Drum brakes on my Polo 9N3 are driving me crazy!

Hello everyone,

To begin with:
I'm not completely inexperienced when it comes to fixing things.
But the drum brakes on my Polo 9N3 are currently driving me crazy.

Background:
The TÜV (German technical inspection agency) noted that the rear brake was braking unevenly.
Following that, I installed new brake pads, wheel cylinders, and drums. A recent brake test revealed that the left brake is also applying pressure even when the vehicle is at rest. As a result, the braking effect was uneven again.
To rule out a problem with the spring shims in the brake system, I purchased another pre-assembled brake kit with the mounting plate. I have now installed this kit. Additionally, I installed new wheel brake cylinders. Of course, I bled the brake system afterwards!
The current situation: the brakes are now rubbing on both sides, even when the car is stationary and I'm not applying the brakes.
Does anyone have any idea what might be causing this? By the way, the initial tension of the wheel brake cylinders cannot be adjusted or changed with this type of drum brake. And I tried releasing a lot of "air" from the handbrake.

Thank you very much!

Let's assume that the handbrake is not engaged and the brake pads are properly installed.

Can you ensure that you have installed the correct replacement parts? Where did you acquire these?

Image of the assembled brake?

Hello,

Thank you very much for the answers!
The replacement parts are from Bosch, and they should be the correct ones.
Attached are photos of the installed brakes.

That looks good to me. Does the old drum fit without needing any modifications?

The new drums were surprisingly difficult to mount.
I've now adjusted the handbrake very loosely, just to see how it feels. That prevented the brake from getting hot; it only got warm.

Therefore, I decided to go ahead with the follow-up inspection at TÜV.
And lo: The braking force is still somewhat uneven, but it's within the acceptable range! Man, I'm so happy!

Despite this, I would still like to do something to optimize the condition of the brakes. Should I just wait and see until things "settle down"?

Nothing needs to be adjusted there. Did you put the old drum back on? How old is the brake fluid?

"On older drums, the resulting rust ridges are removed using a flexible grinder or a Bosch grinder, and the brake shoes are adjusted slightly to ensure they can move freely."

What's noticeable is that the levers can be pulled quite far; possibly, the initial adjustment wasn't made when the brake cables were disconnected.

Hi,

Is the centering wedge really all the way at the back, or did it slide in a bit during installation?

Best regards, Rainer.

Quote:

I have now, as a trial, set the handbrake very weakly, according to my feeling. With that, the brake would no longer get hot, only warm.

So, it wasn't loose enough.
To begin, completely loosen the cable linkages of the handbrake. Assemble the brake; ensure the adjustment wedges are fully retracted. After installing the drums and wheels, repeatedly depress the brake pedal to allow the adjustment mechanism to calibrate, then adjust the handbrake.
hg
Herbert.

Quote:

So, not loose enough. To begin, completely loosen the cable adjustments of the handbrake. Assemble the brake; ensure the adjustment wedges are fully retracted. After mounting the drums and wheels, repeatedly depress the brake pedal so that the adjustment can calibrate, then adjust the handbrake.

Exactly. And... before starting, check if the handbrake levers on the rear brake shoes move freely. Sometimes they are too tightly compressed, so they can already be stuck even when new... (they may need to be adjusted). Furthermore, the levers should be permanently lubricated to prevent them from seizing due to rust. The shims must not be lubricated.

Before installing the brake drum, it is important to ensure that everything is working correctly by repeatedly engaging and disengaging the handbrake, making sure that the handbrake levers return fully to their original position.

And... as Herbert writes, the parking brake is only adjusted at the very end ........and not before, as you tried to do. Sorry, but when I see the first photo, my hair really stands on end. In the future, please be more attentive... a car is not a PlayStation, after all.

dieselschrauber wrote:

Hi, Is the centering wedge really all the way at the back, or did it slide in a bit during installation?

Hello Rainer,

Thank you for your comment!
Actually, I made sure to pay special attention to the proper placement of the wedge. I'll double-check that again!

Best regards, Volker.

Autoservice wrote:

Quote: So, not loose enough. To begin, completely loosen the cable adjustments of the handbrake. Assemble the brake; ensure the adjustment wedges are fully retracted. After mounting the drums and wheels, repeatedly depress the brake pedal so that the adjustment can calibrate, then adjust the handbrake. Exactly. And... before starting, check if the handbrake levers on the rear brake shoes move freely. Sometimes they are too tightly compressed, so they can already be stuck even when new... (they may need to be adjusted). Furthermore, the levers should be permanently lubricated to prevent them from seizing due to rust. The shims must not be lubricated. Before installing the brake drum, it is important to ensure that everything is working correctly by repeatedly engaging and disengaging the handbrake, making sure that the handbrake levers return fully to their original position. And... as Herbert writes, the parking brake is only adjusted at the very end ........and not before, as you tried to do. Sorry, but when I see the first photo, my hair really stands on end. So, in the future, please be more careful... a car is not a PlayStation, after all.

Thank you for your note regarding the potential issue with the handbrake lever sticking.
And of course, I adjusted the handbrake at the very end; otherwise, I wouldn't have been able to mount the drum.
But you didn't mean that seriously, did you?

And what is wrong with the first photo?

Quote:

Thank you for your note regarding the parking brake lever, which may be sticking. And of course, I adjusted the handbrake at the very end; otherwise, I wouldn't have been able to mount the drum. But you didn't mean that, did you?!

Sorry, but you didn't understand. The parking brake should only be engaged after the service brake has been applied several times (see Herbert's post).

For you, the best approach is to adjust it after a test drive, so you can better understand how it works.

Quote:

And what is wrong with the first photo???

You can clearly see that the handbrake lever is engaged, and that it's almost touching the wheel hub.

Okay.
Make sure to review it again, taking into account the new findings!
Perhaps I'll also replace the handbrake cables at the same time to eliminate another potential source of problems.

Thank you very much, and I will let you know!

And while you're at it, take the handbrake lever too...
Don't you realize that you're undermining the solution by focusing on the details?
hg
Herbert.