Zentralausrücker zum 3. Mal defekt | Posts 16+

Hello and a happy new year to everyone!

I've made some progress with my problem diesel engine...
We have now installed a new clutch, including the dual-mass flywheel (DMF), central release bearing, and slave cylinder (all from LuK).

I also spoke with some friendly customer service representatives from LuK, and finally, someone was able to give me a potentially helpful tip. According to them, the problem could be caused by two things: Firstly, it has happened before that there is a problem within the hydraulic line of the clutch, which prevents the brake fluid from flowing back to the master cylinder quickly enough. This means that when the pedal is released and the bleed valve in the master cylinder is opened, brake fluid re-enters the system. As a result, there is more fluid in the system than expected, which eventually overpressurizes the master cylinder, causing it to burst.

According to LuK employees, another possibility is that my clutch has excessive axial play, which causes the sensor to fail. This would manifest as vibrations in the clutch pedal when it's slightly depressed. I'm experiencing vibrations in the pedal... However, I've also read that vibrations in the clutch pedal are quite common, especially in Golf 4 and 5 models (which have similar or identical engines to mine).

My questions are as follows:

Does anyone know about issues with axial play in the gearbox? Could something like that really cause a release bearing to fail? (There would have to be a noticeable amount of movement, right?)

And does anyone know what the permissible or recommended amount of axial play is in the KW exhaust system from the factory?

I am grateful for any help!

Best regards,

Marshall.

"The issue with axial play might exist in the T5 (5-cylinder) engine, and possibly in others. However, it's not the same problem as the one you're experiencing, where the slave cylinder fails."
After a long drive on the highway, the clutch pedal on the T5 will sometimes stay down when first pressed. This is supposedly caused by excessive axial play.

"However, you can easily check the axial play, even when the unit is assembled. Try moving the crankshaft back and forth by hand or with a large screwdriver on the pulley. If you feel any play, I think that's too much. I can't tell you exactly how much axial play is acceptable, but it will likely be around 0.1mm."

I found something here that confirms my estimate.
https://www.youtube.com/watch?v=Ld8OHQTA-K4

Quote:

I also spoke with some friendly customer service representatives from LuK, and finally, someone was able to give me a potentially helpful tip. According to them, it could be due to one of two things: Firstly, it has happened before that there is a problem within the hydraulic line of the clutch, which prevents the brake fluid from flowing back to the master cylinder quickly enough. This means that when the pedal is released and the bleed valve in the master cylinder is opened, brake fluid enters the system again. Consequently, there is more fluid in the system than expected, which eventually overpressurizes the master cylinder, causing it to burst.

How is that supposed to work? With the pedal in its resting position, the inlet is open.
The master cylinder (on the pedal) has the correct part number, and the pedal is adjusted according to specifications?
hg
Herbert.

The issue with axial play exists in the T5 (5-cylinder) engine, possibly also in others. But it's not the same problem as what you're experiencing, where the clutch cylinder fails.
After a long drive on the highway, the clutch pedal on the T5 will sometimes stay down when first pressed. This is supposedly caused by excessive axial play.

'However, you can easily check the axial play, even when the unit is assembled. Try moving the crankshaft back and forth by hand or with a large screwdriver at the pulley. If you feel any play there, I think it's already too much. I can't tell you exactly how much axial play is acceptable, but it will likely be around 0.1mm.'

I found something that confirms my estimate.
https://www.youtube.com/watch?v=Ld8OHQTA-K4

Yes, for me too, it usually happens after a longer drive on the highway at high speed...
The axial play will be checked tonight.


How is that supposed to work? With the pedal in its resting position, the inflow is open.
The master cylinder (on the pedal) has the correct part number, and the pedal is adjusted according to specifications?
hg
Herbert.


According to LuK, there are valves in the clutch line (I was thinking perhaps of the frequency modulator that is attached directly to the master cylinder). If one of these valves is broken, it's possible that the brake fluid flows normally when the pedal is pressed, but when the pedal is released, the slave cylinder retracts, but the brake fluid doesn't return quickly enough. This creates a vacuum, which is then immediately filled with brake fluid as soon as the supply is opened in the pedal's resting position. Consequently, the slave cylinder or central release bearing remains extended a small amount, which can also cause the clutch to slip. If this happens frequently, there is probably too much fluid in the line, and eventually, something will break.

These problems can also be caused by incorrect sealing rings or too many sealing rings (according to LuK, this was often the case with Opel).

The supplier is definitely correct. I have the OEM part number from Seat that matches this part.

What adjustments should be possible for the clutch pedal?

I'm honestly at a loss as to what it could be. I don't want to just keep driving and hoping for the best, because everything might be fine for 3000 km, and then it could break down again... This just can't be right.

You can only check the clutch pedal to see if there is any play in the piston rod.

I once replaced the clutch on an Opel Vectra, and it immediately started leaking again. I don't remember if it was a Sachs or LUK clutch.

I have a minimal amount of play in the clutch pedal, maybe just the first centimeter. However, I don't see any leaks there. Other cars with hydraulic clutches also have this play, for example, I noticed it in a Polo.

Hello,
The clutch pedal already feels correct in its initial travel. If it didn't, it would be difficult to rule out some slight engagement of the clutch.
If you don't find any other issues, I would recommend replacing the lines connected to the clutch at the same time. I've already had brake hoses that swelled up internally, which caused them to fail and overheat.

