Lackluster brake performance on my 4-ton motorhome

[roadwarrior]

i have got a 4 ton mercedes sprinter based winchcombe, it has got new disks and pads all round but i have to stand on them if there is a sudden stopping situation, they are bedded in as i have just returned from the pyranees, but they are still lackluster and dont inspire confidence - your thoughts ? they take a couple of seconds to bite and are fine in normal circumstances but.. as they are all round new discs im surprised they are not better.

 

[roadwarrior]

clamping the hose was an old school idea i never agreed with, if only because it can crush and damage the hose meaning you have to bleed the vehicle and replace the hose - silly idea

 

[AndyT4]

clamping the hose was an old school idea i never agreed with, if only because it can crush and damage the hose meaning you have to bleed the vehicle and replace the hose - silly idea

Unloaded completely our Hymer T554 for Hab check brakes brilliantly, Fully loaded 3850 different world. Mway sliprroads an closed lanes attract Aholes and late braking.

 

[RV72 SAM 🏴]

Think after reading your complaints Roadwarrior I wouldn't bother taking it back to original workshop, just get a 2nd opinon off a Specialist or even a main stealer. Just book it in for a brake report and see what they find wrong, as they will fond something that is not right, they will test the brake fluid for a start, as that as you say has not been replaced
I would think they have fitted spurious pads like Eicher (Very Poor Quality) Euro Car Parts were selling these off at £5 a set many moon's ago ! You need them taking out and Inspecting, then repkace anyway with Padgid/Brembo/Ferodo etc . . .
You can't carry on not knowing if you can stop in an Emergency can you???

 

[Gringo2]

OP Said new discs and pads fitted which would mean the removal of calipers..
Now any mechanic who did not clean calipers and sliders and associated area IMHO is a cowboy.
Question to OP... do you think the mechanic? Was competent enough to carry out this procedure???

Think the clue is in the original post "New Discs & Pads fitted all round" which means calliper's should have tbeen removed. Unless the mechanic is a total cowboy the Brakes should have had a complete bleed/fluid change. Some do not remove the front caliper's as they are on flexible hoses but I doubt the rear discs could be removed without undoing a steel brake hose joint. Instantly requires bleeding.

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[Clive Beeza]

Think the clue is in the original post "New Discs & Pads fitted all round" which means calliper's should have tbeen removed. Unless the mechanic is a total cowboy the Brakes should have had a complete bleed/fluid change. Some do not remove the front caliper's as they are on flexible hoses but I doubt the rear discs could be removed without undoing a steel brake hose joint. Instantly requires bleeding.

calipers have to be removed before the actual disc can be taken off the hub
there is no need to disconnect the flexi hoses (as their name suggests they are flexible hoses )
and are generally tied up away fron the disc, to allow working space,
and then refitted after the new disc is in position
but it would be normal practice to then change the brake fluid,
but not essential if the fluid tests good for moisture.

 

[poppycamper]

Think the clue is in the original post "New Discs & Pads fitted all round" which means calliper's should have tbeen removed. Unless the mechanic is a total cowboy the Brakes should have had a complete bleed/fluid change. Some do not remove the front caliper's as they are on flexible hoses but I doubt the rear discs could be removed without undoing a steel brake hose joint. Instantly requires bleeding.

Sorry...
Can not understand if you agreeing with me or disagreeing with me.
What you said...'I think is what I said' so what is the point of your post????

 

[busbuddy]

i have got a 4 ton mercedes sprinter based winchcombe, it has got new disks and pads all round but i have to stand on them if there is a sudden stopping situation, they are bedded in as i have just returned from the pyranees, but they are still lackluster and dont inspire confidence - your thoughts ? they take a couple of seconds to bite and are fine in normal circumstances but.. as they are all round new discs im surprised they are not better.

So....were the brakes just as bad before you had them replaced...what are you comparing them too ?

 

[A-Mech]

Hi All.
I've been reading all the forum postings intently, but had to take the plunge and pay me money!

I would like to add my opinion and this is based on my miniscule experience in life and also working as an engineer in army and now for a UK car manufacturer for 22 years. Retirement coming hence my interest in this forum.

