How bad is bad... Brakes.

[CitroJim]

Now heres the thing - if, before I drive off, I fully depress the brake pedal a couple of times while stationary, when I go to stop the first time at a stop sign, the brakes are a lot more sensitive than they would have otherwise been.

Exactly as mine are! I'm in the habit of always applying the brakes a few times before setting off now...

Your theory sounds very good Simon.

I don't suppose you'd be willing to do so and report back to us then ?

I will do so as we both have virtually identical symptoms and it'll show one way or another if the flexis are the culprit. It may be a week or more as us poor Poms are in the grip of winter and my "garage" is open to the sky

[wrinklet1]

Could the problem be arising from a tired hp pump?the steering runs on low pressure and brakes/suspension run on hi pressure. Therefore, the brakes could go but steering could remain?
Only an idea

Paul

[weety]

if its any help twenty years ago when i was riding around on motorbikes we all used to change the brake hose from rubber to braided steel....

made an immediate noticeable difference....

if its not that on the xantias could it be pumps starting to fail and not supplying enough pressure to the system?.... if you try braking whilst driving on full steering lock (supermarket car park time) are your brakes worse than if you do the same driving in a straight line?

[Mandrake]

For what its worth, I don't see how the symptoms could be caused by a weak pump.

It would have to be a very sad pump indeed if it couldn't even reach the regulator cutout pressure with no load, and would probably be incapable of lifting the car.

When the cutout pressure is reached you have 10-20 brake applications available from the stored pressure in the accumulator sphere whether the pump was running or not, so if the pump was weak, the first brake application would be good, not the other way around.

Besides, I've replaced the pump on mine for other reasons - no difference at all to this problem.

Now the pressure regulator on the other hand - if it was not reliably maintaining the cutout pressure, could have an effect, but I've measured the cutout pressure on mine and it's spot on. (At least at the time when I measured it, I'm not sure if its possible for a pressure regulator to be intermitant in its function)

Thanks for the comment on the motorbike hoses - when you say it was better, in what way ?

Regards,
Simon

[weety]

the brakes would become a lot sharper/faster...... on a bike there is no servo so there is loads of 'feel' to the brakes....

not as usually noticeable on cars as the servo provides loads of pressure

if its not a brutally expensive mod i would try it (or just replace the rubber pipes with new rubber pipes)... if your pipes are expanding like that there must be an increased risk that one could burst under braking!

[Mandrake]

the brakes would become a lot sharper/faster...... on a bike there is no servo so there is loads of 'feel' to the brakes....

Ok, thats what I thought.

if its not a brutally expensive mod i would try it (or just replace the rubber pipes with new rubber pipes)... if your pipes are expanding like that there must be an increased risk that one could burst under braking!

With collapsed brake hoses its not the outside of the house that expands, but the inner layer. (So you won't see anything wrong on the outside)

Brake hoses are made with multiple layers so that when they're bent they don't collapse internally, blocking the hole. If the inner layer delaminates from the outer layers a bend in the hose can cause that inner layer to fold over and block the hole, partly, or completely. (Imagine bending a garden hose until it cuts off)

The pressure from applying the brakes hard reinflates the inner layer so its pressed fully in contact with the outer layer again.

Regards,
Simon

[CitroJim]

I had a bit of an investigation into this problem on my Activa yesterday although not to the extent of replacing the flexi hoses. That is next.

I bled my brakes and found zero air in the fronts but a massive gulp of air in my offside rear. A good 250mL of frothy LHM came out. Strangely, the other side rear was completely air-free.

That has cured my initial delay problem. I also replaced the pedal spring to make the test a harder one and what I find now is although I have no delay, the first few cold applications are not really very good but once the brakes are up to temperature, they're OK. The hotter they get, the better they work. I'm suspecting it has racing pads in it. They're about 3/4 worn now so come the next bout of fine weather, new discs, pads and flexis will go on.

The air worries me although it may have been a result of upsetting things replacing a front height corrector, else I have a leaking sphere. They're all very recent except the anti-sink. If the problem (and air) returns, this sphere has to be No.1 suspect...

A blast around last night and a 100 mile round trip today leaves me fairly content with my brakes although they're still not quite as good as my 2.1...

