Brake Master

[Monty]

Brake pedal sinks when engine running, not running firm pedal. No fluid loss, suspect master cylinder. tried to get one on ebay no one lists for 2003 3Lt ( found one listed but shop came back as 2.7) so I have ordered a kit off of big red on ebay. Question any problems fitting this kit ?, done other kits before on other cars.

 

[Banshee]

Brake pedal sinks when engine running, not running firm pedal. No fluid loss, suspect master cylinder. tried to get one on ebay no one lists for 2003 3Lt ( found one listed but shop came back as 2.7) so I have ordered a kit off of big red on ebay. Question any problems fitting this kit ?, done other kits before on other cars.

Send me a picture of yours mate, I may have a spare in the garden you can have cheap

 

[Monty]

Decided to replace with new cylinder (with abs), and fit new flex hoses all around as they look original and the vehicle has done 150,000 miles. Question it has only one flex hose to the rear axle how does the abs work on the rear? it has all the abs pipes and abs unit under the bonnet. The master has 2 pipes coming out(one at the front one at the rear) with an outlet in the middle at the bottom fitted with a blanking plug (looks factory)

 

[macabethiel]

Pedal Sinking panic ?

Brake pedal sinks when engine running, not running firm pedal. No fluid loss, suspect master cylinder. tried to get one on ebay no one lists for 2003 3Lt ( found one listed but shop came back as 2.7) so I have ordered a kit off of big red on ebay. Question any problems fitting this kit ?, done other kits before on other cars.

This topic has been discussed many times it is my view that if the brakes are fine when driving then all is well. I would only worry if the pedal sank when engine not running.

I suspect that within modern ABS systems there is a small valve somewhere that passes fluid causing the pedal to sink when the brake servo / pedal booster is working. A part of an MoT check is that when starting up with brake pedal depressed the pedal should sink slightly. On many Mercs (brand new) and my Jeep if you keep the pedal pressure up for several minutes it will eventually sink almost to the floor I think this is how many brake systems today are.

 

[macabethiel]

Decided to replace with new cylinder (with abs), and fit new flex hoses all around as they look original and the vehicle has done 150,000 miles. Question it has only one flex hose to the rear axle how does the abs work on the rear? it has all the abs pipes and abs unit under the bonnet. The master has 2 pipes coming out(one at the front one at the rear) with an outlet in the middle at the bottom fitted with a blanking plug (looks factory)

Does this explain why your system only has one flexi pipe is it 3 ch 3 sensor ?


Anti-lock braking systems use different schemes depending on the type of brakes in use. They can be differentiated by the number of channels: that is, how many valves that are individually controlled—and the number of speed sensors.[18]
Four-channel, four-sensor ABS
This is the best scheme. There is a speed sensor on all four wheels and a separate valve for all four wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force.
Three-channel, four-sensor ABS
There is a speed sensor on all four wheels and a separate valve for each of the front wheels, but only one valve for both of the rear wheels. Older vehicles with four-wheel ABS usually use this type.
Three-channel, three-sensor ABS
This scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. The speed sensor for the rear wheels is located in the rear axle. This system provides individual control of the front wheels, so they can both achieve maximum braking force. The rear wheels, however, are monitored together; they both have to start to lock up before the ABS will activate on the rear. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness. This system is easy to identify, as there are no individual speed sensors for the rear wheels.
Two-channel, four sensor ABS
This system, commonly found on passenger cars from the late '80s through early 2000s (before government mandated stability control), uses a speed sensor at each wheel, with one control valve each for the front and rear wheels as a pair. If the speed sensor detect lock up at any individual wheel, the control module pulses the valve for both wheels on that end of the car.
One-channel, one-sensor ABS
This system is commonly found on pickup trucks with rear-wheel ABS. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle. This system operates the same as the rear end of a three-channel system. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness. This system is also easy to identify, as there are no individual speed sensors for any of the wh

 

[Monty]

Does this explain why your system only has one flexi pipe is it 3 ch 3 sensor ?


