Spongie brake pedal

[richbids]

Hi guys
Been having a issue with my brakes on my 04 plate 2.7 terrano . The brake pedal is spongie and sinks away .
I have checked and adjusted the brakes ,bleeded the brakes a couple of times but they are still spongie when the engine is running .
When engine is off the brake pedal is hard .
I have replaced the brake servo hoping that was the problem which has improved the pedal but it still sinks away when the car is running .
The pedal does pump up hard when the car is running but sinks if u stop pumping .
The big question is do I need to change the vacuum pump ?.
If I pull the vacuum pipe off at the servo it does suck the end of finger in to the pipe .
Any help would be appreciated

 

[solarman216]

sounds more like the master cylinder is passing fluid due to worn rubbers, I did start a thread on here re this issue with the earlier models and found a design fault but ran out of time and have not completed it, sorry, Rick

 

[kitchenman]

I have a similar problem, but it does take quite a while to get the pedal to the floor, passed its MOT OK, I asked the MOT tester about it as I was a bit worried, he said it was not uncommon BUT the brakes work OK for the test and there is no signs of leakage.

 

[AlexD333]

Wasn't there a test it leave something on the pedal and check if it sinks entirely to the floor rick?

 

[macabethiel]

Brake Pedal going to floor eventually !!

Hi guys
Been having a issue with my brakes on my 04 plate 2.7 terrano . The brake pedal is spongie and sinks away .
I have checked and adjusted the brakes ,bleeded the brakes a couple of times but they are still spongie when the engine is running .
When engine is off the brake pedal is hard .
I have replaced the brake servo hoping that was the problem which has improved the pedal but it still sinks away when the car is running .
The pedal does pump up hard when the car is running but sinks if u stop pumping .
The big question is do I need to change the vacuum pump ?.
If I pull the vacuum pipe off at the servo it does suck the end of finger in to the pipe .
Any help would be appreciated

1) When driving normally and you apply the brakes do they seem okay ?
2) Does the problem only appear if you maintain pressure on the pedal whilst stationary with the engine running ?
3) If with the engine off and any residual vacuum depleted you then apply brake pedal pressure and hold it does pedal feel okay and solid.

If all 3 answers are YES then I think you have no problem.
Almost every modern car I have driven (especially Mercs) with ABS and power assisted brakes (including brake assist that detects panic braking) tend to have "spongy feel brakes" no one has been able to explain what causes this but it is common on many new cars.

 

[richbids]

Bloody servo

Had another look at the terrano tonight and I have noticed that my replacement servo sound s like a lorrys air brake .
I reckon my the servo is leaking slightly .
So I think I will see if I can get a matching pair =servo and master cylinder .

 

[solarman216]

check the rubber O ring between master and servo, they can be devils to seat, Rick

 

[richbids]

Rick would that cause a hissing sound when the brake pedal is pressed from in side the car

 

[solarman216]

if it continues to his once the pedal has stopped moving then yes, was the servo a new one or used? Rick

 

[richbids]

Hi Rick the servo was second hand from cnc fabs
Spoke to cnc fabs and he's sorting me out a replacement servo with master cylinder. Hopefully a matching pair .
So will try that and hope that solves the problem .

 

[solarman216]

I have had similar problems with my off roader and also with Alex motor, Alex turned out to be stuffed vac pump (but his pedal was hard all the time) my off roader was more complex, and the main cause was the O ring tween master and servo having said that after removing said servos from other scrappers and trying them it seems that they do not like to be disturbed as perfectly working ones did not work on refitting to my off roader, I am still researching this one and soon as get some time will dis assemble a servo to get to the root of the problem, Rick

 

[solarman216]

there is an adjustment between master and servo that could well be causing the issue but as yet not had time to look at it, Rick

 

[richbids]

Rick there is adjustment on the end of the push rod .
But u would need to be careful not to adjust it to far or the brake could be slightly on .
That's why I am going to get a matching pair servo and master cylinder
Cheers rich

 

[micktheshed]

1) When driving normally and you apply the brakes do they seem okay ?
2) Does the problem only appear if you maintain pressure on the pedal whilst stationary with the engine running ?
3) If with the engine off and any residual vacuum depleted you then apply brake pedal pressure and hold it does pedal feel okay and solid.

If all 3 answers are YES then I think you have no problem.
Almost every modern car I have driven (especially Mercs) with ABS and power assisted brakes (including brake assist that detects panic braking) tend to have "spongy feel brakes" no one has been able to explain what causes this but it is common on many new cars.

This is a well documented condition called 'diesel creep' and is more prevalent on larger vehicles such as 4X4's due to their higher boost ratios & made worse by ABS. This assumes there is no fluid or vacuum leek or other brake fault. As macabethiel states, the above 3 must be OK. Going by mine (& other terranos) the brakes are normaly on the 'soft' side, known as 'progressive' in b******t-speak, which doesn’t help.

It's sod's law that it's usually only noticed after the brakes have been bled or 'interfered with' LOL.

Note it can also happen on petrol engines where it is more likely to be (but not 100%) a fluid-leek based problem.

Guess how I came to know the above, had me worried for a long time LOL.

Ref: www. brakesint.co.uk for more info. technical assistance 201,202 etc.

 

[rustic]

I will just add to the thread, if there has been any stud welding, or cutting near the exhaust or exhaust manifold, then hot sparks could perforate the thin plastic vacuum pipes, this will affect the strength of the vacuum.
Probably not the case in this application, but something to remember when working on the vacuum system.
Rustic