Brake ?

[C man]

Is it me or Does the Park Ave/ H body cars have bad rear brakes. I read that they don't have the best brakes before. I was nearly in a potential 5 car crash on the interstate today. I didn't even slam on the brakes and my rear brakes locked up as usual. When this happens it the rear of the car always tend to tail spin to the right. So the back of my car almost went into the next lane.

I'm really thinking I should get an ABS unit from the junkyard. but I think it only works when you slam on the brakes (all the way to the floor). I don't even have to slam on brakes, just hit the brakes hard and mine will lock up or it seems .

Is there a remedy for this. Could their be other factors such as lack of weight in the rear of the car that causes this, or because drum brakes react slower than disc brakes and this causes this causes the back to still be moving at a faster speed than the front brakes and then it loses traction.

I have duralast brake shoes on the rear brakes. If I switch to another brand will this help the problem. Well, It even had that problem before I switched brake shoes. This is a problem at lower speeds such as 40mph if you step on the brakes hard.

I'm afraid that one day I'll avoid one accident and cause another with the rear of my car. If its just something I'll have to worry about can anyone give good panic braking tips without ABS.

[Mag00]

We have the same car, and I can say that I dont have that problem.
Ive only rarely had to slam/press hard on my brakes, and they don't lock up
unless I havent had to do it like you have, although I have had it use the ABS before... worked fine.

but I will say, that I have had to replace brake components more times than anything else in the car.
mostly the Master Cylinder has problems for me, but I digress.

[HotZ28]

Originally Posted by Cman

Is there a remedy for this. Could their be other factors such as lack of weight in the rear of the car that causes this, or because drum brakes react slower than disc brakes and this causes this causes the back to still be moving at a faster speed than the front brakes and then it loses traction.

This certainly is not normal! In fact, the front disc/ rear drum system should actuate the rear brakes before the front! That in effect prevents the “nose dive” effect of the front-end. Several things could be causing what you described.


1) Rear shoe adjustment to tight.
2) Rear drums turned with a rough surface.
3) Malfunction, or blockage of the portioning valve.
4) Mismatched shoe/drum configuration.
5) Front pads & rotors that are not up to the task!

Remember, the front brakes should provide about 80% of the braking and the rear only about 20%. In addition, if your ABS is functioning properly, it should sense rear wheel lock-up, then pulsate the brakes, therefore preventing total lock-up! I would start with readjusting the rear shoes. Leave room for heat expansion when the drums & shoes get hot! You should have a good 1/8 in clearance between the shoe and drum (all the way around) when cold. Next, check the front pads & rotors. Do not, and I repeat, DO NOT use Duralast rotors & pads on the front of these cars! They simply will not handle the demand of weight & speed.

[HotZ28]

Originally Posted by Mag00

We have the same car, and I can say that I dont have that problem.
Ive only rarely had to slam/press hard on my brakes, and they don't lock up
unless I havent had to do it like you have, although I have had it use the ABS before... worked fine.

but I will say, that I have had to replace brake components more times than anything else in the car.
mostly the Master Cylinder has problems for me, but I digress.

Master cylinder failures are usually the result of compressing the caliper without opening the bleed screw. This maneuver will push contaminated fluid back into the MC. In addition to opening the bleed screw while compressing the piston, I use a vacuum bleeder to bleed all of the old fluid out of the system when changing brakes, or MC. Fluid is cheap; compared to replacing parts damaged by contamination! BTW, the best tool (at a reasonable price) for vacuum bleeding is one like the shown in the pic below. In addition, this tool can be used for testing vacuum leaks, A/C blend door diaphragm function, A/C vacuum reservoir leaks, MAP sensor function, SC nose/snout oil evacuation, power steering fluid evacuation, and engine vacuum testing! If interested in one, PM me for the best price. (My company is an authorized distributor for the whole line of Mityvac products)


Do not interpret this as an advertisement for this product, I already have a whole network of customers, I am simply offering advice along with a good preventative maintenance & troubleshooting tool to fellow AF members only, PM me for details!

[C man]

This certainly is not normal! In fact, the front disc/ rear drum system should actuate the rear brakes before the front! That in effect prevents the “nose dive” effect of the front-end. Several things could be causing what you described

.

You're right I forgot about that, been a while since I took my brakes class.

Next, check the front pads & rotors. Do not, and I repeat, DO NOT use Duralast rotors & pads on the front of these cars! They simply will not handle the demand of weight & speed.

http://www.automotiveforums.com/vbul...d.php?t=900995

I learned my lesson on that already. Bendix pads and Wagner quiet stop brakes.

1) Rear shoe adjustment to tight.
2) Rear drums turned with a rough surface.
3) Malfunction, or blockage of the portioning valve.
4) Mismatched shoe/drum configuration.
5) Front pads & rotors that are not up to the task!

I'm thinking 1,3&4 as possible suspects. Replaced The rear drums when I did the shoes. But the shoes are duralast. Also with the portioning valve, isn't it setup on the park avenue as a combination valve (proportion/metering) valve with the master cylinder?
If this is the case does that means that I need to change the master cylinder.
I also need to change out the ABS pump it doesn't work. Used a Tech 2 at school awhile ago and there was a short in the LF solenoid circuit.

[HotZ28]

Originally Posted by Cman

Also with the portioning valve, isn't it setup on the park avenue as a combination valve (proportion/metering) valve with the master cylinder?
If this is the case does that means that I need to change the master cylinder.
I also need to change out the ABS pump it doesn't work. Used a Tech 2 at school awhile ago and there was a short in the LF solenoid circuit.

The portioning valve is not part of the MC. You may be thinking about the Electronic Brake Control Module (ECBM) or modulator. The ECBM monitors the speed of each wheel and the electrical status of the hydraulic modulator. The function of the ECBM is to detect wheel locking and control the brake system while in the antilock mode and to monitor the system for proper electrical operation. In addition, the ECBM controls the display of ABS faults while in the diagnostic mode.

There is a separate hydraulic line from the modulator to each rear wheel, as well as an individual rear brake circuit proportioning valves. The ABS system can decrease or hold hyd pressure to the rear brakes; however, it cannot increase hyd pressure above the amount transmitted by the MC. Under normal braking conditions, the ABS functions exactly like a conventional vacuum boost brake system. If you have a DTC in your ABS system, it might be better to pull the fuse to disable the system, until the problem is corrected. The ECBM & hyd modulator are not normal serviceable parts, they must be replaced as a unit!

[C man]

Problem solved.

I went to the junkyard today and got a good ABS pump for $52. I Installed it which was fairly easy, but very messy. Bleed the system with a brake bleeder like the one in Hotz28 post (looks exactly like it). I had already had one.

Took it for a test drive and no tail spin or squealing tires. Couldn't be happier.

This was one of those issues that was way easier to do than I anticipated. Could have did this a long time ago. These cars need ABS.