Having a clutch chatter problem? Read this before dropping the transmission.

For the last year or so, I've been battling this odd clutch chatter that would only begin once the car had been warmed up. If I started the car up and drove somewhere, the clutch would initially engage smoothly. But once up to full operating temp, engaging the clutch would become increasingly more difficult. The more driving that was done, the worse it would get. Only by giving everything time to cool off (hours) could I get it to behave normally.

Initially, I thought it must be that the flywheel needed to be resurfaced, since that was really the only cause of clutch chatter I knew of. But after checking around a bit under the hood, I found the passenger-side engine mount was broken clean off. I figured that had to be the cause, although I didn't exactly understand how temperature change fit into the picture. I was guessing that the rubber softened with added heat, which could allow more movement. But even after replacing the mounts, I found the problem was still there. Scratch that idea.

So after that failure and some searching around car forums, I decided to try the clutch hydraulics. I wanted to do an overhaul on the system anyway, since parts were getting old, but I ended up finding the source of my chatter. When I cleared the intercooler out of the way, I found the end of my clutch line was rusty and a little bit of brake fluid in the surrounding area. I had had the intercooler off in the past, but the rubber coupler leading to the TB had blocked my view of the slave connection, so I missed it. Once I got the master cylinder out, I found a layer of black sludge in the bottom that I can only assume is rubber from the inside of the hose. Apparently the hose was only allowing fluid to leak out once the temperature rose. When the brake fluid was cold, everything behaved itself. The strangest part of it is that the pedal never lost pressure or felt different. It just became impossible to smoothly engage the clutch.

Over the weekend I had some time to test everything out, and the chatter is finally GONE. So the moral of the story is if you have clutch chatter, check the hydraulics out.

Here are some pictures of the old master cylinder and clutch line. I bought a brand new master cylinder and stainless braided hose as replacements. The slave is only 2 years old, so I did not change it out.

 

I have the opposite problem. My clutch is grabby as hell when cold and smooth when warm. I have new motor mounts and trans mounts too. I guess its the disc material, as far as I can surmise.

 

What kind of a clutch are you using, and how old is it? Any other symptoms that might be related?

I'm using a modified organic disk with a heavy duty pressure plate, so engagement is supposed to be smooth.

 

This thread is quite interesting. When I bought my car a few years ago, I used to have shift quality issues when the car was cold that improved when the car was warmer. I assumed it was a worn 2nd gear synchro because it felt as if I was getting a slight grind when shifting up from first to second, again only when outside temperatures were below about 50 degrees and the car wasn't warmed up. I switched to Redline MT90 which didn't really help. Then I changed my clutch fluid and the problem went away completely! I also saw some black sludgy debris in the bottom of my clutch master reservoir when I changed fluid and it is gradually returning, despite no visible leaks anywhere and no current shift quality issues. I bought all new hydraulics and will be putting them in when I get a chance.

I guess the moral of the story is that old clutch hydraulics can cause problems even when there is nothing obvious wrong with the hydraulic system (like leaks or total failure).

 

I see I'm not the only one with strange clutch/shifting behavior.

It's also only about $100 for a new master, slave and clutch line, so I think I'd do it again even if it all looked ok. The actual labor only takes about an hour, so it's really not that big of a deal.

 

Rotary Rocket, I do have a question for you. I've already gotten my new slave, master and flexible line. When you installed your clutch master, did you bench bleed it? I'll be using a Motive Products pressure bleeder (which I've used for brake and clutch fluid swaps) as seen here:

http://store.motiveproducts.com/bleeders-c15.aspx

 

No other symptoms. I am using the stock mazda pressure plate and aftermarket (but stock equivalent) organic disc.

 

I didn't bench bleed it; I just bled the whole system from the slave cylinder's bleeder. It was actually pretty painless. I routed a 3.5mm hose from the bleeder directly back into the master's reservoir, and bled it until no more bubbles came out. After about 10-15 repetitions of opening and closing the valve, the bubbles were gone and pedal pressure was nice and firm.

It sounds like you've got a mystery of your own then. Maybe you should give the hydraulics a purge and some new fluid, then see if anything changes.

 

I just bled the entire system and replaced the soft line with a steel braided one a month ago. I dunno...

 

Today I got around to replacing my clutch hydraulics. It took me closer to two hours if you count the time it took me to pull out all the tools, put everything away and clean up the shop. But I also cleaned the parts of the firewall that are usually hidden beneath the clutch master, put some Lexol on some of the rubber stuff that's hard to reach, etc.

Anyway, I also have been getting some sludge in my clutch master. I changed the clutch fluid about 4000 miles ago and it was already almost as sludgy as in RotaryRocket's photos. With the new parts in place, I find clutch effort is a little lighter which makes sense because my car seemed to have higher clutch effort than any other FC I've driven. Engagement is good for me, but it was fine before.

I did notice something interesting; there's about a 1/2" gap between the engine side of the firewall and the interior panel that the clutch master bolts to. This gap is filled with some kind of insulating material and there is a rubber grommet on the passenger compartment side. My master was seeping fluid down into this insulation but I never got a visible leak in the driver's footwell, which everyone says is the telltale place to look for leaking fluid when your clutch master is going bad.

 

My clutch master leaks slowly into the engine compartment, at the firewall, but not inside the car. It leaks SO SLOW, it takes a year before I have to fill it back up to the full mark.

I still haven't figured out why my flywheel is so damn chattery when hot either, mystery unsolved.

 

Mine was about that slow too; more of seepage than an actual leak. But nothing visible on either side of the firewall; it was all going into that insulation stuff. I think I had to add a tiny bit of fluid once in the last 4000 miles.

 

The thing is any leak at all could have an effect on pressure applied to the clutch assembly. Not to mention rust will ultimately start to form if it's on a metal surface. I think I'd change out any leaky part just to be on the safe side.

 

If your master is leaking, change it. The slightest weep or leak will cause inconsistency in clutch take up, and let moisture into the system, which again will cause inconsistency.

I had a leaky master and just changed it. The clutch feels much better, and smoother.

 

Dude, I need a window regulator and a bunch of other stuff too. After spending $6000 on engine and related components, the clutch master and slave are on the back burner until I can get a window regulator, or am forced to buy one because it died.

 

Interesting thread. My 88 Vert has been very chatty in the past few days. I never thought it was heat related, but it's been hot as hell around here this week. and now that I think about it, it does seem to act up more when it's hot.

I do think I have a worn or broken tranny mount. when it gets to chattering I can feel the tranny bouncing around on the cross member. Guess I'll look at the fluid situation too.

A note on the master/slave/line replace.... for my SE, I got rebuild kits for the master and slave, and ordered a braided line from Mazdatrix. I was amazed that O'Reilly's had the kits in the store! they were only $8 or $9 apiece.

 

See, I thought I had a broken mount or something too, but new motor mounts and trans mounts made no difference. When mine chatters, I mean it chatters bad. It sounds like it is bouncing back and forth off the flywheel and pressure plate. Like a metallic bang bang bang. I know all of the components are good as I checked them out when the motor was out of the car.