Technical Fiat ducato 2.8idtd brake problems

[Kestas]

Hi everyone,just have a big problem with my motorhome brakes,after installing new brake pipes (copper ones) i get a problem,after bleeding the brakes they become stuck,as example:i press the pedal and brakes won't release for minute or two...try to drive all four wheels are heating,then i have bought everything new brake flexi pipes,new front calipers,rear calipers,master cylinder,now i have replaced everything,after bleeding,when engine is off the brake pedal is hard,but when i start engine it goes down slowly to the end,....today i got the pump for brake bleeding,still the same...have no more ideas what to do...plz.help
Many thanks

 

[bugsymike]

Hi everyone,just have a big problem with my motorhome brakes,after installing new brake pipes (copper ones) i get a problem,after bleeding the brakes they become stuck,as example:i press the pedal and brakes won't release for minute or two...try to drive all four wheels are heating,then i have bought everything new brake flexi pipes,new front calipers,rear calipers,master cylinder,now i have replaced everything,after bleeding,when engine is off the brake pedal is hard,but when i start engine it goes down slowly to the end,....today i got the pump for brake bleeding,still the same...have no more ideas what to do...plz.help
Many thanks

First thing is re the new master cylinder, I assume a good quality make?
Next, there must be a small amount of free play at brake pedal before rod comes in contact with the master cylinder, otherwise after a few applications the pedal goes hard and all the brakes stay on. Even a badly adjusted brake light switch on the pedal can cause it, or wires around the pedal.
Has the correct brake fluid all ways been used? Incorrect fluid damages the rubbers.
The pedal slowly going down to the floor can be a faulty master cylinder, however as the whole system has been worked on there are plenty of other areas to check. When pedal goes down if you do it several times , do you lose brake fluid from the reservoir?

 

[Kestas]

No,fluid stays same...

 

[bugsymike]

No,fluid stays same...

So no external leaks.
Another thing to check is with top off the brake reservoir have someone carefully watch the level, then as brake pedal is pressed and it starts to drop, it is normal to see the level go down very slightly on pushing on a hard pedal, but if master cylinder is faulty and pedal still being pushed down, what you may see is the level start to rise again.
This is down to faulty pressure seals in the master cylinder allowing the brake fluid back past the seals and into the reservoir again instead of pushing the brake cylinders under the car.
On a good master cylinder the fluid will only return to reservoir as brake pedal is released.
Other faults in regards to excessive brake travel can be bad adjustment at the wheels and another is loose wheel bearings.
A common indication of brake master cylinder fault is, if you smack the pedal on hard it works, but if you press gently and then relax the pressure but continue to lightly press the brake pedal , it slowly drops down towards the floor. This is due to the rubber seals spreading and sealing in the cylinder on hard application, but relax and don't seal on gentle pedal pressure.
The only small conciliation is most vehicles have Dual Circuit brake systems these days so although the pedal drops it should have some stopping ability near to the floor if you are lucky.
Over 50 years ago I went out on a breakdown with the garages old 1950s Land Rover, I had gone down a very steep hill at usual apprentice "high speed", got to the broken down vehicle and decided to swing around in the road to be near it, I went to stop and the brake pedal (pre Dual Circuit) brakes went straight to the floor resulting in the Land Rover driving up the grassy bank! I fixed the car and then drove back to garage slowly using the hand brake.

 

[Communicator]

So no external leaks.
Another thing to check is with top off the brake reservoir have someone carefully watch the level, then as brake pedal is pressed and it starts to drop, it is normal to see the level go down very slightly on pushing on a hard pedal, but if master cylinder is faulty and pedal still being pushed down, what you may see is the level start to rise again.
This is down to faulty pressure seals in the master cylinder allowing the brake fluid back past the seals and into the reservoir again instead of pushing the brake cylinders under the car.
On a good master cylinder the fluid will only return to reservoir as brake pedal is released.
Other faults in regards to excessive brake travel can be bad adjustment at the wheels and another is loose wheel bearings.
A common indication of brake master cylinder fault is, if you smack the pedal on hard it works, but if you press gently and then relax the pressure but continue to lightly press the brake pedal , it slowly drops down towards the floor. This is due to the rubber seals spreading and sealing in the cylinder on hard application, but relax and don't seal on gentle pedal pressure.
The only small conciliation is most vehicles have Dual Circuit brake systems these days so although the pedal drops it should have some stopping ability near to the floor if you are lucky.
Over 50 years ago I went out on a breakdown with the garages old 1950s Land Rover, I had gone down a very steep hill at usual apprentice "high speed", got to the broken down vehicle and decided to swing around in the road to be near it, I went to stop and the brake pedal (pre Dual Circuit) brakes went straight to the floor resulting in the Land Rover driving up the grassy bank! I fixed the car and then drove back to garage slowly using the hand brake.

