engine and drivetrain Brake Issues - 73 - 2002

[Link]

Hey Guys, totally new to the forum and to 2002's in general. Long time BMW owner, never vintage.

I searched for another thread depicting my issue and couldn't find anything...

So my issue is I just purchased a 73' 02 and from what I was told the brakes are pretty stock and haven't been replaced in some time, due to non use.

During the initial drive all was well, the pedal felt a little stiff, but couldn't be sure, since the car was new to me.

The drive home, surface streets stop and go traffic over 20 miles. Brakes felt fine. Had some light to medium braking over traffic conditions.

Two blocks from home, I stopped to let my girlfriend park her car and get in. Sat for maybe a minute and a half. Pulled away to the stop sign and the brake pedal went to the floor, tried pumping it, nothing. I limped home with maybe 5% braking power. Turned it off sat for 5 min while is inspected for leaks, there were none, opened what I think was the brake fluid reservoir (blue button, wires coming out of the lid) please forgive me I'm learning.

Started her up and drove down the street with the brakes feeling better, not as stiff as before, but not feeling 100%. This car is new to me and passed inspection, the previous owner did state he hadn't driven it as far as I have in the time he owned it.

I'm going to inspect further in the daylight tomorrow and see if it's low on fluid, but I'm just confused as to why 20 miles later the brakes would get so soft.

Any thoughts? Thank you in advance.

I'll post engine photos if needed.

[FunkyLaneO]

look at all four wheels and see if it looks wet, check the reservoir to see if it is losing fluid, if neither of those is the issue then I would be looking at the master cylinder, if it is leaking internally then you could get these symptoms.  It could be air in the system but that usually is not intermittent like what you are experiencing.

 

What I would do (if there are no visible fluid leaks) is bleed the brakes really well and look at the flexible lines while you are there, once you are sure there is no air in the system and your flexible lines aren't bulging, test the brakes and see if they work, you can do a preliminary test without driving by starting the car and holding the brake down very hard, hold it for a minute or two and see if the brake slowly goes to the floor, if it does then you most likely have an issue with the master cylinder.

 

Until you have this figured out be VERY careful driving it and keep your hand on the parking brake. Intermittent brake problems are scary stuff!

[GoFaSSter]

You should also look at the vacuum line and check valve. It may be sealing and not sealing as the engine flexes or as heat gets into the hose.

[peterschop]

If the car sat for a long time, the rubber seals may have started to dry out letting fluid by. Check your fluid level and top off if necessary. The reservoir has three hoses, top one going to the clutch and bottom two to the brake master cylinder. Check for leaks. If it is holding fluid and still has the same symptoms, I would suspect the master cylinder. I would flush and bleed lines.

[riggs]

My 73 Master cylinder JUST went out too. I had no leak though - and pumping the brakes brings back pressure. I changed the fluid before storing it for the winter, so I'm suspecting the new fluid may have corroded my seals...?

Perhaps your previous owner changed the fluid before he sold it to you. I was told that Prestone brake fluid will not corrode my rubber seals but some other brands would..?

 

Anyway I've heard it's not a great idea to rebuild these.

So - can I buy a URO master cylinder ($119) or do I need to buy the BMW one ($226)

 

Thanks for any Advice. Hope this helps you Link

[FunkyLaneO]

Last MC I got was made by Ate, I think it was like $150 but that was a few years ago.  If your car is not a TII, shop around you can get better prices than those.

[Link]

look at all four wheels and see if it looks wet, check the reservoir to see if it is losing fluid, if neither of those is the issue then I would be looking at the master cylinder, if it is leaking internally then you could get these symptoms.  It could be air in the system but that usually is not intermittent like what you are experiencing.

 

What I would do (if there are no visible fluid leaks) is bleed the brakes really well and look at the flexible lines while you are there, once you are sure there is no air in the system and your flexible lines aren't bulging, test the brakes and see if they work, you can do a preliminary test without driving by starting the car and holding the brake down very hard, hold it for a minute or two and see if the brake slowly goes to the floor, if it does then you most likely have an issue with the master cylinder.

