99OBW. Mysterious brake leak.

[987687]

I have a 99obw on my case. It was ran dry of brake fluid, I filled it up again, and pumped some pressure into the braking system.

If I pump up the pedal and hold down on it, it slowly sinks to the floor, I did this probably 15-20 times and the reservoir did drop a little bit. So it's not leaky seals in the MC.

 

But what's annoying me, is I cannot find where it's leaking. There are no drips on the floor, and nothing I can see is wet. So, where do these usually leak, where's the common spot I should look for the leak?

[Rooster2]

Pedal slowly going to the floor means you have air in the brake lines that will need to be bled out.

 

Look for wetness (brake fluid) on the inside of each road wheel and tire. If you find that, then you will have found your leak.

[987687]

Pedal slowly going to the floor means you have air in the brake lines that will need to be bled out.

 

Look for wetness (brake fluid) on the inside of each road wheel and tire. If you find that, then you will have found your leak.

 

Maybe I should elaborate on pedal going to the floor. If I pump it up, it gets pretty hard. Then it slowly bleeds down to the floor. Sort of like when you're bleeding brakes and the bleeder is just barely opened. So it's squeezing fluid out somewhere. And yes, of course there is air in the lines now. That's not my current concern.

I looked in the wheels hoping it was a leaky caliper, but no dice.

[ivans imports]

rear drum ? wheel cly if not master leaking into booster not likly but posibble rusty line ?

[987687]

rear drum ? wheel cly if not master leaking into booster not likly but posibble rusty line ?

 

Rear disc. The brake booster is completely dry.

Maybe it has a rusty line, I ased where to look. Which ones like to rust out. Care to elaborate?

[porcupine73]

Based on that description it could still be a master cyl issue. If you pumped it 15-20 times and it kept dropping to the floor, but the reservoir dropped only a little, I would say that little drop was due to some of the trapped air coming out. 15-20 pumps to the floor would otherwise drop the level a lot more than a little if it were a leak. Though since your reservoir did for some reason run empty that would likely point to a leak somewhere.

 

Also note that pushing the pedal to the floor is very bad, esp for older master cyls. Often there is rust in the bore near the bottom, since the piston doesn't normally travel in this area. So when pushed to the floor, this rusty area can cut up the seals, and then you've got a faulty master.

 

But that said on those years it seems pretty common for the rear brake lines to rust out, especially where they go over the fuel tank. I've had to replace those on a few soobs.

 

So at the minimum the entire brake system, probably including the master, needs bleeding. The ABS unit may also have air trapped so it may need to go through sequence control a few times.