Yeti Owners Club banner
1 - 20 of 23 Posts

·
Registered
Joined
·
71 Posts
Discussion Starter · #1 ·
Just before my last inspection I replaced all four disks and pads, and it passed easily. The brakes work very well indeed, very quick and evenly, but I noticed after the inspection that the pedal would slooowly go all the way to the floor if I kept full pressure on it, (only with the engine running). My suspicion was the master cylinder, which I have replaced (can't fix them any more :-( ) and bled the brake lines multiple times (new fluid), but it is still soft. Also done a number of ABS stops as was sugested. So before I start replacing all the rubber parts in the calipers, I thought I would see if any of you guys have any ideas or suggestions.
At least I don't have the fuel temperature sensor telling me the fuel is -40°C any more ;-)
Thanks...
 

·
Registered
Joined
·
450 Posts
the pedal would slooowly go all the way to the floor if I kept full pressure on it, (only with the engine running)
I would suspect a problem with the brake servo if the pedal goes to the floor with the engine running, but does not go to the floor with the engine stopped.
 

·
Registered
Joined
·
450 Posts
Another possibility is an air lock in the ABS pump, which may need VCDS to bleed it properly.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #4 ·
I tend to agree with the ABS idea, the more I read up on it. I have VCDS, but I don't have a pump/filling thingie to get the pressure to the required 1 bar. I do have a small compressor though that can be adjusted to 1 bar. Would just need an adapter for the reservoir, ... might be able to make one if I can find a cap that fits. Hmmm.... have to think about that. Thanks!
 

·
Premium Member
Yeti S+ 2010 2.0TDi CR110 2WD Manual
Joined
·
7,039 Posts
Danlicks,

In UK, Screwfix (and other online retailers) sell a kit called "Eezibleed", made by a company called "Gunsons". That contains all the parts needed to do a pressurised brake fluid bleed. Kit costs £20-£25, depending what discounts apply on the day.

The kit includes adapters fit a range of common master reservoir caps. To provide the pressure, you can use either a spare wheel, or even one of the car's road wheels, adjusted to the right pressure.

As here:

When not using a pressure system to bleed the brakes, but using the traditional method (with an assistant to push and release the pedal while you control the bleed nipples at the wheel end), it is not unknown to find difficulty in getting any trapped air bubbles out of the hydraulic system. Especially on ABS equipped vehicles.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #6 ·
I have been looking into just that system. Problem is, after Brexit, it is much more expensive to order things from the UK. From Germany it runs about €45, so still cheaper from the UK. In the long run, it would be good to have something like that.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #8 ·


My home made bleeder jobbie.... Bled the clutch and the brakes again (twice), works a treat, but the pedal still sinks slowly to the floor. I will try to bleed the ABS system tomorrow when I will have someone here to push the pedal. It is very strange. With the engine off the pedal is hard as a rock and I can push it till my leg falls off, but if I start the engine it is soft. Hopefully by this time tomorrow I will know more.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #9 ·
Well, so much for that... Did the whole ABS bleed... didn't see a single air bubble, then bled the brakes, again, no bubbles at all, and there is no difference in the pedal. Still goes slowly to the floor with the engine running. I can't believe that the brand new master cylinder is bad because the pedal is rock hard without the engine running. Will try one more time after lunch, but I fear this one is beyond me...
 

·
Registered
Joined
·
1,417 Posts
If the pedal is hard with the engine off, keep your foot on the pedal and start the engine. There should be some 'give' in the pedal as the servo adds its assistance to your foot pressure. The pedal should not sink slowly to the floor. Without evidence of a leak the pedal going to the floor says there is still air in the system and sometimes that's very difficult to remove.

You could try taking driving the car and doing a few hard stops - hard enough to make the ABS work. With luck that will move any remaining air along the system such that it will emerge at yet another round of bleeding.

Another last ditch effort would be to raise the front of the car when bleeding the front calipers and the rear when bleeding the rear ones. A bit of a PITA to do but . . . .
 

·
Registered
Joined
·
1,417 Posts
If the pedal is hard with the engine off, keep your foot on the pedal and start the engine.
Just been out in the Yeti so I tried this. On starting the engine the pedal went a fair way down but not to the floor. Are you sure your pedal actually reaches the floor?
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #12 ·
Yes, if I start the engine I can feel the assist kick in as it should. And yes, it just keeps going. No evidence of a leak anywhere. The fluid level stays constant. I will try the end raising trick.
My experience with air in the system is that the pedal feels too soft, but eventually reaches an end point. This one feels like in the old days when the master cylinder started to go, the pedal just keeps sinking steadily all the way to the floor, a little like the way it feels when bleeding the brakes the old fashioned way with the bleeder valve only slightly open.
Maybe the new cylinder (Stark) is bad, but then why would it feel hard without the engine running? Maybe if I pushed harder.... but I push as hard as I can, and it feels good.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #13 ·
Ran through the whole sequence again this afternoon, ABS and pressure bleeding. Not a bubble to be seen. But still not right.
 

·
Registered
Joined
·
450 Posts
Old school, before ABS, these symptoms would usually be cured by replacing the brake servo, as mentioned in post #2.
It's not a 5 minute job, though, so I don't blame you for exhausting all options with bleeding the ABS pump first.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #16 ·
Ah yes, and I have done a number of ABS stops with two wheels in the grass and the others on the road. Can hear and feel the ABS working as it should, and the brakes work really well!
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #17 ·
Wouldn't a leak in the vacuum hose result in the servo not assisting enough? Will check it in the morning.
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #18 ·
It FEELS like a leak, maybe a rubber part (hose) that is still tight enough that I can't force fluid through without the servo. Will have a good look. I haven't seen anything obviously "wet" while bleeding the brakes, but the hoses are a good ten years old now so maybe I have overlooked something.....
 

·
Registered
Joined
·
71 Posts
Discussion Starter · #20 ·
I think it would burst if it started ballooning. There is a LOT of pressure in those lines! The hoses all look good, no sigh of cracking or other damage. Checked everything.... dry as a bone. Then I filled the reservoir to the rim and started the engine. Pushed the pedal to the floor 15 times and then checked everything again. Dry everywhere, and the fluid level did not drop at all. Bled the whole system again, about 400ml each wheel. Not a single bubble.
The more I think about it the more I feel that the replacement master cylinder is buggy, and that I just can't push it hard enough without the servo to make it give. Must be some way to test it....
But the brakes work great! The ABS works as it should. I just don't like the was it gives.
 
1 - 20 of 23 Posts
Top