Two things where corners should not be cut. These are steering and brakes!!!
Scrolling through the many postings offered on this thread give, some good advice and no so good advice.
The original replacement of discs & pads could result in lesser performance than the owner remembers giving a lack of confidence when braking. (no one wants confidence issues when steering or braking)
Mercedes, Fiat, iveco etc.... Do not make the vast majority of components that go into there vehicles. They purchase and assemble these parts to make the van.
My experience of friction materials are, OEM or aftermarket OEM is best. They may have bought this part from the makers of friction components, namely Brembo, ferodo or TRW. These parts will conform to the OEM manufacturing specifications and in short gives best braking performance.
Although the brake pad or disk may have "Mercedes, Fiat" etc printed on part, the same part may have come from a number of, QUALITY suppliers depending on that month's supply of parts. (cost)
All these parts are made to manufacturers specification.
The visable sign on new cars/cans are tyres. One sprinter may have continental and the next one could have Bridgestone. They order 100,000 at any one time. All those tyres go on production line with just in time delivery as vehicles are made. The production line doesn't stop, but the supply of the next tyres do change.
Go to any motor factor sites and type in your registration for brake pads. You will get a choice from £30 to £80 for the correct part to fit your vehicle.
Advice from members about clamping, bleeding fluid, seized calipers, sticking sliders maybe true but isn't what happens in today's world.
The garage will remove the caliper to replace the disks by hanging on the suspension/coil/or any other place it will balance! They will push back the caliper pistons on front and wind back on rear. The rear calipers have flexi hose as live axle which floats. No need to remove fluid to atmosphere.
Vacuum advice spot on by exhausting brake pressure and start up with foot on brake.
Master cylinder seal, maybe not in my opinion. Bigger van, longer stopping distance. That's the general law of physics.
Boiling brake fluid would be a sign of water ingress from neglect to replace fluid and prolonged brake usage. In my experience, servicing intervals of changing the brake fluid is a money spinner, but still have to conform to manufacture recommended intervals. My father in laws astra is 16 years old with original brake fluid?
The are plenty of OEM parts available online from dealers. Buy online the correct parts and pay labour to your garage to carry out work. They are not going to say no! Find out, what the book time for work is and you can save more, but your garage may think your too much hassle to do the work anyway. Difficult one! The garage supplying parts, allows them to maximise more profit.

My advice about any garage is, when the service and invoices seem reasonable. You don't have misdiagnosed problems and you feel good about the work carried out. Keep hold of them!
I can assure you that, there are plenty of idiots work for main dealers.

Advice about race pads true, but I doubt it. I suspect, the pads and disks are the cheapest on the market and generally charged to customers are top quality. The garage maximises profit and that maybe not you want to hear, but it's reality.

Buy OEM / quality parts for steering and suspension. I would probably say the same for timing belt kits.

 

[martin2603]

Had this conversation with a colleague yesterday who has been an HGV Technician all his working life he is 62 so I would take his opinion seriously. Mercedes Sprinter s are notoriously bad for.braking but if you want it to stop only fit Genuine parts. Cheap aftermarket products will not do the job.

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[roadwarrior]

So....were the brakes just as bad before you had them replaced...what are you comparing them too ?

The brakes were bad and rear discs corroded and tramlined, I am comparing it to my 3 previous fiat ducato same weight motorhomes.

 

[Bessy765]

Have you got a balance compensator in the system some vans used to have one linked to the back axle to divide braking force dependant on how heavy the van was loaded. If that is out of sinc it can effect the braking performance.

 

[Silver-Fox]

Mercedes Sprinter s are notoriously bad for.braking but if you want it to stop only fit Genuine parts. Cheap aftermarket products will not do the job.

I agree cheap aftermarket parts are to be avoided.

But what are genuine Merc parts as Merc don’t make their own discs and pads.

If the parts supplier, I tend to use GSF, they flag up if it’s OE so use them.

It’s the same with cam belt kits for Fiat.
Much discussion about using Fiat parts but again they don’t make them.

It can be a mine field out there

 

[roadwarrior]

Here is my dilemma and question - given that OEM is best and it's known that sprinter brakes are bad (fitted with OEM pads and disks.. ) I have noted that the disks are bigger than fiats and fronts are twin calipers so they should be better than fiat but clearly not. My brakes are now better but only adequate not good, new fluid, no air in the system and properly bled with new all round discs and pads of unknown make and quality. Not how I do things but had no control as fronts fitted by dealer for MOT/sale before I bought it and rears fitted by local garage but failed to check what went on. But when I brake, it does not dip at front as I would expect giving me the impression the fronts are not biting as I might expect them too. Especially as they are twin pistons. I am quite prepared to accept by other posters that sprinter brakes are crap, so my question is, how can I improve them ? I am even pondering green stuff, not used that for maybe 30 years and not cheap either. I wonder if the servo is to blame for poor braking on sprinters ? As an old git I really don't need this greif.

 

[roadwarrior]

Have you got a balance compensator in the system some vans used to have one linked to the back axle to divide braking force dependant on how heavy the van was loaded. If that is out of sinc it can effect the braking performance.

It crossed my mind too, but how do I find out and what do I do about it ? And then.. if we assume air bags prop up the rear suspension is it in some way upsetting the compensator ?

