Brake Issue

I had to have my rear calipers on my 1981 308 GTSi rebuilt due to them leaking. Everything is reassembled, but no matter what the dealer does the pedal is much lower than when the calipers were removed. Several bleedings of all four corners and the master cylinder give no difference. The pedal is firm when it goes down and pumping the brakes does not cause the pedal to get any higher. The only difference is the system is the rebuilding of the calipers. Even when they leaked the pedal was right at the top. Bad rebuild job? Any suggestions? Should we send them to a different place for another rebuild?

 

Hmmmm, is there a mechanical portion to the adjustment at the calipers anyone?

 

The emergency brake is set by the mechanical adjuster screw! If my old brain recalls correctly the clearance is .030. This my be your problem. Tom

 

i set the pad to rotor clearance at .004 as per birdman's procedure

 

Thanks for your input. I will check to see if this was done. I know that the rear calipers are in two halves but there is only one bleed screw. If during the rebuild something was done that doesn't permit the fluid to move between the halves would that cause the problem?

 

I can't imagine what one could screw up to stop the fluid transfer from one half to the other. T

 

Following everyone's advice the clearances on the rear pads were checked and were as they should be. The only thing that was done was the rebuilding of the rear calipers, everything else stayed the same. Multiple pressure bleedings of the system, calipers and the master cylinder, and the pedal is significantly lower than before the rebuild. Pumping the pedal does not bring it up or make it firmer, so it doesn't seem to be air in the system. Since there is only one bleed nipple and two sides to the caliper, could the fluid be blocked from getting to the outer side of the caliper? Since the rebuild, I found a few threads that have some not so nice things to say about the place that did the work, and this has me thinking that there my be an internal blockage that is not letting the fluid take its correct path.

I am giving some thought to pulling them again and sending then to another place, but would like to avoid that if possible. To avoid downtime, I have a pair of 914 calipers that are the same except for the spacer between the two halves to accomodate the thicker rotor. If I could find the right spacers I could get the 914's rebuilt and do a quick swap. Failing that, I could get the 914's rebuilt and then take the spacers from the 308 and split the 914's and install the spacers.

Any thoughts? Thanks in advance.

 

Negative. The 914 is not the same, the 914-6 is almost but the bleed screw is in the wrong orientation so they would be tough to bleed through.

One way to determine if it's the rebuilt calliper is to removed them and fit any old calliper or even blank end - bleed it and see if you get firm pedal. These callipers are not particularly complicated to get wrong.

Lee

 

Lee,

Thanks for your reply. You say that they are not hard to get wrong in the rebuild. What are the common things that go wrong and what can I look for if I decide to open them up?

Carl

 

The rear brakes are complicated, depending on how far you take them apart anyway. Removing the pistons is probably not a good idea....ask me how I know.

Birdman seems to have done it though so what do I know. There are at least 2 shops that guys seem to have had good luck with. ]

http://www.goldlinebrakes.com/Ferrari308.htm is who I used. I really don't understand what about the rebuild would make the pedal lower. Getting fluid from one side to the other of the caliper is relatively simple. There are holes on each side of the center piece with little o-rings around them. The complicated part is the mechanism to allow adjustment of the pads to set the correct spacing. If that is working correctly then I'd suspect the rebuild is ok. Just my 2 cents from doing this a few months ago...

Do the brakes work ok? it's just a pedal height issue??

 

If you're careful and work slowly then a reasonably proficient DIYer can rebuild the rear brakes no problem. I'd suggest staying away from the Superformance "rebuild kits" as the seals are not sized properly and you'll end up with leaks. Others sell better seal kits. Do a search and you'll find a couple threads covering the rebuilding process - it's involved but doable with care.

Re: 914 calipers, I believe the piston sizing is different also IIRC.

 

The pedal height is the major difference. The pedal doesn't seem as firm as it did even when it was leaking. Before the rebuild the pedal was just above the level of the gas pedal so a heel and toe was very easy to do. Now the pedal is much lower and makes the process much less easy.

 

Master cylinder bleed? That one catches a few people off but air does get trapped in that thing.

 

It was done twice. That is what has us stumped. The dealer went through everything a least twice. The master was never without fluid while the calipers were off. The only thing different is the rebuild on the rear calipers. I am ready to invest a few dollars and have them sent out to a different place. They were great when they were leaking.

 

can you get the calipers on the wrong side or reversed?? I did this on a jeep that i had rebult the calipers and put them back on and had the same problem even took it to a shop and they could not figure out what was wrong, then a friend told me to look at the caliper bleed screws if they are on the bottom of the caliper i had them on backwards they should always be on top so i switched them and what do you know perfect brakes!!!

 

Do the rear adjusters work correctly? I mean when you have the rear jacked up with a wheel off, you should be able to adjust each pad independently (inner and outer), until the pad drags on the rotor and stops it from turning. Then, you back it out just slightly to set the spacing at .004. Does that system work right for all four rear pistons?

Here's a picture of mine if you really think it's possible they're upside down. The bleed screw should be on top, along with the parking brake lever. The brake line should be attached on the bottom with the U shaped line.
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Clamp the brake hoses going to the rebuilt calipers. If the pedal gets firm you have isolated the problem there. If the pedal is still soft the problem is closer to or at the master.
Cheers,
Tom

 

I was thinking about this quite a bit last night. If the brakes had not been bleed and worked on in quite some time, it may be possible one of the seals in the master cylinder went bad/tore causing more cylinder travel than before. Press the brakes pedal with the engine running and see if it at all continues after holding it down for a good amount of time. It should not budge. Might be something to check. The seal kits are cheap enough, it's just a PIA of a job. I hate brake fluid

 

The calipers are on the right sides and the emergency brake cables are hooked up and working. When I took the car back in the pads were again set as you described and all of the adjustments worked. I have SS brake lines so it will be a little harder to block them off, but when I get some time we'll do some more diagnostic work and I will let you know what we find out.

One reason we have been looking at the calipers, besides being to only thing in the system that was changed, is that Rifledriver made a comment that he had a 100% failure rate on everything he had done by the shop that rebuilt the calipers. That does not inspire confidence and leads me to concentrate on them over the rest of the system. The car remains driveable, but I don't like the pedal travel.

 

When shops we use screw stuff up, can you mention who it is? Why bother if we don't know the answer? Gives shops a chance to tighten up their act, at least. And if not, they have no one to blame but themselves...

 

When shops we use screw stuff up, can you mention who it is? Why bother if we don't know the answer? Gives shops a chance to tighten up their act, at least. And if not, they have no one to blame but themselves...