Help !! Cant get pressure to stay on brake pedal

[1536Z4]

Hi,

I have refurbed brake calipers and fitted braided brake lines . I pressure bled with an Eezibleed starting at the furthest caliper and finishing at drivers but I cant get the brake to hold pressure it still goes all the way to the floor unless you pump it a few times and then it goes to the floor again . I then tried the traditional method but still the same . I have gone round and checked all the connections and no leaks . With the brake fluid reservoir open but with the bleed nipples all closed and pushing the brake pedal down I can still hear the noise you get when one of the nipples is open I am supposed to be taking it somewhere tomorrow so is a bit urgent Any advice appreciated .

Thank you

[TheDan]

Couple of questions to try to help diagnose:

• Did you top up the reservoir to make sure it didn't drop below the minimum line during the bleeding?

• Have you had someone pressing the brake pedal as you check for leaks at all four corners and under the car (where the lines run and below master cylinder).

Based on what you said though, it sounds like you might have a leaking brake line or master cylinder.

[1536Z4]

Did you top up the reservoir to make sure it didn't drop below the minimum line during the bleeding?
Have you had someone pressing the brake pedal as you check for leaks at all four corners and under the car (where the lines run and below master cylinder).

Yes the reservoir was kept topped up all the time and checked for leaks whilst brake pedal was being pressed . I did have a small leak on one of the joins but that stopped after being tightened . The system was not drained as I used the clingfilm method .

I noticed that the reservoir has 2 exit points on it . Do you know what these are for ? Are they for draining or bleeding purposes .

Thanks

[TheDan]

I noticed that the reservoir has 2 exit points on it . Do you know what these are for ? Are they for draining or bleeding purposes .

I'll be honest, I don't I am afraid. As the reservoir doubles as the expansion tank any chance one is a pressure relief valve?

Hopefully someone will be along soon who is more expert in brakes than myself. Sorry!

[1536Z4]

Hopefully someone will be along soon who is more expert in brakes than myself. Sorry!

That`s ok I appreciate you trying to help . I have been doing some searching on tinternet and it seems it could be air in the ABS unit

[patriot66]

I recently did a full 3.0i brake transplant onto my 2.5i and bled/flushed the system using a new pressure brake bleeder I bought on Ebay for about £40. It keeps the Z4 brake reservoir pressurised with fresh brake fluid from its own reservoir, virtually eliminating any chance of air entering the system and therefore avoiding having to purge the ABS pump using INPA etc.
I used to have an old Gunson Eezibleed and this new one is a huge improvement

6.jpg (196.69 KiB) Viewed 758 times

7.jpg (175.68 KiB) Viewed 758 times

[enuff_zed]

A problem I have encountered before is within the master cylinder: admittedly, not on a Z4 though.
During normal usage the piston in the MC only moves a short way. Over time it builds up a thin ridge of 'varnish' at the end of that normal travel.
If you then bleed the brakes by pushing the pedal all the way down, the piston rides over that ridge and can damage the seal. Then when you pump the pedal the fluid simply moves from one side of the piston to the other. By pumping fast you can build up a bit of pressure, before the fluid then slowly seeps past again.
If there are no other signs of leaks and the fluid level is not dropping (and you are 100% certain no air remains) then maybe its the MC failing?

[1536Z4]

I used to have an old Gunson Eezibleed and this new one is a huge improvement

I think that may be a good investment as the eezibleed is a pain to seal .

Cheers

[1536Z4]

By pumping fast you can build up a bit of pressure, before the fluid then slowly seeps past again.

Thanks enuff_zed this was my reason for using the eezibleed but thought I would give the traditional way a go in desperation . I am hoping that as the problem was there before using the trad method its not the MC but will add it to my list to check . I am currently checking all the caliper seals .

Cheers

[Rockhopper]

You'll probably need to bleed the ABS pump and you'll need software to do that.

[Jakg]

You'll probably need to bleed the ABS pump and you'll need software to do that.

Alternatively you can just brake on a loose surface to open the valves a couple of times.

It sounds like you've done the right things - I had the same problem on a Golf before and the master cylinder needed bleeding - I'm not sure if the Z4 can be bled there?

[Haro]

The air is trapped in the abs pump, you need to active it to purge the air. Inpa or you could try driving it and braking hard to kick in the abs to try and move the air, then bleed it again.

[Rucky]

You obviously haver air in the system
There are two pipes out of the master as the brake system is split .
Cars have been this way for years either front to back or side to side ot now more usually diaginally so that if one brake fails you still have effective braking.

You can bleed as much as you like but I ended up having to plug into INPA and activate the ABS service bleed programme.
This runs the ABS pump for about 10-15 seconds each time allowing the ABS/DSC pump and valves to be bled also.

After that the brakes were perfect.

[pvr]

When I did this first on the E85, I did not realise that the reservoir is split between the clutch and the brake. I was keeping an eye on the wrong side and that did not move (as it was the clutch), but the brake one was empty, hence pumping air ...

[1536Z4]

What a great forum this is . Thank you to all of you for your comments and suggestions . I have stripped down all the calipers just to check I hadn`t put them together properly and they all seemed fine so bled the system again making sure reservoir kept topped up and again and again and again no leaks to be seen anywhere so it seems that I am going to invest in getting a decent pressure bleeder or vacuum and INPA as it will help with other problems I may get in the future .

Is INSTA the best option ?

Can anyone advise on the best place to get INPA and a cable .

I am running windows 10 64 bit on my laptop if that makes a difference .

Thanks again