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[Bessy765]

Here is my dilemma and question - given that OEM is best and it's known that sprinter brakes are bad (fitted with OEM pads and disks.. ) I have noted that the disks are bigger than fiats and fronts are twin calipers so they should be better than fiat but clearly not. My brakes are now better but only adequate not good, new fluid, no air in the system and properly bled with new all round discs and pads of unknown make and quality. Not how I do things but had no control as fronts fitted by dealer for MOT/sale before I bought it and rears fitted by local garage but failed to check what went on. But when I brake, it does not dip at front as I would expect giving me the impression the fronts are not biting as I might expect them too. Especially as they are twin pistons. I am quite prepared to accept by other posters that sprinter brakes are crap, so my question is, how can I improve them ? I am even pondering green stuff, not used that for maybe 30 years and not cheap either. I wonder if the servo is to blame for poor braking on sprinters ? As an old git I really don't need this greif.

If the fronts not dipping as I stated check if you have a load compensator it reduces rear braking according to how the van is loaded so if empty the rear wheels don't skid then puts more to the rear if heavily loaded so if it’s out of sinc it may affect the fronts? Not sure about mercy though and its on older vans?

 

[Bessy765]

Not sure if your van has shoes for the handbrake or it uses the pads, if it uses the pads just try putting the handbrake Ona couple of clicks and see if the foot brake improves, it could be the callipers are worn

 

[Landy Andy]

I would start with quality pads at the front, whilst fitting them get the pistons to come out of the calliper a bit and check they are not corroded and also check any slides if fitted. I would stay with quality pads, not race (green stuff and the like) pads. That would be my starting point.

 

[A-Mech]

The brakes were bad and rear discs corroded and tramlined, I am comparing it to my 3 previous fiat ducato same weight motorhomes.

I would say that they are cheap Chinese steel disks and similar pads with low friction property. (Not the general discription, I would normally use)
Landrover had same problem with new Freelander when the bought by price and not quality. The fix was to replace pads/discs and slider kit under warranty.
You should not have any rust marks or lines on braking surface area(after driving) If its been parked up all winter, you will have rusty disks.
Rough rule of brake balance is 75f/25r. You will go through 2/3 sets of front pads to one set rear pads. (Automatic gearbox will increase front wear)
My first post mentions that manufacturers don't make parts. I seem to remember (grey fog) that, brembo are OEM supplier?
Confidence is the major factor for anyone and compromise should not be an option.
Take MH to MOT Centre and ask for brake test.

 

[Silver-Fox]

My first post mentions that manufacturers don't make parts. I seem to remember (grey fog) that, brembo are OEM supplier?

I’ve got a Merc Rapido 2006.
The brakes arnt sports car stoppers but work ok.

I just checked GSF parts and they list and keep Delphi discs as OE.

Didn’t check pads.

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[Clive Beeza]

I would start with quality pads at the front, whilst fitting them get the pistons to come out of the calliper a bit and check they are not corroded and also check any slides if fitted. I would stay with quality pads, not race (green stuff and the like) pads. That would be my starting point.

absolutely agree with Landy Andy here, a lot of the advice posted on here appears to be clutching at straws,
and some well intentioned but very dubious advice too.
regarding does it, or does it not have a balance compensator device, go to a merc commercial main dealer, and get a definitive answer
then go back to A-Mech, and Landy Andy's advice,
bite the bullet and purchase OEM front pads, bed them in slowly and see if that puts things right for you,
if still dissatisfied research upgraded front brake calipers

 

[Spriddler]

Deleted. My suggestion has already been mentioned.

 

[jockaneezer]

Lots of counterfeit brake pads out there, the packaging is superb, actually the cardboard they use is probably an ingredient in their pads too !
A workmate changed the pads on his old Astra, using a G clamp to drive the piston back, the brakes were terrible and it was suspected that he had rolled the master cylinder seal back on itself as a new MC sorted it. When we had a bit think about it, as we were sure the seal shouldn't have suffered, we came to the conclusion that the larger area of the caliper's piston, coupled with a bfo G clamp must have over pressured the smaller MC seal ? We should have stripped the MC to check our theory, but he got a refund for handing the old unit in as a service exchange.
I always crack the nipple open when pushing the piston back to prevent any likelihood of this happening and it also allows fresh fluid down into the calliper to replace the stuff that's ejected.

 

[donkey]

It crossed my mind too, but how do I find out and what do I do about it ? And then.. if we assume air bags prop up the rear suspension is it in some way upsetting the compensator ?

If the vehicle has both air bags and brake load sensing valve, then the valve linkage should have been adjusted at the time of the suspension up-grade. Failing to do this will result in insufficient pressure to rear brakes.

