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Sun Nov 15, 2009 10:16 am

My brake peddle pulsates - I've checked the front end and rotors are at 11mm (so machining is not an option, only replacing if that is where the problem is). Front brake rubber hoses seem pretty old so I will replace these soon.
I removed the rear brake drums today - both look ok, no gouging or scratches but I can't tell if they need machining (except if they are causing the pulsating pedal). I want to clean up inside the drums as it looks like it hasn't been done in a while - see pics below:

Do these look particularly cruddy? What should I use to clean them?
But back to the main problem of the pulsating pedal - how do i know which part of the braking system is causing this?
Its my first brake work so any help is appreciated.

Sun Nov 15, 2009 10:26 am

Since you have your drums off at this point you can take them by your local brake shop and have them miked to see how far out of round they are.

Whoever has adjusted your brakes in the past appears to have been only adjusting one of the two adjusters on each side, or have been turning the one adjuster the wrong way. You should probably even them out when you go back together, this alone may help with the pulsation.

Dirt wise you brakes look pretty normal and you have a lot of wear left in the shoes.

Sun Nov 15, 2009 10:48 am

Exactly what Wildthings said. Adjust the brake shoes.

Wed Nov 18, 2009 2:03 am

Thanks for the advice.

I took the drums into a shop today. They measured the diameter with calipers and both were 251mm but they said that they couldn't machine them as the metal on the back surface (the disc shape part where the bolts fit) is a different metal (softer) than the metal on the rim where the pads rub. They said it would vibrate on the machine and they wouldn't do a good job. They said it was a problem with these types of drums.

Please bear in mind:
- I live in Greece and don't speak very good greek - my wife had to translate for me as they don't speak any nenglish. Hence the basic description above.
- To get *ANYTHING* done here is always difficult. It is the lifestyle!

I have some difficultly believing that these drums can't be machined. Shouldn't new drums also be machined before fitting (if so then I am screwed even if i replace the drums if i can't find a shop to machine them). Could it be that they don't have the best machine for the job, and that is the problem? Though I did see other drums in the shop to be repaired.

Would it help if i posted a pic of the drums to be sure that they are stock?

Thanks,
Nick

Wed Nov 18, 2009 2:13 am

It appear's that you have a leaking wheel cyl on the drivers side. pull back the boot and see if it is wet.

Wed Nov 18, 2009 4:55 am

This is probably a equipment problem on the part of the machine shop. I have never had any problem myself. Did you have the drums installed on the hubs when you took them in or had you removed them? Maybe they would be willing to try turning them with the drums still installed on the hubs. Use the lug nuts and some washers make sure the drums are held tight to the hubs.

Wed Nov 18, 2009 5:02 am

No, the drums weren't on the hubs. I left the drums with the shop as they said they can at least check if they need machining - not sure how they do this without turning them ??
I'll see what they say tomorrow and suggest putting them on the hubs... anyone got a greek mechanical phrase book :roll:

Wed Nov 18, 2009 5:19 am

Sorry, I just rechecked some pictures from the manual and my last post was wrong. Both drum and hub were taken to the shop.

Wed Nov 18, 2009 7:47 am

there is a tool. here in the USA we can find inexpensive versions at a company called Harbor Freight, don't know what companies you have there. The tool would be a dial indicator and a magnetic base. This tool measures .001 of an inch by pushing on the tip. The magnetic base will hold it. With the arms on it, you can stick it on a metal part and spin the rotor on the front and see how much runout it has in it. You can also adjust the wheel bearings or use it to set the engine end play when/if you ever rebuild the engine. If the rotors have more runout than specified in the Bentley VW manual, then they are the source of your problem. I would consider replacing the fronts with new or thicker used ones if they are down to minimums. Continue trying to have the rears checked and machined if need be. I've had VW drums machined many times in my life. What year VW bus is this?

Wed Nov 18, 2009 8:10 am

It is a 1979 bus with a T1 1600 DP engine.
If I don't get any joy out of the machine shop in the morning I'll go looking for another.

Thanks,
Nick

Sat Nov 21, 2009 10:42 am

An update. I finally found a brake specialist shop that could machine my drums. This place was doing trucks and buses so they meant business! They needed the wheels bolted to the hubs as well. Charged 50 euro for the two.

I checked under the boots of the cylinders and they are dry - no leaks. Cleaned the brakes, installed and adjusted. All ready to test drive tomorrow after I do a tune.

One question on the brakes for future reference. If I just want to go straight into the drums, is the best/easiest/recommended way just to back off the star adjusters, remove the hub nut and take off the drum, hub and wheel all at once?

Sat Nov 21, 2009 11:19 am

I've forgotten what year your bus is (please add that to your sig line), but if it's a 71 or newer leave the hub on and just remove the drum.

Sat Nov 21, 2009 12:01 pm

If you cleaned both cylinders before you replaced the drums....good. What I would suggest it to pull them off after a 1000 or so miles and check them for the same condition as in the first photos. If so I would change them and at the same time replace the the two front hoses. There is nothing worse than having to pay for a new set of brake shoes and clean up the mess from the brake fluid.

