Air in 360 Clutch hydraulics?

I have an F355. About 5 years ago, at a race track, the clutch pedal started to do something like what you describe. I blead the system at the track, only to have it happen again. Blead again. On the drive home it happened again. I started to correlate that it happens when I let off the clutch rapidly, but remained fine when I let the clutch out slowly. After we took the clutch apart at the shop, we found the shaft the slave seal slides on had a few corrosion groves that would let air in when the clutch let go fast. We changed this part and upgraded to the slave with the teflon seals, we also insulated the line leading to the slave (close to the exhaust) and its been fine ever since.

 

Seems to me you're describing the classic symptoms of a failing clutch master cylinder.
Sometimes the seals hold and you push fluid down the line to move the slave, and sometimes they don't.

 

Sounds like the master cylinder, Afew years back my Ford Explorer did the same thing felt like the pedal was not connected the anything at all.

 

Master cylinder is ****ed!

 

Your 360 slave is basically the same as the 355.

We quit rebuilding the factory unit even with the updated seals and began installing the Hill Engineering unit about 5 years ago......

 

So the clutch seems ok now mate?

I guess it could be worn/flat seals in the slave unit. When you push the pedal down, the worn seals allow fluid to push past them causing the pedal to go to the floor.

Same as what I/some thought of your master cylinder.

Hope its all good mate and I hope you are sitting down when you read through the bill.

 

Hehe!! Ok, cool mate. Let us know how you get on.

 

It doesn't make sense to me that it could be the slave cylinder. In contrast to the master, the slave is just a cylinder of metal with the piston in one end and the hydralic fluid line in the other. When you depress the clutch pedal the master cylinder pushes fluid into the slave cylinder. The extra volume has to go somewhere, so the piston moves outward.

When you take your foot off the clutch the pressure plate springs push the piston back into the slave cylinder and the fluid moves back to the master cylinder.

The only way a slave cylinder can fail is to 1)leak or 2) seize. If it leaks your fluid reservoir empties and fluid spills out around the slave cylinder. If it seizes it is impossible to depress the clutch pedal.

Unless the 360 has some kind of unusual, complicated slave cylinder, I think your dealer's tech messed up.

 

Yep, the 360 has a complicated slave cylinder.

Well, not really. But its not like the convential one you are thinking of.

If you havent seen one before, here is a pic of one from Ricambi's website.
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Pap, that's the throwout bearing. it's part of the 'salve' if you will, in that it would be analogous to the piston. the shaft it fits on has the oil ports that fill the bearing cavity and cause it to move. It is in constant contact with the pressure plate. those blue rings are the seals that keep the hydrolic oil from leaking out, when they wear it'll leak. On the F1 system it runs 50bar pressure in there.

 

Thanks for the explanation Scott.

I didnt know that it runs at 50 bar pressure!!

 

I agree Pantdino with your slave cylinder diagnosis, well said.

Cwwhk, if there was no fluid loss or leakage in the system then the clutch master cylinder piston seals may be bypassing at times.

An easy way to tell if the clutch master cylinder seals are bypassing is to have someone step on the clutch pedal while someone looks very carefully at the fluid level in the reservoir, if the fluid level increases in the reservoir slightly when the pedal is pressed that means the clutch master cylinder is pumping the fluid past the seals back into the reservoir thru the compensation port instead of down the tubing to the clutch slave cylinder.

You have to do this when the dropping pedal problem exists to catch it happening.

 

If the pressure accumulator on the F1 pump is getting weak, the pump could be running overtime. I've seen this before on several 360s and thought it could be causing the ATF to cavitate causing air
bubbles and then all kinds of shifting issues
these were very hard to bleed all the air out if not impossible
problem is the accumulator is sold with the pump as a unit
this accumulator is very similar to other accumulator on brake and clutch pedal assist that are prone to failure
just a thought.......

 

The slave can leak fluid out, or leak air in. The slave can seize up (no go), or just have enough friction that the clutch springs have a hard time pushing it back (slow go), or it can get canted so most of the time it works correctly, and a couple of times it gets canted and goes into the high friction mode (no go this time).

 

Hi Dave,

I don’t want to be a confrontational ass, but I don’t think there are any pressure accumulators on the 6-speed manual clutch system or the braking system on a 360.

The clutch pressure system is master, lines & blocks, slave.

The ABS system is a pump and valve increase-decrease-hold type of pressure system, not the high pressure accumulator storage system.

Mike

 

I did not read the whole post, I was referring to the pressure accumulator on the F1 shifter which is also the same fluid that passes through the slave/release bearing mechanism.

The pressure accumulator looks exactly as it does on a Porsche Twin Turbo 996/997 for the clutch assistance and also the same as any Bosch ABS4/5 system which go bad all the time.

I've seen frothing in the 360 F1 trans system from the pump running all the time and thus causing the shifting to go erratic or pop out of gear with no loss of fluid in the system

Sorry to throw you off....thought it might be relative, but then again, my fault for not reading the entire post....my time is limited on the internet these days, I'm too busy fixing cars in the real world ;-)

 

You mean too busy with your race cars to engage yourself on a road car...

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