Clutch not returning fully, occasionally sticking

[killerkali]

So I have searched, and am pretty familiar with what could be causing my clutch pedal to not return fully, or stay mostly on the floor. Just looking for some fresh input , especially as my whole clutch setup is new.
~5k miles ago or so. Slave failed. Replaced everything with a TTV B7 FW, B7 RS4 PP , JHM stage3 Disk, Duralast slave, stainless line. New reservoir as the original was corroding apart, but did NOT replace the master( I presume its OEM still). Everything worked out perfectly and operated with no issues.
For the first time this week, on a cold start the pedal began to not fully return after I reversed out. The clutch starts to engage in the same scenarios and will drag even with the pedal almost fully down, until I recycle it essentially then the pedal is back to normal. It sounds like the slave starts to back out after holding the pedal down. When it sticks to the floor it ISNT fully dropping, but staying an inch or so up. The clutch actually operates just fine when it is doing that, even though I only have to press it that tiny inch to disengage. Seems to be only occurring at stops or low speeds. I can pull the pedal back up and its springs back to normal. I’m assuming this is a slave or master issue as everything else seems to work ok. What are the chances this could be my master, and is it even worth replacing the master first? If the master is allowing fluid by I imagine this is what would be happening right?

[audinutt]

I usually change the master and slave and the hose all at once and I'm just done with it.. I would recommend changing the Master that is probably the issue.

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[killerkali]

I'm just hoping to verify the master can cause the issues I'm having, then I'll have no reservations about replacing it and bleeding again. Its getting parked if its my slave or clutch...

[CELison]

Could be the clutch pedal spring, like with all the RR clutches. S4 spring is too stiff, A4 clutch pedal spring is the fix for that.

[killerkali]

I thought that also, but I don't think that would have any bearing on the clutch engaging eventually with the pedal depressed?

[CELison]

I thought that also, but I don't think that would have any bearing on the clutch engaging eventually with the pedal depressed?

I agree, that won't effect the clutch engagement. Maybe a SAC issue?

[killerkali]

I agree, that won't effect the clutch engagement. Maybe a SAC issue?

Never experienced any SAC problems so I couldn't say, don't know the symptoms.
It looked appropriately set visually when I installed. Just feels like this is a hydraulic issue based on whats going on.

[Zba]

Air in the system from a leaking master is my guess. Have you inspected the master for dampness? The only other issue aside from air (which could be introduced by the master) is a bad pp. I don’t know about you but I’d much rather slap a master in than yank the trans to look at the pp.

[VR6Bomber]

Was the car completely level when you did the bleeding?

[killerkali]

Air in the system from a leaking master is my guess. Have you inspected the master for dampness? The only other issue aside from air (which could be introduced by the master) is a bad pp. I don’t know about you but I’d much rather slap a master in than yank the trans to look at the pp.

I didn't know a master could even let air in, assumed it would just leak out under pressure. Ill take a second look at it, but seems like tossing the Duralast master in their to test isn't a bad idea. Would be under 100 with the master and new fluid

Was the car completely level when you did the bleeding?

I had the rear slightly raised as JHM and others recommended. Gravity bled initially and it felt perfect right away, but I finished it up with my power bleeder from the top. Could def still be air in there somewhere though

[james 408]

Never experienced any SAC problems so I couldn't say, don't know the symptoms.
It looked appropriately set visually when I installed. Just feels like this is a hydraulic issue based on whats going on.

the spring tension inside the pressure plate is the SAC. This and hydro leak/air have same symptoms (although air explains the inconsistency better unless bind/unbind on loose finger clip/housing?). Also the pedal bushing/spring have the same effect on feel/return, but not in terms of distance/engagement (typically, unless it's moving the pivot points/linkage which I can't imagine is likely unless it's obvious when looking).

agree with zba: Start with a bleed cause easiest and most likely imho, look for leaks on the master/slave/hoses you can see while you're at it. check under dash while depressing make sure it looks good. if none of it resolves, SAC next (in which case I'd probably just have a replacement ordered before I pull it, resetting and reinstalling can suck if you need to pull it back out again for a secondary issue, rather just drop the 500-1000 bucks on a new unit).

[julex]

replace the pedal spring with the soft one and this will no longer be an issue.

[CELison]

replace the pedal spring with the soft one and this will no longer be an issue.

Doesn't solve the pp not disengaging when the clutch is depressed. That was my first thought as well.

[killerkali]

Good input everyone. I think I may have found the issue, the USP line is wet/lleaking now where it connects to the duralast slave See my thread below for all the trouble I had with that initially
https://www.audizine.com/forum/showt...t-amp-USP-line

So, obviously these parts have some tolerance issues. Odd that it held fluid for 5k miles until now. Sucks that I went with what I thought were quality parts to ensure no failures.

