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Sometimes knocking sound when braking.
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Ovally
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PostPosted: Thu Nov 07, 2019 2:51 am    Post subject: Sometimes knocking sound when braking. Reply with quote

Early Oval, same hydraulic brakes as a Zwitter.
Sometimes there is a slight knocking noise when braking.
The sound comes from the right rear brake.
I removed the drum and everything looks good.
The drums are checked for ovality.
The entire braking system was renewed not long ago.

I think I have this problem.
Someone who is familiar with these types of washers / spacers?
They look square.
A picture with dimensions would be welcome.
VW part number is 11 609 161


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Thanks and regards.
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PostPosted: Thu Nov 07, 2019 9:14 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

I found that loose shoes can knock or slap the drum on the trailing edges, after a brake job when the drums are new or turned. I believe it to be the cause of the additional friction between the new shoes and fresh surface area in the drums. They are seating. The additional friction “grabs” onto the leading edge and causes the trailing edge to “slap” the drum.

So, are the shoes adjusted correctly? To a light drag. I typically adjust out till the wheel locks up then back off three clicks. Go pump the brake pedal, 3 or 4 times. That recenters the shoes. Then go readjust for slight drag on each shoe.

Should take care of your noise, if it is what I believe it to be. This same noise can be made to disappear when you slam on the brakes. During that hard braking. The shoe never is allowed to relax, it is continually being forced into the drum with very high pressure.

Hope that’s it!
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Ovally
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PostPosted: Fri Nov 08, 2019 12:49 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

VW_Jimbo wrote:
I typically adjust out till the wheel locks up then back off three clicks. Go pump the brake pedal, 3 or 4 times. That recenters the shoes. Then go readjust for slight drag on each shoe.


Thanks, that's what I do but never readjusted the shoes for slight drag.
I always readjusted the shoes until they just do not touch the drums.
Had no problems before but will try that.

I will also check the backing plate where the shoes rides.
If it is grooved or worn out too much, it's possible that the shoes are getting hung up.
Always use some copper grease there but who knows after 66 years.

Regards.
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PostPosted: Fri Nov 08, 2019 7:31 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

Not sure if when you say "knock" if it might be chatter...

We had this just after rebuilding everything (in the rear). We also thought a few clicks back from locked up to not touching the drum & also got an errant chatter. After a few days of head scratching trying to figure it out we came up with the same fix as outlined by Jimbo above. Soon as we had some light friction, it immediately went away... And then after 100 miles of driving, readjusted & it's been smooth sailing ever since...

Now, if you were saying "knocking" and were hearing it upon acceleration as well them maybe you might check the axle splines or the drum spline axle holes for wear then, possibly.
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Ovally
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PostPosted: Fri Nov 08, 2019 9:47 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

0nebadbug wrote:


Now, if you were saying "knocking" and were hearing it upon acceleration as well them maybe you might check the axle splines or the drum spline axle holes for wear then, possibly.


Thanks, no knocking upon acceleration.
There is no wear in the axle / drum splines or fulcrum plates.
I only hear it sometimes (not always) during soft/gentle braking on the right rear side.
I will also look at the right rear parking brake mechanism.

Regards.
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Last edited by Ovally on Fri Nov 08, 2019 1:57 pm; edited 2 times in total
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PostPosted: Fri Nov 08, 2019 12:25 pm    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

[quote="Ovally"]
0nebadbug wrote:
I will also look at the right rear parking brake mechanism.

Regards.


The cable should be preloaded. Thus keeping the mechanism in check, IF installed correctly.

However, I have seen where the lock plate on the lever stud breaks off due to over crimping. Also have seen the cross bar installed back asswards. Also, check shoe to adjusters and at wheel cylinder interaction. Have seen both installed incorrectly and also worn out enough to have a large amount of side play, that will make noise or lock up.
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Ovally
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PostPosted: Sat Nov 09, 2019 7:37 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

VW_Jimbo wrote:


The cable should be preloaded. Thus keeping the mechanism in check, IF installed correctly.

