VW T4 Forum - VW T5 Forum banner

1 - 20 of 35 Posts

·
Registered
Joined
·
24 Posts
Discussion Starter #1
Hi

I have an issue where, with the van running (hence with Servo operational) it won't hold a solid brake pedal. It slowly drops to nearly the floor. When you are driving you can't notice it, but if stationary and you hold the brake pedal on hard, it drops.

I have had front pads and discs changed, and also the master cylinder (new) but it is still as bad. The garage changed the master cylinder as clamping the front flexes made it hold a pedal and clamping the rears made no difference.

Any ideas?

there's no ticking from vac pump and no leaks on the brake pipes or bulges on flexes.

Was thinking it could be the load sensor on the rear now, as can't think of anything else, unless you guys think it could be the servo?

It's a 53 plate 2.5 AJT T4

many thanks on any ideas, as me and the garage are at a loss at the moment, and I'm already down over £450 . :*

Cheers T:
 

·
Registered
Joined
·
117 Posts
If you drive down the road at 50-60 mph and slam on the anchors and it stops, bingo, you've nothing to worry about if however you don't stop and the pedal crashes into the floor before you crash into anything then you have a problem! (state the obvious I know lol) but do take into consideration that being a diesel the vacumn pump is running constantly and can have this effect on your brake pedal. Also bear in mind that the pedal always feels a bit weird after brake linings have been replaced while they are bedding in. If you are in doubt, bleed the brakes out just in case.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #3
Its been bled to replace the master cylinder, so that's not the issue. It's not that it's soft or spongy, it sinks slowly as if leaking pressure.

Any other idea's anyone?
 

·
Super Moderator
Joined
·
5,165 Posts
I have just failed an mot with this exact problem! Been in the garage for a week, no leaks anywhere n the system, when the engine is of if you pump brake it would go firm and hold its position how ever the moment you start the engine your foot would slowly sink to the floor. As a result the garage said it wasn't the master cylinder and got a second opinion and it was said to be the servo. Forked out £246 for a new one from euro car parts and fitted it and it made no difference. :mad: pulled the vacuum pipe off to check for cracks and to check the non return valve and all was fine. Re attached vacuum pipe to the vacuum pump and placed my thumb on the other end and it was sucking as it should. Went for a drive and brakes felt ok and functioned as it should when performing an emergency stop. Took it back today and said to them it made no difference. They re bled the brake system again and said there was slight improvement. Mot tester took it out for a drive and retested, they said the pedal still sinks but brakes perform as they should when driving. Sorry I know this isn't much help but others had told me theirs do the same
 

·
Registered
Joined
·
24 Posts
Discussion Starter #5
Yep, sound same as mine.
We were thinking load sensor valve next bit I'm not convinced. Anyone else got any ideas?
Seems a really strange on this
 

·
Premium Member
Joined
·
2,481 Posts
Normally bleeding or master cylinder. Try clamping all the rubber hoses, 2 front & 1 rear and then release each 1 until you get the symptoms. Pressure bleeding can sometimes clear it.
 

·
Registered
Joined
·
2,661 Posts
I replaced calipers on my daughters Citroen C5 and had a similar issue. I ended up taking into garage and getting pressure bled!!! Seems at least on the C5 that you can get air into the AntiLockBracking dodah which is hard to get out, end result is functional but soft/sinking pedal action and occasional pedal straight to the floor (no resistance and not a repeatable feature) . Anyway "pressure bleeding" sorted it. When initially asking around I was also told that C5's need jacking up very high at one end to bleed the brakes successfully.

For me, Brake pedals are not meant to sink so there is something wrong somewhere. Yes it might stop in time today but what about tomorrow, could you forgive yourself if the worst happened? Personally I wouldn't drive it until sorted.:no

Best wishes with getting it sorted.
 

·
Registered
Joined
·
2,661 Posts
Just reread your opening post
The garage changed the master cylinder as clamping the front flexes made it hold a pedal and clamping the rears made no difference.
That says the cause of the fault was after the clamps so why on earth did they change the master cylinder. :confused:
 

·
Registered
Joined
·
353 Posts
Just reread your opening post

That says the cause of the fault was after the clamps so why on earth did they change the master cylinder. :confused:
I was thinking that immediately I saw it!! As regards the sinking pedal, i would definitely try pressure bleed. Gunsons do a kit for about £30 if i remember correctly and it seems odd to push fluid through the system with air :* to remove air bubbles, but it does work. The only way I could get a decent pedal on my wifes Micra.
 

·
Registered
Joined
·
24 Posts
Discussion Starter #10
Mmm, food for thought, thanks for the replies. I will double check that clamping the fronts stops the problem myself. If so, it has to be front flexi's or calipers I guess
 

·
Registered
Joined
·
112 Posts
get someone to hold the pressure on the pedal and check the brake flexi hoses for bulging, if the hoses are starting to break up inside they can start ballooning under the rubber.
 

·
Registered
Joined
·
335 Posts
It happens to pretty much every t4, mine included, mine was gonna fail mot for it untill i showed the tester all the posts about it happening on various van forums, then he passsed it !
 

·
Premium Member
Joined
·
2,509 Posts
I've had this after changing a hissing servo & master cylinder - faffed about for ages bleeding the brakes, then bit the bullet & bought a Sealey pressure bleeder (with pump & reservoir) for about £50; 5 mins & 2 litres of dot4 later, the pedal was rock solid :ILU:

ps. you should have seen the state of the fluid & amount of trapped air that finally came out of the rears, you need the full 2 litres to change the lot ( including the clutch, that shares the fluid ) :cool:
 

·
Registered
Joined
·
531 Posts
Pressurized bleed kits are Awesome=, I have the Gunson Eazi-bleed kit with reservoir
about £30 from what I remember, they also Get tons of Crud out the system.

Only easy way to bleed the brakes these days!!
 

·
Registered
Joined
·
24 Posts
Discussion Starter #15
Just had a master technician at a VW commercial dealer look at it, and he has confirmed it is fine, and that its a 'feature' of the T4's. Apparently their was a tech bulletin about it in the early days of T4's as so many people were returning them complaining about the issue. So basically its fine!T:

Dealer (Imperial Derby) was great, didn't even charge me :ILU:
 

·
Premium Member
Joined
·
2,509 Posts
Just had a master technician at a VW commercial dealer look at it, and he has confirmed it is fine, and that its a 'feature' of the T4's. Apparently their was a tech bulletin about it in the early days of T4's as so many people were returning them complaining about the issue. So basically its fine!T:

Dealer (Imperial Derby) was great, didn't even charge me :ILU:
That's funny coz mine aint like it & neither was my last T4....:*
 

·
Registered
Joined
·
265 Posts
I have a strange variant of this.

If I step hard on the brakepedal - no problem.

If I push very lightly on the brakepedal, it will travel all the way to the floor.

ANy ideas on what that could be?
 

·
Registered
Joined
·
3,836 Posts
according to the bentley/brooklands transporter manual you test the servo is working like this, you pump pedal with engine off, it should be nice and firm then hold the pedal down and start the van if servo works correctly the pedal should drop slowly. simples.
 
1 - 20 of 35 Posts
Top