3000Gt VR4 Clutch Pedal Issue

Sorry, I initially posted this in the wrong place...

I recently purchased a 1992 3000GT VR4. The clutch was working fine. then, suddenly the clutch pedal would only travel about an inch or two and hit a hard stop. The clutch won't disengage and the car won't even turn over. I looked at the mechanism and the pedal moves but appears to "bottom out" inside the clutch booster well before it gets to the floor. There's a second mechanism (lever) that looks like it should move with the clutch master cylinder activation. It also should move the switch to allow the car to start. It doesn't move at all. I can press on the clutch pedal as hard as possible but it still will only move about an inch or two. It won't go anywhere near all the way to the floor. I do wee the rod going into the booster moving as it should.

I started to change the master and slave until I realized something else is up. I pulled the slave off and still no difference. I don't want to change the master if it's something else. The fluid in the master never even moves so it appears as if there's some sort of disconnect between the booster and the master. It would logically seem that the clutch should still work even if the booster is completely shot.

Can anyone help me figure out what's going on? I've been searching the internet but can't find anything about this. I've looked at the manual and online diagrams but cannot figure out what's going on.

Thanks!

Sounds like your throw out bearing seized. I had the same issue once. I had to literally STAND on the pedal with both feet to get the neutral safety switch to disengage so I could start the car and move it into the garage. Trans has to come out to fix it. You may want to look into just getting a whole new clutch assembly and possibly a new flywheel or have your current flywheel machined.

That makes sense except that the slave cylinder is completely removed from the transmission and dangling in place. And it doesn't move at all, even when disconnected. The issue has to be forward from that. But thanks for the suggestion.

Hmm. Well maybe your issue is related to the booster after all.

Booster locking up is unlikely... I'm betting your master cylinder or slave seized. Open the bleeder and see if the pedal moves after. If not, Unbolt the master from the booster and see if you get pedal travel back.

Listen to Larry. He knows his shit.

Thanks! The car was sitting in an old storage area for about 5 years before I got it. It all worked for a few days then suddenly stopped. I was actually kinda shocked so much stuff worked. The car has been on the trailer this entire time and I've been concentrating on the bodywork, getting it ready to be painted. I'd rather it run and drive when I take it to the paint shop (I'm sure they would too). .

If you have to pull the master, it looks next to impossible, but it's not that bad... pull the rear IC pipe, unbolt the brake master from the booster, yank it up next to the steering reservoir without pulling the lines. Unbolt the A/C line over the the booster and flex it on the rubber sections, tying it up by the intake. Pull the 4 nuts and the linkage from the booster under the dash, and completely remove the brake booster... Once that's out, it's cake to do the clutch master.

Wow, thanks for the tips! This looked like a major PITA due to the lack of space. But your procedure will give me enough working room to at least minimize the pain.

I was going to trailer this to a local shop and have them look at it. But the 3000gt VR4 is so obscure I'm not sure how much help they can be. I'm an ex-motorcycle mechanic and mechanical engineer and if it has me stumped...

Besides, there's going to be a LOT of satisfaction in NOT having this issue beat me! :pride:

Owning these cars should be a requirement to get master mechanic, lol.

Silly question. If you look under the dash at the pedal assembly, is the pin & cotter still in place linking your pedal to the clutch master rod?

Then there wouldn't be many master mechanics!

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Originally Posted by Alex3000gt

Silly question. If you look under the dash at the pedal assembly, is the pin & cotter still in place linking your pedal to the clutch master rod?

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Yeah, it was all there. In fact, i just pulled it out.

So here's what was happening... you push the clutch pedal and it pushes the rod that goes into the booster. But after about 1 1/2" of movement, the pedal won't push any further. You can see the rod going into the booster move but then it acts as if it bottoms against a solid object internally. And no reasonable amount of force will budge it (I'm over 200 lbs and was afraid I was going to bend something if I pushed the pedal any harder).

Looking inside the clutch master cylinder, there's no fluid movement with the pedal movement. And this is with the slave cylinder dangling loose from the transmission. I would have expected the booster, even with no vacuum, to activate the clutch master cylinder. It doesn't seem to be doing that.