It looks like the back shoe adjuster is frozen. If it is the other one is not far behind. Then I would do both sides.

Sun Nov 22, 2009 2:33 am

looks like you were right. Gave it a test drive today and the right (p/s) rear brake was clattering. Took a look under the cylinder boot and some fluid ran out. Damn! I haven't heard the rear brakes clatter before so can someone confirm that other than seeing a lot of fluid, the clatter can also be a symptom of a stuffed cylinder? I'm sure the pads are seated well and were adjusted properly.

Just want to get a handle on when this happened. As there was no fluid before, could the seal have gone when my wife was vigorously pumping the brake to center the shoes while i was underneath adjusting them? Not wanting to lay blame here, just wanting to prevent it happening again. If so i guess the cylinder was about to go anyway if it wasn't already bad.

Also note that the dirty cylinder pictured in my first post is the d/s, not the one leaking now.

Sun Nov 22, 2009 2:44 am

On my 71 I replaced both rear cylinders, brakes and had the drums turned. On the front I replaced the calipers turned the disks and replaced the hoses and master cylinder. Nothing last forever.

It took almost a quart of fluid to clean the system out and get the brakes braking. I have a lot of hills where I live.

Sun Nov 22, 2009 3:10 am

yeah i am also living on top of a hill with the steepest driveway i have ever seen, so i'd like the brakes to work a bit better. I will replace the cylinders, but i just watched the justkampers brake removal video and noted that i don't have the "anti-rattle" pins, so i guess this could be the cause of the rattle, particularly as the drums were machined but the pads weren't ground to match.

Sun Nov 22, 2009 3:44 am

I just took a look at your brakes and yes they are missing. There is two on each side or one for each brake. Anti rattle, well not really from what I remember what I was told many years ago they are to keep the brake face square/paraelle to the drum and against the backing plate.
What year is your bus?

Sun Nov 22, 2009 4:13 am

When the seal of a piston is located in an area of the cylinder bore that it hasn't been operating in previously, it is apt to start seeping. With all the loosening and tightening, bleeding, R & R of the shoes, the seals were in different positions and they easily get damaged from contaminents or even rust pits in the cylinder. Plus being old seals. You will probably put in new cylinders so take an old one apart and see all the contaminents and goop inside. And your photos show the pistons way out of their normal positioning. Did they measure the drum out of roundness before they machined them?
I don't see how bad cylinders would cause clatter. Your clatter- How rapidly is it? One or two times per wheel revolution or much quicker? Depending on the frequency it would be hard to tell what the cause is. You could jack up a wheel and rotate it, and look at the clearance between the SHOE and the drum thru the inspection hole in the backing plate. You might even back off a shoe just a bit and stick a feeler gauge in the gap between the shoe and drum. I'd think you could discern any out of roundness within .001 or .002". When you put it back together did you check the raised points on the backing plate where the shoes rest? If they have ridges from wear the shoes can grab and jerk. Smooth those spots if need be and give them a little smear of lube.
Arching or grinding shoes to match drums used to be commonplace here. Now I don't know of anyone that does it. They just let the shoes wear to match the drums.
From your pictures it looks like your rear bearings might be dry and lacking sufficient lube. That's an important service maintainance item that most people ignore. But it's important.
If you replace a brake cylinder, do both sides.
My bus has the shoe retainers. But people here say that later years don't use them even though all the holes are there. The big springs hold the shoes against the backing plate.

Sun Nov 22, 2009 5:48 am

I'm confused here. Why does everyone expect the rear breaks to be giving him his pulsating at the brake pedal. It has been my experience that front rotors that are out of spec give you this problem more than rear drums. Replace the front rotors or have them turned, replace the pads, bleed the brakes and I think you will find that your problem goes away. I will agree that your rear brakes need some attending to but I'm putting my money on the front rotors as being your problem.

Sun Nov 22, 2009 6:13 am

Sawsalesman wrote: I'm confused here. Why does everyone expect the rear breaks to be giving him his pulsating at the brake pedal. It has been my experience that front rotors that are out of spec give you this problem more than rear drums. Replace the front rotors or have them turned, replace the pads, bleed the brakes and I think you will find that your problem goes away. I will agree that your rear brakes need some attending to but I'm putting my money on the front rotors as being your problem.

Correct.
Front rotors being warped/rusted will cause a pulsating pedal/vibration in steering wheel. Rear drums will cause the back of the vehicle to vibrate, usually felt in the seat.
Many have argued that front rotors do not warp. Call it what you want, warping, exessive material buildup, but if the rotor has excessive runout it will cause the pedal to pulsate.

The " "anti-rattle" pins" are actually called brake holddown pins. They keep the shoes in contact with the backing plate and away from the spinning drum. They are NOT USED on some model years. The design of the upper brake return spring being mounted on the back of the shoes causes the shoes to be pulled towards the backing plate.

Make sure you put a drop of neverseize or other brake lubricant on the 6 shoe to backing plate contact points, also where the shoes contact the wheel cyl and the brake adjusters. The threads on the adjusters should also be lubed.