1997 Astra - rear drum brakes.

[ChrisM]

Ok,
In my MOT, I was told that the nearside rear brake was 'slow to react...'

In testing rear brakes individually, both give required stopping power, but
testing together, offside stops first, then nearside...

Speaking to a friend, his first thought was that the 'flexitube' to this
drum may be restricted in some way. On further discussion with another
mechanic however, they came to the conclusion that due to some sort of
'balancing' valves in the system, the problem could actually be on the other
side, as the faulty valve was allowing all the hydraulic pressure to the
offside, and only to the nearside when the offside was fully activated.

I've probably explained this rather badly, but does anyone know what I'm
saying and care to add anything??

(Astra is 1997 (R) - older shape).

Thanks,

Chris.

 

[Malcolm Stewart]

Ok,
In my MOT, I was told that the nearside rear brake was 'slow to react...'

In testing rear brakes individually, both give required stopping power,
but testing together, offside stops first, then nearside...

Speaking to a friend, his first thought was that the 'flexitube' to this
drum may be restricted in some way. On further discussion with another
mechanic however, they came to the conclusion that due to some sort of
'balancing' valves in the system, the problem could actually be on the
other side, as the faulty valve was allowing all the hydraulic pressure to
the offside, and only to the nearside when the offside was fully
activated.

I've had MoT failures on proportioning valves (think that's the name?) in
the past, and there were suggestions that my normal style of driving and
braking wasn't sharp enough, so I wasn't exercising the valve in normal
usage. (Car was a Renault or Honda from memory. My Astra seems OK in this
respect.)

 

[me140]

Have you had the drum off and looked inside and made sure that one side of
the wheel cylinder hasn't seized?
The valves you mean and near the back in each brake pipe - about the
thickness of a C battery but a bit longer. There are different ones and
Vauxhall had the idea of wrapping a coloured paper band round them to
identify the pressure - so of course by the 3rd year or so the paper has
fallen off.
If you need on and can't tell which one it should be just replace them both
with 2 the same and it will be fine.

 

[ChrisM]

Yea, both wheel cylinders were leaking slightly, so we replaced both sides.
Will look for these valves.

Any thoughts about anything else that could be causing this problem??

Thanks,

Chris.

 

[adder1969]

Yea, both wheel cylinders were leaking slightly, so we replaced both sides.
Will look for these valves.

Any thoughts about anything else that could be causing this problem??

Thanks,

Chris.

Could be adjuster one side has seized thus needing more travel to
actuate the brakes. If the cylinders were laking there could also be
air in the system which I guess you'll fix when the system is bled.

 

[ChrisM]

Could be adjuster one side has seized thus needing more travel to
actuate the brakes. If the cylinders were laking there could also be
air in the system which I guess you'll fix when the system is bled.

Well, we bled the system when we changed the cylinders.
One side (offside) squirted out like a good-un(as per normal) when brake
pedal was pressed.
Otherside (nearside - the 'slow' side) only oozed out slowly.
We checked the adjusters both sides and all seemed to be well.

Cheers,

Chris.

 

[adder1969]

Well, we bled the system when we changed the cylinders.
One side (offside) squirted out like a good-un(as per normal) when brake
pedal was pressed.
Otherside (nearside - the 'slow' side) only oozed out slowly.
We checked the adjusters both sides and all seemed to be well.

Cheers,

Chris.

Ah, might be a rubber pipe that's gone bad inside. I don't know about
the brake valve things so can't comment on those.

 

[ChrisM]

Ah, might be a rubber pipe that's gone bad inside. I don't know about
the brake valve things so can't comment on those.

How do you mean, 'bad inside'? Are these pipes made up of multiple layers or
somthing? Can the inside f*** up without the outside showing anything?

Cheers,

Chris.

 

[me140]

Just undo the pipe before the flexi - if the fluid pours out the same on
both sides when you press the pedal then the flexi must be the problem - if
not I suspect the valves.

 

[adder1969]

How do you mean, 'bad inside'? Are these pipes made up of multiple layers or
somthing? Can the inside f*** up without the outside showing anything?

Yes. Usually the inner pipe is braided for strength and the outer pipe
over this is for protection.

 

[Roger R]

[snip]
If you need on and can't tell which one it should be just replace them
both with 2 the same and it will be fine.

Don't forget to take your credit card with you if buying new.
One cost me 107.51 at the beginning of 2005.

Roger

 

[adder1969]

[snip]
If you need on and can't tell which one it should be just replace them
both with 2 the same and it will be fine.

Don't forget to take your credit card with you if buying new.
One cost me 107.51 at the beginning of 2005.

Roger

Main dealer price?

 

[Roger R]

[snip]
If you need on and can't tell which one it should be just replace them
both with 2 the same and it will be fine.

Don't forget to take your credit card with you if buying new.
One cost me 107.51 at the beginning of 2005.

Roger

Main dealer price?

Yes, 'fraid so. - Such a bargain I bought two!

Roger

 

[me140]

Wow - are they gold plated?

[snip]
If you need on and can't tell which one it should be just replace them
both with 2 the same and it will be fine.

Don't forget to take your credit card with you if buying new.
One cost me 107.51 at the beginning of 2005.

Roger

Main dealer price?

Yes, 'fraid so. - Such a bargain I bought two!

Roger

 

[Roger R]

Wow - are they gold plated?

Looking at the receipt under 'Modulator brake' the Qty is 1, though I fitted
two new units. Possibly they were sold only as a matched pair in a single
box. (to avoid fitting individual units of different rating)
The unit price is therefore 53.75 ea, but they couldn't be bought singly.

...and yes they were yellow zinc plated so they looked like gold.

Roger