Geoff

 

[roadwarrior]

As I understand the compensation valve correcty, as weight is added to the rear axle, it allows. GREATER fluid into the rear brakes which will remove braking force from the front brakes to prevent a skid ect. If that is correct then that is what I assume is what I have right now. The van will not dip as I expect it to. Previous Inspection underneath revealed the leaf spring looking sorry for itself nowhere near it's legal limit, and that fact was instrumental in me deciding to have bags fitted and share the load. Now is all that is true and the valve reacts to the hight of the body....A little more air in the bags,,,

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[Silver-Fox]

Previous Inspection underneath revealed the leaf spring looking sorry for itself nowhere near it's legal limit,

If you thought the spring was iffy I’m surprised you didn’t change the pair.

The air bags are more of an assist than to compensate for poor springs.

As said before I’d nip along to a mot station that can give you a print out of the brake efficiency.
That should give you an idea of the brake % front to rear.

 

[donkey]

As I understand the compensation valve correcty, as weight is added to the rear axle, it allows. GREATER fluid into the rear brakes which will remove braking force from the front brakes to prevent a skid ect. If that is correct then that is what I assume is what I have right now. The van will not dip as I expect it to. Previous Inspection underneath revealed the leaf spring looking sorry for itself nowhere near it's legal limit, and that fact was instrumental in me deciding to have bags fitted and share the load. Now is all that is true and the valve reacts to the hight of the body....A little more air in the bags,,,

Your thinking is flawed, in that the load sensing valve only limits fluid pressure to the rear brakes, it does not, as far as I am aware, have any effect on the front brakes. Having said that, if the brakes are applied but the driver feels the need to press harder, then yes the front brakes will be called upon to work harder.
The fitting of air bags to the rear axle has the effect of lifting the chassis. This is signalled incorrectly to the load sensing valve, that the vehicle is unladen, as it only gets its information from setting of the linkage. It is therefore essential to re-adjust the load sensing valve to compensate for the raising of the chassis. All good suspension kits come with comprehensive information about this vital adjustment.

Geoff

 

[roadwarrior]

Hello Geoff, your thinking is also flawed, given that the pressure provided by me is finite, ANY pressure allowed at the back MUST be taken from the front, or if you prefer shared. Either way it will reduce front braking power.
Also I have stated already the bags were fitted to help the tired leaf springs and would have lowered the chassis and confused the valve to increase to the back...sooo.. I will raise the body with airbags to rectify that. And before anybody suggests I should have replaced the spring, consider this , costing about the same, I can replace the springs, or I can fit airbags and raise my legal carrying capacity. What would YOU do ?

 

[donkey]

Hello Geoff, your thinking is also flawed, given that the pressure provided by me is finite, ANY pressure allowed at the back MUST be taken from the front, or if you prefer shared. Either way it will reduce front braking power.
Also I have stated alreadyand confused the valve to increase to the back...sooo.. I will raise the body with airbags to rectify that. And before anybody suggests I should have replaced the spring, consider this , costing about the same, I can replace the springs, or I can fit airbags and raise my legal carrying capacity. What would YOU do ?

Why would pressure to the rear be taken from the front. They both rely on different power sources. The unit is called a dual master cylinder, both work independently. If one circuit fails the other will still provide emergency braking.

Not sure about your statement " the bags were fitted to help the tired leaf springs and would have lowered the chassis ". Before inflation the chassis ride height would have been unaltered. The introduction of any air pressure into the air bags would have raised the chassis. It could not have lowered the chassis.

Geoff

 

[roadwarrior]

So have the front pads been previously fitted to old corroded disks ?
That could be your problem if I read it correctly ?
New quality front pads needed

No new discs and new pads at the same time

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[roadwarrior]

Why would pressure to the rear be taken from the front. They both rely on different power sources. The unit is called a dual master cylinder, both work independently. If one circuit fails the other will still provide emergency braking.

Not sure about your statement " the bags were fitted to help the tired leaf springs and would have lowered the chassis ". Before inflation the chassis ride height would have been unaltered. The introduction of any air pressure into the air bags would have raised the chassis. It could not have lowered the chassis.

Geoff

Geoff, I'm going to type this slowly so you understand. Back to school for you I think. Let's pretend I push the pedal at 5psi - that 5psi is distributed as 2.5 psi each way half to the front half to the back, If I have a valve that suddenly allows more fluid IE more pressure to the rear wheels it MUST alter the pressure to say 2 front and 3 rear, that is physical scientific law, you can't give without taking away. See Einstein for details. Something about for every action there must be an an equal and opposite reaction. A valve cannot MAKE power it can only direct it.