However, I have seen where the lock plate on the lever stud breaks off due to over crimping. Also have seen the cross bar installed back asswards. Also, check shoe to adjusters and at wheel cylinder interaction. Have seen both installed incorrectly and also worn out enough to have a large amount of side play, that will make noise or lock up.


I will check the rear brakes and the entire handbrake mechanism again.
Strange, just driven the car and everything now seems normal during gentle braking.
Intermittent errors are sometimes difficult to find.

Regards.
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PostPosted: Sat Nov 09, 2019 11:33 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

Ovally wrote:
VW_Jimbo wrote:


The cable should be preloaded. Thus keeping the mechanism in check, IF installed correctly.

However, I have seen where the lock plate on the lever stud breaks off due to over crimping. Also have seen the cross bar installed back asswards. Also, check shoe to adjusters and at wheel cylinder interaction. Have seen both installed incorrectly and also worn out enough to have a large amount of side play, that will make noise or lock up.


I will check the rear brakes and the entire handbrake mechanism again.
Strange, just driven the car and everything now seems normal during gentle braking.
Intermittent errors are sometimes difficult to find.

Regards.


They are referred to as “Drivability Complaint(s)”. They are some of the worst problems to find and locate. It is what I specialized in as a mechanic. I worked primarily on fuel and spark management system issues, but was often handed other out of the normal, issues.

I did not find them all. I had about a 88% record for finding them. I thought it was fun!

Part of a brake system check is slamming on the brakes a few times. Maybe the issue is in the higher heat range, as well. Worth going for a drive to determine.
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PostPosted: Sun Nov 10, 2019 10:29 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

Do you have original rear wheels /lugnuts? Is the axlenit tight/torqued to spec and are the drum splines in good condition and not “undercut”?
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Ovally
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PostPosted: Sun Nov 10, 2019 11:56 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

Mr. OGPaint wrote:
Do you have original rear wheels /lugnuts? Is the axlenit tight/torqued to spec and are the drum splines in good condition and not “undercut”?


Yes, original wheels/nuts, axle nut tight and torqued to 300 Nm, no wear or play in axle and drum splines, drums not undercut.

Regards.
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Ovally
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PostPosted: Wed Nov 13, 2019 9:45 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

I have re-checked and adjusted both rear brakes and the handbrake mechanism.
I noticed that the right handbrake cable sometimes did not come all the way back.May have been the cause.
To exclude other things, I replaced the brake shoe levers(12), the brake shoe push bars(13) and the upper and lower return springs(9,10) on both sides with VW NOS parts that I had collected as spare parts.

Drove the car a few times, braked gently and so far everything seems to be fine.

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Regards.
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PostPosted: Thu Nov 14, 2019 6:04 pm    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

Sounds like you got it!
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Ovally
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PostPosted: Fri Nov 15, 2019 7:26 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

VW_Jimbo wrote:
Sounds like you got it!


Thanks, I think so and hope so.

During the brake job, I saw that the left torsion bar cover started to rust again.
The inner and outer bushings have been replaced with WW ones.
At that time, there were no reproduction covers available.
Now I see that Mika makes them : https://www.thesamba.com/vw/classifieds/detail.php?id=1368858

What do you think it's the best way to replace the left cover?
Car with wheels on the ground or jacked up till the spring plate is at the stop?
In both situations there is enough room to do this.
I would think with the wheels on the ground?

Regards.
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Last edited by Ovally on Fri Nov 15, 2019 10:02 am; edited 1 time in total
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PostPosted: Fri Nov 15, 2019 9:38 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

I would disagree with installing fully with the car on the ground. I would speculate that the original car was assembled on a production line and those seals were installed before there was a load on the suspension. I have always installed them while the vehicle was in the air. Never have had an issue.

I use a light smearing of silicon grease on the inner and outer surfaces to allow the bushing to slip in rather than drag into place. When fully seated. I bounce the car, using the rear bumper before final tightening. Drive it around a few hundred loosen the bolts back up a few turns and retighten them.
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Ovally
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PostPosted: Fri Nov 15, 2019 10:20 am    Post subject: Re: Sometimes knocking sound when braking. Reply with quote

OK thanks, will do it that way.

Regards.
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