Club 80-90 Forums

Hi, our van has an odd brake issue. We aren't losing fluid and the discs, pads, shoes and drums are good. Also all the brake lines were replaced a year ago. Handbrake is good.

The symptoms are:

With the engine running, rapid repeated brake applications results in a hard pedal after second press.
First brake application is good and feels normal. But second and subsequent applications feel like your pressing directly on the brakes with no servo assistance. You then struggle to stop in a reasonable distance!

I suspect the servo is knackered? What do you think?

Could it be the master cylinder?

I'd be tempted to bleed lines first as its a cheap-ish solution if the problem vanishes as a result. After all, if you replaced master, you'd have to bleed it all anyway. Wilco seem to sell brake fluid at reasonable cost if you only need to purge and topup.

The one way valve in the servo vacuum hose (left hand side of inlet manifold, assuming WBX there) not working as it should?

Thanks chaps. I'll have a further look next week when I'm on leave.

It's the AFN 1.9Tdi not the WBX...

Interesting... I have a similar but opposite issue: While generally the brakes are fine for 'normal' driving, when requiring a more sudden stop they just don't come up to par... until the second pump of the pedal then they're great!

The brakes are SO much more positive and sure footed on the second (immediate) pump every time - I've rulled out leaky pipes as the fluid is still fine and the pedal pressure remains firm for as long as I hold the pedal ie it doesn't slowly sink to the floor.

'89 2.1 MV WBX Auto

Sorry for jumping in on the topic for my first post!
Thanks

c7

vacuum pump perhaps?

Thanks for the quick reply - I might be being stupid but I can't find any reference to vacuum pumps other than for diesels... am I missing something?

chris7ian wrote:Thanks for the quick reply - I might be being stupid but I can't find any reference to vacuum pumps other than for diesels... am I missing something?

Chris....he was replying to the OP....your issue is rear drum brake adjustment on the shoes. The clearance between the shoes and drum is too large which typically leads to longer 'initial' foot pedal movement, higher with a second 'quick' application. Although, a very small amount of air in the system can have a similar effect, however the brakes would generally feel on the 'spongy side'.
When driving, pull your handbrake up just before it starts to work, now try the foot brake....if it gives a good high foot pedal on the first application this would back up the theory of excessive shoe to drum clearance.

As for the OP: I agree, mechanical vacuum pump issue, or perhaps a leak somewhere in the vacuum pipe, however, with the engine turned off, have you got two pumps before the pedal goes hard? This is the normal test for the servo/one way valve.

In my experience, T25's don't have bags of vacuum reserve and it seems pretty normal to exhaust the vacuum on the third pump, although I guess this may vary...The pedal going hard on the second pump does sound like an issue.

Martin

To the OP, I had a similar issue, not on my van but on my now deceased Sharan. The problem was a cracked vacuum line, so it was able to hold enough vacuum while driving for just one initial application of the brakes. If you then eased off the brakes and took another bite at it, you were done for. I still come out in a sweat when I remember trying to stop family laden Sharan plus 1750kg caravan with no vacuum assistance. It's a wonder I didn't push the seat back off and rip the steering wheel off too!

But there my help for you ends, I don't know where the VAC lines are on the van. Someone else will know though. On the Sharan (1.9TDI) it was a hard plastic pipe tucked at the back right of the engine. Is that the same engine as on your camper? I found it with help from the vwaudi forum, which had loads of help for knackered Sharan.

chris7ian wrote:Thanks for the quick reply - I might be being stupid but I can't find any reference to vacuum pumps other than for diesels... am I missing something?

He he, thats what happens when you hijack somebodies thread:D

Here...http://www.vwaudiforum.co.uk/forum/show ... ake+vacuum" onclick="window.open(this.href);return false;

Thanks California Dreamin' and Itchy feet

Sorry chaps, should have closed this page with the answer: there was a vacuum leak caused by a perished blank in a vacuum pipe.