320D No brakes on start up

Techen · 5 Mar 2018 at 20:30

So, Winters been harsh here and my cars been fine up until now when the snows melting. Was rolling down a massive hill and I went to hit the brakes and well, It was a solid pedal. I smashed my foot into the floor and pretty much nothing happen, Handbrake helped me there. But after that, The brake pedal went on to be fine, No problem all the way home.

So its only happening when I switch off the car for a little while. Vacuum leak or worse booster? Gonna throw it into the garage on friday but I dont want them sly dogs making up that I need a new master cylinder. Any ideas?

UnworthyBean · 5 Mar 2018 at 21:13

Could it not just be ice/water on the pads and discs if it's been sitting in freezing conditions for a while.

~~Has your car got drums on the rear?~~ Nevermind, you posted which car it was.

Techen · 5 Mar 2018 at 22:13

UnworthyBean said:
Could it not just be ice/water on the pads and discs if it's been sitting in freezing conditions for a while.

~~Has your car got drums on the rear?~~ Nevermind, you posted which car it was.

At first I could have believed that as my car was outside for 10 hours, However. I drove it within 1 hour of turning it off and it still did it. Not entirely sure what it could be :S

IAmATeaf · 6 Mar 2018 at 07:40

Did the pedal feel normal or did it go all the way to the floor?

GeX · 6 Mar 2018 at 10:16

By the description it sounds solid, and an issue with the vacuum assist / servo / vacuum pump / non return valve / whatever dirty dervs have.

IAmATeaf · 6 Mar 2018 at 11:42

GeX said:
By the description it sounds solid, and an issue with the vacuum assist / servo / vacuum pump / non return valve / whatever dirty dervs have.

You’re right, missed the solid pedal in the original post.

fastwunz · 6 Mar 2018 at 16:08

That’s scary - I absolutely wouldn’t drive it at all and would even consider a tow to a garage. Sounds like a death trap

Scania · 6 Mar 2018 at 18:21

fastwunz said:
That’s scary - I absolutely wouldn’t drive it at all and would even consider a tow to a garage. Sounds like a death trap

+1

That’s a serious and potentially dangerous fault, I certainly wouldn’t take a chance on driving it again until it’s fixed.

Techen · 6 Mar 2018 at 18:49

I did manage to find out the issue, Its a common fault with the E90s it seems and incase anyone else suffers from it.

SUBJECT
Additional Effort Required to Press Brake Pedal Prior to Engine Initial Start
MODEL
E90, E91, E92, E93 (3 Series) produced up to 9/07
SITUATION
A customer may report increased brake pedal effort prior to engine start. This situation can occur if the vehicle sits for extended periods of time. Although the brake pedal can be depressed, the customer may note a change in pedal feel.
CAUSE
The vacuum check valve, fitted at the brake booster, may leak due to component tolerances within the valve assembly.
CORRECTION
Replace the vacuum valve and hose assembly for the brake booster; refer to Repair Instruction RA 34 33 051.
PARTS INFORMATION
Part Number
Description
Quantity
34 33 7 577 336
Vacuum Pipe

GeX · 6 Mar 2018 at 19:27

Ah, just the non-return valve leaking then.

Clarkey · 6 Mar 2018 at 19:56

Unlikely I would say, the vacuum pump should replenish the vacuum very quickly after engine startup.

Techen · 6 Mar 2018 at 19:59

Clarkey said:
Unlikely I would say, the vacuum pump should replenish the vacuum very quickly after engine startup.

Pedal returns to normal around 2-3 minutes of running the car. Its only during start up and driving

Clarkey · 6 Mar 2018 at 20:03

Well if it loses servo while it's off then the check valve is definitely shot but minutes seems way too long to build vacuum I would suspect the pump has issues too.

Once it's back to normal, if you pump the brake repeatedly does the pedal go solid again?

Techen · 6 Mar 2018 at 20:10

Clarkey said:
Well if it loses servo while it's off then the check valve is definitely shot but minutes seems way too long to build vacuum I would suspect the pump has issues too.

Once it's back to normal, if you pump the brake repeatedly does the pedal go solid again?

Nope, Its back to its normal self after it returns to normal. No stiffness.