broken brakes.. still.

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65ghiabug67
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broken brakes.. still.

Post by 65ghiabug67 » Wed Jun 11, 2008 2:01 pm

about 2 years ago, we replaced the shoes and drums on my brothers 67 bug after we drove it a while on the worn out shoes and drums we bought it with off the PO. Since then, we haven't been able to drive the car due to them seizing unpredictably.

Wheels have been off and back on numerous times, nothing seems to be snagging anywhere, everything seems to be functioning perfectly until the brakes are applied. They seize up sometimes to the point of not being able to move the car at all. One day, somehow, we finally got them to work properly, drove it to inspection, about 8 miles, without a problem, it failed for emissions, and then on the way home, they started to act up again. By the time we parked it, the next time we went to move it, they were seized enough to hold the car in the driveway as if the pedal were to the floor. We replaced the MC after that, just today bled everything out, and its still doing the same thing in the front. Also, during the bleeding, the first time we open the valve on the pass. side, the pedal moves a small bit and then won't move at all during successive attempts on the fronts.

Does anybody have any suggestions? Thanks for the help.

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Gabe
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Post by Gabe » Wed Jun 11, 2008 2:46 pm

I know it's not much help, but brakes are something I deliberately choose not to work on and always have a "professional" do. Electrical, fuel, mechanical, I am more than happy to work on, but I will not touch brakes; the most critical component of an automobile IMO (life and death).

And it can be a dirty/unhealthy job . . .

Good luck though. I'm sure someone will come along who can help out.

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Post by Ol'fogasaurus » Wed Jun 11, 2008 3:16 pm

The first hing I would look at is the soft lines. They can get old and collapse (at least inside). There are four soft lines to look at, two in fronta nd two for the rear.

If the brakes are not adjusted properly, it is possible that the piston in the wheel cylinder could be blocking the return line. Only seen this happen once. When you adjust the brakes, make sure that you adjust the brakes until the drum lock, then back off the star until, when rotating the wheel/drum, you hear a slight acraping sound.

Next, maybe replace the wheel cylinders.

A place to start.
Lee

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Marc
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Post by Marc » Wed Jun 11, 2008 5:47 pm

Ol'fogasaurus wrote:The first thing I would look at is the soft lines. They can get old and collapse (at least inside). There are four soft lines to look at, two in front and two for the rear....Next, maybe replace the wheel cylinders...
Agreed, it does sound like a classic flex-hose problem...four new flex hoses will run you about $50; even if they look OK on the outside they're 'way overdue for replacement if they're the factory originals.
Sticking wheel cylinders are also a possibility, but before replacing them also check that the pedal stop is adjusted properly and if necessary adjust the master cylinder pushrod length (if there's no freeplay the compensating ports in the M/C will be blocked and pressure will build in the system as the fluid heats up):
http://www.shoptalkforums.com/viewtopic.php?t=890528

Another common mistake made by first-timers when replacing shoes on `65 and later VWs is installing the adjuster screws upside-down - their slots are tapered to match the angle of the end of the shoe, and if they're backwards the shoes can catch and cause false adjustment/intermittent symptoms. If `58-`64 shoes are used by mistake, those aren't angled at the end and you can have the same problem.

Four new flex hoses will run you about $50; even if they look OK on the outside they're 'way overdue for replacement if they're the factory originals.

65ghiabug67
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Post by 65ghiabug67 » Wed Jun 11, 2008 6:28 pm

the front rubber lines replaced relatively new lines, that was one of our first ideas.. the rears should be fine, the scraping and seizing has been localized to the fronts. I caught the adjusting stars issue the last time we had the wheels off after watching a bug me video on the topic..

for the mc pushrod, i thought that should be set and not messed with? or is that simply from the VW factory? i readjusted the fronts, the pedals stiff and moving with bleeding, though they're still sticking slightly when adjusted fairly loosely. ill check out the pedal stop and see what happens.

thanks for all your help, its nice to almost have it back to operational condition..

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Post by Scott Novak » Wed Jun 11, 2008 7:19 pm

NEVER assume that ANYTHING on a 30+ year old car is the way it is supposed to be and that hasn't been messed with!

Check EVERYTHING. If anything looks suspicious double check it.

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Post by Ol'fogasaurus » Wed Jun 11, 2008 8:09 pm

Did you bench bleed the MC before you installed it? (Did you go too far when you pumped the MC piston)

Have you done a complete fluid change, not just bleed the brakes?

Replace both of the front wheel cylinders. The PO or you may have messed them up. Overheating of the units can score the cylinders and pistons. (A good rule of thumb; new shoes, rebuild or new cylinders.) After re-reading your first post, I would start here first.

Look for pinches/flat spots/collapses in bends in the metal lines.

Don't assume that the rear soft lines are OK. If you felt that the fronts needed replacing, replace the rears too. Honestly, you just never know.

Does either of the front wheel cylinders bleed slow (see replace wheel cylinders)?

Do you have the MC hooked up correctly to the front and back (not turned around)

Do you have anything such as turning brakes or a line lock or park lock on your car? They're a good place for stuff like this to happen.

There is just so many things on a brake system that can go wrong. I would also look for foreign matter in the brake lines. Since the fronts are short, this is also a good place to look after the wheel cylinders are replaced.
Lee

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Post by 65ghiabug67 » Wed Jun 11, 2008 10:48 pm

the mc was bled before it was installed, the endplay on it seems to be alright, at the pedal its around 1/4 inch, as per bentley's instructions. fluid is most likely brand new by now, we've been bleeding, rebleeding, so on and so forth. every time we mess with them at all, we bleed until the fluid runs through looking like new. all the hard lines look good, no kinks or rust or anything of the sort.. also have checked the wheel cylinders, they are both fairly new, no scoring of the bores, all passages clean and clear, rust-free.

not sure what you mean about turning brakes or a line lock/park lock.. in any case, i think ill be out there again tomorrow trying to tune the carb once again until itll stay running, adjust and tighten down the tie rods/ends. only then will there be any decent test of whether or not any of todays work on the brakes made any difference.

thanks again..

