Brake Pedal Travel Issue

[Eastlight]

80" Spider w/carburetor.

In the past couple months I have replaced everything in the brake system, calipers, rotors (disks), hoses and pads. The only part not replaced is the master cylinder.

The first problem was the servo (booster), which I replaced with a salvaged one a friend gave me. It seems to work nicely.

After replacing everything on the front brakes, the brake pedal depressed much further (about half way down) than it did previously but the brakes worked nicely - except for a sticky hand-brake cam on the rear calipers.

After replacing the rear calipers, pads, discs and hoses (I do not have a compensator) the brakes work great but the pedal now travels nearly to the floor before they grab. Seriously, the pedal goes down so far my foot actually hits the accelerator pedal linkage but the brakes grab solid and will lock the wheels.

The servo pin (behind master cylinder) is adjusted properly. The brakes are bled and there is no air in the lines. I even replaced the hand-brake cable. Everything seems to function properly but it is dangerious having the brake pedal travel nearly to the floor before I get brakes.

I am thinking maybe the servo is not functioning properly because it is a salvaged part. I tried disconnecting it with no result except the expected additional pressure necessary on the pedal. The pedal still traveled nearly to the floor.
I have difficulty considering a malfunctioning master cylinder but that and the servo/booster are the only two parts left that have not been replaced with new or rebuilt parts. Any suggestions would be helpful.

[calvinconrad]

is the brake pedal bent?

[kmead]

Are you sure the pedal servo pin is properly adjusted? With the car on stands, at what point do the front brakes grab? They should start to grab pretty early as the pedal starts to be depressed. It shouldn't need that much travel to engage them.

Are your rear brakes properly adjusted? If the pistons haven't adjusted out, then they have to travel a long distance to engage. When you pull the hand brake up does it take more than three clicks to keep the rear wheels from rotating? If not then you should adjust the cable appropriately. This should take some of the travel out.

[Eastlight]

Thank you very much for your kind replies.

The brake pedal isn't bent. Is that humanly possible?
I considered the yoke connected to the brake pedal but that push-rod is connected to the servo pin and I do not think the enormous pedal travel distance could be caused by a small adjustment on that - although I've been wrong once or twice in my life.

None of the brakes grab until the pedal is nearly to the floor but they do easily stop the car.

The Servo Pin is adjusted properly, I checked it yesterday.

I had my mechanic install all four calipers (two front last month, two rear this week) because I do not have anyone around to help me bleed the brakes. He is good mechanic but not a Fiat specialist.
The garage down the street, that only works on Rolls Royce, Lamborghini and Jaguars, won't touch a Fiat (*#%@). My mechanic (who I've delt with for over 20-years) calls my car a "Ronzoni Downhill Racer", so I have adopted that name for my car.

Rear/front brake adjustment?
The pedal problem did begin a little with the installation of the front calipers but not nearly as severe as it is now after installing the rear calipers and pads.
Your reply induced me to read further about the rear brakes and brake cable adjustment, which I find requires pumping the brake pedal six times then fully actuating the brake handle six times then leaving the handle up two clicks before adjusting the cable. I am wondering if that could be at least part of the problem since it is possible my mechanic might not have been aware of that method.
Since that adjustment technique does not require opening the hydraulic system, I will try that when the weather drops to a more reasonable mid-80's over the weekend. If it works, I'll let you know. If it doesn't, I'll let you know

It just does not seem like the solution could be complicated - of course, I say that everytime I work on the RDR (Ronzoni Downhill Racer) then spend two days on a job I thought would take an hour. I am sure we've all been there.

Comments, suggestions, describing feats of strength bending a brake pedal are certainly welcome.

[dmwhiteoak]

I'm thinking you have an air pocket trapped in your lines. If you pump the pedel a couple of times does the travel go away?

[Eastlight]

Thank you for taking your time to write.
There is no air in the brakes anywhere. I know that mushey feeling and how the brake pedal rises significantly when pumping the brake pedal. The system is bled properly. The brakes are solid, it is the pedal travel distance that is the problem.
Going out now to loosen the brake cable and try seating the rear pads as the on-line manual instructs. I hope it solves the problem. I'll keep you all informed. Have a grease-pit in my garage makes this type of job a lot easier.

[burgandy81]

Nothing useful to ad other than I am watching with interest as I have a similar issue that arose after a brake upgrade.

I have almost everything you have and still have a pedal that far too close to the floor when it decides to grab.

Please post any updates if your find a problem.

I have been working on the theory that I have some air still.

Cheers,

Jordan

[Eastlight]

Hi Jordan and all,

Thank you for your replies. Sorry you are having a similar problem Jordan. Logic seems to indicate there is one common problem causing this difficulty.

I tried re-adjusting the parking brake as specified in the on-line manual. It seemed to help a tiny bit but pedal travel is still too far down. The cam actuator on the rear wheel calipers seems to be adjusting way futher than I think it should before it stops wheel rotation (off the ground).

All my brake problems began several months ago when my servo/booster broke.
I replaced the servo with a salvaged one then had to take it to my mechanic to have him bleed the system for me.
At that time I had him replaced the front calipers and hoses. The brake pedal traveled down further than it used to but not near the floor like it is now.
Then the rear brakes would not release when using the parking brake. I temporarily stopped using the parking brake.
Later, my mechanic replaced the rear calipers, pads, discs, hoses and brake cable.
Now the brake pedal is no where near where it used to bite and is very frustrating not being able to figure this out.

During braking, pumping the pedal a couple times temporarily brings the pedal up a little higher but not much.
Those are all the clues as accurately as I can describe them.

