Brake failure after changing pads

[yeoblade]

So after putting new front a pads in my Vivaro Van, 2012, they don't work.

There is a loud hissing inside the cab when pedal is pressed , engine on, and pedal will slowly drop to the floor.
(ABS is fitted)
Engine off and the pedal stays firm OK.
Just wondered what I have messed up, having changed pads many times before on vauxhall, nissan , Porche, .... never had an issue before.
Must be the servo hissing but what do I do to fix it?
ALL was absolutely fine BEFORE I worked on it.
Yes I did push the pistons back in without opening any bleed valve etc.

Edited by yeoblade on Sunday 18th December 18:38

[yeoblade]

Bdevo3 said:

Sounds like you've twisted the seals in the brake master cylinder. Probably forgot to open the cap on the reservoir

Ok thanks for that posibility, but I did loosen the cap prior to any work, fluid level was never low, efore or after work.

[yeoblade]

[quote=Ian Geary]Evening,

The law of sod says it's probably something you've done, or disturbed. I once caused poor braking by fitted new pads to lipped discs, but that's not relevant here.

I would recommend going back to the principles.

A servo is a vacumn,................/snip

Thanks Ian,any ideas are appreciated, as I didn't touch the servo at all I couldn't have damaged it, well externally anyway.
I have heard, now, that often people clamp the brake hose and open bleed valve before pushing pistons back in to avoid any reverse pressure messing things up . I'll do that next time. But as it's my work van I need to fix this now.

[yeoblade]

kev b said:

Have you driven it yet? If not then give it a short run if safe to do so, using the hand brake to slow, sometimes the abs plays up until the wheels have rotated a few times.

Yes, took it round the block, no improvement.

It don't think it can be losing fluid as pedal is working fine, (as normal)can't see any leaks and level in res is OK. It all goes wrong when I start the engine.

As has been said above I'm leaning towards master cylinder seals, as I pushed the fluid back up that way. Though I don't understand how this would make the servo hiss when brakes are applied, can any one explain that.

[yeoblade]

shake n bake said:

It's worth pointing out this generation of Trafic van have an adjustive servo (or called something similar)
We get an occasional customer who is concerned that the pedal goes to the floor if you keep your foot on the pedal. Don't assume the hissing sound is a fault as they always make this sound when you press/hold the pedal down.
Are you sure the pads are located correctly, locator pins in correctly ect?

Ah didn't know that, yes I had noticed that prior to me working on it, pedal slowly sinks to floor, and did wonder why.!
I have had the van from new and this is the first change of pads.

Definitely hissing really loudly now. After I had changed one side I had to turn the van around to get to the other side and immediately noticed the noise and V poor brakes.

I will check they're fitted correctly tomorrow.

Having done this job numerous times on various cars I'm really peed off this time

[yeoblade]

E30M3SE said:

Are you sure the pads are fitted correctly?



On a serious not are you sure the pads don't just need to bed in and you are not just experiencing 'diesel creep' given that the pedal pumps up and remains firm with the engine off and there are no fluid leaks. I'm assuming your Vivaro is a diesel?

Yeap,
Those in your pic look the same as the ones on my Boxster, I fitted yellowstuff. And had NO problems

[yeoblade]

Josho said:

So are there any brakes?

I had similar on a Crafter last month. Caliper slider was seized so the pistols were going back between each brake pedal press.

Yes brakes work, but pedal falls slowly to the floor with loud hissing.

I didn't strip the caliper slider mec. as they were sliding quite freely and it all felt good.

[yeoblade]

Got out this morning and took off the first side I did and took out pads, not sure that they were in straight or not,but all back together and

Working OK now

I did notice the hissing in the cab still but of course when they're working OK there is less pedal travel and noise.

thanks for all the help / suggestions, must check my work better next time . Doh