Clutch bleeding patterns

[Heathx4]

I have a 350 Chev powered MQ whose clutch that would get gradually less effective (only driven every couple of months) until the other day it wouldn't disengage at all. After screwing around getting the slave off, thinking I could space it out to bodge it up, I noticed the reservoir was empty.

I tightened everything back up and set about bleeding. After spending 30 minutes loosening the bleed nipple (aren't cars fun) I was able to get lots of air out. I thought I was getting somewhere, but now seem to be going around in circles:

Note this is a one-man show - I used bricks to keep pressure on the clutch peddle.

1. Open nipple.
2. Pump peddle slowly 5-7 times. Hold peddle down.
3. Close nipple.
4. Pump peddle 3 times, hold peddle down.
5. Open nipple, let it drain.
6. Go to 3.

Now repeatedly at step 5 I get: first a little bit of air, then bubbly fluid, then a nice long consistent fluid flow (confidence goes up at this point) then right at the end a geyser of fluid and then just air.

Weight on peddle is bugger all, easily pushing with my hand.

I guess it's probably clear - I need a new slave right? And I may as well do master at same time, right? Shit.

Now how do I get a master/slave pair by tomorrow, when I don't know what model it is? The slave bolts into the bellhousing between the 350 and a Nissan diesel 5 speed. There is a single bleed nipple on top of the slave and a plastic reservoir.

There's lots of good clutch info already here (this one is particularly relevant) but I thought someone might have some input on the peculiar bleed pattern or particular cylinder set up.

Am in a real pickle and would love some input.

[lay80n]

Yo heath, what time are you home from work this afternoon. I might be able to swing past and give you a hand bleeing it and sorting the issues out. I'm pretty sure there wered issues with the clutch when you did the chev swap. Did you replace the slave cylinder then? If the resoviour is empty then you are leaking fluid, and you have to find and stop this leak or you will continue to have problems.

Layto....

[Heathx4]

I think it was leaking just a little bit from where the pipe goes into the slave. I tightened that up and it doesn't appear to be leaking any more. Regardless, I could deal with a slow leak if I could get my clutch back!

They look like this:





Layto, I'm not home until after 7pm, but would love a hand. Will be working on it all day Friday too.

[v6hilux]

How close does the exhaust run to the slave cylinder?

The heat causes problems with the seals in it.

[shorty_f0rty]

ive managed to bleed my clutch successfully on my own..

get a water bottle (500ml will do) some wire to hang it from the chassis rails and a 1 man bleeder tube from superheap.. make sure there is enough fluid in the bottle so the end is submerged..

put that on the end, loosen nipple, pump until no more bubbles, tighten and your done.. I also found that if you'd back the bleed nipple of a tiny bit it would be loose.. so i used some thread tape to fix that..

hope this helps out.

[Heathx4]

Exhaust is on the other side, headers on same side are not real close, but the engine got very hot recently. Could be related...

So it's possible I just need to bleed a heap more? Like go through a reservoir or two? I've been through about half a reservoir with no change (same pattern I described). If I'm going to go through a lot more, then that return hose and catch bottle sounds like a good idea! I'm sick of lying in brake fluid...

Note in the first photo there are several coils of excess tubing just below the master. Maybe there's still air there. Still, I'm worried the slave is simply drawing in air.

[v6hilux]

The leak might be from a fractured tube or slave piston cup seal.

One thing I noticed in the images is you seem to have a copper line for the clutch fluid. This is a no no when it comes to break lines, due to the fact that when copper vibrates, it ends-up micro-fracturing. This is relevant to clutch fluid too, so if there is a chance the tube is fractured, replace it and the slave piston cup while your at it. It you have enough spare, at the end of the copper tube, you can have 1 cm cut off, then get it flared again and re-fit it.

[Heathx4]

Did a bunch more bleeding to no avail. Have taken the unit off now.

