DJAngelicon

Hey guys,

I am just wondering if FBs are hard on the brake booster because this is my second Rx7 and it feels that the booster is going again. I press the brakes and it slowly very, slowly go down. I also see the RPM Tech niddle bounce which I am not sure if someone here told me that it is one way to tell that the Booster have a leak. However, I am not sure if that was what I was told.

Anyways, my question is this. Can the booster be fixed with out buying a new whole booster? Maybe some washers or rubbers got worn out?

Thanks In Advance!

-Angel

Siraniko

iTrader: (13)

grab a can of carb cleaner and spray it to the soft and hard lines for leaks
>>>> line between manifold and brake booster.

DJAngelicon

I spray around but I didn't notices anything like hesitation on the engine. I started playing around with the brakes trying to see how low the pedal go and I notices it go slowly from time to time after a few pumps. I also notices when that happens my RPM Tech go crazy from bouncing to a flat 0 rpm drop and it stay there for a while until I press the gas pedal again. Any idea?

Jeff20B

iTrader: (13)

Sounds like the flexing of the firewall whenever you press the brake pedal is causing a problem with your tach. It's electrical. Does the engine die when the tach goes to 0?

The slight dip in RPM is mostly normal because the booster uses some engine vacuum each time you press the pedal. The brake lights also turn on producing a load on the alternator which slows the engine a tiny bit.

The symptoms you describe of a slowly falling brake pedal sound more like a worn brake master cylinder than a problem with the booster.

DJAngelicon

The engine dosen't die when the Tech go to 0.

hmm I c,

Jeff20B

iTrader: (13)

Wiggle the wires up under the dash and see if the tach needle bounces around then becomes steady. If it does, you have a bad connection. That might be enough to fix it (until the rainy season returns lol).

DJAngelicon

ok thanks I will do that and see.

Rogue_Wulff

Tach bouncing when the pedal is depressed could be an indication of a weak charging system as well. Mine will occasionally do that when I have a heavy load on the alt, such as lights, defroster, blower motor, and turn signals, while idling.
I agree that the pedal slowly falling is something in the hydralic system. Either a bad master cyl, or a small leak somewhere.

DJAngelicon

I c, thanks Rogue_Wulff.

Thats when I get my Tach neddle bounding when I press the brake and have the Headlights, even turn signal and radio is playing along maybe with the A/C etc...

So, is there a way to fix that problem?

Also about the hydralic system, It works find but ocasionaly the pedal will go lower slowly.

Is there a way to repair it like a Repair kit or do I have to buy the entire Master Cylinder?

Rogue_Wulff

I swapped to an S4 alt, which almost totally eliminated the tach bounce at idle with the heavy load, but it did not totally solve it. The S4 alt I used was just a 60A, while most are 70A. A 70A alt would probably take care of it. Even when I had the original 50A alt, I never had any issues with the battery not getting charged, but the tach issue bugged me.
As for the master cyl, there are rebuilt kits available, generally around $15-20. While these are not hard to rebuild, they are very sensitive items, and can be troublesome for a person with little experience in working on them. If you have never attempted this task before, see if you can find someone who done it a few times, and ask them to assist you.

Rogue_Wulff

One more thing, if your brake fluid is extremely dark, try flushing the entire brake system.
Old brake fluid will have a lot of moisture and grit in it, which can actually cause the rubber seals to leak internally. Many times, flushing the system will restore pedal firmness and extend the life span of every component in the hydralic system.

DJAngelicon

I replace last year on my 81 Rx7 the Brake booster on the Master Cylinder. I also drop a washer inside the booster which made me remove the entire system out and put it back together. It was fixed so that was good. =) I think I will go to the auto shop and fix a repair kit for the Booster.

I also change last year on my old car the Alternator to a 70A Alternator and didn't get the niddle to bounce anymore. That was taken care of from the getto and that was also adding a new battery which I have here already. Maybe I will do that later on again.

I c, maybe I sould do that as well but doing that can be a pain dealing with the bubbles. lol Hopefully I can get it all done and how many bottle dose it take to fill the brake system? also what kind of brake fluid should I use?

I also notices the cluch have the liquid dark should I change that too and what kind of liquid you put there?

Rogue_Wulff

I think I used a little over a quart of brake fluid to flush both the brake and clutch systems.

DJAngelicon

By the way is it a Master Cylinder Repair Kit that I need? I notice Schuck's having it for $44 dollars.

DwArF

I just put the engine in my new car and have never driven it before, as I bought it with a wrecked engine. The brakes are really soft and go all the way to the floor and I bled them twice and it still does it. And when I pump my brakes to try and build pressure my RPMS go down and the engine stutters and sounds like its going to die.

Do I need a MC?

DJAngelicon

Hey DwArF, I had that problem with a old Rx7 I had last year, I just replace the Master Cylinder and it fixed my problem.

Right now I am looking at some expensive Repair kit for Master Cylinder and is actually cheaper to replace it with a Rebuilt from a AutoShop like Schuck's or AutoZone. I Chucks have them for $37.00 and they need to order it. I hate ordering with Schuck's because I have to wait a few days. I like going to Action Auto Parts here in Washington State because they would have it if not the same day by the next day. But is a bit more like $43.00 but I pay to have it ealier than late since I am moving soon.

Good luck with that. By the way rebuilt kits are like $90 dollars. Good Lord! That is expensive.