Brake bleeding problems

[The_Laird]

I’ve had all my calipers refurbished at BCS, having had them removed and refitted by a local garage. But the garage is having trouble bleeding the brakes. Apparently, there is brake fluid at the calipers, but no pressure.

My usual garage (who didn’t want my car on a lift for days whilst the calipers were refurbished) have bled the brakes before with excellent results (my brakes had never been better). The garage that has the car just now is making noises about dirty brake fluid, ancient master cylinder and very high mileage, but I have no idea if any of this is valid.

Are there any key tips that might help get this sorted? All thoughts welcome as the car is due for a service and MOT on Monday.

Thanks, Jim

[steamship]

I wonder if when all the calipers were off, the brake fluid leaked out enough and there's now air in the ABS unit. Hopefully MJ will spot this and give you the definitive answer, as opposed to some thoughts.

Hope you get it sorted by MOT time Monday.

[Adrian E]

I presume they're following the correct procedure to bleed the ABS pump using VCDS.......

[The_Laird]

Is there a link to the correct procedure somewhere?

[MikkiJayne]

They are probably either trying to vacuum bleed it which simply won't work, or bleeding it with the pedal which is very high risk on a 20 year old car as any moisture or corrosion in the far travel of the master cylinder (inevitable in D2s which seem to mostly have brake fluid like seawater) will trash the seals when you press the pedal to the floor.

The solution is to pressure bleed it with 2 bar of pressure required to get through the ABS unit. You have to have a proper tool for this. Good luck to anyone trying to pull 2 bar of vacuum

Just changing the calipers doesn't need the ESP pump bleeding, but if they have let it run dry it'll need basic settings running on the pump to cycle the fluid through.

[Ronin]

There is a pdf with instructions here:

https://****************/viewtopic.php?t=17

MJ is right, doing it with a proper tool makes all the difference, the last time I had it done 2l of brake fluid was enough to flush through and bleed everything.

The tool looks like this:

https://www.ebay.co.uk/itm/223639876...Bk9SR4LxirSJYw

[The_Laird]

Thanks guys. They’ve managed to get it bled - apparently there was a lot of air in the system, which I don’t really understand as they’d used hose clamps at the wheels. Going to pick it up shortly.

[The_Laird]

Just in case, are the master cylinders still available? I think I might get one to put on the shelf

[steamship]

Originally Posted by The_Laird

Is there a link to the correct procedure somewhere?

They've already sorted it, but for future reference, it starts on page 161 of the following PDF:

Service Manual Brake System.pdf

Since you'll only be doing routine 2 year changes, use a pressure bleeder as MJ suggests, as it's a doddle and you don't have to worry about the ABS unit (just make sure there's enough fluid in the pressure bleeder).

Originally Posted by The_Laird

Just in case, are the master cylinders still available? I think I might get one to put on the shelf

Part number for the brake master cylinder is 4D0611021B. Audi Tradition don't have any, but Dean might be able to source an OEM one. As they say, other brands are available, but MJ can probably recommend particular ones to use.