Brake Booster Replacement

[spederman85]

I recently posted on a problem with lack of brake power with a hissing noise. It was thought to be a vacuum hose leak but it appears now that the air leak is coming from the booster itself.

I would appreciate any advice on:
1. How difficult is this to replace? I do brakes on my own but never have replaced a master cylinder or brake booster.
2. Should I buy a new booster? I have seen kits to fix the old booster; although, they may be tough to come by. I know Fiat International does not have them.
3. What steps are involved in replacing the booster?

Thanks for your help.

Rich

P.S. I am often asked how is your Fiat running from friends. I tell them it runs great - stopping is another story.

[mbouse]

replacing the booster itself is a P.O.C. getting the pedal off with that quirky safety clip can be a little frustrating if you don't understand the clip. working on your knees with your head buried under the dashboard should be second nature to you by now.

getting the master cylinder off the booster is no big deal either. and replacing the master cylinder is straight forward. just realize that it cannot be done without bleeding all four corners.

i've heard some had issues with aftermarket, new boosters. if you are lucky like me, a used booster may be just the ticket for you.

so, is your leak coming from the seam between the booster halves? or, is it coming from the gasket at the hole for the check valve? is the leak due to brake fluid eating the booster from the inside?

[Foster48x]

I picked up a booster repair kit from PerformanceFiat.com for $20. It's got the rubber seals and the diaphragm you'll need to rebuild the internals. Still haven't tried it yet. Who knows it may not work but for $20 it was worth a try seeing how a new one will run you over $200 and a used one may be in the same condition soon that your old one is in. I also saw a thread where people have had them rebuilt by professionals for $80-$100.

When I get around to rebuilding mine it I'll post up how it went.

Rick

[htchevyii]

I bought the kit, but for the love of god couldn't get the booster part. If you figure it out let me know.

[manoa matt]

I think the Haynes manual covers how to rebuild the booster. You have to squeeze it in a vice and then turn it to unlock the two halves. I'm thinking a special jig for the vice to hold one half, and some tool to help turn the other half is needed. It won't be easy I know that.

I'm pretty sure there is a big spring in there. So when you go to take it out of the vice remember to keep it together.

I have experience with one of the aftermarket boosters, very expensive. The mounting studs are slightly different. After two years I still don't have a firm pedal, maybe I just need to adjust the pushrod. I dread bleeding all 4 wheels just to turn that acorn nut another 1/2 turn out.

I think If I had the choice of buying a new booster, rebuilding my own for $20, or finding a used one for $50, I'd take my chances on the used one. How's it working Mike?

[Foster48x]

[Edit] Trey, Matt beat me to the punch.
I may try it this week if I have time. If so I'll let you know how it goes.

You may have already tried this? lmk if you did so I can come up with a new game plan myself. I read in the Factory Service Manual to put the booster in a vise with two blocks of wood on each side and squeeze it just a little to release the seal. Twist the two halves apart then slowly release the vice so everything doesn't fly out of it.

Rick

[htchevyii]

It couldn't really be clamped in my vise, so I cut two squares of plywood, with a bolt thru each corner. It was cut so that one side would be able to turn. I was unable to devise a way to turn it with enough force to unscrew it. When I was finally fed up I tried a punch and finally a pry bar between the mcyl mounting studs. All this did was bend the studs. At no point did it move at all. At this point I said "screw it", I'm either going to get a used booster or try the conversion to manual brakes on Mira's Racers Forum. This is the first booster I've ever had go bad, so I wouldn't be too afraid to go with a used one.

[Foster48x]

Well that sucks
I should have known better than to think I could get away with only spending $20 on anything to do with a 30 yr old car.
I'll give it a try and let you know how it goes.

Rick

[mbouse]

I think If I had the choice of buying a new booster, rebuilding my own for $20, or finding a used one for $50, I'd take my chances on the used one. How's it working Mike?

i had the "fortune" of installing this booster twice, because i forgot that donut the first time.

the used booster is working great. my highly critical wife/driver only complains that the E-brake handle needs adjusting, which clearly says the feel of the pedal is first rate. i'd recommend trying a used booster first, before even thinking about a booster rebuild kit.

[mdrburchette]

There is no way I'd try disassembling the original booster to rebuild it. It takes an act of Congress just to cut the dang thing in half to pull the rod out for the boosterless conversion! BTW, that conversion isn't bad at all and the brake pedal needs only a little more force to activate the brakes than with a booster. Just think, an X19 doesn't even come with a booster and they brake just fine.

[mbouse]

so we gotta wait for obama to get back from vacation before we can rebuild a booster? cheeze!

[So Cal Mark]

what does the Pres have to do with rebuilding a booster?

[Foster48x]

I'm either going to get a used booster or try the conversion to manual brakes on Mira's Racers Forum.

Trey,
Do you have a link to Mira's brake booster conversion? I cant seem to find it.

Thanks,
Rick

[clarkedj]

My son and I replaced the brake booster in his 78 fiat 124 1800. Not a big deal. I made him get under the dash and unhook the fork from the pedal. He found it a little frustrating because you are working upside down and backwards. Bleeding the brakes was probable the big pain in the a--. I finally made a pressure brake bleeder so you could perform the bleeding without pumping the brakes. Just dont use too much pressure. BTW I went with a new booster worked fine. I would plan on using most of the day to get the job done. Although my son and I are only weekend mechanics.

Thanks

Ed

[htchevyii]

I'm either going to get a used booster or try the conversion to manual brakes on Mira's Racers Forum.

Trey,
Do you have a link to Mira's brake booster conversion? I cant seem to find it.

Thanks,
Rick

http://forum.mirafiori.com/mirafiorum/m ... 95&frames=

I modified the booster mounting bracket today, you have to weld a piece of metal on the center to reduce the hole to the size of the master. The old rod, once removed from the booster, is a perfect fit, ( actually, mine might be a tiny bit too long, it is pushing the piston in about 1/8" with the pedal all the way up). If it causes a drag, I'll make a shim to go behind the master. I didn't center the new hole, but moved it down a little, it seems to line up perfect. I don't know if it's needed, but I will install a guide like Jim did. You will need to use small headed bolts or notch the firewall for clearance. I'll report back when I try it out. I have also installed front calipers and pads on the rear and will install a Willwood adj proportioning valve. This is suposed to give improved rear braking, but can lockup without the adjuster.

These are Jim Scurria's pictures: