Hello everyone, I hope you’re all well? 

This is my first post here but I’ve been reading for a while.  I’ve got a 2011, 140bhp 4x4 diesel yeti. When I first got it I drive back from York to sheffield and the brakes were awesome. I went out for a drive in the peaks that evening and I pulled over in a gravelly lay-by and then the abs cut in and the car stopped the pedal wend virtually down to the floor. For the 8 mile drive home the brakes were rubbish with hardly any pedal! The next day they had come back mostly but not as good as the day before. A couple of weeks later I had the cam belt done and I asked the garage to check the brakes and they said they were fine. Over the last few months they have got worse and worse to the point now where I have to pump to get them to work!  I noticed in the snow that after setting off if the traction control kicks in the brakes pedal gets instantly worse!  There’s no fluid loss. A friend put it on a computer yesterday and run the brake system but there are no faults at all. He says it’s more than likely the abs module but I thought before I shelled out for one of those I’d check here to see if anyone had come across this and had any ideas?

Thank you for any help

Edited 18 January, 20224 yr by ColinD
Formatting of text colour

Just a thought; have you had the brake fluid checked for moisture and general condition?

I had a similar issue on my VW Golf once. Brake Fluid was leaking through the master brake cylinder (? the one the Brake Pedal is connected to), so I had to pump the brake pedal to get any serious braking. Replacing that cylinder fixed the issue so it might be worth examining your one.

How often in the past 10 years has the brake fluid been changed and when was the last time changed or checked for H2O?   When the garage said the brakes were OK had they checked the fluid?

Check the stiff vacuum pipe from the brake reservoir going back to the vacuum pump, check carefully for splits in the pipework at the points there is a join, at the reservoir,at the pump and in between any valves and branches. The  hard plastic VAG uses, goes brittle over time and spilts at the connection joints allowing air to be drawn in and so lose full vacuum and reserve braking assistance. Ultimately you risk losing all braking assistance so this is a vital safety inspection that should be carried out regularly.

I've had similar issues on a Roomster. So some tests:
 1) With the engine off if you push the brake down once hard and release, then repush hard - it should be hard with the pedal stuck high up and no creep downwards with sustained hard pressure. 

 2) Keeping the pressure on the pedal then start the engine. The pedal should drop down a little and then still remain firm.

My Roomster on test 2) the pedal almost went to the floor. It was due to air in the ABS and I had to do the ABS bleed procedure with VCDS. After bleeding the ABS all was perfect, note a normal brake bleed would not of cleared the ABS of air on that model. I'm unsure if the Yeti ABS unit has a similar procedure or it will air bleed using a normal pressure bleeder.

Out of interest I just looked at the Yeti service manual and it states to prebleed the ABS you open both nipples together and OBD do Basic Settings once done. The instructions say :

A pre-pressure of 0.2 MPa (2 bar) is required to bleed the brake system.

– Unscrew cap -1- from the brake fluid reservoir

– Connect the thread plug -1- of the brake filling and bleeding device e.g. -VAS 5234- to the brake fluid reservoir.

– Provide a suitable catch pan for used brake fluid.

1. Bleed the front left and front right brake calipers at the same time.

2. Bleed the rear left and rear right brake calipers/cylinders at the same time.

– Allow brake fluid to drain until even the smallest air bubbles have escaped.

– Initiate basic setting ⇒ Vehicle diagnostic tester.

– Then perform normal bleeding

Edited 18 January, 20224 yr by aubrey