Need a little help with the brakes on my 1.6td

[Robb]

I have been having a couple of problems with the brakes on my 1.6td Golf MK2, basically when coming to an almost stop the pedal will go really light and almost hit the floor, I can also be sat at a set of lights and suddenly the car will begin to creep forward despite my foot nothing moving.

I have had all the brake lines and such replaced and bled, however the problem still pesists.

I am led to believe it is probably something to do with the vacuum side of the brake system, I have noticed there is oil leaking from the vacuum pump on the engine, is this likely to be the cause? If so what can I do to try and solve the problem.

I have had a good look at the vacuum hose and there is no leaking in that I am aware of.

Any help anyone can give me please let me know I really want to get this one sorted and Im not happy having a braking system that is not working 100%

Thank You

[toywagen]

If your pedal goes to the floor at any time, and you have no external leaks or air in the system, it's most likely your master cylinder. Vacuum booster trouble won't cause master to not seal and pump fluid if that makes sense. Many VWs had no booster at one time. Good luck and maybe don't drive it until it's sorted.

[Robb]

No pedal never goes to the floor, just goes light and looses its pressure sort of thing if you know know I mean.

As in It will go solid whilst sat still at the lights and very slowly begin to go lower and lower, however lifting off the brakes and reapplying my foot solves the problem.

I am driving the car as little as possible at the moment due to the fault, for actual road driving it doesnt seem to be making any difference, its just at very slow almost stopping speeds it causes a problem.

Thanks again

[the caveman]

How are the pads/shoes? Are the rears adjusting properly.They are self adjusting, but if the springs and hardware are worn, they may not adjusting by themselves anymore.

[Robb]

Brand New brakes and hoses all round including new rear drums complete with new cables, I wanted to make sure my brakes are tip top anyway so had all these done and making sure there was no fluid leaks, but the problem still persists so now looking at what it could be.

Thanks

[Robb]

What would the symptoms be of a vacuum leak? different to my own?

Thanks

[Quantum TD]

Sounds like a master cylinder leak into the booster. Are you losing fluid and can't see where?

I've been seeing this alot lately on MK1 and MK2 cars. As they get older, the MC leaks into the booster. It may leak an imperceptible amount, but eventually, your booster if full to the brim with fluid and you end up replacing both the booster and the MC.

Either way, I'd plan on replacing the MC. When it's off, take a peek inside the booster. If there's juice in there, you can forget about saving it. Replace it and rebleed the whole car.

Bleed in this sequence:
Right rear
Left rear
Right front
Left front

Basically, you want to bleed the cylinder/caliper that is furthest from the MC, and work closer to the MC.

[Robb]

Ok I will go about getting a new MC and replacing that anyway as they are not too expensive and worth replacing even if it isnt the cause.

However I have no idea where I can get a booster from in the UK?

The 1.6td engine is quite rare over here and parts are extremely hard to come by, is the same unit used on any other engines?

[Mark(The Miser)UK]

 Robb, stick your rough location in your identity blurb.

Do you have one of those Gunsens type vaccuum/pressure gauges. If so stick it into trhe vaccuum line. This will check for leaks on your power assist side.

Air in the hydraulic lines will make the pedal spongy, not drop.  It may well be your master cylinder rubber seals slightly scored. If pedal sinks but then stops, say half way, I'd guess it is on the vaccuum side where the trouble lies.
If by booster, you mean the vaccuum pump, then the non diaphragm type, which looks like a cylinder with a vaccuum line out the top, are easily serviced. Just clean the gauze and the vane slots. Ensure the 'o' ring is not split.


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Either way, get a gauge though, which can also double up as a turbo bioost/ airfilter blockage gauge.

[bajacalal]

If your brake pedal "bleeds down" i.e. you slowly lose braking ability while you hold your foot on the brake, your master cylinder is bad. It sounds like this is happening to you.

They mostly fail in 2 ways- either fluid leaks out the master cylinder or an internal bypass develops where fluid leaks between the different sections of the master cylinder but does not leak externally.

If you loose your vacuum assist, the brake pedal will get hard, not easier to push, like when you shut off the car.

[Robb]

Hey mark im in kendal cumaria, will update my profile later.

From what you all describe it sounds more like my MC than anything, me and my foreman are going to replace it next week.

As for the vacuum i will take a picture and upload it, i do havea boost gauge knocking about, how do i go about testing it? Just apply the brakes with the engine running and check for pressure?

Thank you

[Mark(The Miser)UK]

The boost gauge has to have the vaccuum side to it, because that is what you are measuring. It should pull 25+ inches at idle. It should hold when engine off, for hours. It should drop a few inches everytime you depress the brake, but replenish within a second.
A trick with the master cylinder seals, and slave seals for that matter, is to bind string underneath them to thrust them harder against the cylinder walls. This can tide you over if replacments are slow to arrive

EDIT:
The offtakes:


Have I detected that your pump is the grotty thing on the LHS

[Merffy]

  Replace the MC, mine did the same thing, last week I replaced it & it solved the peddle fade,   

[Robb]

Well the Master Cylinder is all set to be replaced next week, however just for information and help this is my vacuum:



As you can see there seems to be quite a bit of oil coming from it? Anything to worry about?

[dennis]

No vacuum on a diesel will result in a very hard pedal. Your master cylinder is bad. It is always better to bleed the hydraulics with a vacuum source as pumping the brakes on an old master cylinder will force the internal seals into a rusty portion of the cylinder thereby cutting them and causing the master cylinder to fail. Always a good ideal to change brake fluid every 2 years because it absorbs moisture.

just my two cents
Dennis