Brakes went soft at slow speed. Back to normal at normal speed.

[Towser42]

I had a problem pop up on my '89 Festiva this morning. I just bought this Festy, and the front brakes were re-done before I bought it. The brakes have been nice and firm at all times, until this morning when I was creeping along in a traffic jam and they suddenly went soft and I had to push down half-way to get any brake power. This went on until the speed of traffic picked up and the brakes went back to normal. This is the first time this has happened.

Anybody have any ideas what this might be? I'm at work now and won't be able to check anything out until I get home.

Thanks,

Pete

[zoom zoom]

Maybe the check valve in the brake booster vacuum line?

[Movin]

Vacuum leak??

[Aaronbrook37]

Take a gander at the brake vacuum hose as stated. I suspected mine was off, and the bracket/hardline was rusty and corroded anyway, so I replaced it with 1/4" tubing I believe it was.

[Towser42]

OK, thank you. I'll check out the line off the booster.

[FestYboy]

don't dismiss the possibility of a master starting to fail (it's 24 years old and how often has the fluid been changed???)

[Towser42]

I checked the hoses to the hard lines leading to the booster. They are all old and stiff, but I don't see any breaks or obvious issues with them. The hard lines have a little corrosion on the outside, but seem to be in good shape. I'll replace the hoses and clamps to be sure.

I can't say anything about the brake fluid change frequency, but I do know the car was garage kept in NYC and only driven about 1,500 miles a year for a lot of it's life.

At lunch I went out, started the car, put it in park and started pushing down slowly on the brake pedal. It was pretty firm and I couldn't get it to "give way" or go to the floor.

Thanks for the suggestions.

[Towser42]

Actually, one other quick question, how difficult is it to get a replacement cap for the brake fluid reservoir? is it possible it could be something as simple as when the brake fluid heats up in the engine compartment the cap expands and isn't sealing as tightly as it should?

Thanks,

Pete

[Aaronbrook37]

Actually, one other quick question, how difficult is it to get a replacement cap for the brake fluid reservoir? is it possible it could be something as simple as when the brake fluid heats up in the engine compartment the cap expands and isn't sealing as tightly as it should?

Thanks,

Pete

Might want to double check to ensure I have the right part number here, but a new reservoir should theoretically come with a new cap!

http://www.fourgreen.com/store/scripts/RESERVOIR-MASTER-CYLINDER_p_5685793

[Banana Bonanza]

don't dismiss the possibility of a master starting to fail (it's 24 years old and how often has the fluid been changed???)

I'd guess master cylinder on way out (most likely) or else leak in brake line or wheel cylinder. I doubt master is original in a 24 year old car. If it is, give the engineer a gold star on his forehead.

[Towser42]

Thanks. I ordered it.

I recall I had a similar problem once with my old VW Rabbit and I found the old cap actual had a crack and was leaking air under pressure. A new cap solved the problem. I had almost forgotten that. It won't hurt anyway.

[Aaronbrook37]

Thanks. I ordered it.

I recall I had a similar problem once with my old VW Rabbit and I found the old cap actual had a crack and was leaking air under pressure. A new cap solved the problem. I had almost forgotten that. It won't hurt anyway.

Alright... hopefully that will do it. Get yourself a one man brake bleeder kit if you don't already have one to help out the process. Also, you may want to spray your brake bleeder valves with some penetrating fluid in advance.

[WmWatt]

I've had my '89 since it was new and have no problem with the original master cyclinder. The brake fluid was changed once when I replaced all the old brake line.Be very careful with the bleeder nipples if they are original. Penertating oil may not be enough. I had to heat mine with a torch and even then broke one. It stayed broke until I eventually replaced the calipers.

[Bathtub Tom]

I'd suggest everyone should be a little more circumspect about renewing brake fluid. It absorbs water (breather hole in reservoir cap) and that can boil if it gets hot enough. The brake pedal then hits the floor! It's happened to me once, that was enough.

I came across this test: http://workshop.search-autoparts.com...759/31710.html The interesting bit's at 1:40.

I tried it on my ten-year-old Nissan that regularly gets some brake fluid bled through. It passed. The hydraulic clutch fluid (that's never been touched) failed.

[Movin]

Are you suggesting we race more to keep moisture boiled out of the brake fluid?