Yes, but the transmission handbrake, located at the rear of main gear box was very effective.

 

[bugsymike]

Yes, but the transmission handbrake, located at the rear of main gear box was very effective.

I agree on the Land Rover due to it's multiplying action through the diff, although they do advise it can break half shafts if used aggressively.
Funny enough I have heard many say how poor the handbrake is on Land rovers, but I think it is more the later ones as laws and Mot regulations relaxed the 25% rule to 16% I believe with the introduction of Dual Circuit braking.
On the early Land Rovers it was a common thing to service and manually adjust the transmission brake whilst also checking the gearbox rear seal was not leaking onto the shoes, later ones went to a poor automatic /self adjuster which I feel was a backward step.
I used to work on one of my customer camper vans a Cherokee Sun Voyager which I believe weighed around 7.5 Tonnes, that had a transmission brake on the auto gearbox it was foot operated and very effective.
Only problem with those systems is, when/if a half shaft fails, then no handbrake.

 

[AsdaPricey]

Hello Kestas

I have a few questions


Are you using a pressurised bleeding system? Or a vacuum bleeding system?
I ask this as it has been known on new master cylinders that from excess pressure the seals have flipped backwards during refill and pressurisation, creating a variety of symptoms from hard pedal to no pressure at all.

Did you replace copper lines one at a time or were all removed at once and some are inadvertently in the wrong port on the master cylinder?

 

[bugsymike]

Generally I prefer the pressure bleeding system as long as the 20 psi pressure is not exceeded . The reason being I have had issues with older master cylinders where the vacuum method "suction" draws air into a brake system.

 

[Kestas]

First thing is re the new master cylinder, I assume a good quality make?
Next, there must be a small amount of free play at brake pedal before rod comes in contact with the master cylinder, otherwise after a few applications the pedal goes hard and all the brakes stay on. Even a badly adjusted brake light switch on the pedal can cause it, or wires around the pedal.
Has the correct brake fluid all ways been used? Incorrect fluid damages the rubbers.
The pedal slowly going down to the floor can be a faulty master cylinder, however as the whole system has been worked on there are plenty of other areas to check. When pedal goes down if you do it several times , do you lose brake fluid from the reservoir?

Hi,thanks for answering,
Not loosing the brake fluid at all,i using Mannol Dot 4 brake fluid,thinking to order another master cylinder,but can't get the bosh one,as it was installed

 

[Kestas]

Hello Kestas

I have a few questions


Are you using a pressurised bleeding system? Or a vacuum bleeding system?
I ask this as it has been known on new master cylinders that from excess pressure the seals have flipped backwards during refill and pressurisation, creating a variety of symptoms from hard pedal to no pressure at all.

Did you replace copper lines one at a time or were all removed at once and some are inadvertently in the wrong port on the master cylinder?

Hi,first i have checked on friends of mine camper for correct ports od pipes,all ok after replacing everything i let the fill the reservoir and waited for gravity to do the job,then when i get fluid out of all nipple then used just pedal pumping method,no luck with that...after this i got that pressure pump for bleed...

 

[bugsymike]

Hi,first i have checked on friends of mine camper for correct ports od pipes,all ok after replacing everything i let the fill the reservoir and waited for gravity to do the job,then when i get fluid out of all nipple then used just pedal pumping method,no luck with that...after this i got that pressure pump for bleed...

Have you read all of my reply at #4 above re testing the master cylinder?