 

Until you have this figured out be VERY careful driving it and keep your hand on the parking brake. Intermittent brake problems are scary stuff!

So there is a little bit of fluid on the underside of the reservoir, the lines to the MC appear to be good, the connector they plug into on the MC are cracking but don't appear to be leaking, all four wheels are clean. I need a partner to check to see of the lines are bulging like suggested,mother fluid is a little low, about 1/4. I should be using Dot 3 correct?

[peterschop]

Dot 4 is a better choice. I used ATE type 200 Dot 4 fluid to flush my system. Brake fluid is hygroscopic and should be replaced every few years as it sucks water out of the atmosphere and can corrode parts in the system.

 

http://www.tirerack.com/brakes/brakes.jsp?make=ATE&model=Type+200+Amber+Brake+Fluid&partnum=ATETYP200&GCID=C13674x012-brakes&KEYWORD=brakes_ATE_Type_200_Amber_Brake_Fluid&code=yes&CAWELAID=530007250000317246&CAGPSPN=pla

 

Clean off any leaked fluid as it will eat the paint off your car. Begin by topping the fluid off and see if it seals up or continues to leak. Maybe it will correct it's self.

[peterschop]

BTW, old brake lines may look good but still be bad. They can deteriorate on the inside. They can swell up on the inside and restrict the flow. If your calipers are slow to release, that is a sure sign of bad lines. They will make it hard to bleed as you can not push the fluid through them.

[chargin]

As stated above, it sounds like a Master going bad. It will leak fluid back into the booster. If you replace the Master be sure and clean the inside of the booster and get out any pooling Brake Fluid.

[Link]

Anyone have a solid DIY for a master cylinder change & brake line replacement. I have a feelings this 02 is gonna be a passion project. Just didn't think I'd have to start so quickly! What brand of brake line should I be using? I'm really handy and follow directions even better. Thank you all for all your advice!!

[Link]

Oh also? Now that I've driven it today, there is an audible click in the break pedal, when pressed. Any thoughts and course of action I should take?

[FunkyLaneO]

Replace the soft lines with stainless steel braid lines, I think you can get them from Ireland Engineering and other places, you could see if Blunt has them even though they are not OEM. For the MC check with Blunt or Autohausaz, both should have better prices that what you posted earlier.  Any leaking you have upstream of the Master Cylinder should not affect your braking (except for maybe running out of fluid or sucking in air) so that leaking is not likely your problem but you should fix it anyway. 

 

The swapping of the MC and the lines is pretty straightforward, just replace them, the important thing is the bleeding of the system, if you have a pressurized brake bleeder that is the best way to do it, do a search on brake bleeding and there should  be a bunch of info.  There is a special order for bleeding the front calipers (they have 3 bleeders each and need to be done in sequence) but that is the only tricky thing.

[FunkyLaneO]

The click is probably in your pedal box, mine has done that on occasion (usually the clutch with me) not a big deal, when I rebuilt my pedal box it went away but there didn't appear to be anything wearing funny because of it when I had the pedal box apart so I would not be too concerned.

Edited August 21, 2014 by FunkyLaneO

[Link]

The click is probably in your pedal box, mine has done that on occasion (usually the clutch with me) not a big deal, when I rebuilt my pedal box it went away but there didn't appear to be anything wearing funny because of it when I had the pedal box apart so I would not be too concerned.

 

Most of the repairs seems to be pretty straight forward, My first car was a 63' Mopar years back & and that was pretty fun and fairly simple to work on. Ive seen a diagram somewhere for the pedal construction, its got lots of pivot points. Is a pedal box rebuild a huge undertaking. 

 

I guess I'm trying to get a sense of what I'm in for. I ultimate goal is to feel comfortable & safe driving from San Jose (Silicon Valley) over Highway 17 to Santa Cruz (the beach). Its a really windy hill highway where brake issues are ABSOLUTELY not welcome.