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.

 

[EuroTrotters]

Unless there is a serious fault/issue with your brakes, its a common complaint with Mercedes 4XX series Chassis.

I ran a Fleet of Sprinters from 1995 to 2004. 3XX, That is 311CDi, 313CDi and 316CDi were fine.

But our 4 Series, 413 and 416Cdi were poor on braking.

Our fully loaded 416Cdi Euramobil Motorhome, could be scary sometimes. I have had a few hard footed moments on the brakes.

Then I would get in my car or work van after driving and then when braking, almost end up nosing the windscreen

I think there may be a way of uprating the discs. Might need to speak with a specialist

 

[Daffy64]

I’m not completely familiar with the sprinter van but I’d be surprised if the brake vacuum comes from the Turbo, normally there is a vacuum pump that is engine driven.

The test described above where you pump the brake with the engine stopped until it goes hard then hold the pedal down and start the engine is a good test of the presence of vacuum at the servo.

That being said, in my experience vacuum pumps rarely fail but the rubber hoses between the vacuum pump and servo do sometimes get contaminated with oil and close up under the vacuum thus reducing the effect. - This is where I would look first.

I’d say that a seized caliper is unlikely and pad material wouldn’t make that much difference to initial bite unless it was a very dodgy pad material but thats very unlikely.

EDIT, just seen Eurotrotters reply above, it could also be the brakes aren’t very good on any of that type.

2nd Edit, to answer the OP’s question, Texstar are a good pad, a little soft so will bite but also not last quite so long.

 

[rod_vw]

Wear sensors are integrated into the pad. I think it's just a filament within the pad material that forms a circuit that gets broken when the pad gets too worn?

Not in all cases nowadays on some vehicles. Sometimes the sensor is supplied separately and inserted in one of the pads when they are changed. Pain in the proverbial at times but that's how it is.

 

[Redken]

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.

Have been told that pushing the pistons back can cause the seal in the master cylinder to flip over and this then results in poor braking at all wheels. If it was a mechanical fault at the calliper it would be some coincidence to have the same fault at the same time on all 4 brakes. Look for something that is capable of affecting all the brakes. When pushing the pistons back, I always release the displaced fluid at the bleed point. If it turns out to be the pad compound EBC do different pads with different performance, try the green ones, the black tend to match the original.

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[Broadway]

I have the same van and whilst I would say the brakes are fairly soft I’ve not had the experience you describe. I would recommend a full check up at a Mercedes truck/van dealership.

 

[SpeedyDux]

Heavy vans need longer braking distances. They are way behind modern cars when it comes to brake performance.

I have always felt that my Ducato is marginal when it comes to emergency stopping. I don't trust it and tend to keep much bigger gaps in front.

Having said that it could be that the OP has a set of counterfeit brake pads from a dodgy supplier.

 

[chesterfield hooligan]

I've run sprinters for 20+ year's and always fit either mintex or genuine Mercedes never a problem

 

[Klondike Ed]

HI, I have a sprinter 3.8 ton and I think the braking is poor but also have to remember its a sprinter running fully loaded all the time, my take on it is 3.8 ton takes a bit of stopping,

 

[roadwarrior]

i have had 3 ducato based MH with no brake problems all uprated to 3882 with no issues, this is my 1st venture into MB based Motorhomes, when i got it it had new front disks and pads, and i decided the braking was poor and had the rear disks replaced, the disc and pads were unknown to me when i looked at the empty boxes but decided to leave judgement till they were bedded in, they are an improvement but not great and as i am upweighting it to 4200k i am worried. On a car the braking ratio is about 70/30% front to back and the fronts do mostly all the work - is it the same on a van ?

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[07790]

I am on my 2nd Mercedes MH first 3880 Kgs second 4500 Kgs with both if you hit the brake pedal in an emergency the ABS kicks in preventing the wheels from locking up, you do not need to stand on the pedal to do this.

