Brake Bleeding methods

rebel.ranter

Hi, I just did a brake bleed job on the car over the weekend & I was paranoid about the feel of the pedal afterwards with the engine idling.

Without the engine running the pedal felt rock hard, with the engine idling the pedal sinks a bit (I know this is meant to happen at start-up if you keep your foot on the pedal) but I noticed that it dips a bit more than I would have expected. Or maybe I'm just being paranoid....

Anyway the method I used is:

1. Car up on axle stands all round.
2. 2 person method
3. Start at furthest wheel away from reservoir working towards the closest wheel.
4. The person in the car pumps the pedal 5 times, holds the pedal down on the 5th pump.
5. Person at the calliper opens the bleed nipple & the person at pedal informs once pedal hits ground. Using a clear tube & plastic bottle to catch fluid. (I think it was actually a one-man bleed kit that was in the garage, with a one way valve at the end of tube too)
6. Bleed nipple is locked & then person at the pedal releases pedal.
7. This was repeated a number of times on each wheel.
8. A different colour brake fluid was used to ensure that all old fluid was gone from system.
9. For the final bleed on each wheel the bleed nipple the nipple was locked half way down the pedal travel.
10. The pedal feels perfect during normal driving I should add, "head through the window" brakes!

I also changed the front pads at the same time so this may be affecting pedal feel too. Car is a 2002 BMW 525i. Used DOT 4 fluid, OEM pads.

Everything does seem fine really but I'm just wondering if any of you use different methods.
I've read in in some Tech manuals that technically you are meant to hook up the car to a diagnostic/servicing machine to "open" ABS unit while bleeding. Does anyone on here have experience with this?

Henry Ford III

Pads will need a bit of time to bed in. Avoid harsh use.

If there's air in the system it should be pretty obvious. Is the pedal firm with the engine running (and servo assistance working)?

I'd recommend using an Easybleed gadget. Worked perfectly for me. 1 man operation.

One issue in your method: Pushing the pedal to the floor several times can damage seals in the master cylinder as the piston moves beyond it's normal travel and the seals can be torn by tiny ridges which may have formed over time. If this happens air will get into the system, and a new m/c or a rebuild will be needed.

rebel.ranter

Henry Ford III wrote: »

One issue in your method: Pushing the pedal to the floor several times can damage seals in the master cylinder as the piston moves beyond it's normal travel and the seals can be torn by tiny ridges which may have formed over time. If this happens air will get into the system, and a new m/c or a rebuild will be needed.

I was thinking about that too in relation to piston travel, but I have heard that any of those one-man kits are rubbish. I've also heard that rebuilds are a waste of time & new is the only way to go.
The pedal is hard with engine off, when I hit brakes during driving they are also hard, it is just while idling that the pedal sinks a bit. May be I am just over thinking this. The servo assist is definitely kicking in, the brakes are working well in normal use.
I was going to let the pads bed in for a few days, should have just done one job at a time.

Henry Ford III

The gadget I mentioned above was recommended to me by a friend in the trade. It works well. I did a fluid change using it.

Last time out I bought a new m/c too. Brakes are worth spending a few € on after all.