 

[Kestas]

So no external leaks.
Another thing to check is with top off the brake reservoir have someone carefully watch the level, then as brake pedal is pressed and it starts to drop, it is normal to see the level go down very slightly on pushing on a hard pedal, but if master cylinder is faulty and pedal still being pushed down, what you may see is the level start to rise again.
This is down to faulty pressure seals in the master cylinder allowing the brake fluid back past the seals and into the reservoir again instead of pushing the brake cylinders under the car.
On a good master cylinder the fluid will only return to reservoir as brake pedal is released.
Other faults in regards to excessive brake travel can be bad adjustment at the wheels and another is loose wheel bearings.
A common indication of brake master cylinder fault is, if you smack the pedal on hard it works, but if you press gently and then relax the pressure but continue to lightly press the brake pedal , it slowly drops down towards the floor. This is due to the rubber seals spreading and sealing in the cylinder on hard application, but relax and don't seal on gentle pedal pressure.
The only small conciliation is most vehicles have Dual Circuit brake systems these days so although the pedal drops it should have some stopping ability near to the floor if you are lucky.
Over 50 years ago I went out on a breakdown with the garages old 1950s Land Rover, I had gone down a very steep hill at usual apprentice "high speed", got to the broken down vehicle and decided to swing around in the road to be near it, I went to stop and the brake pedal (pre Dual Circuit) brakes went straight to the floor resulting in the Land Rover driving up the grassy bank! I fixed the car and then drove back to garage slowly using the hand brake.

Will check that,really appreciate for your help

 

[Kestas]

Have you read all of my reply at #4 above re testing the master cylinder?

Yes i did,after posting another reply,me new on them forums,sry

 

[Kestas]

Yes i did,after posting another reply,me new on them forums,sry

Another quick question,so Dot 4 is the best fluid to use?or maybe there is another for old vehicles?

 

[bugsymike]

Another quick question,so Dot 4 is the best fluid to use?or maybe there is another for old vehicles?

Personally apart from odd green stuff in some Citroens like 2CVs, I use Dot 4 in everything.
Others may have a preference for more advanced spec. brands.
Just don't use engine oil like one of our old customers did in the 1970s in his Rover, destroying all the rubber seals.

 

[AsdaPricey]

Hi,first i have checked on friends of mine camper for correct ports od pipes,all ok after replacing everything i let the fill the reservoir and waited for gravity to do the job,then when i get fluid out of all nipple then used just pedal pumping method,no luck with that...after this i got that pressure pump for bleed...

Hello

Ok, so just to confirm, was the system working ok before changing the copper pipes?
If so, logically it has to be something done at the point of strip down or replacement of the copper pipes….I would bet on the master cylinder seals flipping on both due to the excessively long first pedal press and that there is also air in the system despite your good efforts.

Go back through what you have done, also comparing old components to new to ensure the introduction of a wrong component has not added to the issue.

There aren’t many components that prevent fluid return - a master cylinder can, flexi rubber brake hoses that have collapsed internally and a front/rear brake bias valve.

Remove the master cylinder and pop the piston out - check the seal lips are the correct orientation and compare its dimensions against your own original. Once happy rebuild with silicone brake grease.

Once you are satisfied all are correct and functioning perform a further methodical re-bleed using your pressure bleeding tool but not too much pressure. Aid the bleed at the calipers by getting each one being bled, higher than the others (I once had to do this on a Renault Extra van that would not bleed properly) You can do this by jacking higher up the corner you are bleeding or by unbolting the caliper and suspending it higher up than the others.

 

[Kestas]

Hello

Ok, so just to confirm, was the system working ok before changing the copper pipes?
If so, logically it has to be something done at the point of strip down or replacement of the copper pipes….I would bet on the master cylinder seals flipping on both due to the excessively long first pedal press and that there is also air in the system despite your good efforts.

Go back through what you have done, also comparing old components to new to ensure the introduction of a wrong component has not added to the issue.

There aren’t many components that prevent fluid return - a master cylinder can, flexi rubber brake hoses that have collapsed internally and a front/rear brake bias valve.

Remove the master cylinder and pop the piston out - check the seal lips are the correct orientation and compare its dimensions against your own original. Once happy rebuild with silicone brake grease.

Once you are satisfied all are correct and functioning perform a further methodical re-bleed using your pressure bleeding tool but not too much pressure. Aid the bleed at the calipers by getting each one being bled, higher than the others (I once had to do this on a Renault Extra van that would not bleed properly) You can do this by jacking higher up the corner you are bleeding or by unbolting the caliper and suspending it higher up than the others.

System was working 100% before i replace the pipes,thanks for advice

 

[AsdaPricey]

System was working 100% before i replace the pipes,thanks for advice

@Kestas did you have any luck in sorting the issue?

 

[bugsymike]

@Kestas did you have any luck in sorting the issue?

Always good to hear of the cure to help others on Forum.

 

[Kestas]

@Kestas did you have any luck in sorting the issue?

Not yet,was waiting for new master cylinder,will try on saturday...