 

[TinaLes]

If we can assume for one moment that the standard brakes on any motorhome that has been upgraded weight wise i.e 3500Kgs to 3850/4000Kgs are not sufficient, or give cause for concern for the driver, then how do we go about getting good advice regarding brake disk/caliper upgrades?
Is there a website where you can enter the van cab/chassis type, along with axel weights front and rear, and can be given from that, the most appropriate upgrades, without having to change wheel rim sizes?
If there is such a site, this I am sure would be very helpful to many.
I was thinking Brembo and such like.
LES

 

[roadwarrior]

I am on my 2nd Mercedes MH first 3880 Kgs second 4500 Kgs with both if you hit the brake pedal in an emergency the ABS kicks in preventing the wheels from locking up, you do not need to stand on the pedal to do this.

sadly there is no chance of my abs kicking in my brakes are just too feeble

 

[Marshy 1]

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.

The rubber brake pipes can collapse internally when they get old and cause this symptom, but you cannot see this on the outside of pipe,

 

[L' Hobo]

Heavy vans need longer braking distances. They are way behind modern cars when it comes to brake performance.

I have always felt that my Ducato is marginal when it comes to emergency stopping. I don't trust it and tend to keep much bigger gaps in front.

Having said that it could be that the OP has a set of counterfeit brake pads from a dodgy supplier.

Sorry to disagree with you but under Vehicle Construction & Use regulations, ALL original vehicles must have EXACTLY the same stopping distance.
That is the reason why there is only one chart for 'thinking and stopping ' in the Highway Code.

It's also the reason why vehicles have different size and number of wheels and brakes.
It's the amount of rubber (footprint) that governs this calculations.

(At least that was the rule when I was a vehicle H&S rep for the TGWU many years ago?)

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[L' Hobo]

sadly there is no chance of my abs kicking in my brakes are just too feeble

Then you should seriously get them inspected by a specialist before you have an accident!
Especially now you have mentioned it on here because of if you're involved in a serious accident, forensics can examine your phone etc.

 

[Clive Beeza]

You have to push the pistons back to get the thicker material in, with all the will in the world this will introduce air even if just in the last foot of pipe you've pinches off.

worked on vehicles all my life and this reply is nonsense

 

[Clive Beeza]

Unless there is a serious fault/issue with your brakes, its a common complaint with Mercedes 4XX series Chassis.

I ran a Fleet of Sprinters from 1995 to 2004. 3XX, That is 311CDi, 313CDi and 316CDi were fine.

But our 4 Series, 413 and 416Cdi were poor on braking.

Our fully loaded 416Cdi Euramobil Motorhome, could be scary sometimes. I have had a few hard footed moments on the brakes.

Then I would get in my car or work van after driving and then when braking, almost end up nosing the windscreen

I think there may be a way of uprating the discs. Might need to speak with a specialist

sensible informative reply, there are multi choices of brands and materials for the brake pads
need advice from pad suppliers/ manufacturers, on uprated pads and alternative performance pad material

 

[Daffy64]

worked on vehicles all my life and this reply is nonsense

Agreed, as are a lot of the others, as they say “a little knowledge is a dangerous thing”

 

[roadwarrior]

Lets not get carried away Hobo, I said that they are lack lustre not non existant, they passed an mot when i bought it from a reputable dealer and since then i have had fitted new rear discs and pads which has improved it , and whilst its lovely to think so, I have no faith in stopping a truck in the same distance as a porsche 911. The highway code is hopelessly out of date on that score but im not going down that road today.
As for your phone theory, while I am aware we live in a police state, they are only going to check my phone to see if i have been chatting while trying to kill myself, and most importantly i dont have motorhomefun on my phone, but do you think we should be hiding that we are members of a potentional breakaway radical group of geriatric hooligoons with motorhomes on here ?

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[TinaLes]

Thats the main issue for me, they still pass an MOT inspection, some garages even provide a copy of the brake test performance front & rear along with hand brake, yet we all know some van/MH brakes are shite in the real world compared with modern cars.
Yes you have to drive within the limitations of your vehicle, make allowances for the fact that you cannot stop the same as a high performance car etc, but the selfish A holes that carve you up and brake hard to get in a motorway exit lane at the last moment don't seem to consider this.
LES

 

[roadwarrior]

indeed Les, im just looking for a little more brake power for those "special " moments, regarding MOT's as far as i am aware they mostly looks for brake differences left to right, poor braking is ignored unless very obviously differant.
I do recall when i was trucker i picked up an almost new 7.5 ton truck and the first time i applied the brakes after getting out of my own old truck i nearly went through the screen they were so good.

