Touran Brake Problem: Stiff or Hard to Engage

Here's a Touran where the left front wheel is difficult to turn.

According to the owner, it was so difficult to turn that the disc was literally glowing red. The brake pads, discs, caliper, and brake hose were replaced at another workshop. However, the left front wheel still turns with difficulty.

"When I loosen the bleed screw, the wheel starts spinning normally again. But when I apply the brakes again, it becomes difficult to turn again. This only happens on the left front wheel. Since all the usual suspects have already been replaced (brake caliper, brake hose), I suspect the hydraulic unit might be the problem."

I'm going to make an adapter now, with threads of 10x1 and 12x1, so I can connect the brake line from the wheel to the one from the master cylinder and see how it works.

Or has anyone else experienced this before, so I can avoid doing the work myself?

Once built up, the pressure obviously doesn't dissipate.
If it's wheel-specific, that suggests an issue with the ABS/ESP system. Or is there a pressure limiter in the line?
What do the control units say?
hg
Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

I will send you a scan tomorrow.
There is no fault code stored in the ABS system.

Hi there,

I once had something similar happen to the back of my Spider. In that case, it was a swollen brake hose.

Best regards from Berlin.
olli

You mean the swollen area is pressing inwards and only expands under pressure? That would certainly explain it. Our colleague says he has already replaced the hoses.
Sure, here's the translation:

"Best regards," or "Sincerely," (depending on the context).
Herbert.

Hello!

"It's extremely rare for brake hoses to swell and expand like that. I've only seen it a couple of times in my life, but those were very old brake hoses, probably 30 years or older."

And he wrote that the brake hose in question had already been replaced.

Another idea, although I see the probability of it happening as 1%: (but it doesn't cost any money).

The brake line on the left front side is the shortest route from the brake assembly to the wheel.

Is it possible to adjust the play between the brake pedal and the master cylinder on this vehicle?
Was anything ever repaired there?

I only know this from my apprenticeship days; with brands like Trabant, you could adjust the pedal feel by adjusting the mechanism that presses against the accelerator cable.
You had to maintain a clearance of about 2-3 millimeters.
Otherwise, the same thing happened as described here.
Specifically, we prioritize the wheel with the shortest wire path first.


I seem to vaguely remember that a similar problem was discussed in this forum a few years ago.
Maybe it's worth searching the archive... I think there might have been something like that there before.

Oops... I completely missed the swapped hose, sorry.
The hose in my car was actually 32 years old. It still had the original design with separate circles for the front and rear, which meant it always took a while after braking for the rear to have enough ventilation.

The master cylinder would also be a possible cause. For example, if the internal components have separated. However, if that's the case, there must also be a problem on the opposite side at the rear.

Best regards,
olli

Hi,
A problem with the master cylinder should typically manifest itself as a diagonally uneven braking effect.
That's why I was thinking about the ABS/EPS system. Maybe the idea of having a separate line between the saddle and the HBZ (hydraulic brake booster) makes sense to isolate the problem.
hg
Herbert.

Or try pushing the brake piston back into the caliper.
Whether it works or not.

With ignition off / With ignition on / With engine running...

Here's the promised car scan.

The piston can be pushed back.
I had also considered the possibility that the issue with the ventilation system was related to the master cylinder, but I thought it would affect multiple wheels.
The shortest cable route should ideally be to the right front wheel. The hydraulic unit is located on the right-hand side when facing forward.

I just used a torque wrench with an analog display to tighten the wheel.
On the right side, 15-18 Nm.
On the left side, after applying the brake, the torque should be 35-40 Nm.
After opening the bleed screw, tighten it to 25-30 Nm.
If I push the piston back, it requires 15 Nm of force.
"Perhaps none of this is entirely accurate, but it seems that when I turn left, the right wheel rotates, while surprisingly, the opposite doesn't happen."
However, when I'm driving and then measure the temperature of the brake disc, I see a difference of approximately 25-30°C.

I briefly connected the brake line from the master cylinder to the one going to the left wheel using an adapter, then drove it. Strangely, the right wheel doesn't seem to be braking at all because the car pulls to the left, but the wheel still feels heavy afterward.
Okay, so I disconnected the line from the main brake cylinder at the hydraulic unit, but the wheel still turns with difficulty. Then I disconnected the line at the hydraulic unit that goes to the left wheel, and it only makes a slight difference. Finally, I loosened the bleed screw, and then the wheel rotates with 25-30 Nm of force.
I then replaced the brake hose, the caliper bracket, the brake disc, and the rubber grommets where the guide pins run, from right to left, but it doesn't make any difference.

I'm only focusing on the brake caliper now, even though it looks new.
The pins on the rubber stoppers of the new ones were extremely difficult to insert, but they now go in easily because I took the rubber stoppers from another saddle.

The entire braking system was likely replaced in the neighboring Czech Republic. It's possible they didn't install a new brake caliper (even though the piston still looks shiny), and only blasted the housing.

Hi there,

Then it seems the only option is the caliper. I've had something similar happen with an Italian-made brake before. It exhibited a very peculiar braking behavior, exactly as described. It would pull to the side where the caliper was sticking during or after braking. Sometimes it's worth rebuilding the caliper (replacing the dust boot and cap).

Best regards from Berlin.
olli

He only pulled to the left when I bypassed the hydroelectric generator.

Sure, I could install new seals and dust covers. But if it's a no-name saddle from the cheapest kind, and the dimensions aren't 100% accurate, then I wouldn't know for sure if the problem is related to that, especially if the seal doesn't properly retract the piston.

"If the sealing ring fits as tightly as the rubber on the guide bolts, then I can imagine that it might not work properly. I had to hammer the guide bolts out. With the rubbers from the other bracket, they come out very easily."

I've now installed a brake caliper from a Volkswagen Golf V. Beforehand, I measured the required force using a torque wrench (20 Nm - from the donor vehicle).

Even in the Touran, you now need 20 Nm of torque to turn it.
Okay, I installed a new brake caliper and measured it again; the result is now 20-22 Nm.
So, whoever believes they can save money by buying a cheap replacement part often ends up buying it twice.

Will it also stop overheating and blocking while driving?
It's quite surprising – previously, opening the ventilation helped to relieve pressure.
hg
Herbert.

After installing the new saddle, I rode it and performed two full-brake stops, just like with the old one. Then, I measured the torque using a torque wrench.
Could it be that there's a slight residual pressure in the system after releasing the brake, and the sealing ring simply couldn't retract back into place?

chli1976 wrote:

H Therefore, anyone who believes they can save money by using a cheap replacement part often ends up buying it twice.

That's right. It matters what you choose. I once had dirt and debris under a rubber seal for the guide pin, which made it difficult to move. And on another car, there were problems during the technical inspection (TÜV) due to uneven braking force caused by two replacement calipers. Both were brand new before the inspection. Those were from those cheap boxes you find. Since then, I prefer replacement calipers from TRW or ATE. Especially the TRW calipers aren't expensive. The price difference is negligible.