Hi Guys,

Started doing some work on the new car I picked up and I've ran into an issue whilst bleeding the clutch. The car is 93 JDM WRX and when I had it the clutch bite was almost on the floor and I was getting the odd crunch on gear change so thought I'd start by changing the fluid to see if it helped. My master cylinder doesn't have a bleed nipple(or doesn't appear to have one) so I've bled the system from the slave cylinder.

I've bled the system by having a bleeding kit connected to the nipple, loosening the bolt a bit and having someone press the clutch down, then tighten the bolt and have them pull the clutch up. Repeated this process and topped up fluid in master until the fluid coming through the pipe was nice and clean and as far as I can tell there is no air bubbles. Now for the problem.

The clutch peddle does not return all the way to the top like it used to. Instead it pops back up about a third of the way maybe a little less and then you can bring the peddle up all the way manually but doing this there is a very much mechanical clunk. When then putting the clutch peddal down, it drops instantly with another mechanical clunk to the third of the way down point and then it feels like a "normal" clutch again with hydraulic feel.

I think the clutch is working in the bottom part as with the clutch fully down I can change between gears smoothly (with engine off due to alarm(another issue but one at a time)) but I need to get the 2/3rds part of the clutch with no feel sorted. Is this down to a faulty master cylinder or does the pedal need adjusting where it connects to the cylinder linkage? Is it more simple then that and I have indeed got air in the system? Apologies if this a simple issue or repeated question - I'm a noob I will admit it but I'm trying to learn by getting my hands dirty.

Thanks in advance.

 

If it was ok before just low pedal and all you have done is bleed it i would say you managed to get air in it.

The way i do it is to have someone inside pump the clutch pedal then hold it down open the bleed just a little to let fluid out then shut it before fluid goes from a strong flow to a drip, then pump pedal and repeat.

Thats the way ive done all mine never had a problem

 

Been a while since I've done one but trying to get air out can be tricky due to the way the slave sits.

Pretty sure I had to unbolt the slave and turn it to allow the air to rise to the point near the bleed nipple. Just imagine a bubble of air inside the slave and I think you'll find he way it sits on the gearbox, the air pocket is trapped at the highest point away from the bleed screw. It should make sense if you have a look.

 

Thanks for the suggestions and sorry for not getting back to you sooner - it was one of those weekends where the little jobs around the house seem to take forever.

Scott I'll give it a go using your technique and see what happens, I was guessing it would most likely be air but as I can't see bubbles its a confusing one. Would make sense if the air is trapped in the cylinder like James suggests though. Is it just a case of loosening the bolts on the slave to free it from the gearbox?

 

We used to use a lever to press the clutch slave cylinder piston back in as far as it would go then bleed the clutch normally. On about the 3rd or 4th press allow the pressure on the piston to slacken and let the piston slowly rise to its usual position by the pressure generated by the pedal pumper. SLOWLY.

Then adjust the fulcrum under the dash. There is an adjustment under there that allows the pedal to travel so far up a rising cone and not go over the top. Sounds like yours is going over the top, whereas it ought to ride to the apex and no further.

Maybe try that first?, as it sounds as if the bleeding is not far off to me.

David

 

It's hard to bleed the clutch with the slave cylinder mounted as the nipple is not at the highest point. I have always unbolted it and clamped it then bled the clutch with light pressure on the pedal but enough to force the piston in the slave cylinder to open the port.
A poorly bled clutch will cause the pedal to spring straight to the floor.