 

[Graham Page]

Unless there is a serious fault/issue with your brakes, its a common complaint with Mercedes 4XX series Chassis.

I ran a Fleet of Sprinters from 1995 to 2004. 3XX, That is 311CDi, 313CDi and 316CDi were fine.

But our 4 Series, 413 and 416Cdi were poor on braking.

Our fully loaded 416Cdi Euramobil Motorhome, could be scary sometimes. I have had a few hard footed moments on the brakes.

Then I would get in my car or work van after driving and then when braking, almost end up nosing the windscreen

I think there may be a way of uprating the discs. Might need to speak with a specialist

I agree with Euro Trotter as I have a 2004 Hymer on a Sprinter 416 chassis. The pads, disks and fluids have all been changed over the 10 years I have owned it by my local Mercedes Truck workshop, so all genuine OEM parts. There is and has always been a fair bit of travel on the pedal until the brakes start to bite, but to be fair when you have to shove the pedal they stop 4.6 tonnes gross fairly efficiently bearing in mind its not a car but a permanently fully loaded van. Changing the fluid regularly is quite key on Mercs service schedule so I would recommend thats done (if not already) as it did improve the feel of the brakes quite considerably when I had mine done about 3 years ago. Even if you don’t do the miles brake fluid should be changed as it slowly absorbs moisture - Scary thing when that causes a boil up coming down the mountain!

 

[Daffy64]

indeed Les, im just looking for a little more brake power for those "special " moments, regarding MOT's as far as i am aware they mostly looks for brake differences left to right, poor braking is ignored unless very obviously differant.
I do recall when i was trucker i picked up an almost new 7.5 ton truck and the first time i applied the brakes after getting out of my own old truck i nearly went through the screen they were so good.

The MOT looks for binding, imbalance and performance so if they have passed an MOT test Like they are then they will achieve the minimum standard, that being said it is a minimum standard.

 

[herald_400rl]

worked on vehicles all my life and this reply is nonsense

Bit unfair given the rest of the thread where corrections were made, but appreciate you feel your 2 cents is worthwhile adding.

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[pappajohn]

You have to push the pistons back to get the thicker material in, with all the will in the world this will introduce air even if just in the last foot of pipe you've pinches off.

Why would you pinch a hose to push pistons back?
Pushing pistons back into their cylinders will NOT introduce air.
It can't because the pressure of fluid within the cylinders being forced back is greater than air pressure trying to get in.

 

[pappajohn]

worked on vehicles all my life and this reply is nonsense

Couldn't agree more.

 

[herald_400rl]

Why would you pinch a hose to push pistons back?
Pushing pistons back into their cylinders will NOT introduce air.
It can't because the pressure of fluid within the cylinders being forced back is greater than air pressure trying to get in.

Again, all covered in the thread if you'd just read it...

 

[L' Hobo]

Lets not get carried away Hobo, I said that they are lack lustre not non existant, they passed an mot when i bought it from a reputable dealer and since then i have had fitted new rear discs and pads which has improved it , and whilst its lovely to think so, I have no faith in stopping a truck in the same distance as a porsche 911. The highway code is hopelessly out of date on that score but im not going down that road today.
As for your phone theory, while I am aware we live in a police state, they are only going to check my phone to see if i have been chatting while trying to kill myself, and most importantly i dont have motorhomefun on my phone, but do you think we should be hiding that we are members of a potentional breakaway radical group of geriatric hooligoons with motorhomes on here ?

When you use words like
'no chance to operate the ABS as brakes too FEEBLE'
others must be forgiven for getting the wrong impression (if that's what it was?)

 

[pappajohn]

I have read all the thread, it's impossible.

I was under the impression its not ideal to do so and instead the rubber flex should be pinched off and the bleed valve opened to allow fluid to come out.

No wonder you get air in.
If the fluid is released to air where does the replacing fluid come from?
Exactly the same place as the fluid you just released.....the brake line.
So what's the point.

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[pappajohn]

Have been told that pushing the pistons back can cause the seal in the master cylinder to flip over and this then results in poor braking

If that were the case the seal would flip when pressing the pedal due to fluid pressure in the master cylinder.
If it was to flip, which is impossible, you wouldn't have poor braking, you'd have no braking.