Checking hydraulic green fluid

[BackintheFold]

(MB ur)
I seem to recall that you do this with the engine running. fill midway between high and low on reservoir.
Can someone please confirm?

I also recall someone topping up and the system overflowing-which would be logical to happen if it was filled with the engine running so contradicts the above!

Mine has about half an inch above the minimum line when cold, drops to minimum when engine running.

I'd like to get it right...

Thanks!

[tractor Dave]

Yes, just been reading up on this. Halfway between the two lines.
From the manual.
Run the engine for two minutes and with the wheels pointing straight ahead. Switch off the engine and immediately check the level which should be between the max and min marks.

[BackintheFold]

Great-thanks.
I need to do this before checking brake operation-too low fluid would give me an error regardless of state of rest of system.

Then its time to take belt off and see if there's any resistance when hand-rotating the pulley on the pump.

[mikes2]

The other way is to run the engine for a while, switch off and pump the pedal 40 odd times to empty the bomb.

Level should be at the max or just below.

If it's above, it's overfilled.

[BackintheFold]

Originally Posted by mikes2

The other way is to run the engine for a while, switch off and pump the pedal 40 odd times to empty the bomb.

Level should be at the max or just below.

If it's above, it's overfilled.

I have a red light showing when i push the pedal hard in use-it then goes out

One of the possible causes may be a faulty bomb, so i think that Dave's setup will be best at this stage. Once I've figured out the issue (replaced the bomb most likely!) i will have to refill-reset the fluid.
Will report back here as usual so there's a record for the next person!

[quattrodave]

Originally Posted by BackintheFold

I have a red light showing when i push the pedal hard in use-it then goes out

That symptom is usually the bomb thats not holding enough pressure, used to get it on my 90 20v quattro, 6 or 7 pumps of the pedal and it was discharged, however worked OK in use with engine running. Never actually managed to get more than 10 pumps before it expired even with a new bomb. !

[BackintheFold]

Originally Posted by mikes2

When you get the light, does the pedal go hard ?

No. The pedal feels fine-the light just flashes on once when pedal
Initially pressed. The brakes work fine during this.


Sent from my iPhone using Tapatalk

[Tun]

With the engine not running, repeatedly press the brake pedal until it goes hard. The reservoir should be at MAX at this point and the light should be on.
Note the light indicates three things;
1 Hand brake on (so make sure it's not for this test).
2 Low fluid in the resevoir.
3 Low pressure in the brake accumulator (brake bomb).
Start the engine, the light should go off within a few seconds but can take longer depending on the efficiency of the pump. If you watch the resevoir the level should fall as the brake accumulator pressurises. The lower the level the more affective the accumulator is i.e. more presses of the brake before it is discharged.
If the level does not fall much it could indicate a problem with the accumulator, with the pump, with the piping or even dirty fluid. There is a gauze fitted the banjo bolt which connects the pump to the base of the brake accumulator which can be prone to clogging up.

[tractor Dave]

Just had my bomb successfully 're charged for £96 all in by these guys.
Pleiades Garage, Sawtry, Huntingdon. 01487 831239 (ask for Phil)
They drill a hole, fit a valve and 're fill with nitrogen. He confirmed my bomb was almost empty of gas.

[BackintheFold]

Originally Posted by tractor Dave

Just had my bomb successfully 're charged for £96 all in by these guys.
Pleiades Garage, Sawtry, Huntingdon. 01487 831239 (ask for Phil)
They drill a hole, fit a valve and 're fill with nitrogen. He confirmed my bomb was almost empty of gas.

Excellent. I am yet to test mine with Tun's process (which i think is good because it removes the uncertainty of "what is a hard pedal" and shows that the pressure warning system works as well as the bomb, and the pump.)

With the engine off (having been run a few minutes)and the ignition lights on, the warning light should be off at first as the bomb has been pressured by the pump.
You then pump the brake pedal. The light will come on when the pressure is lost in the bomb.

If this is after 2-4 pumps, that's not good news for the bomb-but it might be that the pump is not pressurising the bomb.

If it takes 25 pumps, the bomb is good, as is the pump.

Starting the engine should pressurise the bomb quickly, and the light should go off. If it does not go off quickly, then the pump is faulty.

If the light goes off quickly, it may be that the pump is pressuring the bomb but if the bomb is faulty then there is only a little pressure being held in it. But we will know from pumping the pedal if a lot of pressure is being stored in the bomb or not so combining these tests will point us to the problem.

If the light goes off slowly, the pump is probably faulty regardless of the state of the bomb.

The pump can be tested by rotating the pulley with the belt off, and feeling for two noticeably hard points in rotation.



My bet is my light comes on after 2 pumps, that the bomb pressurises quickly after starting car, and that there is resistance when hand turning the pump.
So the pump works, but there is not much pressure stored in the bomb (so the bomb need to be fixed).


I am also checking that the injectors are not leaking when sat. Thus i do not want to repeatedly start the car until that test is done. And its raining. etc