I have a 2000 4runner 5spd. I did search but didn't fine anything the same.

the other night coming home I stopped at light, with the clutch pedal depressed and the brake on, two seconds later the clutch released and the vehicle tried to lurch forward like I popped the clutch. Pedal still at the floor.

As I made my way home i found that the clutch worked fine the hydrolics seemed to be leaking past one of the plungers??? (master or slave)

Got home.. barely any (no) fluid loss.

So.. I took of the line to the master cylinder, made a plug, put the plug in and tested the pedal.. firm no change.

When it is hooked up to the system I had someone depress the pedal, I could see the lever at the end of the slave cylinder slowely start to retract.

So... I beleive it is the slave cylinder which needs replacement. could it be anything else? I checked for a break in the line and air (bled the system once using one of those one man bleeding kits.

I just want to get a second opinion before I start trying to squeeze under there in the wet snowy driveway.

Thanks everyone

 

I would replace the master cyl. If the slave was bypassing you would be seeing it leak

 

Try puling the rubber dust boot back on the slave. It may not be leaking on the ground but the dust boot might be filling up with fluid. sonds to me like it is your slave but double check just in case.

 

Does that four runner have the hydrolic flex hose on the passenger side fire wall like the 2nd gen. trucks and four runners that always leaked. See if you are leaking fluid there, if indeed you have this hydrolic hose. Also look inside the truck where the clutch pedal attaches to the master cylinder at the firewall. I have seen fluid leaks inside the vehicle. Only other place I can think to check would be between the master cylinder and the brake booster. Sometimes a visual inspection of the brake booster will show signs of leakage. Look for peeling paint and an oily surface at the base of the booster.

 

X2

if the fluid is leaking past the seal in the slave you will have fluid filling the boot and/or leaking out like toytech said, if the master is "bypassing" most of the time the fluid will just go back into the reservoir, and may leak into the cab.

 

Like he said, little or no fluid loss. The boot on the slave wouldnt hold that much fluid that was being bypassed. The master will just bypass it internally or like joe said, leak a bit into the cab

 

So if it was my master cylinder, wouldn't I have the same problem when I isolated it with a plug? or is my theory off.

I'm not seeing any leaks in the cab or externally, and I haven't gone through that much fluid.??? I did see some minor amount on the firewall but that was after I was doing some work in the area. when I plugged the outlet on the Master, and put my foot on the pedal the pedal stayed, no change in height.

I did check the rubber hose it looks ok.. But my hour drive I didn't see any real fluid loss. I would have thought if it was a leak... I could keep pumping the pedal and it would keep seeping out... but maybe it is a small enought crack to let a the pressure off the slave and not loose much fluid.. but then wouldn't the pedal return to its original position?

I picked up a new slave today and was going to put it in.. I guess I should double check the lines and the boot on the existing slave.

Thanks

 

let us know what happens. I want to see if you had to go back to the parts store for the master cyl

 

Yep... ordered the master today.

When I got home I checked the slave for leakage, didn't find any, but by then I had the part, and they charge me a restocking free to take it back so I figured what the heck.... I should try it.

Bled the system.. and same problem... more or less. With someone depressing the pedal I could see the lever on the clutch slowely retract.

So.. must be master. I did the following tests

Watched the fluid in the master as the pedal was depressed and held. sure enough ever so slightly there was fluid draining back in. (you could almost barely tell, took me a couple of tries with various lighting)

I took the line of the master and put a section of 12 hose with a plug at the end and tried the pedal pressure at different points in the travel. it pretty much held fine until the pedal was almost fully to the floor, then it didn't hold. So... I guess it is at the end of the travel or so that is the problem?

I pulled the Master cylinder out took out the snap ring and inspected.
There is a small crease in the first rubber cub on the push rod. I don't know, maybe it gets to a point and folds over or something.

There also looks to be some type of scratch on the cylinder wall about 1/2 way down. about 1/2 inch long, and about 1/8th to 1/4 wide.

Well. I ordered a new Master cylinder from Nappa 95$. Live and learn I guess... should have started there in stead of the slave.

Oh well.

Thanks for your help.

 

Did you bleed it after this test?

Either way, sounds like master because of the lack of fluid loss. When my slave went out it was leaking at the slave cylinder and I lost fluid. If the master blows by, the fluid is just bypassed and not leaked out. Try pumping the pedal to build/keep pressure up.

 

Yep bled it twice.

I 've ordered the master... lucky for me Nappa just called to let me know they can not locate the part... lol...

not looking good for the weekend... I usually go to the stealer for parts but thought saving something like 85$ was a good idea... live and learn.

 

I had the same problem and the slave cylinder did exactly what you are talking about. I changed the Clutch MC and it solved the issue.

I didn't look at the MC after I changed it (dumb) but I am sure that fluid was just pushing past the seals in the MC.