Speeder165

iTrader: (7)

Well, still .

I was having cold idle issues on my car as stated in another thread. To try something quick, I sprayed out my throttle body with some carb cleaner. Never had any hint of a brake problem before that moment. After I was done, I took the car down the road. Made it about a mile from my house before........had to press hard.....REAL hard on the brake pedal to get the car to slow down!!! Checked the vacuum hose going from the manifold to the metal brake booster pipe. Seemed a little loose. Replaced it with a new hose because it was hard. Checked to see that air would only go one way on the other hose with the valve in it which attaches to the brake booster. Tonight after driving my car for 3 days like this.....No. I don`t recommend it to anyone.... my new brake booster came in. Installed it. SAME FREAKING PROBLEM!!!! I am starting to get a little irritated.

My only other thought is that MAYBE the master cylinder is toast. Never had one just freeze up like that before. I had replaced the master cylinder awhile back. Seems like I remember the brake pedal feeling mushy before the replacement of the MC. The pedal feel I have now is very stiff. Even when you start the car with your foot on the brake pedal........the shop manual says it should drop down just a bit. Mine doesn`t.

I have vacuum to the brake booster.

Think I may have covered all of my angles. Stumped.

Anyone else have a problem like this that was solved later? Would a MC just freeze up with no warning? Proportioning valve maybe?

I like brakes. I need brakes. The car is so much more enjoyable with working brakes.

Uh boy...................

83Limited

Long shot, but try opening your right rear bleeder valve and push the pedal....see if the pedal drops like a rock.....if it does, you might simply want to try bleeding the entire system and see if it will bleed correctly before replacing the master cylinder....if it doesnt, its more than likely the mastrer cylinder/and/or a caliper shot....

hornbm

It almost sounds like an obstruction. But I agree with the post above. Pop one of the bleeders and see if you can easily get fluid out.

85rotarypower

Check your proportioning valve. I would crack a line on the bottom that heads to the rear and push the pedal down, see if you get fluid out of it. If not, crack a line on the top of the proportioning valve and see if you get fluid there. Its possible the internals have either gotten blocked up or broken down entirely causing a clog.

I've never heard of a master cylinder locking up when it goes bad. They always get mushy or the pedal just goes to the floor or leaks down when they go bad.

Speeder165

iTrader: (7)

I am not sure what the deal is. I went to get a burger last night. All the way to McD`s, the cars brakes weren`t working like they should. Same hard pedal, longer time than normal to come to a stop. Got my burger, fries & drink and headed home. Drink was placed between my legs with the spill proof lid on it. Down the road I went. Came to the first light and put on the brakes. Drink went airborne. Last I saw of it before that sound of the spill proof lid not working like it should when the cup hit the floor, was the back end of the LARGE soda pop cup sailing through space.

Brakes are working now. Been fine all day.


Hmmmmm..............

I like brakes.
Car now stops quicker with them.

Hope I have no more problems.

Well.......I think I am going to have a new problem. Especially when that soda pop in the carpet starts drying.

83Limited

Even though they are working, i would investigate....first recomendation would be to drain the lines as best you can, and then refill and rebleed the system. Could have been a piece of trash blocked something in the MC or prop valve, and it could do it again, by bleeding the brakes you might just flush the trash out and be done with it...plus, bleeding the brakes is way cheaper than replacing parts....but definately follow up on it, ya want the brakes to work EVERY time you push the pedal....good luck!

Speeder165

iTrader: (7)

Good advice! I`m with ya` on that one. More work to do on the car. I like my brakes to be dependable and not having them work on a moments whim is not something I want to experience again. Keeps my insurance rates lower to say the least.

Thanks everyone for the suggestions! I really appreciate it!

Siraniko

iTrader: (13)

A one man bleeder kit from HP and a good compressor will ease the pain of manually bleeding all lines. buy the cheapest brake fluid from WalMart to flush out the old fluid, thus entire system. Had similar issue in my prior old school project...clogged lines due to dirt and contaminated old brake fluid combined

lets spin

i had the smae issue a while back and ended up taking the intake off to clean out the hard line when the brake booster hose attached due to carbon build up. i had the same issue where it came and went. after cleaning its been good for 2 years

Speeder165

iTrader: (7)

Haven`t had much of an opportunity to run down this problem. I notice every morning that when my car rolls out of the driveway coasting in reverse, my brake pedal feel is hard and the car doesn`t want to slow down like it should. Upon going forward down the street to the end of my subdivision and coming to a stop to pull out onto the main road, everything is fine. No more problem after that. Hmmm....

RX-7 Chris

iTrader: (19)

It really sounds line a booster problem to me. I know you replaced it but maybe it still is a problem with the line.

Have you tried pulling the line off at the booster with the car running to see if it has vacuum? Maybe there is something stuck at the manifold. Spray carb cleaner on line while the car is running, if there is any change in idle than you have a vacuum leak.

Speeder165

iTrader: (7)

Chris, I wonder about all of this. I never had a problem until I sprayed out the throttle body trying to fix a idle issue I was having. Throttle body was attached to the intake manifold at the time.

I am wondering after thinking about all of this, just exactly how big of an opening from the manifold to the brake booster hose fitting that there is. It is a large hose fitting and all but I am also wondering if maybe the true diameter of the manifold hole might be very much smaller. It may have gotten partially clogged from gunk when I was spraying out the TB.

Anyone ever had their intake manifold off to see just how big of a hole it is that connects the brake booster line to the manifold?

85rotarypower

If I remember correctly, the hole is reletively large, probably at least 1/4".

theNeanderthol

iTrader: (1)

I agree with the obstruction theory. I've worked on cars with obstructions in brake lines and mechanically frozen brake parts. They always brake-steered. They braked unevenly.

Is there a banjo bolt you can take off the manifold that holds the tube for the rubber booster line on there? I bet that's a small enough orifice to clog up. Mazda uses it on the 12a manifold, even though it's a big fat vacuum line. So yeah, I'd for an obstruction for sure.

RX-7 Chris

iTrader: (19)

Maybe try spaying carb cleaner down that fitting on the intake while the car is running?

Speeder165

iTrader: (7)

Well, figured out what the problem was.
To all of the guys running old cars with lots of miles on them, look at the lower intake manifold. Mine had a ton of carbon buildup in it. The hole going into the fitting for the brake booster was completely clogged up. Cleaned it out and all is fine. Have good solid brake pedal feel now.

Was amazing how much carbon and gunk was in that area.

Tui

iTrader: (2)

I was just about to say check the vacuum supply to the booster.

Glad you got this sorted.