Stripped it down and everything looks good. Couldn't identify a leak and all seals looked healthy. I played around with it for ages, pumping fluid through it. Now is this normal: with the slave disconnected, I couldn't get a stream to flow through the pipe. Is it normal for the master to suck the fluid back up the pipe on the up stroke? I couldn't see how that couldn't happen.

Master is a PBR P5490 (which I found zero info on) and the slave is a PBR P4519 (which I found examples of).

I'll ring around some shops tomorrow and see if I can get it serviced or replaced. I'm hoping it would be easy for a clutch place to recondition a master/slave combo off the car.

[Ruggers]

did you have the spring on when bleeding it is better to remove it if oyu still have trouble reverse bleed it by forcing fluid up though the slave you can do this at home by using a hose of the brake caliper and pumping the brake pedal and like bleeding the brake but sending the fluid up the clutch, also dont pump the pedal with the bleeder open it will suck air back up, also bleed the master first by cracking the hose and pumping it out there

[mrw82]

couple of things, firstly if your trying to bleed it on your own go to supercheap (as mentioned by shorty) spend $15 and get a 1 man bleeder kit. they make life real easy!

second it looks like the whole line is copper pipe, is there flexible hose anywhere inbetween because it really should have. i can see it does have flex coils but without a flexi (rubber or braided) hose the copper tube can fracture from vibrations and may have a hairline split in it somewhere.
also the copper tube can work harden and the flared ends will not seal anymore. better to use bundytube.

thirdly, and im not trying to be a smart arse about this but are you keeping the resivour topped up while bleeding the system, if it gets too low it will suck a gut full of air thru just as you think your making progress

without the 1man bleeder you need to fill resivour, open nipple, depress pedal, close nipple, release pedal, check fluid level and do it all over again. pretty hard on your own.

hope some of this helps.
Mark.

[Chucky]

I have never done any work on a datsun so it will most likely be different.

But when I have bleed my clutch on teh 80 all I have done is removed the blled nipple totally formt eh slave cylinder. I have found the fluid just runs down of it's own accord and all I have to do is keep filling teh resivouir up.
when good clean fluid comes out I just put the nipple back in. I've done this a couple of times now and never had a issue with air in the system.
I can see people not agreeing with this method, but it has worked for me.

[high n mighty]

I am happy to help out if ya need an extra hand Heath, not sure that I have any useful advice but would be only too happy to help.

[chimpboy]

I couldn't get a stream to flow through the pipe. Is it normal for the master to suck the fluid back up the pipe on the up stroke? I couldn't see how that couldn't happen.

Yes, I am pretty sure it's normal. I can't tell you exactly how the master cyl does this but if you have a clear tube on the nipple you can see the fluid getting sucked back in. So if no tube, then it would be air getting sucked back in.

Whenever I have bled a clutch I have only done ONE pump at a time, ie:

- open nipple
- press clutch in
- close nipple
- release clutch

Repeat. I think you are just sucking air in through the nipple if you pump 3, 5, 7, or whatever times.

It's always a frustrating bugger of a job though.

Incidentally with a Nissan G60 you can open and close the slave nipple while you're sitting in the driver's seat, just a cover plate needs to come off. I reckon that is a pretty cool concept.

[Heathx4]

Cheers everyone. Took the unit to a brake and clutch dude. He reckoned the cylinders were too wrecked to seal. Sold me a new master ($115, was expecting $65!) and a new rubber for the slave.

Used some 800 grit and some petrol on the slave cylinder until it was still discoloured but nicely smooth. Whacked it all back together with the new rubber, fluid up, plugged my new one-man-beeder on and pumped away.

Long story short, it worked for the weekend. Dunno how long the slave will seal. Didn't seem to lose any fluid though.

[bazzle]

Fill reservoir

1. With nipple closed, pump slowly a few times.
2. Hold peddle down, release nipple for a fraction of a second and nip back up.
3. Release pedal slowly.

Check reservoir.

Repeat.

Bazzle