So, it appears as if the clutch booster is internally jamming up and not pushing on the clutch master cylinder. But the rod does move that 1 1/2". Now, if whatever connects the booster to the cylinder got jammed solid, that would create similar symptoms. But I have no clue what's inside there or in between the two. Also, it seems as if the engineers would have designed this so that couldn't happen. At least that's how they design brake systems and boosters.

I just removed the clevis from the rod going into the clutch booster. Now the pedal goes to the floor and (obviously) allows the starter to engage. The car won't run because everything is removed to remove the slave cylinder.

There's this LITTLE part of my brain that wonders what happens when there's no vacuum to the booster... One would think it would still transfer movement, just not boost anything.

Well, time to go back out in the Texas heat and work on it again...

May you should stay out of that Texas sun for a while... You just stopped making any kind of sense.... :D

Quote:

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Originally Posted by extremeRacer

So here's what was happening... you push the clutch pedal and it pushes the rod that goes into the booster. But after about 1 1/2" of movement, the pedal won't push any further. You can see the rod going into the booster move but then it acts as if it bottoms against a solid object internally. And no reasonable amount of force will budge it (I'm over 200 lbs and was afraid I was going to bend something if I pushed the pedal any harder).

Looking inside the clutch master cylinder, there's no fluid movement with the pedal movement. And this is with the slave cylinder dangling loose from the transmission. I would have expected the booster, even with no vacuum, to activate the clutch master cylinder. It doesn't seem to be doing that.

So, it appears as if the clutch booster is internally jamming up and not pushing on the clutch master cylinder. But the rod does move that 1 1/2". Now, if whatever connects the booster to the cylinder got jammed solid, that would create similar symptoms. But I have no clue what's inside there or in between the two. Also, it seems as if the engineers would have designed this so that couldn't happen. At least that's how they design brake systems and boosters.

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You don't know what's really happening, because you haven't tested anything... I already told you how to diagnose the problem. There is nothing an engineer could do differently to prevent a part from failing from old age, neglect, contamination, and corrosion... The clutch hydraulic system is designed EXACTLY like the brake system, and there is nothing magical about the design of a brake system that prevents the same thing from happening. It can and does happen to brake systems... I just last week replaced the master cylinder in a Corvette for the exact same symptoms. it sat for ten years, and the master seized... You could have put a jack on the pedal and probably just damaged the firewall, because that cylinder was not going to move.

You are correct... I don't know what's happening because I haven't gotten it all apart yet. I was merely restating what I DO know and the history while I was taking a break from working out in the heat and looking for the online diagram of the entire assembly.

Thank you for letting me know that the clutch booster works EXACTLY like a brake booster. I suspected as much but wasn't sure. A brake booster would NEVER be designed to "lock up" in the case of catastrophic failure because to do so would cause the driver to lose all braking ability and crash. But, since the clutch wouldn't necessarily lead to a crash, I wasn't positive.

I intuitively found it unlikely that the clutch master suddenly seized up since it worked just fine a week ago. It just seems strange to go from "working great" to "completely seized up" in a less than a day. My expectation would have been that it would have gotten progressively more difficult, not a black and white thing. But, that's not to say that isn't the issue. I'm down to removing two nuts, one on the brake booster and one on the clutch pedal assembly. I don't have my tool set here and I need at least a universal joint and a deep socket to get either of those last two nuts off.

I have an appointment with a local shop in about an hour. I've reached my limit of alloted time for this project. I have an entire fleet of project cars and I just need to sell this one. I figure it will bring more money running and driving but there's a tradeoff of time/money/selling price there. I can always sell it was "running but clutch doesn't work" if I have to. A friend of mine keeps telling me "Just sell the stupid thing 'as is' and get it over with!".

How did this turn out? I recall another user having a similar issue where the clutch would go straight to the floor. They finally traced the issue back to a the slave cylinder flex line. It had severed at the end and allowed air into the system. Bought a new line and was back on the road.