Where to service drum brakes on 1989 MB 1017A?

[gvvaughan]

Plea for help....

Short version: Truck is stuck in the Sacramento area, but shakes uncontrollably when foot brakes are applied. Any clues for who can help diagnose what parts to order and then fit very very much appreciated!

Long version: After an overly long box refurb in Sacramento, CA I had a local diesel shop change all the fluids and filters before collecting to start adventuring and the refurb shop jump started before I arrived... but a loose drain plug meant reduced oil pressure ending with a break down shortly after reaching highway speeds. Dead batteries hadn't been charging off the alternator so I couldn't even crank the engine to get started again. A short 1.5 mile tow back to the shop with front wheels off the ground, and air back fed into the air system by the tow truck to release the air brakes... but must have damaged the rear drums/brakes/something. Importing parts is expensive, so I'm hoping to find someone who can at least tell me what is damaged and needs replacing to make me roadworthy again in one go.

Trailering to someone who can handle the whole repair would be even better.

Thanks so much for any help or pointers!

Gary

 

[VerMonsterRV]

Crawl under the rear of the truck. Remove the rock shields on the inside of the wheel hubs (4 bolts on each side). Have someone else use both the service and parking brakes while you watch the brake shoes. They should be.7mm away from the drum surface when not engaged. Then tight against the drum when the brakes are in use.

 

[DiploStrat]

Try Rob Pickering, Terry Lee Enterprises, La Junta, Colorado.

 

[gvvaughan]

Crawl under the rear of the truck. Remove the rock shields on the inside of the wheel hubs (4 bolts on each side). Have someone else use both the service and parking brakes while you watch the brake shoes. They should be.7mm away from the drum surface when not engaged. Then tight against the drum when the brakes are in use.

Thanks for the advice. Considering the severe shaking, I'm almost certain that the distance will not be .7mm... how do I tell wether the drums are warped, shoes are misaligned, whether they can be adjusted or need resurfacing or replacing after that?

 

[gvvaughan]

Try Rob Pickering, Terry Lee Enterprises, La Junta, Colorado.

Left a voice mail, thank you!

 

[Neil]

Hi Gary

Sorry to hear your issues.

I'm a bit confused by the description.

I'm assuming it was all good before the two truck put air in the system.

Pressurising the system to just over 6 bar will be sufficient . To get the parking brake off . You cannot over pressurecthe system as it will start to dump air at 8.1 bar . This pressure would not be sufficient to damage anything in the hub. In addition the hubs would not get this pressure unless the foot pedal was applied to activate the hydraulic circuits .

It's hard to work out exacly why this violent shake is occurring . Is it definitely the rear.

Are there any extra red warning lights that have appeared on the dash board

Neil
( I have a 1017a)

 

[Neil]

Gary

More questions

We're you present when it was pulled into the loader. If so was the air system definitely up to full pressure and the parking brake fully released or could it have been still on and was pulled against the brakes friction causing damage inside the drums.

I'm with Jon , take the plates of the back of the drums and start looking inside .

The brake shew adjusters are very fragile, if these have been damaged or bent than it could cause everything to be out of place

Neil

This might help

 

[VerMonsterRV]

Although a little late, if you ever need to be towed there are bolts in the end of the rear brake combination cylinders. Right on the end in the middle. If you run these bolts all the way out until they stop, they compress the parking brake spring. No need to air up.

To really check things, jack up the rear and put in stands. Take the wheels off along with the rock shields. Then you should be able to turn the drum checking the clearances. At that point the drums should come off easily so if you want you can look at the shoes and wedge units.

I just completed a diy brake refresh (1120AF) including cylinders, wedge units, drums and linings. They are not terribly complex, just got to be willing, have basic skills and the parts. All the parts did come out of Europe. The parts weren't inexpensive but now I know the brakes are 100% and feel comfortable working on them.

 

[gvvaughan]

Hi Gary

Sorry to hear your issues.

I'm a bit confused by the description.

I'm assuming it was all good before the two truck put air in the system.

Pressurising the system to just over 6 bar will be sufficient . To get the parking brake off . You cannot over pressurecthe system as it will start to dump air at 8.1 bar . This pressure would not be sufficient to damage anything in the hub. In addition the hubs would not get this pressure unless the foot pedal was applied to activate the hydraulic circuits .

It's hard to work out exacly why this violent shake is occurring . Is it definitely the rear.

Are there any extra red warning lights that have appeared on the dash board

Neil
( I have a 1017a)

Hi Neil,

Thanks for the advice! Yes, I was up and down mountain roads using foot and air brakes with no issues until the break down. And AFAIK (from the refurb shop who test drove it after replacing the dead batteries) the shaking is from the rear of the truck, and no warning lights on the dash... but I'll call today and have them confirm.

Are you saying that after lifting the truck and back feeding air, I should have pumped the foot brake to release the rear shoes before starting the tow? Parking brake was off, but I didn't pump the foot brake once the air was pressurized, so a 1.5 mile tow with the brakes (even partially) engaged would certainly not have been good for them

Cheers,
Gary

 

[gvvaughan]

Although a little late, if you ever need to be towed there are bolts in the end of the rear brake combination cylinders. Right on the end in the middle. If you run these bolts all the way out until they stop, they compress the parking brake spring. No need to air up.

No, that is great to know. I'll be very happy to never have to go through this again, should I ever need to be towed in future.

To really check things, jack up the rear and put in stands. Take the wheels off along with the rock shields. Then you should be able to turn the drum checking the clearances. At that point the drums should come off easily so if you want you can look at the shoes and wedge units.

