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Old 13-09-21, 08:45 AM   #1
BackintheFold
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Default Checking hydraulic green fluid

(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!
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Old 13-09-21, 10:17 AM   #2
tractor Dave
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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.

Last edited by tractor Dave; 13-09-21 at 10:35 AM.
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Old 13-09-21, 10:56 AM   #3
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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.
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Old 13-09-21, 11:09 AM   #4
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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.
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Old 13-09-21, 11:21 AM   #5
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Quote:
Originally Posted by mikes2 View Post
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!
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Old 13-09-21, 03:41 PM   #6
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Quote:
Originally Posted by BackintheFold View Post
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. !
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Old 13-09-21, 04:59 PM   #7
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When you get the light, does the pedal go hard ?
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Old 13-09-21, 09:24 PM   #8
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Quote:
Originally Posted by mikes2 View Post
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.


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Old 14-09-21, 07:18 AM   #9
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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.
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Old 15-09-21, 09:04 AM   #10
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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.
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