Brake pedal travel to the floor at idle when pressed

[pietern740il]

but works fine while driving.
The car is 1986 535i with 191K, 5 speed.

Trying to get my car ready for 5erfest, but cannot solve this problem.

At idle when I press the brake, I hear a pressure sound coming from the power steering pump. At idle the brake pedal feels hard. The longer I keep my foot on the brake pedal the more i hear the sound coming from the power steering.

I don't know if its a pressure problem, any help would be great. Thanks

Nigel

[jimoreno]

A brake pedal that goes all the way to the floor usually means a bad master cylinder. Have you checked for ATF leaks?

[RAYADAM]

but works fine while driving.
The car is 1986 535i with 191K, 5 speed.

Trying to get my car ready for 5erfest, but cannot solve this problem.

At idle when I press the brake, I hear a pressure sound coming from the power steering pump. At idle the brake pedal feels hard. The longer I keep my foot on the brake pedal the more i hear the sound coming from the power steering.

I don't know if its a pressure problem, any help would be great. Thanks

Nigel

Your Problem most likely lies in the pressure accumulator located under a valve block(weirdly called a voltage regulator) whereas 4 lines running in/out of .. the accumulator is about the size of a softball(cant miss it)..
the noise from the steering is becuase your car does not use a vacuum brake booster,it shares hydraulic assist from the power steering pump.

[jimoreno]

I thought about that "the bomb" but when mine was bad all I got was a hard pedal not one going all the way to the floor, but then again it's another car!

[pietern740il]

Thank Ray,

That part is hidden never thought that could be a problem. I will order a replacement this week, and report back.

[jimoreno]

Nigel:

You'll need to remove the pressure regulator in order to remove the pressure accumulator so you will need flare wrenches. It is a good time to change your PS fluid (ATF) and the filter in the metal PS fluid reservoir which could also be the source of your PS pump noise. It's easy to replace and cheap. Check your pressure switches on the regulator to see if they are leaking and replace if necessary.

[pietern740il]

Jim Thanks

For some reason my reservoir has no filter in it. So should I use any ATF, where is the drain plug for the PS fluid?

[jimoreno]

I don't think there is a drain plug. In my case I just removed the lower PS hose and let it drain. I think it calls for Dexron II but I use Mobil 1 Synthetic ATF. You mentioned that your car has no filter, did you remove the screens and PS fluid from your reservoir? During normal operating conditions you won't see it. The filter is item #11 below:

[pietern740il]

I had drained out all the fluid found no filter, no spring (#9). How about CHF 7.1 fluid, I was told to use it in my 84 533. Can I use it in the 535 as well?

[jimoreno]

I think that somebody tried to replace the filter and found difficult to install the parts (I had to work at it for a little while!). You reservoir lid should have a sticker with the required fluid. You might consider either getting a used reservoir with all the parts or order them from your dealer so you can have a proper installation with filter.

[pietern740il]

I already ordered the filter and spring. Thanks again for you help.

[victory1auto]

OP:

The brake pedal feels hard at idle, yet slowly sinks to the floor?

Vic

[pietern740il]

That is correct Vic

[garyegloff]

i have what seems a similar problem: i'm a recent owner of a 1988 535is. i had the brakes rebuilt with stock parts before making a long (9,000 mile) drive around the coutry this summer (the master cylinder was not replaced). while the brakes function fine, normally, when starting out, when i have driven for a while, perhaps 5 minutes or more (and frequently on the highway), and whether at high speed or low speed, if i need to use the brakes, i sometimes encounter a rock-hard pedal, which if i hit it a 2nd time, responds, and then the brakes perform quickly and perfectly. i had a similar experience years ago with an a 325e, but time has taken its toll, and i've forgotten how it was repaired. does the master cylinder need rebuiling or replacing? thanks