After car on jackstands, brakes are mushy.

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Jamie - 07 Aug 2006 17:22 GMT

I had my 1987 740's front end up on jackstands for a few days. When I
lowered the car and went for a test drive the front brakes barely
worked. I drove the neighborhood pumping them and slowly they came
back.

First thing this morning they felt very mushy until I pumped them. I
inspected the brakes, pads and calipers a few weeks ago and they are
good.

Could having my cars front end jacked up have done something with the
brake fluid or system? My brakes have felt a little soft for the 6
months I've had the car, but never this bad. I don't see fluid anywhere
and was thinking it might be time to bleed the system and refill it.

Any suggestions?

Thanks,
JB

Reply to this Message

John Horner - 07 Aug 2006 18:26 GMT

> I had my 1987 740's front end up on jackstands for a few days. When I
> lowered the car and went for a test drive the front brakes barely
[quoted text clipped - 4 lines]
> inspected the brakes, pads and calipers a few weeks ago and they are
> good.

My guess would be a failing master cylinder. If pumping up gets things
sort of working then that is probably the problem.

Jack stands is probably a coincidence.

John

Reply to this Message

Jamie - 07 Aug 2006 21:10 GMT

I test drove it at lunch and here's what I found. If while driving I
fully depress the pedal, it will not begin to engage the brakes until I
am about 2/3 down. Pumping the brakes has no effect, the brakes do not
engage until around 2/3 depressed.

However, if I hold the pedal down about 2/3 and begin pumping the pedal
only the bottom 1/3 over and over, it grabs and grabs. So, as long as I
keep the pedal 2/3 depressed, I can repeatedly engage the brakes, it's
that first 2/3rds that do nothing and the bottom 1/3 doing all the
work.

Is that still a master cylinder, booster or air?

Reply to this Message

lolo - 08 Aug 2006 00:58 GMT

Exact same thing happened to me on my 1986 Toyota truck. Here's what
it was; The brake master cylinder 'O' rings had desintegrated, and
fluid started leaking into the brake booster, corroding the diagphram.
The back of the master cylinder is conveniently aimed so if it leaks it
goes right into the booster. I got a used booster and a rebuilt master
cylinder and it went back to normal, although I bled the crap out of
the brake system after that in case of contamination, and rebuilt the
rear wheel cylinders.

This is hard to see because the fluid goes into the brake booster, not
onto the ground. Brake fluid is corrosive, so it doesn't take much to
kill the internals of the booster. I didn't even notice that much of a
drop in fluid, I just thought it was the wheel cylinders leaking a
little, which I wasn't too worried about.

Having the front of the car raised may have simply let more than the
usual small amount of brake fluid into the booster, and killed it
excecutioner style...

> I test drove it at lunch and here's what I found. If while driving I
> fully depress the pedal, it will not begin to engage the brakes until I
[quoted text clipped - 8 lines]
>
> Is that still a master cylinder, booster or air?

Reply to this Message

Jamie - 08 Aug 2006 01:14 GMT

Aha. That seems reasonable. I checked FCP Groton and they want about
$125 for a master cylinder. Not sure about a booster. Looks like I may
need to see about those.

Thanks!

> Exact same thing happened to me on my 1986 Toyota truck. Here's what
> it was; The brake master cylinder 'O' rings had desintegrated, and
[quoted text clipped - 27 lines]
> >
> > Is that still a master cylinder, booster or air?

Reply to this Message

John Horner - 08 Aug 2006 01:24 GMT

> Aha. That seems reasonable. I checked FCP Groton and they want about
> $125 for a master cylinder. Not sure about a booster. Looks like I may
> need to see about those.

Check you local auto parts stores as well. Sometimes with rebuildable
items it is easier and about the same cost to buy locally.

John

Reply to this Message