New brakes feel off - air i lines or master cylinder issue?

[Scotti8]

I have a 2021 T6.1
6 Days ago I had all 4 pads replaced as an alert came up on my dash. Prior to this the brakes were super sensitive and I could emergency stop with just a short press on the pedal.

After the change they were super spongy for 2 days. The garage said they just needed to bed in. I thought they were too spongy but said I would see what its like in a couple more days.

Today (day 6, 200 miles later) this is what the brakes are like:
- "hissing" noise when I press the pedal louder than it was before
- have to press the pedal about twice as far or more for the same stopping power
- when the engine is off and I press the pedal repeatedly it hardens (which I would expect)
- when the engine is ON and I press the pedal repeatedly it hardens, if I then keep my foot on the pedal it slowly depresses.

I took it back to the garage today and they test drove it and put in on a rolling brake test. They said the front brakes were off the scales and the back were at 400 (whatever that means).

They said the softer response will be due to them being brembo pads, they are chamfered and will slowly get stronger, that they are coated for anti corrosion and that will wear off, and that the fact they were so responsive before will be because the chamfering had worn flat.

They insisted there wasn't a master cylinder issue or air in the lines. They said they didn't even open the lines up (should they have replaced the brake fluid for a full brake change?)

Should I be concerned that the master cylinder may be shot at and the brakes may fail? Is it just air? Am I completely wrong and they sound OK? Should I take it to a second garage and have the master cylinder checked and the fluid replaced?

Thanks in advance!

 

[Bigsidavies]

There's no need to touch the brake fluid during a pad change. Have you bedded the pads in properly? Driving up to speed then braking progressively until nearly stopped. Then repeat about 15 times then allow to cool..

 

[Dundee_Kev]

Were new discs fitted at the same time? If not, it may well still be bedding in. The hissing sounds normal, as does the sinking pedal.

When you evacuate the servo vacuum with the engine off, what is the play like then? If there is very little, then I doubt there is air in the system. If they haven't opened the hydraulic side of things up, then I see no reason for air getting in.

Only other thing could be the pad carriers haven't been cleaned properly and the pads are sticking, forcing them to bend to apply the brake. This is very much doubt on the age of van though

 

[Scotti8]

There's no need to touch the brake fluid during a pad change. Have you bedded the pads in properly? Driving up to speed then braking progressively until nearly stopped. Then repeat about 15 times then allow to cool..

I did, I drove about 5 miles the first day. Then about 20 the next. And about 50 yesterday. In total its been about 200 miles and 6 days

 

[Scotti8]

Were new discs fitted at the same time? If not, it may well still be bedding in. The hissing sounds normal, as does the sinking pedal.

When you evacuate the servo vacuum with the engine off, what is the play like then? If there is very little, then I doubt there is air in the system. If they haven't opened the hydraulic side of things up, then I see no reason for air getting in.

Only other thing could be the pad carriers haven't been cleaned properly and the pads are sticking, forcing them to bend to apply the brake. This is very much doubt on the age of van though

No new disk, no. When the engine is off, after multiples presses the pedal does goes hard, and stays hard with little play.

Is it not unusual for the pedal to harden up tho when the engine is running?

 

[Dundee_Kev]

No new disk, no. When the engine is off, after multiples presses the pedal does goes hard, and stays hard with little play.

Is it not unusual for the pedal to harden up tho when the engine is running?

No, not unusual if you are pumping the pedal quickly. If you bring the revs up and try it, it may help keep the vacuum there better as the pump is running faster.

It's not normal behaviour to sit pumping the brake at idle speed, so I wouldn't worry.about it going hard like that. Now if it's doing it during normal braking conditions, then yes you do have an issue

 

[Dellmassive]

new pads can take up to 100miles to bed in depending on the driving conditions.

 

[NickW]

I have a 2021 T6.1
6 Days ago I had all 4 pads replaced as an alert came up on my dash. Prior to this the brakes were super sensitive and I could emergency stop with just a short press on the pedal.

After the change they were super spongy for 2 days. The garage said they just needed to bed in. I thought they were too spongy but said I would see what its like in a couple more days.

Today (day 6, 200 miles later) this is what the brakes are like:
- "hissing" noise when I press the pedal louder than it was before
- have to press the pedal about twice as far or more for the same stopping power
- when the engine is off and I press the pedal repeatedly it hardens (which I would expect)
- when the engine is ON and I press the pedal repeatedly it hardens, if I then keep my foot on the pedal it slowly depresses.

I took it back to the garage today and they test drove it and put in on a rolling brake test. They said the front brakes were off the scales and the back were at 400 (whatever that means).

They said the softer response will be due to them being brembo pads, they are chamfered and will slowly get stronger, that they are coated for anti corrosion and that will wear off, and that the fact they were so responsive before will be because the chamfering had worn flat.

They insisted there wasn't a master cylinder issue or air in the lines. They said they didn't even open the lines up (should they have replaced the brake fluid for a full brake change?)

Should I be concerned that the master cylinder may be shot at and the brakes may fail? Is it just air? Am I completely wrong and they sound OK? Should I take it to a second garage and have the master cylinder checked and the fluid replaced?

Thanks in advance!

Did you resolve this what was the resolution?