Brake problem - Mk1 75 2.0 V6 / Auto / Connie

[RoyalBlue75]

Hello, would anyone be able to help with an obscure brake problem?

Last Jan my 75 failed the MOT on the brakes - had been working fine but the day I took it in I could tell there was something wrong - hard pedal, poor response and a strange vibration from the brakes. Servo was diagnosed and replaced with a new one.

During the summer I noticed that the pedal had got a bit harder again – recently became very hard, way too much pressure needed to stop the car moving when drive was engaged, so took it back again. Garage checked everything out, couldn’t find anything wrong but suggested a ‘lazy servo’. Replaced Servo again (new one came from Rimmers), brakes bled, pads checked, pressure tested. Now a lot better – the hard pedal has gone – but they agree with me that it isn’t right even if it would pass the MOT. The pedal travels too far before there is a firm response from the brakes. I have another 75 so can compare – on the other vehicle the response is almost immediate and only the lightest touch activates the brakes firmly.

The garage look after a lot of older vehicles and the mechanic trained with Rover, they have a good reputation so I think they are genuinely stumped. I’m also interested in why the other new Servo may have developed problems and if some underlying fault will gradually do for the new one (again?).

Any pointers appreciated.

Thanks

Nigel

[Fusilier]

Originally Posted by RoyalBlue75

Hello, would anyone be able to help with an obscure brake problem?

Last Jan my 75 failed the MOT on the brakes - had been working fine but the day I took it in I could tell there was something wrong - hard pedal, poor response and a strange vibration from the brakes. Servo was diagnosed and replaced with a new one.

During the summer I noticed that the pedal had got a bit harder again – recently became very hard, way too much pressure needed to stop the car moving when drive was engaged, so took it back again. Garage checked everything out, couldn’t find anything wrong but suggested a ‘lazy servo’. Replaced Servo again (new one came from Rimmers), brakes bled, pads checked, pressure tested. Now a lot better – the hard pedal has gone – but they agree with me that it isn’t right even if it would pass the MOT. The pedal travels too far before there is a firm response from the brakes. I have another 75 so can compare – on the other vehicle the response is almost immediate and only the lightest touch activates the brakes firmly.

The garage look after a lot of older vehicles and the mechanic trained with Rover, they have a good reputation so I think they are genuinely stumped. I’m also interested in why the other new Servo may have developed problems and if some underlying fault will gradually do for the new one (again?).

Any pointers appreciated.

Thanks

Nigel

Nigel

if pedal is travelling to far before you get any pressure then I believe that you have got air in the system, suspect it is trapped in master cylinder, and the best option and only option is to get one of the T4 Guru's to bleed if via a T4 session, to get rid of all the air from the master cylinder

Nearest T4 operator I believe is PhilT4, who is based in Milton Keynes
Stu

[SD1too]

Originally Posted by RoyalBlue75

I’m also interested in why the other new Servo may have developed problems ...

Nigel, you are not going to like the answer to this question for the following reason:

... the mechanic trained with Rover, they have a good reputation ..

It's because the servo was not the problem in the first place.

In your shoes I would be looking at the vacuum supply, and its non-return valve, to the servo. I would also consider whether the brake fluid needs renewing (hard pedal can mean water absorption as brake fluid is hygroscopic) and bleed the system myself. T4 should not be required since the default condition is that all hydraulic lines are open unless the ABS activates.

Simon

[COLVERT]

I agree with Simon. The servo was not the problem in the first place as a hard pedal means you weren't pulling enough vacuum in it.

Two servos later you still have that poor vacuum leak that needs to be fixed.

That soggy pedal is as others have said, you have air in the system.--

[Avulon]

Originally Posted by SD1too

Nigel, you are not going to like the answer to this question for the following reason:

It's because the servo was not the problem in the first place.

In your shoes I would be looking at the vacuum supply, and its non-return valve, to the servo. I would also consider whether the brake fluid needs renewing (hard pedal can mean water absorption as brake fluid is hygroscopic) and bleed the system myself. T4 should not be required since the default condition is that all hydraulic lines are open unless the ABS activates.

Simon

Except that if you do have air in the system that won't come out with a normal bleed procedure then do bleed with T4 - it'll be much more effective at both clearing out old brake fluid and also at making sure that all the air gets expelled from the system.

Onto the replacement Servo - it's clearly dubious that the first replacement was necessary. But what is clear is that a brake servo should not fail for any reason other than a manufacturing defect or fitting error after less than a year. Most of the cars in the club will be on the original brake servo after a decade and half. Certainly if the garage wants to blame it again then I think that they ought to be replacing it free of charge (assuming the same garage). As already said the most likely culprits for the hard pedal are vaccuum problems so make sure the pipes and non-return valve are replaced and that the vacuuum pump itself is properly tested.

One other question has anyone actually inspected the calipers and pads for proper operation?

[RoyalBlue75]

Thank you everyone who's replied so far. I know the calipers and pads were checked.

The first servo had a hairline crack in the diaphragm, but may be there's more than one issue here? Perhaps it's the orher things they did when replacing it for a second time that helped rather than the servo itself?
I plan to take it in again this week so I'll be raising the useful suggestions from you all. Thanks again.

Nigel

[SD1too]

Originally Posted by RoyalBlue75

The first servo had a hairline crack in the diaphragm ..

That's just supposition by the garage Nigel. They would have had to break open the servo to make that diagnosis and that will not have been done.

I would not return to that garage. In which area of London are you? Can you take the car up the M1 to Milton Keynes to see Phil-T4?

Simon