Dr.Trevorkian

I've got a buddy who is on his third clutch master cylinder from Advance autoparts. He says that at 142k the first one went out, would push the clutch down and the pedal would stay on the floor. Replaced the master and slave cylinder and worked like a champ, for a few months, then same issues. Replaced the master, worked well again for a few months, now it is doing the same thing. Are they just cheap master cylinders? I recommend buying an Aisin master, but Advance has warrantied the ones he bought but is getting tired of changing them out. It is not using or losing fluid, bleeding the system makes no difference.

Beto

Not quite sure, but the 99 runner may have the same clutch setup as the 98 taco, if that's the case - there is a spring return on the pedal, and a very stiff one at that. I don't think you could rely on the pressure feedback from the master to lift that pedal back up time and time again. There was absolutely NO WAY the pedal would stay stuck to the floor in a 98 V6 taco. Might be worth a peek under the dash to see if there is (or was) a spring in it.

eddieleephd

I especially agree with this if the clutch is disengaged when the pedal is on the floor!!! basically if the pedal is on the floor and the truck is able to go through the gears with out grinding!! then the cylinder is most likely not bad but the springs or the pressure plate would be culprit...
as well it could actually be the slave cylinder...

Beto

I ran a stock clutch and PP, a TRD clutch and PP, and a clutchmasters stage II clutch and PP. The spings on the pressure plate were not the main resistance to pushing down the pedal - it was that darned double torsion spring on the top of the pedal. If you didn't have that spring, I think that there would be a bunch of extra stress on things trying to transmit the PP spring force back up to the pedal with hydraulics. I guess it would lift the pedal but it's not meant to work that way.

Maybe it's eating through master cylinders, because of a missing/broken spring forcing the entire assembly to transmit force both ways?

eddieleephd

I was just getting at the fact that the pressure plate should push the pedal up some and the return spring on the pedal lifts it fully so that the throw out bearing is not being worn at all times I recon it could need to be lubed where the rod goes through the firewall to push on the MasterCyl.

Dr.Trevorkian

Maybe i just don't get it, but if the spring were bad then replacing the master wouldnt make it run like everything is ok again would it? Where is the spring located? Can you see it down in the footwell or engine bay. Again not my truck just trying to help out a co-worker.

Beto

You have to look up under dash, it's at the top of the clutch pedal - it's like a torsion spring on a garage door, kind of - runs parallel to the dash. I was thinking that maybe when a clutch master is new, it pushes back on the pedal when the slave gets pushed back by the pressure plate -- but if it's only meant to transmit the force the other way with that spring normally pulling the pedal up instead - maybe it's blowing seals out or something..

eddieleephd

yes there is a spring in the Cyl. and it is an assistant in the full return, however there 3 springs in the dynamic here first the return spring on the pedal, second in the Master, third the pressure plate,

Between the pressure plate you get the return to the mid point and this returns the system to an engaged situation, the return spring on the pedal returns the pedal to the top and takes any pressure off of the hydraulic system....

When I replaced my clutch visually looking at the pressure plate you can see waves in the splines showing a weakened state of the pressure plate.

all three springs work together and no one spring can do all of the work!!!

So I am going to say that most likely it is time for a new clutch and return spring.... A good strong pressure plate will help with fuel mileage as well as the return of the system to the top!!!

the spring in the master is going to pull the pressure off of the slave Cylinder as well fully disengaging the pressure from the throw out bearing...

When you replace a clutch it is highly recommended you replace the pressure plate, and throw out bearing as well as the rear main seal $10.00 and the front trans. seal $10.00....