Bleeding clutch fluid

Hi guys, first time posting here. I don't remember the last time I created a thread, I usually find answers by searching but I'm out of ideas with this one... Any help or suggestions would be appreciated.

I have a 1999 4runner SR5, manual, 3.4L. long story short, my pedal fell to floor so I decided to tackle the master and/or slave cylinder first, as I suspected one of the 2 over clutch (just a guess based on experience and the little knowledge I have doing all the work on my cars myself). I've done this a dozen times and never ran into this issue...

Upon inspecting the master cylinder, it looked good. No leaks, etc... It even looked newish like it might have been changed recently. The slave also had no leaks, but was rusty and I figured I'd do that first since master looked better than slave. I should've just done both together lol, but didn't want to swap out master without knowing it needed to be for sure... So I swapped the slave, installed new one and began to bleed the system.

Issue I'm having with bleeding is this - when clutch is pressed down and I open the bleeder, barely any fluid comes out, next to none. I've done all bleeding procedures that I can do alone (pressing clutch and having it being pressed down, open bleeder, close bleeder, pop clutch pedal back up. Tried manually by pressing in slave cylinder rod. Also tried with vacuum). Made sure reservoir always had fluid...

Only time I get fluid flowing is by using vacuum. I've tried to do this and mix and match with pressing clutch. But aside from using vacuum I get barely any to 0 fluid coming from bleeder. When using vacuum, the fluid flows but the bubbles are never ending. Almost seems as if there is air being entered into system somehow. Without vacuum, I get next to no fluid coming out... Also tried gravity bleeding many times, fluid barely comes out even for 15-20 mins.

So, the question I have is - is it possible for the master cylinder to be shot that's causing this? Want to make sure before I go swapping it. It's almost like the master is not pumping properly. Only way I get fluid is by force (vacuum). The fluid level in reservoir barely goes down, unless I vacuum it or pump clutch pedal with bleeder open. Even then I feel as if the fluid is not decreasing fast enough.

Anyways, if anyone has been through something like this please holler. I was about to just swap out the master and give it a go but figured I'd get some advice before doing so...

Hope all this makes sense... I've been through 2 bottles of fluid with 0 success lol. Clutch pedal still has no pressure. Thank you for taking the time and reading this. God bless!

 

You really only have 3 options for failure. Clutch master, slave cylinder, or line connecting them. If you aren’t getting flow then there is an obstruction.

The only time in 20 years of having a clutch hit the floor board for me (92 DSM) it was my clutch master. Regardless of what it looks like on the outside, the diaphragm internally could be compromised preventing flow. However…

I would start by recommending you changing out the soft line between the two. It’s the cheaper option and probably the original and 23 years old. It’s rubber and under high pressure all the time.

 

I've bleed my clutch fluid before, it didn't take a lot of fluid. I filled the bottom quarter of a clear water bottle before clean fluid started coming out. But I took a syringe and sucked up the dirty fluid at the clutch master cylinder and added in new brake fluid before I started bleeding. The bleeder at the slave cylinder can get clogged, brush it down with a soapy toothbrush to make sure it's not dirty.

This sounds like a master cylinder failure, but check the components between it and the slave cylinder. Is the master cylinder OEM or aftermarket?

 

Hi guys, sorry been MIA. I finally got my parts in yesterday and did the job. Changed the hose out first just to know and it didn't change anything. So I swapped the new Master in and all is good now. Had to bleed it a bunch of times. It was hard to get it into gear, just didn't feel right. Finally had a buddy come by and help me bleed it with 2 people. That helped quite a bit. Still didn't feel quite right but adjusting the pedal position/master rod helped sort that problem out.

I appreciate all the help and recommendations! And ya, now that I think of it, every time I've had this issue, I've always just changed the master and it resolved issue. But this time, for some reason (based on online research and advice from others), I ended up doing the slave first. I guess it's worth just doing both at the same time anyways if they are old... They seem to be cheap enough.

And as for the brand, I naturally bought an Exedy slave (I'm typically a Honda guy and exedy is usually the go-to brand). I discovered later that Aisin is OEM. I've never had to change anything clutch related in my mr2 (yet) so learning Aisin is typically OEM for Toyota was news to me. Therefore, I went with Aisin for the Master.

Anyways, thanks again y'all! Much appreciated and much Love! Drive safe!

 

Glad you got it sorted out. Never hurts to replace a 20+ year old rubber line anyways.

I am on year 2, and about 15k miles on a new clutch in my 02’ is300. It is only the second one in the vehicle at my current 232k miles.

Aisin, mishiboto, denso and numerous others all provide OE parts to Toyota/Lexus.