The only thing I can think of now is:
1 - Have a friend come over and help me bleed every connection in the system (I do not have a compensator, just a brake line junction block).
*If that doesn't work,
2 - Replace the servo.
*If that doesn't work,
3 - Put up with it and see if the brake pads eventually seat themselves.
*If that doesn't work,
4 - Replace the master cylinder - the only thing left that hasn't been replaced.

[burgandy81]

Well, in the interest of exploration here is my story. Maybe the two stories combined will provide insight.

Car ran fine and brakes worked well for a couple of years of ownership prior to upgrade.

I upgraded to a Performance Fiat brake kit (Uno Turbo calipers and larger vented rotors) in the hopes of improving stopping performance.

At the same time I exchanged my booster and MC for used items from a forum member who indicate they had very little use. upon inspection and installation I agree and see no signs of failure for either component.

Upon re-assembly I could not bleed the brakes enough to build pressure. I tried a complete bleed 4 separate times with more than a litre of fluid in total going through the system. I tried both traditional pedal bleed with assistant and vacuum bleed. The result was a pedal that was very low and soft. The car would slow down and stop but not with enough confidence to drive it comfortably.

Following my (failed) efforts I took the car to local Fiat Guru. He re-bled the brakes, adjusted piston in MC, confirmed booster was OK, replaced suspect rear caliper and bled again for a total of 3 tries on each wheel. As the pedal pushing assistant I could achieve reasonable pedal pressure at reasonable pedal height on the hoist while bleeding at the shop although once on the ground and running the pedal was very low again.

I will add that the car does stop although the pedal is very low. The car will even stop relatively quickly with strong pressure.

Hopefully someone has a stroke of genius that will help us and a possible future member.

Cheers,

Jordan

[Eastlight]

Hi Jordan,

Thank you for sharing your experience, it may be helpful. Like you, my brakes worked great too for a couple years until my servo decided to quit.

I am noticing the same parts appears in both our stories - MC and brake servo/booster. We both install used servos too, however I can't be sure if that is consequential to the common issue. And removing/installing a servo is a real pain, as I am sure you know.
While I have not messed with my MC at all, it would seem the MC is putting out pressure because the brakes eventually work, although after that long pedal travel.
That leads me to consider the servo (as it is entitled in the manual) because that part directly pushes on the MC. Although the servo is making the pedal pressure easy it may not be developing enough pressure to fully actuate the MC, until the pedal is depressed nearly all the way. I can feel the servo kicking in almost immediately when I depress the brake pedal. Sitting in neutral and stepping on the brake does slow down the RPMs a litte but I think that is normal because of the servo using engine vacuum.

On-the-other-hand, depressing the brakes when the engine is off gives a higher pedal, but then, if the servo is leaking, the engine would seemingly run rough because of a vacuum leak, which is why I replaced the original servo. Also, disconnecting the servo does not give a higher pedal. I don't know, this is pure speculation because I am fishing for every possible answer. Every scenario I think of seems to have a reason that contradicts the problem originating from one part or another.

It just seems like something is not developing enough hydraulic pressure soon enough to actuate the brakes quickly.

I am thinking (sometimes I do that) that a rebuilt MC is relatively inexpensive and easier to install than a servo, so I am considering replacing the MC just to see if that improves the brakes.
If that doesn't help, since one of my friends kindly gave me two salvaged servos and one is now in the car, I may try rebuilding the original, damaged one, myself. They do not seem that complicated - of course, neither does the brake system, yet here we are.

One day we are going to figure this out and smile because it is probably something easy. Then when we read about someone else having this problem we will be able to help immediately.

I will continue posting what happens when I try this and that.

[SouthwestSpider]

I'm in the process of dealing with the spongy brakes etc. also I've bled them thoroughly. Still not the best, I've replaced the servo, still spongy and long pedal travel, and now I'm going to replace the master cylinder. With that done, I hope that I get rid of the spongy feel. The only crucial aspect is the acorn nut adjustment at the servo/master cylinder. That will be thoroughly done when I put the new master cylinder on.
I hope to be able to finalize this process with the answer to spongy brakes, and brake pedal travel issues.

[seabeelt]

Did Eastlight or Burgandy81 ever get their issues resolved?

[burgandy81]

I have not fixed this yet as the car is off the road.

A forum member (ManoaMatt) has offered some advice that I will be exploring.

It seems the master cylinder of the Spider is not horizontal when the car is sitting normally. The forward end of the MC is inclined. This can allow air bubbles to get trapped ahead of the sift supply lines and the hard system lines. No amount of traditional bleeding will free these poor bubbles.

The advice is this. Raise the back of the car as high as safely possible and then bleed the MC while gently tapping the MC body with a screw driver. This will change the angle of the MC and allow the bubbles to escape.

This makes good sense to me and I will give it a try as soon as I get to the under-hood portion of my winter projects.

I am also interested in more suggestions if they are out there.

Jordan

[Weelan]

This is good info. I'm going to check mine over the weekend. My brakes aren't too bad but not immediately biting. Thanks!

[Eastlight]

Guess I was busy and forgot to update my brake issue. After a complete brake job (except replacing master cylinder) the pedal went down to the acelerator pedal. When applying the brakes my shoe would actually touch the accelerator.
A couple weeks driving time and pumping the brakes have eventually seated the brake cylinders. They are working perfectly, pedal still travels somewhat, probably normal, but not nearly as far down as it did. Now, it only takes a light pedal pressure to stop and I'm happy with it.

I found out my servo was bad because the engine would stall from the vacuum leak in the servo diaphram. Temporarily plugging the servo vacuum line solved the stalling and so that indicated the problem was in the servo.