I recently put new brake shoes on the rear of my 95 3.0L shorty. The rear brakes now make a loud clunk when applied. I had the same problem when I last did the rear brakes 2-1/2 years ago, but the problem went away after a week or so. This time around it seems to be getting progressively worse.

I bought a set of "Premium" shoes and a spring kit from Canadian Tire, but due to a family illness, I did not change the brakes until a couple months later. Unfortunately, I did not find the spring kit until the brakes were done , so I re-used the old hardware. The drums were not scored or pitted, so they want back on as is. I made sure the self-adjusters were moving freely, and I released the parking brake self-tensioner. The axle seals weep a bit, but not enough to get any oil on the linings. I washed everything down with brake cleaner before I touched anything, too. The old shoes were worn remarkably evenly, so I don't suspect any wheel cylinder problems.

I have been doing brake jobs for myself and family for almost 20 years (I suddenly feel old), and I have never had a problem like this one before. I typically also flush the brake fluid when I do a brake job, but this one was outside in December, so I skipped it this time.

At first the clunk was relatively minor, and only happened the first time braking forward after backing up (back up & brake - fine; shift to drive, move forward and brake ***clunk***; move forward agin and brake - fine). It happened the same after the last brake job, but it went away. This time, according to my wife (her daily driver), it now happens almost every time, and it has gotten so severe it is pulling the rear of the van down (locking?)

The van has RABS, but the light is not coming on.

Anybody have any suggestions?

Cheers,
Eric

 

I had the same problem with my F 100. I had reversed the small and large shoes. Maybe?
007BRONCO

 

I think the large shoe goes to the rear. When you step on the brake, the friction on the front would wedge the rear shoe in really tight. That's why it is larger and made either of tougher material or thicker.

 

I'll pull the drums off and check it tomorrow morning - my wife has the an at work right now & I have to go to work before she gets home. Not looking forward to it, though, because the temperature here lately has been cold as a witch's... refrigerator.

I always make a point of replacing the large with the large & the small with the small, but maybe they were already reversed before I got the van.

Can anyone confirm for sure that the large shoe goes to the rear?

Thanks for your help.

Cheers,
Eric

PS: I'll put the new spring kit in, too.

 

Hi Eric:

Here's what I got from the Ford CD. This is how they explain it:

The primary (front) and secondary (rear) brake shoes are the same size and shape, but the linings are different. Because the secondary shoe does more work, its lining is thicker and covers more surface than the lining of the primary shoe.

In addition, the primary and secondary linings may be made of different materials and are selected to match with the front brake pads. For all these reasons, you must be careful to put the specified shoe lining on the vehicle. You must also be careful not to switch the shoes front to back.

"Self-Energizing" Action

First of all, the brake linings don't merely push up against the drum and hold as they do when the vehicle is standing still. Friction between the moving drum and the brake linings drag the brakes shoes in the direction of the rotation. As a result, several important things happen.

1. When the brakes are applied, the drag forces cause the primary shoe to rotate.

2. The same thing happens to the secondary shoe. But in this case, the secondary shoe quickly comes to a stop against the anchor pin.

3. When the secondary shoe comes to a stop against the anchor pin, neither shoe can rotate further even though the drag forces are still in effect.

4. These drag forces create a force which wants to pivot the brake shoe outward, creating increased outward pressure against the drum. We call this a "wedging" or "self-energizing" action. As the shoes are forced outward, the linings wedge themselves tighter to the drum than would occur if the components weren't free to move.

5. In this process, the secondary shoe has more force applied to it than the primary shoe. Both shoes experience force from the wheel cylinder pistons and both experience drag forces due to the rotation of the drum. But the secondary shoe also gets additional force from the movement of the primary shoe which is transmitted through the self-adjusting link. For this reason, the secondary shoe does more of the braking work than the primary shoe. To take advantage of this, the secondary lining has a larger surface area. It is also thicker because more wear will occur.

Hope that helps.

Regards

 

WOW, good explanation!
007BRONCO

 

Thanks, copper! I knew about the self-energizing stuff - I didn't sleep through that class in mech eng 330!

Hopefully I can check them tomorrow evening (Sunday was too cold & I slept in).

I did find that my wife had exaggerated the situation some, though.

