Ok, I think I know the problem. I searched to verify it, but didn't find a good post on it. Hopefully, this will be a good search post for the future.

It recently started to get pretty cold here. In the morning, my shifts grind a little bit. Its not the hard grind that you would get if you missed a shift or tried to shift without the clutch, but you can hear (and feel it in the stick) a little grind like the teeth in the tranny aren't meshing as well as they should. Once the car warms up it stops completely and the shifts are smooth (even when shifting hard or fast).

Now, I encountered this on my last car (Accord at about 120k to 140k miles). My mechanic replaced the clutch master cylinder and it never happened again, even on really cold mornings.


So I just wanted to verify. If you get a grind as you are shifting, but it happens all the time, you may have a bad synchro in the tranny (very expensive). But if you only get the small grind when its cold out, but once the car warms up it goes away, it may be the clutch master cylinder (or clutch slave cylinder).

BTW, my tranny fluids are good and I just had a tranny flush not that long ago.

Someone please verify this for me. Thanks.

 

Your definatly right about the synchros. Im not really sure how the cold weather would afect the clutch master or slave, but it would be ok when warm. Its really sort of a normal condition. When the fluid is cold its thick and syroupy and does not produce the same friction coeficient so the shifts will feel noticicable different. More of a hard shifting thou. Not so much grinding. Its just not "smooth".

 

Well I can understand it not being as smooth, but it shouldn't grind at all. I honestly am not sure why the cold weather effects this condition and the clutch master cylinder, but I know replacing it fixed the problem on my Honda. I really don't know what the clutch master and slave cylinder do either (what is the difference between the two). I understand what a master cylinder does, but what are is the clutch master cylinder controlling...is that the hydraulic actuator that separates the clutch plate from the flywheel?

 

Well I had the car at the shop this morning because I didn't feel like changing out the clutch master cylinder in the cold weather.

The mechanic said that my clutch is shot and I need a new one ($915 for clutch and labor, not including a replacment flywheel). His reasoning was that the clutch catches too high, which I think is wrong. The clutch does catch very high, but I have read that this is the way all Audis are. My clutch catches in the top 1/3 of the pedal travel. In other words, I will push the clutch pedal all the way to the floor, shift, then bring the pedal up 2/3 of the way before it starts to catch.

I didn't think it was slipping, so I checked it after I left the shop (didn't have anything done to the car). I got the car up to 30mph, put it in 5th gear, and floored it. If the RPMs climb but the car doesn't accelerate, then the clutch is slipping. My RPMs didn't budge, so the clutch isn't slipping at all.



I am still thinking it is a clutch master or slave cylinder even though he said he didn't find any leaks. I know we have some smart guys around here that know their cars. Someone please give me some input on this. Thanks.

 

Naw, your clutch is not shot.

You did the appropriate test, and the pedal engagement is normal.

I would gues that a new slave/master cylinder would maybe give you better pressure in the system even when its cold out. It sounded like they tested both the slave and master for leaks, so they must be within spec. So, I wouldn't be too concerned, especially since you had the system flushed recently as well.

Is there a good way to test the slave and master pressure yourself? Maybe that would ease your mind. It may not be leaking, but maybe the pressure in the system is lower than it should be?

 

I have not been impressed with this shop in the two times I have been there and I will be searching for a new Audi shop. I would not assume that they checked anything. My guess is that the mechanic took it for a ride, felt the high clutch catch point and immediately said that it was the clutch. I would bet he did not check for leaks in the master or slave cylinder. Though neither did I.


If the pressure in the system was tested low, couldn't that be an internal leak inside the master cylinder instead of say an external leak like a cracked hose? For brake master cylinders I have read about certain symptoms that tell you that the master cylinder has an internal leak. I won't get into the details of that now since thats brakes, but I would assume the internals of a brake master cylinder and a clutch master cylinder are fairly similiar.

 

IDK,

Do you have a haynes or Bently? If not get one.

I am sure there has got to be some type of test for the master/slave cylinder. I have a manual at home, but not here at work. I can take a look this evening if you dont have one, and post the procedure if someone else doesn't beat me to it.

Dave, you out there?

 

I have a Bentley manual. I perused it enough to decide to take this over to the shop. Replacement required removing the ECU and its housing I believe. It looked like there was a hole under where the ECU is and that I would need to reach down in there to play with hoses and to remove the unit. I wasn't looking forward to doing that and the shop had good prices on my last work there so I figured I would let them mess with it. Now that I don't like their diagnosis, I will have to take a harder look at exactly what was in the manual and go out there and poke around a little bit.

Thanks for your input Acetrobo, I appreciate it. I wanted to make sure I was on the right track and not missing something.

Looking forward to any more info people might have about all of this.

 

Bump for the night crowd. What other components should I be looking at to fix this?

 

I looked over the haynes.
I dont see any tests that can be done.

Basically, they say it can be bled, similar to your brake lines. If its not leaking, and it is bled, then it shoud be OK. Of course, if the master or slave is bad, it could be causing your problem i suppose. (just a guess). You said it works fine when warmed up.

But, if you are getting grinding? That is a sign of wear, maybe its just an early sign of the clutch going out. So maybe its time to start saving for a stage 3 or 4 clutch, you might have the perfect excuse