Fading clutch pedal is driving me nutz

I've seen similar threads on this topic, but my problem seems a little bit... extra.

'96 V6 4WD Taco has been having intermittent clutch pedal fade issue. Pedal doesn't return to top of throw, then sometimes it barely comes off floorboard. Most of the time it returns almost to top of throw. Truck still drives (mostly), problem comes and goes, with pedal returning to random points between floorboard and top of throw, then suddenly will fade altogether and fail to where I can't get it in gear at all. Have been stranded twice and had it towed to two different shops in Philly.

The first place bled the system. It started fading shortly after, they did same thing again (under warranty).

Then it failed again and I had it towed to a different mechanic. Of course, the problem went away as soon as they got it, so they blamed the floormats. That was just dumb.

Problem came back, so I brought it back and they replaced master cylinder. But the pedal was still soft and not returning to top of throw. They didn't back up their warranty so I brought it to a third place.

Third mechanic replaced pressure plate, gave it back to me with pedal still soft. I told them they didn't fix the problem and they rubbed their chins and took another crack at it, replacing master and slave cylinders and lines. Returned it to me with pedal almost right but not perfect, still not returning to top of throw, shy by about an inch or two.

In less than a week, pedal started fading again, more and more, to the point where I couldn't get it in gear at all after starting it up, with pedal pretty slack by this point. Oddly, just on a whim, I ran the 4WD shifter up and down, after which I was able to get it in gear (barely) and drive off. Drove it straight back to shop (who have been doing all return visits since pressure plate repair under warranty, so I don't think they're trying to scam me).

They bled the system overnight, but that didn't do the trick so they're replacing the master yet again. I asked if they really think that's the problem. They say there's not much else to replace.



In all these cases, there hasn't been any visible leak or loss of fluid.

Sorry for the long story, but how can three separate shops not get this right? Is there something they're all missing?

(An underlying complicating issue is I'm a stranger in a strange land, in Philly for a few months on a job, but the past month has been a disaster and now I'm just trying to get my truck and tools back to Seattle where I have access to resources and mechanics I can trust.)

Any help/ideas at this point would be greatly appreciated. Thanks!

 

as with all internet fixes for problem repairs you kind of have to be there to see the big picture... the next time the pedal hangs you are going to have to crawl under the truck and grab the throw out lever... thats the lever that sticks out from the trans that the slave cylinder acuates... and see if there is slop/play in it. What we are attempting to do here is to figure out if the pressure plate, the disc or the throw out bearing is hanging up. If there isnt a mechanical issue in the clutch actuation then inspect the pedal/lever/return spring for wear. One final thing to inspect is the freeplay in the clutch adjustment rod or wear at the clevis pivot point. Inside the clutch master cylinder there is a spool valve with a seal. This seal MUST return all the way to the end of the master cylinder or the "feed port" will not be exposed in the master cylinder for a fresh charge of hydraulic fluid. Anything that prevents the full return of the spool valve will have the effects of what you are experiencing. All of the above assumes that there isnt someting out of the ordinay like a kinked hydraulic line or ???

 

I had a similar problem although nowhere near as severe. My mechanic replaced the master and slave cylinders. The problem persisted so he made an adjustment to the pedal and it improved but didn't go away. I got tired of it and decided to educate myself and try to fix it. I found the pedal height and free play were way out of the FSM spec - height was too low and no free play. After adjusting to within spec the problem went away.

 

This is exactly what mine did. After throwing money at new master and slave cylinders, flushing and bleeding the fluid I finally found the problem, and it was a five minute, six dollar fix! It was my clutch pedal return spring. It’s a goofy coil spring setup. It’s designed to help you hold the pedal down as well as pull it up. The plastic bushings on it wear out, and then the slot in the clutch pedal that it rides in wears deeper. Most people just pop the coil spring out and replace it with a brake pedal return spring. It’s a linear spring. Here is a thread about it https://www.tacomaworld.com/threads/clutch-pedal-truffle-shuffle.499079/ You can also use a clutch pedal return spring from a 4-cylinder Tacoma. There is a pin with a grove on the clutch pedal that you hook one end on, and a metal tab with a hole way up under the dash you hook the other end on. The connection points are already there because the 4-cylinder models use them.

 

I was going to suggest the return spring but glad you got it figured out!

 

The return spring is not necessary but helps keep the pedal from rattling. If your hydraulic system is functioning correctly the clutch pedal will return to position without the spring

 

It will return most of the way, but frequently not high enough to hit the cruise control cut off switch making your cruise not engage. Otherwise you are correct.

 

Just want to update that the master cylinder was replaced three times by two different pro mechanics. (This in addition to slave, all hoses, pressure plate, throwout bearing, etc.) After the third replacement it felt pretty good (mostly), but I had my doubts and stopped as little as possible on drive from Philly to Ohio, and now it is useless again and a 4th mechanic is going to replace master cylinder for the 4th time. He suspects that each replacement was being fouled by improper pedal adjustments. What do you all think? I have officially lost my mind and entered a much happier place where I find it hard to give a crap about anything any more.

 

Have you tried removing the return spring?

 

I haven't personally and I stressed to prior mechanics to check all aspects of the pedal mechanism but for some reason they resisted the suggestion. The guy working on it now is more open-minded and comprehensive in his approach so hopefully he takes that into account. I did personally look at the spring and everything else under the dash and could see no obvious problem with any of it, but then again I have no basis for comparison and might be blind to a subtle flaw. But then again, even when pedal seems to return normally, when truck sits overnight the pedal will be soft as hell in the morning. Spring doesn't appear to be the big problem, but maybe it's a contributing factor? I don't know. Thanks!

 

Quit spending money on master cylinders. I can almost guarantee your problem is the return spring. This problem with the spring is common to these trucks, but not at all common in vehicles in general, so I would not expect many mechanics to know about it.

This is something you can easily do yourself. The only hard part is laying on the floorboard and looking up under the dash. If that's going to be a problem for you, recruit someone smaller and more flexible. All you need is a screwdriver or something to pry with. Probably a flashlight too. Stick the screwdriver between the end of the spring and the bracket, and pry on it. It will come out fairly easily.


Once the spring is out take it for a test drive. It's OK to drive it without a return spring, the clutch will push the pedal up. If the problem is gone, pick up a brake pedal return spring, or a clutch pedal return spring for a 4-cylinder Tacoma, and hook it on like this:

 

Update:

Looks like the problem was finally solved by mechanic #4, a retired super veteran in Ohio who takes jobs on the side--and it took *him* 2 tries to properly bleed system, replace messed up master cylinder, and adjust pedal to where it feels and functions right. He took his time with it and he seems to think there were two things previous attempts missed:

1) To bleed system, it helps to have truck front end pointed somewhat downward.

2) He adjusted clutch pedal rod under dash so it wasn't pushing too far into cylinder.

As I said before, the nutty South Philly mechanics neglected to do this last step every time, and he theorizes that quickly messed up the cylinders they kept replacing.

I can't vouch for this theory, but now it's been holding for a week now as I drive it a bunch, so maybe he's on to something because the other guys never got it close to feeling right.

He also noted that the fluid was milky in appearance and he guesses that it was getting aerated somehow (again, maybe due to misadjusted rod), which led to loss of pedal due to lack of proper hydraulic pressure.

I'm not stating this as an authority, but just so anyone who's experiencing a similar issue might have another angle on the problem.

If anyone has further insight into this, I'd like to hear it. Thanks!

 

I like threads where people come back with their solutions.