Help: questions about replacing brake fluid

[elbert]

Originally Posted by rumatt

No, just the bolt that goes into the guide pin, to hold the caliper in position. According to the bentley, you need new ones every time you change the front pads.

Thanks for the other answers.

BTW, there's a chance I'll be in Columbus in June. If so, you, Andy and I should have a .

Really? That's the first I've heard that they need replacing. Uh, needless to say, I don't replace them.
Sure, just lemme know when you're in town

EDIT: wait, what car is this for?

[rumatt]

Originally Posted by elbert

EDIT: wait, what car is this for?

E30

[lip277]

I've used one of these for years and years......



It has many nice aspects - Some of them are-

• One Person bleeding
  The same cap works on both my BMW's and Mercedes.
  I use the spare tire as the pressure source. Forces me to check (refill) the tire pressure when I'm finished
  I don't have to get my wife to help.
  I can be finished doing all 4 wheels in 20 minutes (2002) and 30 minutes (420SEL)

Cost me ~$35 and worth every penny IMHO.

[Pinecone]

Originally Posted by rumatt

Hey Elbert! Thanks, that's pretty cool. I did pick up some 1/4" inside diameter at home depot and it fits fine. Changing brake pads is ridiculously easy. But I got stuck on the rear because I don't have an allen wrench large enough.

A few more questions, for those willing to put up with me:

1) The bentley says that the "mounting bolts" are self locking and must be discarded. WTF? Do people buy a new bolt every time they swap pads?

2) Do I need anti-squeel on the back of the track pads? Is that functional, or just for getting streed pads ultra-quiet

3) My hub/rotor's aren't the cleanest (pic 1). What would you attack that with?

4) I've got some red gunk (see pic 2.) It looks like rust in the blurry pictures, but in person it looked more like some kind of buildup. Should I be removing this with some kind of brake cleaner?

5) My "guide pin protective boot" is old and torn. (see pic 3) I'm thinking of replacing this after the track event, unless someone convinces me that's a bad idea.

Thanks

Get a hex socket, I have a very nice Snap On one that is a solid piece, unlike the Craftman which look like a chunk of allen key shoved into a socket. They should be 7 mm front and rear for the caliper guide bolts.

1) I never have, unless you over torque them, ala DIY on BF.

2) Street only. Smells bad when you seriously overcook the track pads.

3) Wire brush, by hand or rotary in drill or other power tool.

4) Same. Maybe hit it first with brake cleaner to see if that works.

5) You should replace it now, as that boot is part of the sleeve that guides the guide pin. I agree that the soild bushing setup from BimmerWorld (you can also buy it from Turner and others, but BW makes them) is nice, but it does require additional maintenance. NOt a big deal if you are swapping pads fairly often. Not good for those who don't swap pads a few times per year.

[John V]

Originally Posted by Roadstergal

Swap pads first. Suck the old fluid out of the reservior, put in the pads, then suck out the stuff that's backed up from pushing the pistons in and bleed.

NONONONONO!

Back out the bleed valve screw when you push the piston in. This is especially important if you have ABS! You do NOT want the rust / water / crud from the caliper going back into the brake system.

John V

[rumatt]

Originally Posted by John V

NONONONONO!

Back out the bleed valve screw when you push the piston in. This is especially important if you have ABS! You do NOT want the rust / water / crud from the caliper going back into the brake system.

Thanks John. I didn't need to push them in at all because the old pads weren't worn much. But FWIW, the Bentley just says to push them in.


I managed to make the rookie mistake of letting the tank run dry and air got in, so I had to start all over. What a dumbass (after a panic'd instant message to Clyde and Nick. Thanks for the advice. ) I was confused because the container didn't look empty, but the pedal went straight to the floor, and wouldn't gain pressure. But after enough pumping, it came back, and I eventually worked the bubbles out the back.

I also changed the fuel filter and fuel pump. That wasn't bad at all, but I was disappointed to see that the fuel pump wasn't original (the tab on the wiring clip was broken off, suggesting it has been changed). Shouldn't they last at least 10 years? I'm wondering if there's too much pressure or something, causing the pump to overwork and keep failing.

[Roadstergal]

Fuel pumps on E30s are a notoriously weak point. Someone might have changed it even asymptomatically as insurance.

I don't always change fluid and pads at the same time, and always just push the piston back. Since it's a closed system (if it isn't, something's wrong!), there's no extra crud there to be pushed back - and everything is flushed clean in the other direction at least yearly when you bleed the fluid.

[John V]

Originally Posted by Roadstergal

Fuel pumps on E30s are a notoriously weak point. Someone might have changed it even asymptomatically as insurance.

I don't always change fluid and pads at the same time, and always just push the piston back. Since it's a closed system (if it isn't, something's wrong!), there's no extra crud there to be pushed back - and everything is flushed clean in the other direction at least yearly when you bleed the fluid.

"closed system."

That would be true if an airtight seal existed at the master cylinder cap and if you never opened the top. The fact is that with brake fluid having such an affinity for water and water being prevalent in the air we breathe, water gets into the brake system.

Calipers are made of ferrous metal, and as such they will rust when there is water present. I'm guessing you've never rebuilt a brake caliper after buying a used car whose previous owner didn't flush the fluid. Rust, rust rust. Even if you do flush yearly, rust will still form and it's most likely to dislodge when you're pushing a piston back into a bore.

Bentley manuals are terrible. They miss all manner of critical steps, at least the E36 version does. Oh, how I miss my 1,000 page RX-7 factory shop manual...

Pushing a piston back without opening the bleed screw is fine if you like gambling. I tend to keep my cars for a long time.

[Roadstergal]

Originally Posted by John V

Pushing a piston back without opening the bleed screw is fine if you like gambling.

In my cars, my friends' cars, local track cars, race cars... I've never heard of a problem with that.

Originally Posted by John V

whose previous owner didn't flush the fluid.

THAT'S where the problem resides.

[John V]

Originally Posted by Roadstergal

In my cars, my friends' cars, local track cars, race cars... I've never heard of a problem with that.

...yet. :P

Originally Posted by Roadstergal

THAT'S where the problem resides.

Not entirely. Brake components still rust, even if the fluid is flushed regularly. It's unavoidable. Unless of course you can hermetically seal your brake fluid container, your master cylinder, AND the transport device between the two.

Oh, did I mention releasing the bleed screw makes it much easier to retract the piston? There's no reason NOT to do it.