Brakes on my 350i Wedge going straight to the floor

[smcquill]

Guys, any ideas what could be wrong, My brakes failed on me, the pedal went to the floor. I rebuilt the front callipers at the weekend, and still no brake pressure when engine on or off, there are no leaks under the car..? Could the be the Brake Master Cylinder...?

Any advise would be very welcome.

thanks
Stewart

[350zwelgje]

If bled and the brake pedal was ok, yes the master cylinder seals can be the cause.
This is why I try to avoid pressing the brake pedal to the floor when bleeding, the seals then go over an area normally not used and can cause them to wear very quickly.

Another can be that air has entered or you have a leak in the system.

Rob

[ElvisWedgely]

Yes, it sounds like the master cylinder internals are at fault. If it was just air, you'd have some braking at the pedal.

Tony.TCB.

[KKson]

It could be the master cylinder. On a previous car mine failed and gradually filled up the servo. Took a while before I noticed fluid eventually leaking from it.

[adam quantrill]

Ditto, master cylinder, there are a few cortina ones on the flea for £50-£60. But I can't see any 3-pipe ones.

This one looks promising - you have to search for Cortina MK5 because even the MK4 had the 2-port type in early production:

http://www.oldpartstore.net/shop/2597-glovebox-lid...

Edited by adam quantrill on Tuesday 16th June 08:29

[adam quantrill]

Found it - £45 including the dreaded vat - might get one myself to make sure...

http://brakeparts.co.uk/#!/shop/FORD/CORTINA/77-82...

[smcquill]

Thanks Adam, I bled the brakes again tonight, just in case, and I have a light brake very very spongy, I did see some fluid bubbling on one of the reservoir rubber washers bubbling, but no significant seepage. Is it possible it could draw some air through this...?

thanks Stewart

adam quantrill said:

Found it - £45 including the dreaded vat - might get one myself to make sure...

http://brakeparts.co.uk/#!/shop/FORD/CORTINA/77-82...

[adam quantrill]

When mine went it was letting air in through the seals and bleeding only lasted a day or so. In fact i never bought a new one just had an old one (with sealed-off pipes) hanging about so I used that. So my one is probably living on borrowed time!

[smcquill]

I've just ordered a new one tonight from your link thanks. Hopefully this helps,

thanks again
Stewart

adam quantrill said:

When mine went it was letting air in through the seals and bleeding only lasted a day or so. In fact i never bought a new one just had an old one (with sealed-off pipes) hanging about so I used that. So my one is probably living on borrowed time!

[smcquill]

Ok guys, back to the drawing board, I fitted a new brake master cylinder tonight, my son helped me bleed the brakes, the pedal no longer goes to the floor however I have the spongiest brake and its close to the floor not quite. I am at a loss.....one thing thats bugging me which may not be anything the vacuum hose from the servo that goes into the bottom of the plenum sounds as though its making a noise when the brake is pressed...is this connected in any way..?

Any more help or advise seriously welcome...
cheers
Stewart

[adam quantrill]

If you run the engine for a bit, turn it off and press the brakes then the vacuum reservoir does make a psssshht noise. What happens when the vacuum is run out - does the pedal get pretty firm/fully firm?

[mrzigazaga]

Hi mate...The servo might be leaking...Just found this online...

Power Brake Booster Test

If the pedal feels "hard" while the engine is running, the booster isn't operating correctly.

Test 1
With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4", this indicates that the booster is working properly.

Test 2
1. Run the engine a couple of minutes.
2. Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.

Test 3
1. Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.

2. Inspect the Check Valve
Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced.
Verify Vacuum
3. Check the operating vacuum pressure when the engine is at normal operating temperature. There should be a minimum of 18 in. of vacuum. Vacuum may be increased by properly tuning the engine, checking for vacuum leaks and blockages in vacuum lines.


Hope it helps...Ziga

[smcquill]

Thanks Adam & Mark, I will test this tomorrow night, too late tonight, might wake up the neighbours....

cheers
Stewart

mrzigazaga said:

Hi mate...The servo might be leaking...Just found this online...

Power Brake Booster Test

If the pedal feels "hard" while the engine is running, the booster isn't operating correctly.

Test 1
With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4", this indicates that the booster is working properly.

Test 2
1. Run the engine a couple of minutes.
2. Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.

Test 3
1. Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.

2. Inspect the Check Valve
Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced.
Verify Vacuum
3. Check the operating vacuum pressure when the engine is at normal operating temperature. There should be a minimum of 18 in. of vacuum. Vacuum may be increased by properly tuning the engine, checking for vacuum leaks and blockages in vacuum lines.


Hope it helps...Ziga

[jindle]

If its a servo problem I'd have thought it would just be harder to brake effectively?

Was everything working before you rebuilt the fronts? Did you bleed the rears?

[smcquill]

Hi Guys, ran the test you suggested tonight I have a working brake albeit its spongy but I do have a brake, tested up and down the drive, but not good enough for the open road, I will have to keep bleeding the system through, I am still getting air bubbles.

So at least there is progress and the brake no longer rests on the floor....

thanks for all your help, very much appreciated..
Stewart

[adam quantrill]

Good news once the bubbles are out it will be done.