Sprinter brakes again!

[FrankiaMH]

Hi,

This is my first post on this forum so here goes,

I have a problem with the brakes on our 2003 316 sprinter based motor home which has clocked up a grand total of 38,000 miles (hardly run in!). The brakes have always been spongy, typical sprinter but not a problem until recently when the pedal goes almost to the floor when it is pressed fully down. In reality there is not a problem stopping quickly but it is very disconcerting!

When the engine is not running the pedal is rock solid and perfect, start the engine and the pedal falls away. My first thought was the servo, but there is no indication of any leaks in the vacuum and the level in the reservoir has not moved since the fluid was renewed (2007) There are no visible leaks of fluid from any of the pistons or hoses.

Perhaps the master cylinder internal seals are letting the fluid back into the reservoir under the heavy pressure from the servo or worst case its the ABS modulator internal seals and that’s expensive!

I have found various threads on this site that have had similar problems and I wonder if anyone has had success curing this before I start work on the van.

Thanks, Neil

 

[louwdj]

I have no experience of the Sprinter but I would check all flex-hoses for bulging under pressure. Although, in retrospect, the brakes should then also be spongy with the engine off.

 

[UKJeffP]

Just posted a similar thread. As you will see mine is a mystery too. But I already have change master cylinder, servo and now the ABS unit all too no avail

 

[FrankiaMH]

Hi Jeff,

Yes I have just found your post too!

This seem to a very common theme and as yet there seems to be no quick answer. Its a bit worrying as you seem to have done all the things I hoped might cure it!
Lets hope that somebody out there has some suggestions.

Thanks for replying,

Neil

 

[Quick Silver]

Hi,

This is my first post on this forum so here goes,

I have a problem with the brakes on our 2003 316 sprinter based motor home which has clocked up a grand total of 38,000 miles (hardly run in!). The brakes have always been spongy, typical sprinter but not a problem until recently when the pedal goes almost to the floor when it is pressed fully down. In reality there is not a problem stopping quickly but it is very disconcerting!

When the engine is not running the pedal is rock solid and perfect, start the engine and the pedal falls away. My first thought was the servo, but there is no indication of any leaks in the vacuum and the level in the reservoir has not moved since the fluid was renewed (2007) There are no visible leaks of fluid from any of the pistons or hoses.

Perhaps the master cylinder internal seals are letting the fluid back into the reservoir under the heavy pressure from the servo or worst case its the ABS modulator internal seals and that’s expensive!

I have found various threads on this site that have had similar problems and I wonder if anyone has had success curing this before I start work on the van.

Thanks, Neil[/QUOTE


Does it feel like it only wants to break on the rear wheels , If so and your vehicle has been converted into a motorhome the load compensator valve may need adjusting .Ive had to do this on both my Vito's that have had a taxi conversion on them . Do not do it by trial and error though ,a rolling road and braking efficiency meters will be required .

 

[UKJeffP]

Hi Neil

As you will see from my post on the same matter I have been through allthe things that you are contemplating and still have no joy.

Jeff

 

[television]

I have sent you 3 papers on the bleeding of the brakes, they are a little bit different, and details of the ABS pump

 

[FrankiaMH]

Hi Malcolm,

Thank you for the reply.....But I am not sure where to find the papers you have sent me! There is nothing in my PM inbox or my email. As I am new here here, am I missing something?

Thanks also to Quicksiver and Jeff. There has been no problem stopping the motor home normally with brakes, it is only the falling pedal which has appeared in the last few months.....thankfully not in the Alps last year!

 

[television]

Hi Malcolm,

Thank you for the reply.....But I am not sure where to find the papers you have sent me! There is nothing in my PM inbox or my email. As I am new here here, am I missing something?

Thanks also to Quicksiver and Jeff. There has been no problem stopping the motor home normally with brakes, it is only the falling pedal which has appeared in the last few months.....thankfully not in the Alps last year!

I sent the papers tro UKjeff, if you would like them, please activate your Email address in your user CP and click save changes

 

[FrankiaMH]

Hi Malcolm,

Yes please, I have activated my email.....I think!

