Brake pedal is going down

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07-02-12, 21:47
alfista_AR

Brake pedal is going down

Hello guys,

After remove the air manifold finally fix the gas leak, the absolute pressure hose is correctly connected and the manifold is mounted again as well.
But now I have a new problem with brakes, looks like the break pedal is becoming too soft and is going down easily, the car is not breaking as usual and two or three "pumps" are needed to break correctly.
I have review the hoses and all are connected in the right place, even that one that goes from the intake manifold to the servo help brake (I don't know if this is the right name) I mean the piece that is below the ABS box.
I appreciate any hint or help.

Thanks.
-Dario.
07-02-12, 21:54
AlfaJack

I would think that the pipe from manifold to servo has a split in it as it feels quite brittle.
Did it happen straight after removing and re-fitting the intake manifold?

If not, are you loosing fluid?
08-02-12, 19:41
alfista_AR

Quote:

Originally Posted by AlfaJack

I would think that the pipe from manifold to servo has a split in it as it feels quite brittle.
Did it happen straight after removing and re-fitting the intake manifold?

If not, are you loosing fluid?

Yep, It happen after removing/refitting the manifold.
I'll re-check that pipe, as this is a rigid plastic one maybe I've bent it during the mounting and cracked in a hidden place.
Not loosing fluid at all.

Thanks Alfajack!
08-02-12, 20:35
Steve Webb

The other cause of a brake pedal going to the floor, is a faulty/worn brake cylinder, but as you've worked on the pipework recently I'd say that this was the problem.

Good luck finding the problem.
10-02-12, 20:33
alfista_AR

Quote:

Originally Posted by Steve Webb

The other cause of a brake pedal going to the floor, is a faulty/worn brake cylinder, but as you've worked on the pipework recently I'd say that this was the problem.

Good luck finding the problem.

Update about the problem.

I've changed the pipe, the problem still there.
I verified that the plug where to connect the pipe at the servo, can turn and can be easily twisted by hand, is it normal?
I noticed too that when I press the brake pedal on idle, the motor accelerate an when release, it decelerate.
Looks like the air is going out from the manifold at some point.

I checked all the connections (6) and pipes in the manifold everything is fitted.

If you have any suggestion I appreciate that.

Thanks.
-Dario.
16-02-12, 19:07
Steve Webb

Quote:

Originally Posted by alfista_AR

I noticed too that when I press the brake pedal on idle, the motor accelerate an when release, it decelerate..

That doesn't sound normal at all. How much does the engine rev when you press the brake, a little or a lot?

Also have you tested to see what the brakes feel like out on the road?
17-02-12, 20:01
jimnielsen

You would typically expect some reaction from the engine revs at idle if you pump the brake pedal. It is possible that the servo unit its self is loosing some air. first I would look at the hose connection... Look on the net for suggestions as to how to test the servo..
19-02-12, 15:50
alfista_AR

Quote:

Originally Posted by Steve Webb

That doesn't sound normal at all. How much does the engine rev when you press the brake, a little or a lot?

Also have you tested to see what the brakes feel like out on the road?

The revs. up just a little.
On the road the brakes doesn't work at first attempt, I've to press a couple of times to brake.
This problem is getting my a little worried, I can't find the possible cause.
I'll keep trying.
Is there any .pdf with brake connections/circuit to check?
What I've is very brief.

Thanks.
-DO.
19-02-12, 15:52
alfista_AR

Quote:

Originally Posted by jimnielsen

You would typically expect some reaction from the engine revs at idle if you pump the brake pedal. It is possible that the servo unit its self is loosing some air. first I would look at the hose connection... Look on the net for suggestions as to how to test the servo..

Ok, Jim I'll start a search for suggestions.
Thanks.

-DO.
19-02-12, 17:57
Steve Webb

Quote:

Originally Posted by alfista_AR

The revs. up just a little.

Ahh thats ok then, I had visions of the car reving to 2k when you touched the brake pedal.

The braking section for the Q4 is fairly short : Q4 Braking manual

But the manual for the regular 155s goes into much more detail : 155 Chassis and brakes.