Hi all.

I've done the braking system on my 84 Trans Am. When I got the car the brakes had no assitance at all, turns out the booster had a huge leak so I replaced that and a new master cylinder while I was at it. Front calipers were recent before I got the car but I had a new set of front pads so fitted them. Rear calipers were nasty so I fit 2 new ones. Adjusted them on the bench so the handbrake works great etc.

Bench bled the master cylinder before I fitted it then bled the brakes as you would. And yet the brake pedal travels a hell of a lot before biting. Pretty much to the floor. What am I missing here ?? Is there anything on the actual pedal I may have disturbed when I removed it to replace the booster.

 

I was in the same spot as you. Let's start with a couple of questions...

When you bench bled the master, how much travel did you have left on the cylinder when you stopped pumping? What method did you use?

When you say the parking brake works well. It may appear to by hand. How much of a gap is there between the arm and the stop when it first seats?

On the rears, are the pads aligned with a tab in the piston face?

I am asking questions about the rears because they are notoriously blamed for a lot of issues because a lot of people just don't get them set up correctly or don't use the parking brake in the autos frequently enough to keep them in proper adjustment.

What method did you use to bleed the Front/Rear Brakes? Is you "Brake" light on in the dash?

What about the brass seals around the hose connections in the front? How is the quality of the old hoses? Flex in any of the 5 hoses could cause excessive pedal travel as well.


Watch out for firewall flex as well. I was unhappy with my pedal travel, but there was a based of distance on the throw that was caused by travel in the master before engagement plus firewall flex. I was trying to get rid of this by continually bleeding and adjusting the rears. In the end, there is just a certain amount these 30 year old cars will have that will never make them feel like a new car.

 

I bled the master cylinder on the bench with the plastic hoses. the travel was just in until it stopped and I kept working it until there were no bubbles and fluid was continuously flowing.

I couldn't get the E brake to work at all at first so I had to take them back off and found a great video for setting these calipers up. So the lever is just off the stop when it locks onto the disc. holds the car on my angled driveway no problem now.

Everything is new basically even the brake lines themselves. bleeding the system, the fluid comes out nicely, it's got new hoses at all 3 corners plus the one above the diff.

Brake light isn't on. it was the first time I done the brakes as the pedal went right to the floor but it's off now as the pedal is better.

I'm comparing this 84 to the 87 Trans Am I had. I done new brakes on that too. calipers and pads up front and new drums, shoes and cylinders at the back. and the pedal in that car felt really good and firm !

 

This is a good method to get air out, but incomplete. You need to put plugs in the outflow ports and then push on the cylinder. Measure the movement traveled before you come to a dead stop against pressure. Should be less than an 1/8 of an inch. I think mine was at about 3/16. Then I left the plugs in as I installed it. Then applied the pedal (no booster assist) to make sure all was well before I connected my lines.

Very common, but again the devil is in the details. What does "just off the stop" mean? 1/4" of gap or 5/16"? It needs, again, to be less than 1/8". Remember, the brake handle has a long throw. and the cables can pull pretty far. Those pads need to be on the verge of grinding on the rotor when in the released state. Don't go by a guess or eyesight if this is the first go around. Measure the gaps.

I did the same thing as well, but put braided stainless lines back on. Air can get to places fluid can't sometimes. Could be sucking air in. So, try this. Actuate the Parking Brake, pump your brakes.... is it firmer? That will be a big indication the issue is in the rear. Regardless, pull the parking brake full travel (Don't lock it in, just hold it up), mash the brake pedal as hard as you can then release everything. Do this about 25 times, then leave the parking brake set. Bleed the rears again. If you see air, you have a situation where it is sucking air back into the system. I had a front brake hose that was hitting the cast caliper body and would't fully seal on the brass compression washers. It was letting air back in. A little Dremel magic and that issue went away.


This is to be expected. The cylinder in the Proportioning valve shift when it didn't see pressure build. Once it can get enough fluid in there it re-centers. It's very difficult to get a good bleed (for obvious reasons) if the valve is shifted.

The 87 had drums and the 84 had disc correct? Both should have a good pedal, no doubt, but setting them up is completely different. You said replacing calipers on the rear, not cylinders. I understand completely what you are saying. My thread where I beat my head against the wall goes through a lot of what you are describing. It is located here. I had an 86 T/A 4 Disc Car, an 89TTA with the 1LE 4Disc, a 95 Z 4 Disc, and a host of others with drums that my brother or I owned (89RS, 87T/A, 85 Iroc, 89Iroc, 87Z... and maybe a few I am forgetting). They all had a good pedal, but admittedly it had been since 2005 since I had been in any of them. How recent is your memory? Even now with a good pedal, the pedal travel is still excessive (IMO) compared to my new (er) cars.

In the end, it took a fellow board member to stop by and push on them and confirm, the pedal travel isn't getting better than where I had it. You could see the Booster/Master assembly flex. He is actually re-enforcing the firewall area to address this since he does road racing events with his. My expectations just exceeded what I had spent. I encourage you to read through my posts, because I feel your pain. However, once I got it out on the road, the brakes perform great, firm hard stop on the pedal, car brakes very straight, and can lock them up tight if I get aggressive. I still wish the pedal travel was less. There are just some things engineered into he car that you have not changed. the fire wall flexes, there is a bit of play in the pedal connection, there is a small dead spot in the master before it starts pushing fluid, the bore size of the master in relation to the bore size of the calipers how much pressure the valve allows the rears to see... what I am saying is, even with all 100% correct the pedal will have travel and more than our new cars do.

 

Thanks for all the info. yes I can pump the pedal with the engine off and the pedal gets really firm. then releases when running. I think the best thing for me to do now is check all the bolts at the calipers etc and see if they will nip up a little more as I have no visible leaks.

The E brake lever on the rear calipers moves just slightly off the stop and locks firm. i didn't measure it as I just went off the video and managed to get it as tight as possible and still get the pads over the disc.

 

I have heard about setting them in a vice and installing them. My personal opinion is they need to be just slightly tighter than that. Try adjusting again installed and measure the gap at the arm. Just my $.02 and preferred way.

 

I've run into this same problem. You've got the windback style rear calipers with the incorporated park brake.

It's common for them to turn back in but not come back out. I've also had brand new calipers do the same thing. The pistons pumps out but won't stay out and returns too far causing a bad pedal. Are you sure the pistons are coming out and not returning too far?

 

This "returns too far" is all about the adjustment and using the parking brake.

 

th8s is going to sound like a crazy answer. but try replacing the master Cylinder reservoir gasket and cap. my gasket was actully getting sucked into the reservoir and not keeping the system sealed. ask me how i know.....

 

KyleF, did your 84 TA come with rear disks, or did a PO swap in a 9 bolt rear with disks and did not change the prop valve?

 

I have not personally owned an 84. My Stepfather did when we were kids (New Black and Gold Z28). Oh, there was also a Silver 86 my Grandfather had... 85IROC / 87T/A / 91RS / 97Z28 that my gf in high schools family had... I have been around a lot of them.