I had the shop do that already, but from there they couldn't figure out what parts need repair or replacement. I'm worried that they are just being lazy and don't want to do the work, but will have them try again with all this new information. Much appreciated!

I just completed a diy brake refresh (1120AF) including cylinders, wedge units, drums and linings. They are not terribly complex, just got to be willing, have basic skills and the parts. All the parts did come out of Europe. The parts weren't inexpensive but now I know the brakes are 100% and feel comfortable working on them.

Seems like something I could tackle myself if all else fails... just need to get some bigger jacks and axle stands, and figure out what parts to order.

Thanks again! Much appreciated!

Gary

 

[gvvaughan]

Gary

More questions

We're you present when it was pulled into the loader. If so was the air system definitely up to full pressure and the parking brake fully released or could it have been still on and was pulled against the brakes friction causing damage inside the drums.

Yes I was with the truck for the tow, parking lever was in the off position, the red hydraulic pressure light was off on the dash, and there was no squealing as the tow truck started pulling. Buuut... I agree that the likely cause is from foot and/or parking brake not being properly disengaged during the tow.

I'm with Jon , take the plates of the back of the drums and start looking inside .

The brake shew adjusters are very fragile, if these have been damaged or bent than it could cause everything to be out of place

Neil

That's a good place to start. Thanks again!

This might help

OMG! Where did you find that? I have only a German owners manual, and no workshop manual at all. You have totally saved the day!!

Cheers,
Gary

 

[Neil]

Gary

I have sent you a PM

Hope they help you

Neil

 

[theangrychicken]

I'm not sure if I can be of much help with my limited mechanical experience or knowledge about these trucks. But I'll be having my brakes/suspension worked on about 100 hours south of you next week in a 917. Sometimes it helps to have a side by side for comparison? I'd might be able to head your way after my repairs.
That region is a busy agriculture pipeline and there should be a lot shops that can assist. But sometimes finding a shop that can help can be challenging. I'm going to the San Leandro site next week:https://bettstruckparts.com I haven't had service there, but I was surprised to find that many places wouldn't help with swapping out a broken leaf spring (I have a spare). They said they could do it and make new U bolts, etc. They are are also helping with swapping out a rear air brake canister.
I see that they have a Sacramento location as well.

 

[gvvaughan]

I'm not sure if I can be of much help with my limited mechanical experience or knowledge about these trucks. But I'll be having my brakes/suspension worked on about 100 hours south of you next week in a 917. Sometimes it helps to have a side by side for comparison? I'd might be able to head your way after my repairs.
That region is a busy agriculture pipeline and there should be a lot shops that can assist. But sometimes finding a shop that can help can be challenging. I'm going to the San Leandro site next week:https://bettstruckparts.com I haven't had service there, but I was surprised to find that many places wouldn't help with swapping out a broken leaf spring (I have a spare). They said they could do it and make new U bolts, etc. They are are also helping with swapping out a rear air brake canister.
I see that they have a Sacramento location as well.

That's very kind of you to offer, thanks. I'll keep in touch as I try to work with the shop that has my truck to get a better diagnosis. Betts truck parts has a shop in Sacramento too, so that's a useful contact to have, thanks!

All the 30+ year old leaf packs on mine were completely flattened out, and I found a fabricator just North of Sacramento who replaced all four sets with better load bearing so I don't bottom out off road now. If it's useful for you, I can dig out their number?

*edit* https://sacspring.com

Cheers,
Gary

 

[VerMonsterRV]

One thing I recommend to all owners of these trucks, especially ones in the USA. Get the EPC/WIS off of eBay and load it up, here is one of them that should work. Even if you do not do the wrenching it will help the mechanic. I have found American shops are a bit reluctant to work on these trucks. They are worried that parts could not be found and we would clog up the bay. When I presented not only all the needed parts and the workshop manual they relented.

Mercedes & smart wis/asra 10.2020 workshop service repair manual 1985 2020 Last! | eBay

You will need a Windows laptop but it will allow you to lookup your truck by VIN and get the part numbers. It is pretty computer resource intensive so make sure your laptop is up to snuff. It will not only allow you to look up parts but is also the workshop manual with the procedures, specifications and if any specialized tools are required.

So back to your brakes. They really are pretty simple in how they work, if you remove the rock guards (4 small bolts on each wheel, best if the wheel is off the ground so you can rotate) and take a look while someone uses the brakes you should see what is wrong. Worst case is to jack up the truck, remove a wheel and pull off the drum, any mechanic should be able to do that in a few minutes. Given how short of a distance you were towed I am betting it is pretty basic, maybe something as simple as a brake shoe return spring that has broken, causing a shoe to drag. After our brake issue I removed the rock guards and had my wife activate the brakes. I immediately saw a couple issues that were the cause of our problem. I am no mechanic but I can usually take things apart and put them back together with a bit of guidance (from others or from the workshop manual). If you do need parts my guess is most, if not all will have to come out of Europe so you will need to plan ahead as shipping can take a bit of time. The drums are the most challenging as they are a bit heavy and requires a pallet to be shipped.

Not sure how much you know about air brakes so this is what I have learned. Your rear brake canisters are combination cylinders. The combination is made up of 2 parts. The service brake and parking brake. When you release the parking brake air is forced into the parking portion compressing the spring I mentioned before that you can manually compress with the bolt. This needs to be pressurized all while you are driving. If you lose air pressure your rear brakes will lock up using the parking brake spring. This is a safety feature. The service brake is normally empty of air and only fills when you press the brake pedal. It is purged when you release the brake pedal.