Anyone think going to the USP or 034 THREADED style of line and Sc would be a good solution to this? I really can't justify going to the clip in style again if this shit happens

[MetalMan]

Good input everyone. I think I may have found the issue, the USP line is wet/lleaking now where it connects to the duralast slave See my thread below for all the trouble I had with that initially
https://www.audizine.com/forum/showt...t-amp-USP-line

So, obviously these parts have some tolerance issues. Odd that it held fluid for 5k miles until now. Sucks that I went with what I thought were quality parts to ensure no failures.

I had this exact issue:
https://www.audizine.com/forum/showt...1#post12835358

Anyone think going to the USP or 034 THREADED style of line and Sc would be a good solution to this? I really can't justify going to the clip in style again if this shit happens

I did, and followed this guide:
https://www.audizine.com/forum/showt...ine-Conversion

Been running that on my S4 for almost a year. Total parts cost was ~$80-90 depending on your skills at price shopping.

[killerkali]

I had this exact issue:
https://www.audizine.com/forum/showt...1#post12835358



I did, and followed this guide:
https://www.audizine.com/forum/showt...ine-Conversion

Been running that on my S4 for almost a year. Total parts cost was ~$80-90 depending on your skills at price shopping.

I remember coming across your thread! My first SC was missing the seal entirely.

That seems like a surefire way of solving this, and preventing it from occurring again. Just for reference, do you remember where you sourced the 3AN adapter and stainless brake line from? Thanks for the input

Also, you fixed the seal in the duralast slave so I thought that solved it. Did it end up leaking on you again?

[MetalMan]

Yeah, I got those off eBay.
For the line, I purchased the 24" version, but they don't have it available presently. 26" would work just fine too:
https://www.ebay.com/itm/3AN-26-Stai...item41ee4fbbb8

And the fitting:
https://www.ebay.com/itm/1-Steel-Bra...item2ef451e602
I had actually bought 2 different versions of this fitting. The first one I installed on my S4, which required a little shaving, and this one which I think was fine as-is (only test fit, never fully installed).

Sadly replacing the Duralast slave's O-ring still resulted in a leak. What better reason did I need to scrap the whole line? haha

[killerkali]

Yeah, I got those off eBay.
For the line, I purchased the 24" version, but they don't have it available presently. 26" would work just fine too:
https://www.ebay.com/itm/3AN-26-Stai...item41ee4fbbb8

And the fitting:
https://www.ebay.com/itm/1-Steel-Bra...item2ef451e602
I had actually bought 2 different versions of this fitting. The first one I installed on my S4, which required a little shaving, and this one which I think was fine as-is (only test fit, never fully installed).

Sadly replacing the Duralast slave's O-ring still resulted in a leak. What better reason did I need to scrap the whole line? haha

Thank you very much. Ordered those and will be going that route. Hopefully this can be referenced in the future for anyone with this issue.

And yea, F that duralast. Anyone want a stainless USP line PM me, will get rid of it cheap lol

[MetalMan]

Just a heads up, it looks like 034 might not have their master cylinder to -3AN adapter fitting in stock. Check with them on expected availability; it could be a few weeks or more if they don't have a run of those scheduled.

[killerkali]

Just a heads up, it looks like 034 might not have their master cylinder to -3AN adapter fitting in stock. Check with them on expected availability; it could be a few weeks or more if they don't have a run of those scheduled.

Do you happen to know what the threads are on the duralast slave? On the body actually where the adapter screws in. Im actually thinking of using the 034 line and thread it directly into the Duralast slave, instead of using their push style adapter at the slave.

https://store.034motorsport.com/clut...5-s4-2-7t.html

[MetalMan]

Nah I don't know what those threads are. It's very possible they are M12x1.0, though.

[killerkali]

Nah I don't know what those threads are. It's very possible they are M12x1.0, though.

Thats what I'm thinking they are also. Thanks again for the input

[killerkali]

Ended up purchasing the 034 line which has a M12x1.0 adapter. That threads directly into the Duralast slave. All is good now

https://store.034motorsport.com/clut...5-s4-2-7t.html

[S4James]

good. My line outright ruptured to to incorrect re-install after my engine upgrade.. Had no luck getting a replacement from USP, ended up just getting the line rebuilt at a local hydrolics shop.

[AudiSportB5S4]

replace the pedal spring with the soft one and this will no longer be an issue.

What is the deal with the pedal spring that I'm reading about for the first time in this thread? Does it have to do with using the B7 RS4 pressure plates on our cars?

[killerkali]

What is the deal with the pedal spring that I'm reading about for the first time in this thread? Does it have to do with using the B7 RS4 pressure plates on our cars?

This had nothing to do with the pedal spring, but thats not the first time I've seen someone recommend swapping it out. No idea what thats about

[james 408]

clutch assist spring rate. basically on some clutches and/or nonlinear designs your pedal feels lumpy to depress or doesn't return fast enough.