850 Hydraulic clutch Issue

[Chuck W]

The clutch fork does have some side-to-side play by default. Not a lot, but some. Your car is pretty low on km, so it's hard to imagine that being worn. Especially worn enough to cause problems. The (used) parts in my car have more than double that, without issue.

Phone a friend. Grab a stranger. You need an extra set of eyes or feet to better investigate this issue, as really you're just guessing at it, without actually seeing what happens.
Take a video of how much the clutch forks moves (without the slave cylinder installed), that could also be of useful reference to those of us not there with you. You could probably set up a cell phone camera to record a video while you press the pedal as well.

Air wouldn't cause the piston to pop out. It's going to compress more than the fluid, and result in reduced clutch actuation, not more, or add side-to-side movement.

[manovlov]

The clutch fork does have some side-to-side play by default. Not a lot, but some.

Okay. Let's consider that the fork is okay, also its internal clip and pin.

Air wouldn't cause the piston to pop out. It's going to compress more than the fluid, and result in reduced clutch actuation, not more, or add side-to-side movement.

Okay : so the last possibility is a hose which in bad plugged.

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My Volvo dealer says :
N°1 come from the pedal. In fact, if the clutch fails, the brakes circuit stays full, which sounds correct to me.

Shall i reverse N°2 & N° 3 ?

[Chuck W]

There should be no connection at the reservoir to the clutch slave. The clutch slave is only connected to the master. The master is connected to the reservoir and fed via gravity.

The slave should only have the port for the connection to the clutch master and the bleeder screw. How are you connecting an additional hose to it?

[manovlov]

I thank you to follow my history...

When I press the slave cylinder via its piston using the clutch fork, the pressure sends fluide to the reservoir. Otherwise, how could I make air bubble get out ?

[Chuck W]

I thank you to follow my history...

When I press the slave cylinder via its piston using the clutch fork, the pressure sends fluide to the reservoir. Otherwise, how could I make air bubble get out ?

Those air bubbles travel back through the line to the clutch master cylinder (at the pedal) and from there travel up to the reservoir.
There is no direct connection from clutch slave to the reservoir. The clutch system has only 1 connection to the reservoir, and that is at the clutch master. If you have 2 connections at the reservoir, there is something wrong.

Also, pushing on the clutch slave isn't the way to bleed the system (at least not well). The reverse bleed method I posted earlier in your thread (using a syringe and NOT the pushing on the slave cylinder piston) forces all of the air in the slave back out through the master and out into the reservoir.

[manovlov]

[If you have 2 connections at the reservoir, there is something wrong.

Does it help to understand the circuit ?

Circuit Dot.png (45.79 KiB) Viewed 853 times

Reservoir Dot.png (164.69 KiB) Viewed 853 times

[Chuck W]

Yes, I understand how the circuit is supposed to work, and that diagram isn't it.

How are you attaching 2 hoses to that slave cylinder? It's no different than any of the others, and it has a connection from the clutch master (at the pedal) and a bleeder nipple. That's it. Where are you connecting that other hose from the reservoir?
Here is the clutch slave in my car. The only connection is from the clutch master.


It works like any other hydraulic pressure circuit, like your brakes. There is a fixed "column" of fluid between the master and the slave. When the piston in the master is pushed/released, it moves the column of fluid and moves the slave piston in/out.
The diagram you show doesn't make any sense, as the slave cylinder doesn't need a reservoir connected to it. That would just cause problems.

[volvolugnut]

How about setting up a camera or phone to record the clutch action on video? Use tape to hold in proper position. Then you do not need a helper to observe.
volvolugnut

[abscate]

Is there a hydraulic pump excepting the steering wheel one, to put the clutch lines under pressure ? Do I have to make the engine run to test properly this installation ?

No for both questions.
Try to bleed it "from below". Take a medical syringe of 20 ccm or greater and a hose which can be fitted to syringe and nipple on the slave cylinder. Then:
Slacken nipple and tight it back slightly
Open fluid reservoire cap.
Connect syringe (filled with fluid) to the nipple, slacken it and push fluid SLOWLY to the cylinder.
Close nipple.
Repeat this until you see fluid raising in reservoire without air bubbles. Remove an excess fluid from reservoir using a syringe. After this your clitch should operate correct, if there is no other defects.

Hy,

Thanks for the advice. I've found that which may correspond to your explanation right ?



Thanks again.

Manov

Bumping this as Grunhilde’s clutch won’t bleed with traditional method, will move to this video approsch

[abscate]

Well, here is a tasty tidbit.

Three failed attempts to bleed the clutch, getting some action but then losing it.

Finally I set it up to gravity bleed to try and get the air out. I noticed that the fluid level dropped very little, like 1.5-2 cm

A flash of inspiration. The clutch pickup tune extends well up into the reservoir so the brake master cylinder reservoir has to be full to overflowing to bleed the clutch. I was basically pushing fluid through until the tube sucked air, then destroying my bleed process.