lousy soft brakes, low power, low vacuum

My 2002 golf has really lousy brakes. I cannot make the abs kick in or skid on dry pavement. The pedal isn't firm, its the same with new or old pads and rotors, the fluid has been changed and bled, and there are no vacuum leaks.

I am also experiencing low power. Occasionally it will have a lot of power, but usually it feels pretty weak. The turbo actuator functions correctly, starting below 5 and stopping at about 15.

My vacuum is 23 on startup, if I tap the brakes it drops to about 15 and then very slowly creeps back up. It takes about a minute to get back to 23.

Is my vacuum pump bad? Or my N75? I have been searching a ton, but these symptoms are slightly different because I don't have the firm brake pedal issue.

How did you confirm you don't have vacuum leaks?

I used a mityvac. Vac seems better today than yesterday, but no change in brakes or power. Simplified system, just brakes,N75, turbo, inlet pipe, and reservoir.

Engine off:
actuator line - holds vac, actuates turbo
brake booster line - holds vac for days
reservoir line - slowly equalizes to atmosphere, takes about a minute

engine running:
after 5 min vac=26
tap brakes once vac=15
after 1 min vac =25

the plastic pipe between the pump and booster is known to crack, its sometimes hard to detect. Also the outlet of the pump becomes loose over time causing a leak.

You perhaps have two (or more) problems. A vacuum source leak would cause a hard pedal (no assist).

If the ABS was not bled with a scan tool, then it was not bled properly.

The next thing would be the condition of the calipers and slides. Any movement in the caliper when the brakes are applied will result in pedal travel. Too much movement will mean a low pedal. With disk brakes there should be very little visible movement at all in the caliper. As in, virtually nothing.

Thanks Oilhammer. I figured I probably had multiple issues. This car has been nothing but a series of complicated learning opportunities.

I will look up the ABS bleeding and take care of that.
The pedal isn't low and pumping it doesn't make any difference.

OK, you said the pedal isn't firm in your first post, but now you say it isn't low.

If it is not firm, it would be soft. If it was soft, then it would go low, yes?

Sorry, just trying to clarify here. If the pedal feels normal, and the car just has lousy stopping power, it may just be poor quality friction to rotor surface.

The ABS module needs to be bled in Basic Settings, then I always go through a couple Output Test runs to make certain all the air is pushed out of the unit... then bleed the brakes again.

How about a plain ole bad booster?

I wasn't very clear. The pedal engages at the right height initially, but I have to really stomp it in order to stop quickly, and by that point it is definitely lower than my previous VWs. The pedal feels pretty similar to my other car, it just isn't stopping like that car did, so I have to push a lot harder and farther.

How can I diagnose a bad booster? It doesn't leak air or fluid.

I think I'll do a complete brake change and bleed when I get the chance, its getting close to that time anyway.

To check the booster:

Get in the car, do not start it, pump on the brake pedal a few times to exhaust any stored vacuum inside the booster... the pedal will normally get harder.

Then, with your foot on the brake, start the engine. Within a second it should soften as assist starts working.

Try it on another car for comparison.

Then if it does get soft and assist is working, shut the engine off and hold your foot on the brake. It should stay put. If there is a leak in the booster or tube, the vacuum will bleed off as soon as the engine is no longer running.

Booster failures are not common, however there were a bunch of 2002s that seem to have issues specifically, but the failure mode was that the brakes would drag, not a loss of assist.

I tee'd my vacuum gauge into the vacuum line going to the 1 way valve.
Had the gauge on the dash and went for a ride,
My vacuum was slow recovering after stopping and would drop a bit here & there.
I found the nipple on the vacuum pump loose and cleaned the area and put some epoxy on it.
Its been OK so far.