1990 740 Braking problem - HELP!!

Hi there,

I really need some help here.

Driving along, minding my own business, went to brake and everything was
very strange. Pedel felt a lot lower than normal. Came to a stop and on
engine idle, the pedel was all the way to the floor.

The RAC man that came to rescue me suggested that it's not the master
cylinder but the servo that's died.

Where can I get one in the UK? How much should I expect to pay and how
difficult is it to fix?

Any other suggestion are more than welcome.

many thanks,

Richard

 

German French & Swedish, or EuroCar Parts. All available via internet.

Tim..

 

We are two people separated by a common language... is "servo" what we yanks
call the "booster" - the vacuum operated assist located between the firewall
and the master cylinder? Or is this an ABS system and the servo is part of
the ABS control?

It sure doesn't sound like a booster to me. Those failures make the brake
harder, and the mechanism just doesn't have the ability to make the pedal
sink to the floor. The new price of a booster is outrageous - over $500 US
last time I checked. However, they are readly available at a breaker for
about 1/6 that price. But unless we are talking about an ABS system, I'd bet
with confidence it is the master cylinder.

If it's ABS, you need somebody who knows about them.

Mike

 

Hi Mike, No ABS on this car so that should make life a bit easier. I'm
thinking that I might try the hose first as it looks a bit tired.

I'll go from there after that.

Thanks for the replies,

Richard

 

Yes servo=booster and I agree, it doesn't sound like the problem here.

 

When the servo goes, the pedal is high and hard, and it seems you need
both feet and all your might, just for a normal stop. Aside from a
linkage failure or a pad falling out, the only thing that will allow the
brake pedal to go to the floor is some kind of fluid leak. Usually this
is an internal leak by the seals in the master cylinder, but can be an
external leak anywhere in the system. Check for brake fluid around the
calipers.
--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Thanks for all the comments so far. I';ve got over the first hudle and
aquired a new master cylinder and servo. Volvo wanted over £500 for the
pair (inc vat). Local scrappy had the two for £25.00.

The swap over will happen tomorrow so I'll keep you posted if you like.
I'm going to take a risk and just swap out the master cylinder first.

Keep those fingers crossed for me!

Richard

 

What???
When the pedal sinks to the floor it usually is a fluid leak.
That may be due to worn seals in master or wheel cylinders or cracked pipes
or hoses.
Worn seals in cylinders are often due to rust on cylinder walls, due to not
changing brake fluid often enouqh.
(By cylinders I mean the Master cylinder and the Wheel cylinders in drum
brakes or Calipers in disk brakes).
Master cylinder leaks are not easily spotted. All cylinders can be honed and
fitted with new seals, but it is not easy.
Brake hoses crack by age or by hitting things, and brake pipes rust
(corrode) from both inside and outside.
They can be changed......

Asbjørn

 

Just for the record, it was the master cylinder that died.

All is now good.

Thanks for all the help,

Richard