Apologies for the lack of response but I have been camping with the kids...
I will have a look for any signs of shredded rubber flecks in the oil and try to see if I can see any difference in the levels when I push the pedal with the engine running. BMW are saying two things at present:
- Their technician believes I should try replacing the pressure vessel, valve and seal. However, this is a lot of money to buy and I am not convinced this is the problem; I did not have the issue before replacing all the parts listed above and the pressure vessel etc are untouched.
- If I want to return the MC for a warranty swap / refund, I have to take the car to BMW who will then check to confirm if this is the issue. However, I somehow have to get the car to them, which with no MOT, Tax or brakes will mean I have to hire a company to ship the car, and if BMW decide that it is not the MC, I have to pay for the test (2h main dealer labour rates = about £300).
This leaves me a bit screwed. I could buy another MC, swap out and bleed the system. If the problem persists I know it is unlikely to be the MC. If the problem clears then I know that the BMW MC is at fault but I still have to prove to BMW that this is the case. Either way I will have bought a second new MC at a cost of around £275 and a couple of hours labour and I am very unlikely to get any refund.
I can't even use the old MC as it has the outlet pipes on the other side to the new BMW MC (and the picture shown in RealOEM) so must have been the wrong MC. I reformed the existing pipes to reach around the other side and connect to the new MC but I don't want to bend them back to test the old MC and then back again to fit the corect MC after the test (for obvious metal fatigue reasons...).
I will talk again to BMW to see if there is a way around this but at this time it looks like I will have to buy another MC just to test and then write off the cost and time, whatever the outcome. The car's previous owner has said he has a second hand pressure vessel and valve so I have asked what he wants for them. I could at least try that first, just to see if the BMW techs guesswork is correct...
NigelC wrote: ↑
Tue Aug 28, 2018 9:39 pm
I researched air trapped in abs units on the internet and the difficulties sometimes removing it.Big dealerships have specialist test gear ( about £4k !) which can cycle the pump and abs valves to purge the air.This got me thinking, so I studied the ETM and traced the circuits.I detached the plug and made a simple switchbox to activate the pump and valves, I then rebleed the brakes using pressure [email protected]
10 psi + pedal pumping.A lot of air came out and now pedal is at top of stroke and servo only takes it down half way. Is master cylinder faulty-I am not certain.
I am very interested in your solution for cycling the ABS pumps, please can you say what wires or pins in the plug you used and what switched where? I would like to try that. However, I am a little concerned about your quote:
NigelC wrote: ↑
Fri Aug 31, 2018 5:41 pm
After my abs purge it was interesting that the pedal came right up to the top and the brakes felt really good on the road but partial sinking does still occur. It takes a long time to sink (about 30 secs. ) using a lot of foot pressure + the 4.5 x boost and I do wonder If I am
causing the sinkage with too much effort applied.
I have tried a number of cars with ABS and Servo assist yesterday / today, some old and some fairly new. None of them have a sinking pedal with or without the engine running, no matter how hard I push and I am pretty much certain I did not have this issue before the brake system renewal. If the pedal still sinks on yours, albeit rather slowly, then there must still be an issue somewhere...?