brake booster leak

[backyardbill]

The car stalls after braking . Also has high idle. I connected a Mighty Vac to the hose to the brake booster, and:

1. I can pull and hold a vacuum when the brake pedal is at rest.
2. Push the brake pedal and vacuum goes to zero.
3. Push and hold the brake pedal, and try to pull a vacuum: nothing.

I assume that the brake booster is leaking. Has anyone been successful in taking their booster apart and fixing a leak?

There was a reference to this issue at the archive.mirafiori.com site but the link to the diagram is dead:

=========== start quote =====================
http://www.fiat-spider.net/servicemanua ... erhaul.htm

In the picture above the rod #4 pulls out. Don't change the acorn nut adjustment! and deep behind it is #3 rubber dime shaped disk/seal that you can
fish out. This is leaking. To repair it buy the cheaper kit for this or just
turn over the disk. One side lays flat against the rod end and the other seals
on a narrow ring. You will see the ring indentation on the disk and it leaks
but the other side is still like new and perfect to the task. Kits and new
parts are cheap but consist of the disk, dust sponge/seal and the rubber
bellows. The bladder replacement is more expensive and wants case splitting.
=========== end quote =====================

Any advice would be appreciated.

[mdrburchette]

I never tried replacing the seal, but it's impossible to open up the case to install a new bladder. I don't know where you'd by the rebuild kit either.

[brunorahl]

Original boosters could be opened. Most, if not all, that are offered now, are not able to be opened. I assume the booster manufacturing industry found they made more money this way.

You may be able to rebuild your booster, but I don't know where you'll find the parts. Any new old stock is going to be 30 year old rubber by now, and it will probably split the first time you hit the brakes. If you are set on rebuilding it, be sure that the parts are recently made.

[mdrburchette]

If you know how to open the case of an original booster, there are many of us that would love to know the trick. Can you enlighten us? Thanks!

[Foster48x]

Last summer I was able to pick up a booster repair kit from PerformanceFiat.com for $20 (its now ClassicRicambi.com) but I don't think they carry them anymore. Didn't really matter though, I was never able to get the brake booster casing apart to replace the parts. If you figure it out let us know.

Here's everyone's input on the same topic from last year. Hope it helps.
http://www.fiatspider.com/f08/viewtopic ... ke+booster

Rick

[htchevyii]

I would have gave you the one that I bought from Performance Fiat, but I threw it away in disgust after deciding it was an impossible task.

[backyardbill]

Wow. Thanks, I would have taken the parts.

I am trying to find any diagram that shows the guts of the brake booster. Specifically that shows the flap that the guy talks about on the miriflori site. My Fiat service manual does not show this valve.

Any ideas?

[mdrburchette]

See if this diagram helps any. The check valve is in the hose:

[Foster48x]

Wow. Thanks, I would have taken the parts.
I am trying to find any diagram that shows the guts of the brake booster. Specifically that shows the flap that the guy talks about on the miriflori site. My Fiat service manual does not show this valve.
Any ideas?

Here ya go Bill.


Here's a link to this pic in Hi-res
http://i155.photobucket.com/albums/s281 ... ooster.jpg

Here's the whole FIAT Ricambi Originali Part Manual in hi-res. Thanks again to the original poster "swede" for hosting these.

Direct Link to the CS:
http://www.detach.se/fiat/fiat-filer/FIAT_CC_CS.pdf

Enjoy, and let us know if you figure out how to get the booster apart.
Rick

[backyardbill]

Oops. My 1980 Spider doesn't have that check valve. I was looking at the early model diagram. But I still don't see where the valve would be internal to the assembly.

[AdiDaHun]

So I got a new master cylinder, and as I was unbolting old one from booster, my booster separated/ popped off. Now I'm trying to push it back and twist it on at the same time. No luck so far. I really don't want to remove the booster.

[18Fiatsandcounting]

So, if I understand you correctly, the "dome" part of the booster unit separated from the square rear plate? The rear plate is the one that holds the booster unit to the firewall (and the large steering column/pedal assembly inside the car) with 4 nuts that screw onto the 4 studs of the plate.

The two parts of the booster aren't meant to come apart that easily, so even if you could reattach the dome part, my concern would be that it would pop off again when you least expect it. Like while braking. So, I'm open to what others suggest, but I'm kinda thinking that the booster should come out to find out what's gone wrong.

-Bryan

[SteinOnkel]

So I got a new master cylinder, and as I was unbolting old one from booster, my booster separated/ popped off. Now I'm trying to push it back and twist it on at the same time. No luck so far. I really don't want to remove the booster.

Yeah, no duh. They use a specialized press at the factory for that.

Take the booster out and show it where your local metal recycler is. If that locking mechanism came apart on its own...it's hard to think of a more sure sign that you need to buy a new one.

C'mon, guys, this is one of the few safety items on these cars that is actually pretty decent and the part is dirt cheap.

[AdiDaHun]

Oh boiii. Yeah as I read everywhere else, it should be really hard to separate them. I've tried pushing and twisting back with no luck. About to tackle removing it and see if i can do it in vice. Oh well, if I have to get new booster, at least I'll be half way done. I wish I woulda waited cpl weeks, the weather is way too nice right now in Portland. Need to get her back on the road!

[18Fiatsandcounting]

If you remove the booster, when you're done you will gladly pay almost any amount of money to lessen your misery. Try this: https://autoricambi.us/brake-booster-au ... i-special/

I'm in agreement with Steiny on this. If your booster came apart just by removing the master cylinder, something is wrong and since you're going to have to remove it anyway, just get a new one.

-Bryan