 

[television]

Yes it works and 2 papers sent

 

[steve hw]

sprinter brakes

The sprinter is reknown for pedal creep.(especially whilst stationary, engine at idle and holding pressure on pedal.)
But, i have found people jump to abs pumps and master cylinders etc before checking the basics. 1...You need to ensure the brake pads are in good condition. Not only the lining(friction materials) but its common for the metal plate part where the piston meets to corode over time. Also the slide areas where the pads locate in to the caliper carriers need to be clean and free from dirt and corrosion, with an anti seize lube. Please check this for front and rear first.
2.. ensure brake fluid is in good condition. Should be changed very 2 years.
3. if after bleeding, the system feels like air still in system there is a process that can be done using hht or star "exceptional bleeding". this is where the system is bled controlled by the abs pump
3 if all the above are done it is not unheard of for internal leakage or fluid transfer inside the abs pump. (but this is NOT a common problem)
Hope this helps
steve

 

[Quick Silver]

Hi Malcolm,

Thank you for the reply.....But I am not sure where to find the papers you have sent me! There is nothing in my PM inbox or my email. As I am new here here, am I missing something?

Thanks also to Quicksiver and Jeff. There has been no problem stopping the motor home normally with brakes, it is only the falling pedal which has appeared in the last few months.....thankfully not in the Alps last year!

Clutching at straws maybe but cheaper option ,completely flush out the brake fluid until you you have replaced all the fluid just maybe it is contaminated with moisture . Secondly I dont know how old your vehicle is but if my memory serves me correct there was a problem with the load compensator on very early models and there was several serious accidents some fatal and I believe their was a recall for a mod . Perhaps one of the Tech boys may pick this up to confirm or deny .

 

[television]

I must say that there are many papers on the brakes and the bleeding, this is hard for me, owing to the variations and amount of different chassis made. One needs to have a lot of information to give exact advice

 

[FrankiaMH]

Thank you all for helpful replies, it looks like I will be busy for the next couple of weekends!

I will let you all know how it progresses.

Regards,
Neil

 

[FrankiaMH]

Hi,
A further update on my Sprinter brakes.
Having checked the compensator valve was fully opened, the brakes were bled with little or no results…no air!
The master cylinder was stripped and examined, both seals and bore….perfect. The only possible explanation could be the joggle pins (one way valve) in each of the tandem pistons could be leaking under heavy servo pressure and allowing fluid to leak back in the reservoir. So do I invest in a new MC on the off chance that it is the culprit? So instead we have made a brake pipe with fittings to go between the two outlet ports on the MC thus effectively isolating the rest of the brake circuits and allowing the MC to be tested under full pressure. The result was good and bad!
Good that there was no pedal falling away proving the MC was not the fault, but bad that it is something else!
So we propose making four blanking plugs to fit on the ABS modulator output and hopefully proving that it’s not the problem either - if it isn’t we will test each circuit one at a time.

Does this sound too easy and has anyone got any further suggestions?


Neil

 

[FrankiaMH]

Hi,

A further, further update on the Sprinter brakes.
As mentioned in my last post, I made four short lengths of flared brake pipe, welded at one end to fit on the ABS modulator output. With all four ports bled and sealed there was NO pedal fall under full brake pressure (with engine running)......sigh of relief... it's not the ABS modulator or the master cylinder!

Connecting one circuit at a time, starting with the front, the pedal began to fall away when the rear brakes were connected. So next week I will follow Steve hw's advice and strip, clean and inspect each wheel in turn. The only thing left unchecked would be the brake proportioning valve.

Neil

 

[Dale Minton]

Correct Wheel bolts for SL R129.

Hi Malcolm, hope you're well. I posted a few weeks ago that I was considering installing a set of the 7 spoke wheels from an SL350 R230. You kindly advised me that it shouldn't prove a problem, as the offset difference is minimal (and it is, I believe it's only 1mm), however, you advised me that the bolts I would require would be 14mm items as opposed to the R129 bolts that are 12mm. I assume you must be talking about the head size and not the thread diameter.

Best Regards
Dale.

 

[mikestrivens]

Sorry Dale but what has this got to do with the original thread?

 

[Dale Minton]

It doesn't directly, but I thought I was in the right section - i.e Technical > Suspension & Brakes - it was placed into the very last post under this section, where should I have put it. Dale.