Regards,
Thilo.

Hi,

Okay, I will wait tonight to see what my colleague says regarding the game in the coming week. If that's not possible or if there's a timeframe, I will replace the main pipe and the bleed valve. Then the entire clutch system will be completely new from A to Z, and if anything else goes wrong, I'll drive it directly to the junkyard without a clutch.

Quote:

According to LuK, there are valves in the clutch line (I was thinking perhaps of the frequency modulator, which is attached directly to the sender). If one of these is broken, it's possible that the brake fluid flows normally when the pedal is pressed, but when the pedal is released, the receiver retracts, but the brake fluid doesn't flow back quickly enough. This creates a vacuum, which is then immediately filled with brake fluid as soon as the supply is opened in the pedal's resting position. Therefore, the receiver or central release mechanism is still extended a small amount, which can also cause the clutch to slip. If this happens frequently, there is probably too much fluid in the line, and eventually, something will break.

When the clutch pedal is pressed, the overrun coupling engages; otherwise, the slave cylinder would not be actuated. When the pedal is released, the pressure is relieved, regardless of whether the overrun coupling is open or closed.
Please stop making assumptions.
The wrong parts were installed, or they weren't assembled correctly.
My suspicion is that you were sold a car that was not in good condition.
hg
H.


PS:

Quote:

According to the workshop invoice when I bought the car, a completely new clutch kit (including flywheel, pressure plate, friction disc, and release bearing) was installed at 172,000 km. I bought the car with 173,000 km and then drove a maximum of 1,000 km before the defect first occurred. The central release bearing was replaced, and then I continued driving. It lasted for about 3000 km, then the same thing happened again. I drove it into the garage, pressed the clutch, and splash, the same mess again. This time, the clutch disc, pressure plate, release bearing, and slave cylinder were replaced. The flywheel was still in good condition and had only been replaced about 8000 km ago. Now, it has happened again.

And how many previous owners did it have?

I can't say how often it was used by the previous owner, or even if it was used at all.
'Every time, I checked the part number to make sure it was the correct one for the car. I even went to a Seat workshop, where they gave me a list of OEM part numbers. I used this list to purchase the parts. I also compared the parts to the ones that were already installed, and they matched. I called the LuK and Sachs service departments multiple times to confirm that the parts I had or was planning to buy were the correct ones, and they always confirmed this.'

I'm making assumptions based on physically logical facts, while you have a 'suspicion' and then tell me to stop doing that? Sorry, but what else am I supposed to do?

Okay, try this: Take a standard plastic syringe, without a needle, of course. Fill a sink with water and hold the syringe underwater, keeping your thumb over the opening and pulling the plunger. This creates a vacuum inside the syringe. (The syringe should, of course, be airtight). As soon as you remove your thumb from the opening, the syringe will naturally fill with water. In this case, the syringe simulates the master cylinder, the opening simulates the bleeder valve, and the sink simulates the brake fluid reservoir. A syringe that isn't pulled back represents the master cylinder when the pedal is pressed, meaning the clutch is engaged. If the brake fluid can't flow back for some reason, the same phenomenon will occur as with the syringe, or am I completely wrong?

'By the way, I never claimed that the bleed valve should be closed when the clutch pedal is depressed. I am aware of that. Otherwise, the entire system wouldn't work. In that closed system, there is pressure as long as the clutch is fully depressed, which is normal, as the pressure will decrease. However, if brake fluid cannot reach the area where the piston moves (e.g., due to a faulty valve or a blocked line), something else must be providing the pressure. Since no air can enter the system, a vacuum must be created, right?'

I might be completely wrong about this, so please correct me if I am.

Besides, I didn't just make this up; it's a known issue with LuK that can occur.

'I've been searching for the problem with the car for 1 1/2 years. I've asked numerous mechanics and people who are knowledgeable about cars, and I even suspected an installation error at one point, but I was told that it's difficult to make significant mistakes during installation.'

If you could tell me where the biggest mistakes can be made during installation, that would be a great help.

It's possible that the car was modified. But I had replaced everything in the clutch system with parts that were the correct fit.

Quote:

Then do the following: Take a standard plastic syringe, without a needle, of course. Fill a sink with water and hold the syringe under the water, keeping your thumb over the opening and pulling on the plunger. This creates a vacuum inside the syringe. (It should naturally be airtight). As soon as you remove your thumb from the opening, the syringe will logically fill with water. In this case, the syringe simulates the master cylinder, the opening at the front simulates the bleed hole, and the sink simulates the brake fluid reservoir. The syringe that hasn't been pulled back simulates the master cylinder with the pedal pressed, meaning the release mechanism is engaged. If the brake fluid cannot flow back for some reason, the same phenomenon occurs as with the syringe, or am I completely wrong?

And why are you telling me this?

Quote:

I make assumptions based on physically logical facts, while you have a "suspicion" and then tell me to stop doing that? Sorry, but what else am I supposed to do?

Physically, it is something that can be measured.
Separate the technical problem from your assumptions, as they might be unfounded.
hg
H.

You're saying that what I'm saying is nonsense, right?

If you don't want to continue the thread, please feel free to do so.
Herbert.

marshall1909 wrote:

You're saying that what I'm saying is nonsense, right?

It's nonsense. Now that they're also doing this Ramba-Zamba chaos, that's the end of it.