Idles waaay down when brakes are applied

[AZ79]

Is there a way to remedy this? I have a carbed motor, no emissions, no vacuum leaks.

[So Cal Mark]

have you confirmed that the booster isn't leaking?

[AZ79]

I thought of that right after I posted this. How do I determine if the booster is leaking?
I have two spares... How can I tell if they're in good condition without having to actually install them to find out?

[manoa matt]

With the car running, push on the brake pedal and listen around the foot well. If you hear a big hiss and the car boggs down and wants to stall you probably have a busted brake booster diaphragm.

To test your other boosters, install a length of hose on the vacumn fitting, make sure the plunger and rubber seal that interacts with the master cylinder is fully seated. Suck on the hose while pushing in on the forked rod that attaches to the brake pedal. If you can suck a bunch of air (and dust, be carefull) then the diaphragm is busted. When you suck on the hose and push in the actuating rod and vacumn remains constant then the diaphragm should be good.

[divace73]

this exactly happened to me only 2 weeks ago, it was the booster.
To test the 2nd unit I acually first tested in on the engine, then cleaned and painted it, then again tested it using a vacuum cleaner, all worked, then fiannly installed in the car (without disconnecting the braking circuit) and all was great.
It would ONLY happended when the brakes where applied. Interestingly this forced me to look up how a booster actually works (you tube is great for this) which then makes you understande what is actually happenening.
When you put you foot on your brakes, you open a valve that lets air into the back side of the diaphragm (which is under vacumm when the engine is running and brakes not applied) forcing it to move forward.

[AZ79]

Thank you Matt, it was definitely a bad booster. I just unplugged it and sealed the vacuum port. The car runs great now, but the brakes are stiff. They do work, though.
I'll check my other ones tomorrow...

[4uall]

[quote="manoa matt"]With the car running, push on the brake pedal and listen around the foot well. If you hear a big hiss and the car boggs down and wants to stall you probably have a busted brake booster diaphragm.quote]


While looking through some old posts I have come to determine that the above describes exactly what happened to my Fiona yesterday I found a diaphram online (http://www.autoricambi.us/cgi/commerce. ... ey=BR8-414) however, before I order I was curious to know how does one replace this item? Photos are a great help

[dmwhiteoak]

Jay, it's a real pain to change the diaphragm but doable. I changed mine but the old one showed no sign of a tear or hole. Installed the new and it still would not hold the vacuum. I have another that I plan to install. If you find the key to replacing the diaphragm and making it work I would be very interested in the technique.

[grittracing]

would that be the same on a fuel injected car? and runs better when motor is warmer in warmer weather . but if I slow down fast like from 70 to 5 or 10 coming off the high way it will stall out a few times than recover and drive fine

[htchevyii]

How in the world did you get your booster apart? I bought a diaphram at some point, but gave up and threw it away and did a manual brake conversion. Even when I didn't care if I ruined it anymore, I couldn't get it apart. Autoricambi sells a reman for $159.
http://www.autoricambi.us/product/BR8-4 ... ufactured/
I think Vicks was advertising a pretty cheap new one, but their website won't work for me.

[4uall]

How in the world did you get your booster apart? I bought a diaphram at some point, but gave up and threw it away and did a manual brake conversion. Even when I didn't care if I ruined it anymore, I couldn't get it apart. Autoricambi sells a reman for $159.
http://www.autoricambi.us/product/BR8-4 ... ufactured/
I think Vicks was advertising a pretty cheap new one, but their website won't work for me.

What do you mean "manual brake conversion"? I saw the AR one (hoping to not have to spend the $ ) to fix Vicks has lost my business. I may just have to bring it in to a shop to have done Anyone have any advice?

[dmwhiteoak]

I had mine apart several times trying to figure out why it would not hold a vacuum. A royal pain every time. You have to compress and turn the two halves at the same time. I would go back with a little grease around the edges each time. Finally I give up and am running with booster disconnected. I have one on the parts car that I will swap with when time permits.

[4uall]

How does run without the booster connected? Is it not needed to make applying the brakes easier? What do we do with the vacuum hose/s?

[dmwhiteoak]

Jay, plug the hose end that is connected to the booster. The brakes will be a little stiff but not bad all. I have driven it everyday for the last year like this but I will replace it.

[4uall]

what did you plug it with?