need to replace brake booster on 1981 FI

[micbrody]

I purchase new booster; went on the board to see if there were any tips. Unfortunately, I saw a few posts stating I would have to remove the "intake manifold" or loosen alternator to get booster out. I "hope" neither is true. I quickly looked at engine bay. I see that it is a tight fit; and that fuel rail probably needs to be removed. But (by eye-balling it), it looks like I should be able to get booster out without messing with alternator or intake manifold. Am I correct?

I was thinking that it would be even easier if I disconnect master cylinder from booster before removing; and then remounting cylinder after booster installed. Since I have never done this job before, is my thinking incorrect? Do I need to keep attached /reattach master cylinder when brake booster out of car?

If anyone has any thoughts, photos, procedures, etc.... it would be greatly appreciated

[Rambo]

Not sure about your 81 but on my 79 carb i had to remove master cylinder and resvoir, remove clutch cable from the clutch fork and pull it out of the way, unbolt carb and pull it up (not sure about FI), and move some other wires, fuel lines etc. I was barely able to force it out but i did not have to remove the intake or anything like that. When installing the new booster note that the mounting plate is not symmetrical and has to be moutned to the booster in the way that it came out or the booster rod will not line up with the pedal. There is also an adjustment nut on the booster rode that goes into the master cylinder it has to be adjusted so that it is not pushing on the master cylinder but also has very little free play. On my booster i had it backed down all the way. Also dont forget to put the rubber ring behind the mounting plate back in when reinstalling or you will have to do it all over again.

[KevAndAndi]

There is also an adjustment nut on the booster rode that goes into the master cylinder it has to be adjusted so that it is not pushing on the master cylinder but also has very little free play. On my booster i had it backed down all the way.

Yes, that adjustment nut is crucial. Get a shop manual with the instructions for adjusting it.

[micbrody]

Ok, Just got out the booster. I had to disconnect speedo cable and clutch cable from tranny. Also, had to remove connection from one of the metal fuel lines to get room to get it out. I also unscrewed fuel rail from engine and disconnected cold injector line so I could rotate fuel rail down.

Now I am re-attaching mounting plate. The booster from AR has longer mounting screws; I am worried that I will not be able to tighten mounting plate because the screws go past the mount plate plane. Did I do something wrong? I did compare the screws of old booster to new, and the new ones are definitely longer.

Also, my booster push rod nut had to be wound all the way down with lock nut to get to the factory manual recommendations of 1-1.9 mm extension from end of booster housing.I that correct?

[Rambo]

Ok, Just got out the booster. I had to disconnect speedo cable and clutch cable from tranny. Also, had to remove connection from one of the metal fuel lines to get room to get it out. I also unscrewed fuel rail from engine and disconnected cold injector line so I could rotate fuel rail down.

Now I am re-attaching mounting plate. The booster from AR has longer mounting screws; I am worried that I will not be able to tighten mounting plate because the screws go past the mount plate plane. Did I do something wrong? I did compare the screws of old booster to new, and the new ones are definitely longer.

Also, my booster push rod nut had to be wound all the way down with lock nut to get to the factory manual recommendations of 1-1.9 mm extension from end of booster housing.I that correct?

I had that same exact problem with their reproduction booster. The studs protruded past the plate and it would not work. I sent it back and ordered the OEM booster and the studs were the correct length. On the master cylinder and OEM booster from AR i am running the adjustment nut all the way down and a small custom spacer in between to obtain clearance.

[micbrody]

Thanks for quick response.

Anyone else use the 3rd party booster from AR? Assuming I just cut down the studs, do the boosters work well?

[micbrody]

http://www.autoricambi.us/product/BR8-4 ... i-Special/


this is what I got

[micbrody]

I was about to cut stud bolts to fit; but decided to check if new booster actually works. Turns out the check valve does not work; lets air in and out. My old check valve (which is good ) does not fit in new booster; so no way to know if new booster actually works.

I am done with this new booster. I will return to AR.

[micbrody]

Talked with AR. They checked their boosters with factory original. The new boosters have longer studs; but when mounted on mounting plate, only two of them protrude too long. They sent me replacement check valve. I tested booster. It held vacuum. (AR was very helpful). I installed on mounting bracket and cut down the two long studs

Before mounting it, I adjusted the push rod a low as it would go with included lock nut. It seemed slightly longer than it should be, but I still mounted it. Re-assembled everything (yes, the brake pedal spring took me an hour of contortion and tension to finally hook back up). Under no load, I had wife hit brake pedal off and on when I turned wheels. All seem great. I took for a ride. Seemed to great. Brake feel was much more responsive and firm. However, by end of quick ride, brake pedal was extremely firm. Also, the car would not passively roll backwards on incline of driveway!!!). I jacked up car, and front wheels were locked; and one of rear wheels dragged at lot on pads. I pulled up on brake pedal on inside of car. Even though it did not seem to move, the fronts became free. I theorized that pushrod needed to be shortened (I also, then recalled that when I went to bleed front brakes, the fluid did not easily come out when I first opened screws; only after some intermittent mityvac suction did it start to flow). I was able to easily disconnect only master cylinder and pull out push rod. I removed lock nut, and replace with a lock washer (and I applied some thread lock). I was able to reduce the length of pushrod by 2 mm. Re-assembled; everything works great!

So hopefully this will help people need to replace their booster in future: 1) need to cut down two of the studs 2) do not include locking nut on pushrod

[DustyDave]

Thanks for sharing this story, I am in the same situation with the long bolts and trying to figure out what I am doing wrong. I will grind the 2 that are long as you did. I also noticed after the fact that the mounting plate is not symmetric... so not sure which way to locate the mount plate. Do you recall if the bolts that needed to be ground shorter were on the top or the bottom when installed? That would help me pick the right orientation. I at least have my engine out at the moment, so much easier to remove/install the brake booster. Expecting your notes on the lock nut as well to be helpful when I get to that part. Thanks, David

[QuebecFiatSpider]

Your story is really helpfull, thanks for sharing it.

If I may ask a question: why at the beginning you've decided to replace your brake booster?

What were the symptoms?

[micbrody]

Unfortunately I do not remember which bolts I cut down. I did get booster from AR- maybe ask them as to which bolts are too long. They can compare the new booster to old one in stock(that’s how they confirmed I was correct as to bolts being too long).

The reason I changed booster was I was chasing a small air leak in Fi engine. One source could be the the brake booster. It did not hold vacuum ; so I figured that was one source of air leak; also by changing I was hoping for huge improvement in braking.

After changing, I really did not notice a huge difference in braking; therefore the check valve was probably the issue; not diaphragm in brake booster. But now I know I have a new brake booster!!! (And learned a lot about brake booster and master cylinder functions!)