Cheers,
Eric

 

Hi Eric:

Didn't mean to sound like a "know-it-all." All the stuff I had in my post is strictly "cut-and-paste" from the Ford CD I have. I claim neither the credit nor the responsibility for any screw-ups

Regards

 

Well I finally got past the bitter cold weather (and my own laziness) & had another go at the brakes. Actually, they locked up when I ran into town on Tuesday & just would not release. Funny how something like that can motivate one into action...

Anyway, the larger shoes are to the rear on both sides of the van. It looks like the self-adjusters were over-tightening the shoes to the drums. I installed the new spring kit and double-checked that all parts were oriented as per the photos in the Haynes manual, and everything was moving freely.

I took the van for a road test and... it still does it. Not nearly as bad, and the brakes don't lock, but they do clunk the first forward stop after a reverse stop.

I asked my wife to listen to see if the clunking gets louder. If it does, I'm considering turning the self-adjusters around so the ratchet mechanism is disabled. Of course then I would have to manually adjust the shoes every couple of months.

Anybody have any other suggestions?

Cheers,
Eric

 

Are you sure that the e-brake tensioner is not causing the problem? have you tried to disconnect it completely to check? I had a huge problem with the tensioner acting up and giving me days of grief. It should have been fine, but just wasn't.

 

Remote possibility #1: The wheel cylinder is loose on its mounting clip allowing it to shift slightly with forward/reverse maneuvers?

Remote possibility #2: If I recall, one of those retainer springs goes behind the shoes rather than across the outside face. If it were installed incorrectly, it may cause one (or both) shoe(s) to bow slightly outward and then clunk back against the backing plate when the brakes are applied.

I get into more trouble like this with those repair manual illustrations. I finally had to resort to making my own drawings as I go along (and doing only one side at time). Its probably something simple, just overlooked.

 

Hi Eric:

I vote with Brokensocket on the parking brake overtension. Happened to me not too long ago. The horizontal bar right below the wheel cylinder is used to actuate the parking brake, and it would not allow one of the shoes to come into full contact with the anchor pin on top when the parking brake is too tight.

The clunk you heard is the rear brake shoe hitting the top anchor pin when you step on the brake. Disengage the parking brake at the T handle where the front cable meets the two rear cables by removing the front cable from the T and see if this still happens.

The clunk happens when you back up also, when the front shoe hits the anchor pin, but it's not as prominent as when you go forward.

Good luck

 

Thanks for the suggestions, people.

Replacing the old spring kit helped a lot, but the clunk is still there - just a lot less noticeable. So far it does not seem to be getting worse.

I don't believe the wheel cylinders are loose. I live in the rust belt and very few things start to loosen up on a 10 year old vehicle around here. Also, I always do the brakes one side at a time & I do not recall ever seeing a spring behind a shoe, expect for the ones on the parking brake cable.

But I am starting to suspect the parking brake cable. I released the tension when I did the brakes the first time, but not when I replaced the spring kit last week (I have to remove my aftermarket console to get at the release hole). This will be next on my list (I'll check the wheel cylinders, too).

But first I need to get my home computer up & running again and unstick the f(^%*^g sliding door AGAIN

I just love old vehicles They keep me from getting bored.

Cheers,
Eric

 

Hi Eric:

Getting at the hole to relieve tension on the parking brake is a chore. I've gone through it countless times, I'm sick of it. If you want to test the theory about the parking brake cable being the problem, why not go under the car, yank on the front cable and clamp a visegrip on it to prevent it from being retracted. That way, you can at least say if it is or is not the problem first.

Regards

 

Problem solved!!!

Turns out it was the parking brake system. I released the parking brake adjuster at the handle & then drove the levers back with a long punch. Each one pulled about an extra 1/2" of cable back into the brake assembly. Once the levers were retracted, all the shoes rested against the anchor pins at the top of the backing plate - there was about 1/16" to 1/8" gap before.

So now there is no more clunking, no more grabbing, just great stopping!

We do not regularly use the parking brake in the van, only occasionally when parking on a hill or with the trailer connected. I was always amazed that the cables still moved freely. I guess they weren't quite free after all.

I guess I will have to make this a practice every time I do a brake job in the future.

Thanks for all your help, folks.

Cheers,
Eric