything(bleeding air, adjusting cables, etc.) I have a low pedal, scary low. It does pump up high and firm, but the first push is low.

First question: The new wheel cylinder's pistons have a tab sticking out. Should the tab be inboard or outboard or doesn't matter? My Bentley makes no mention and the new cylinders have a lot more prominent tab than the old ones.

Second question: The pumping up firm suggests the system is bled properly, but the shoes are out of adjustment. Is there a trick to encourage the adjusting wedge to take up the slack?

Third: Could my master cylinder be going south? It's ironic it happening at the same time as the wheel cylinder, but possible.

Thanks.

Edit: I found that both of the old cylinders each had one stuck piston! So maybe I was driving around without working rear brakes all along....

[82vdub]

Is the adjusting wedge installed backwards where the little tab is pressing against the brake mechanism? I've has that very issue and the rear brakes never adjusted as they should have.

[Caerbannog]

Is the adjusting wedge installed backwards where the little tab is pressing against the brake mechanism? I've has that very issue and the rear brakes never adjusted as they should have.

Hmm, I'll have to take look. As I recall, I didn't disturb the orientation of the parts, but it's possible. Are you talking about the tab on the piston?

Thanks for your input. I really would like to take care of this low pedal situation, it's a little spooky.

[bscutt]

I think he was referring to the small nub that is on the back (I think) if the adjusting wedge. If facing the wrong way it will not work properly. PONe thing I did that someone recommended (Quantum man I think) was to remove the rear tire and locate the wedge through one of the lug nut holes. Then push it down which forces the shoes all the way out. Then rap on the drum with a rubber hammer to let things settle. Same for the other side. This got me brand new rear brakes seated properly against the new drums (my drums were too worn to get good contact even with new shoes) and the pedal position came up where it should be. I don't think the self-adjusting wedge design is great so this helped it along and got my brakes working very well..

[82vdub]

I think he was referring to the small nub that is on the back (I think) if the adjusting wedge. If facing the wrong way it will not work properly. PONe thing I did that someone recommended (Quantum man I think) was to remove the rear tire and locate the wedge through one of the lug nut holes. Then push it down which forces the shoes all the way out. Then rap on the drum with a rubber hammer to let things settle.

Yes and I agree to manually move the wedge. I believe the rear brakes are supposed to be adjusted when you use the hand brake initially, but if the wedge doesn't press against anything when you service the brakes, I don't think the wedge will drop at all when the brakes are pressed. In this case, you try to push the wedge so that it drops to engage with the rear shoes.

[TylerDurden]

Handbrake off, to get the wedge to drop when the pedal is pressed.

If the wedge doesn't drop just from the spring tension, there is a problem.



brake service pictorial:
http://faculty.ccp.edu/faculty/dreed/Ca ... /reardrum/

[air-cooled or diesel]

maybe shot shoes; i had this prob a long time ago when i beat on a lemon. though when you had it apart you would have seen the thickness of shoe/pad. doing so much work i would have replaced most or all as the parts list indicates. having a pic or example to work off of helps alot as it can come apart quickly and is a bit of a puzzle to get back together.
a couple of grease points too

[bscutt]

The other thing I did with my brakes was a full flush of the brake fluid. I ended up buying the Motive Products tool. After the flush those brakes were nice and solid. All the air and nasty old fluid came out and got replaced with new. The tool with the VW adapter was under $60 and local service facilities here charge at least $120 and many are $160. With all the VWs in the family and other cars with the same master cylinder cap it was worth it.

[air-cooled or diesel]

i not sure of tool; if its what i think it is; easily replaceable with a basting 'tool'. like you use for birds, funny its that day too , suck fluid all out of m/c reservoir, takes a few extra times to bleed, can be done for a couple of bucks and a can of dot3/4 brake fluid, and voila you have fresh fluid!

[bscutt]

true but pumping the master cylinder while you open the bleeder valves can be pretty challenging. I get no help. So I buy tools.

[air-cooled or diesel]

help with a feel for the work helps in every way, takes 2 people for almost every part/avenue of work at one time or another, makes the work alot simpler. &quicker.

[bscutt]

yes it was easier when my boys were still home. Getting help is harder to come by now.

[TylerDurden]

Brakes are easy enough solo...

Vinyl tube & glass jar (or store-bought "one man bleeder")
broomstick

Loosen the bleeder, pump the pedal x times; on last pump, hold the pedal down with broomstick onto driver's seat. Close bleeder.


It's helpful to put heavy grease or antiseize on the bleeder threads, they are loosey-goosey on remanned parts and tend to suck in air on the upstroke. The bleeders will be easier next year too.

[bscutt]

well I have probably tried all of those in 45 years of working on cars including a mityvac, a homemade vacuum pump arrangement (sucked air around the bleeder threads too!), tubing into a jar of fluid, etc. The Motive thing has worked better than any of those as long as you have a decent adapter for the master cylinder. The VW threaded caps are perfect. For older GM's the flat plate adapter is fair at best. For the old Corolla I made one in our machine shop at work with an o-ring seal that worked perfectly; Motive has no decent one of these. The only problem is that the adapters tend to be pricey like $30-$60 so if you have lots of brands of cars in the stable it starts getting expensive and you have to be committed to those 20000 mile flushes to get your money's worth out of it. But all I can say is my brakes never worked so well on the older cars and I never got the perfect firm pedal from manual bleeding. Close yes but there is a clear difference with a pressure bleeder. Anyway I'm not their salesman, just sharing my experiences with this. There are lots of cheap ways of getting "good enough" and I think I've used them all over the years.

So for the purposes of this thread I'd say making sure the rear shoes are properly adjusted, front pads and rotors good, and all the air is out of all of the lines should get the pedal where it should be and the car stopping on a dime. My Rabbit stops in less distance than any other vehicles I own including the 4 wheel disk brake Jetta. We will see how that one does after I get my Hawk HPS pads installed next year.

[Caerbannog]

Thanks for all your replies. I ended up pulling off the drum just far enough to get a punch on the top of the wedge and tapping it down. I had previously used a die grinder on the inboard edge of the drum to take off the wear step so the shoes would slide on smoothly.

Also X2 on using a pressure bleeder -- I have a Schraeder valve from an old inner tube attached to an old BMW master cylinder cap, the kind that had a fluid level switch(An ATE IIRC). That and a few pumps from a bicycle pump works great. Especially since I usually work solo.

I have a rock solid, high pedal, that I tested through the Nor'easter a couple of days ago.