Changing Brake Discs and hoses on MB Vario

[docka]

Hi guys, need a bit of help with this as my local garage doesn't have the space to do my Vario.

She's been off he road for a while and needs discs, pads and flexi hoses doing, the air system is ok.
My nephew is a competent pro car mechanic and has offered to come by and help but he's not familiar with the air assisted brakes on these trucks.
So, some questions, sorry if they're stupid ones...!

Can we change discs/pads/hoses as normal and just bleed off the hydraulic side or will we need to do the air aswell?

Do the rear hubs need to be removed to change discs as I've heard they can be a bit tricky on Varios?

Thanks chaps

Docka

 

[Ullie]

In the front you can just change and bleet the system, as long as the ABS-unit didn't got dry. Otherwise you have to put the breaking fluid in the system starting at the wheel. (with a presure pump) Otherwise you won't get all the air out of the ABS-unit. (We had to change the front breaking fluid metal circuit starting at the ABS-unit)
We've got drums in the back, and these can be changed and bled like a normal car.

On our Vario (1997) the air is only for the parking break. So no connection with the disk or drum system.

Good luck, nice and easy job.

 

[docka]

Thanks Ullie
We will have a go at the front and see how we get on.
The front driver's side brake is sticking on but may just be pads on disc. I assume we will find out if ABS unit is dry...

Mine's a 2002 so I assume it's not just the parking brake that's air-assisted but the whole system, can anyone confirm?
I realise there's a lot I don't know about my van...

Cheers

 

[ianc]

If you have disks on the back then the hubs need to come off to change them. The risk is that they will not seal when refitted and the whole bearing needs to be replaced . One of my hubs has leaked a little since doing the disks (I had someone do them)

 

[docka]

Thanks Ian

Yes, I've got discs on the back. The bearing is what I was worried about as I know they're expensive to replace. Fronts appear easy enough though...

Having looked again at the picture in the manual it looks as though the rear hub doesn't have to come off, just the wheel flange ring or am I reading that wrong?

Edit. the picture appears to show the axle/wheel bearing already removed so you're right.
Ian, did your mechanic fit new hub seals when rear discs were done?

 

[ianc]

No

 

[Ullie]

My English is not good enough to know what the hub exactly is.
But with our wheeldrums, we had to take out the entire axle of the scharft to repare the brakes in the back. (to take off the drums) Never had to replace any bearing or joint. We've drivin 10000 km since and everything is still OK.

 

[docka]

Thanks Ullie and Ian

Have done pads on front, had to remove callipers and pistons and clean out as they were seized. Snapped one of the copper brake lines so fresh one fitted. Front disks are ok but I'm definitely going to have to do the back ones, I'll let you know how I get on with the hubs...

 

[ianc]

Any chance you can take photos and share?

 

[docka]

Yes, it's about time I contributed more to the forum after having learned a lot from other builds.
I will do some more research first so I have a better idea of what I'm getting into. Failing that I'll just steam into it...!
The load sensing valve also appears seized so I'll have a wee look at that too...
Cheers

 

[andylod]

Hi docka
You'll find that removing the rear hubs isn't a problem but be very careful not to damage the seals to much. You can't replace the bearings and seals you have to replace the whole hub ( approx £350 each ).
I have had leaky seals on the back for approx 2 yrs and cover 15k miles / yr ...... It doesn't affect anything and only looses about an egg cup full of oil every year.
Sticky brakes on varios that aren't used regularly seem to be the biggest problem so make sure all caliber sliders and pistons are nice and clean. Company in Birmingham does recon calipers and are very efficient should you need any.
Cheers
Andy

 

[docka]

Thanks Andy
Yeah the £350 price tag is more than enough to make me a bit worried about tackling this job but I'm gonna give it a go. Just waiting for some new discs/pads etc.
The rear brake limit/load valve appears to be stuck too, anyone else had this problem and managed to free it off or is it a case of a new valve?
Also, when bleeding the hydraulic fluid of the brakes, does this affect the air part of the system?
Cheers
Joss

 

[andylod]

Hi joss

If you know how a braking system works on a car, air over hydraulic brakes work in basically the same way exempt the handbrake.
When you press the brake pedal you are operating an air valve (just like a vacuum servo on a car ) that then operates the master cylinder..... this just means you don't have to press the brake pedal so hard. The hand brake is applied by 2 big springs, it's air pressure in the spring chambers that compress the springs and release the handbrake .... No air and the handbrake stays on ( unless you carry the 2 release bolts just in case ).
So no you won't need to do anything with the air just bleed the brakes like you would on a car. Try not to loose to much fluid because if you drain the abs unit you will probably need to back fill it from the calipers which can be pain.
Hope this helps
Andy

 

[docka]

Andy, thanks for the explanation, that makes a lot more sense now. Still trying to figure out the load sensing valve however as it appears seized, anyone any experience of that?
I've ordered rear discs and pads and the job is pencilled in for wk end after this, I'll take some pics and do a little write up (from my layman's perspective anyhow).
I had to replace both front flexi hoses when I put new pads on and did lose some fluid but from above the caliper so I'm hoping they're ok. How do you know if the ABS unit goes dry, will it flag a warning light up?
Thanks
Joss

 

[andylod]

No the abs unit will just have air in that you can't get out and the pedal will either feel spongy or the brakes will be really sharp.... Like all or nothing........I had a broken pipe and lost all the fluid out of one of the master cylinders and it bleed through fine. To be sure what you can do is once you have blead normally jack the brake pedal down with a Length of something wedged under the steering wheel and leave it over night. If there are any air pockets they will normally rise up to the master cylinder and come out when you release the pedal. If that doesn't work Merc will have to pressurise the caliper and operate the abs with a diagnostic computer......... Anyway I'm sure you won't have any problem