Anti-lock braking systems use different schemes depending on the type of brakes in use. They can be differentiated by the number of channels: that is, how many valves that are individually controlled—and the number of speed sensors.[18]
Four-channel, four-sensor ABS
This is the best scheme. There is a speed sensor on all four wheels and a separate valve for all four wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force.
Three-channel, four-sensor ABS
There is a speed sensor on all four wheels and a separate valve for each of the front wheels, but only one valve for both of the rear wheels. Older vehicles with four-wheel ABS usually use this type.
Three-channel, three-sensor ABS
This scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. The speed sensor for the rear wheels is located in the rear axle. This system provides individual control of the front wheels, so they can both achieve maximum braking force. The rear wheels, however, are monitored together; they both have to start to lock up before the ABS will activate on the rear. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness. This system is easy to identify, as there are no individual speed sensors for the rear wheels.
Two-channel, four sensor ABS
This system, commonly found on passenger cars from the late '80s through early 2000s (before government mandated stability control), uses a speed sensor at each wheel, with one control valve each for the front and rear wheels as a pair. If the speed sensor detect lock up at any individual wheel, the control module pulses the valve for both wheels on that end of the car.
One-channel, one-sensor ABS
This system is commonly found on pickup trucks with rear-wheel ABS. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle. This system operates the same as the rear end of a three-channel system. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness. This system is also easy to identify, as there are no individual speed sensors for any of the wh

Answers all my questions. Thanks

 

[Monty]

sale

Fitted new brake master cylinder, 2 rear wheel cylinders that were leaking, 2 new front brake calipers ( were not releasing), set of 3 flexible hoses, rear section exhaust, 2 new tyres spent over £650 MOT June 2016 165,000 miles dark red 2003, £1500 , PM me for pictures if interested, quite a clean motor I have had it about a month paid £1500, absolutely hate deriving it been used to driving a sports coupé, cant get used to it , I bought it to tow a large trailer but will get someone to tow for me, going back to the coupé It will go on ebay Sat evening. In Cambridgeshire

 

[Monty]

forgot

Forgot to put 3 Lt turbo diesel SVE

 

[solarman216]

Decided to replace with new cylinder (with abs), and fit new flex hoses all around as they look original and the vehicle has done 150,000 miles. Question it has only one flex hose to the rear axle how does the abs work on the rear? it has all the abs pipes and abs unit under the bonnet. The master has 2 pipes coming out(one at the front one at the rear) with an outlet in the middle at the bottom fitted with a blanking plug (looks factory)

I will point out for macabethiel's benefit re his excellent post on ABS operation that there is one more to be added, and that is the 3 that we have here, and as tested by me re harlowmaveric's motor, the master cylinder is connected direct to the rear brakes and does not go through the ABS pump unit, the front brakes do, now what happens is weird, (as Phils motor has a weep from the OSR cylinder) because it has not been used for a while and on my dirt road this wheel locked up easily, and I mean locked, but the ABS kicked in with a juddering pedal, as it has 4 wheel sensors, so at a bit of a loss to see the reasoning behind this, Rick

 

[Monty]

I will point out for macabethiel's benefit re his excellent post on ABS operation that there is one more to be added, and that is the 3 that we have here, and as tested by me re harlowmaveric's motor, the master cylinder is connected direct to the rear brakes and does not go through the ABS pump unit, the front brakes do, now what happens is weird, (as Phils motor has a weep from the OSR cylinder) because it has not been used for a while and on my dirt road this wheel locked up easily, and I mean locked, but the ABS kicked in with a juddering pedal, as it has 4 wheel sensors, so at a bit of a loss to see the reasoning behind this, Rick

On the abs block it has MC1 and MC2 LHF RHF R So how do they go direct to the rear? If both master cylinder connections go to the abs unit?

 

[solarman216]

On the abs block it has MC1 and MC2 LHF RHF R So how do they go direct to the rear? If both master cylinder connections go to the abs unit?

I have not got Phils motor here now to check but as I needed to replace most of the rear brake pipe cos of rust I traced it right up to the master, but the eating of the pud is the fact Phils OSR locked completely even though the ABS was kicking in, Rick