[Stempy]

Does the 2.1 have different callipers to the Activa? When I was shopping around for replacement pads I was looking at EBC ones and I noticed that they did an uprated 'green' pad for the 2.1 but not for the V6. My brakes are pretty good at lower speed but are complete pants for stopping quickly from high speed, they just seem to fade away. I have considered fitting 2.1 calipers and from what you say that could be a route worth taking.

[CitroJim]

Thanks Stempy, those EBC pads could well be what my Activa has fitted. If so, they don't suit my driving style at all They take too long to warm up and become really efficient. As I say, when you can fry eggs on them, they're not bad at all.

According to pr.net the 2.1TD and Activa do have the same calipers but different to the V6 which appears to share its calipers with the 2.0 16V but with smaller discs

My 2.1TD has brakes that are in every way supurb. It has 283mm discs (as has the Activa) whereas your V6 has 288mm so in theory the V6 should have the better brakes

It may well be worth the swap (if the 2.1 calipers will fit the V6) as they look massive, as are the pads.

[jeremy]

I had a problem with lack of efficient brakes on our ZX which I eventually found was due to me fitting new pads that were a different shape to the originals.

Briefly git the thing - pads gone. Got some Delphi ones - fitted them - and left the disc as it seemed OK. They never worked well so I got new discs and pads and all was fine when I fitted them. However when I went to do the job I looked again at the discs which seemed perfectly serviceable. What was happening was that the pads I had fitted were rubbing on a rusted section of the disc near the hub and this was interfering with their contact.

So if I'd been persistent I'd have discovered the problem and shaved the offending bit of the pad off with a chisel. Never mind - the bits weren't expensive.

[Mandrake]

I had a bit of an investigation into this problem on my Activa yesterday although not to the extent of replacing the flexi hoses. That is next.

Good - I await with interest

I bled my brakes and found zero air in the fronts but a massive gulp of air in my offside rear. A good 250mL of frothy LHM came out. Strangely, the other side rear was completely air-free.

Yep, thats exactly what was happening on Dad's car - always on the right hand side (offside ?) and never on the left. There was so much air that you could brake hard and the rear suspension had time to hit the TOP bump stops before the brakes would activate and pull it down again.

That has cured my initial delay problem. I also replaced the pedal spring to make the test a harder one and what I find now is although I have no delay, the first few cold applications are not really very good but once the brakes are up to temperature, they're OK. The hotter they get, the better they work. I'm suspecting it has racing pads in it.

Are you sure its temperature related though ? Didn't you say that a few hard applications of the brakes while stationary had the same effect ?

They're about 3/4 worn now so come the next bout of fine weather, new discs, pads and flexis will go on.

Great - but could you do them as two seperate jobs ? Otherwise we will never know which one was the problem and/or how much of what symptoms were related to each item.

The air worries me although it may have been a result of upsetting things replacing a front height corrector, else I have a leaking sphere. They're all very recent except the anti-sink. If the problem (and air) returns, this sphere has to be No.1 suspect...

That'll be anti-sink sphere for sure, based on your other comments.

A blast around last night and a 100 mile round trip today leaves me fairly content with my brakes although they're still not quite as good as my 2.1...

See what they're like after a day or two of not driving them...

Regards,
Simon

[CitroJim]

Hi Simon,

The deeper I go, the deeper it gets

Yes, the delay was a result of the air I'm sure. It has not returned so far and yes, previously, a few hard applications would resolve that but the inefficiency of the brakes when cold was discovered as a result of resolving the first issue The delay was masking the cold efficiency problem to great extent.

It was the same this morning. Light frost, cool air, no delay but the first applications were poor followied by an improvement as the pads warmed up. By the time I got to work (10Km) they were working fine.

Yes, offside is the drivers side (right-hand). The air must be in the in the common line to the rear calipers and hence why it only bleeds from one side. By habit I seem always to bleed the offside first so next time I'll make a point of bleeding the nearside first.

I'll certainly do the job in stages. Flexis next and then after a settling period, discs and pads.

[jgra1]

hi all, my V6 auto HA2 certainly [had] the same symptoms..
After sitting for a night or so, the brake was ineffective on first application, not every time though.

hmm..
sorry not much help

John