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Post by Ol'fogasaurus » Thu Jun 12, 2008 12:01 am

Whst I was referring to was extra stuff in line. Just because this is the Type I forum, there could be people with "extra" stuff addedinto the braking system.

If everything is n ew or checks out OK, and the brakes at both ends are adjusted correctly (I am talking about locking the brake shoes up, using the adjuster screw, before final adjustment), I find it hard to think of anything that could have been missed, but there must be if you still are having problems. Let me (and others) think about it.
Lee

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Post by Ol'fogasaurus » Fri Jun 13, 2008 10:07 am

As far as I can think, there are only a couple of things that can cause what you are talking about, the intermittent hang-up or lock up. Since you are not off-roading and don’t know about the other stuff, I assume you don’t have it. The MC being bad from the factory is a possibility (but then the lock-up problem was there before, and was the reason you changed it in the first place), the soft lines are swollen or collapsing (replacing the front ones with used ones is not a good idea). Or the wheel cylinders are hanging up and closing off the brake line port (you never mentioned servicing them).

Try this. (I am assuming here that the brakes are all properly centered and adjusted and the wheel bearings are all in good shape and packed and not causing the brakes to drag and get hot. Also, there is not any grease or anything on the shoes to cause them to hang/lock.) Jack the car with all for corners off the ground (use jack stands please). Spin all four tires to be sure they are turning free. Now apply the brakes and see if there is some hang up on any of the four corners. Repeat until you get something to happen. Continue to check/rotate all four of the tires, not just the front.

If one corner hangs up, you then know where the problem probably lies.

If other tires, or all four, (also) stiffen up then I would suspect the rear soft lines (yes, the rears can affect the fronts even with a dual chambered MC. You have a single piston rod with two pistons machined on it. If one chamber/end hangs up, so does the other one.). If it is only one wheel, then I would suspect the wheel cylinder in that wheel need to be replaced. They are relatively cheap to replace (unless you are broke). If a car has been sitting for a long time, I would replace them all anyway especially if there has been moisture in the fluid from sitting (brake fluid is hydroscopic and can absorb moisture from the air.)

Soft lines are all too often ignored and should have regular maintenance meaning replacing them. Remember, they are constantly being flexed or worked during driving, turning (fronts) and during braking.

If the brakes overheat (say from the shoes in one wheel dragging from not releasing completely) and the brake fluid get hot enough to vaporize, you also can get brake lock-up.
Lee

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Post by 65ghiabug67 » Sun Jun 15, 2008 11:26 pm

i got to adjusting and cinching down the tie rod ends, and it was warm enough for the car to stay running long enough, with a little clutch-popping, to take the car around the neighborhood. it was working alright after i had readjusted all 4 one more time. i drove it around a bit again, and it was getting hung up a bit on the ramp up to the drive, but was still rolling.. i backed off the adjusters just a hair more, the wheels spin completely freely and the pedals still stiff, but by the time i had used the brakes some, it was seizing enough to hold the car in the driveway again..

we've had the car up as soon as we get back after seizing, and the fronts are the ones getting hung up. it often takes a few minutes of driving to get them seizing, so im not sure how easy itd be to simulate that with the car up on jacks. the major PIA is the fact that the only thing we changed from the functional, albeit barely, brakes of 2 years ago was new drums and shoes up front. since then its the MC and soft lines up front. but none of this was a problem before.

i appreciate all the help, and i may take a look at them again tomorrow, but otherwise, it may be off on the flatbed to somebody who can do something right. anybody know any good VW guys near the jersey shore?

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bugman742002
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Post by bugman742002 » Mon Jun 16, 2008 5:16 pm

ok how easily does the front tires rotate? you may have over tightend the nut that hold the hub on. or it needs more grease. ihad this happen to my 1980 datsun and it turned out that it needed grease and to be loosened up a little bit.

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Post by Piledriver » Mon Jun 16, 2008 11:37 pm

When the pedal is all the way back, the pistons in the master cylinder open back up to the fluid inlet to vent pressure and or suck more fluid in.

You absolutely must make sure the piston is coming all the way back up.
(I know you checked free play, but I have seen stuff...)

It only takes the tiniest amount of rust or crud in the master cylinder fluid inlet ports for this to be buggered up and hold pressure. (The drillings are pretty small)
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

65ghiabug67
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Post by 65ghiabug67 » Sun Jul 06, 2008 3:40 pm

so, after a little hiatus here, we got back into the brakes.. we jacked it up, spun the tires, and pumped the brakes but could not simulate the problem.. so we drove it around the neighborhood a bit, using only the e-brake to stop. the same problem occurred. after we parked in the driveway, we jacked it up, the wheels were lightly stuck, and came loose with a little pressure.

now we're thinking its something associated with the weight of the car on the vehicle.. bearings had been replaced, seals all new, we set/reset the races, packed and repacked the entire hub with grease. is there something we're missing? some way the spindle could have come loose or something like that to the point where the hub spinning on it would be restricted?

thanks again for all your input.

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Post by Class 11 streeter » Sun Jul 06, 2008 3:56 pm

How are the backing plates little rubbing blocks where they touch the shoes? If they are too worn they could be "grabbing" the shoes and not letting them retract smoothly.

BTW you are about to the point of justifying a disk brake conversion! :shock:
So you think your project is taking forever eh? Well you've got nothing on me.....

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