ls1247

iTrader: (2)

Trying to figure out why we have a "check valve" in our clutch line and found this....

http://www.uucmotorwerks.com/html_te...heck_valve.htm

ryridesmotox

The thing about them is, they a susceptible to foreign matter. The design is sound, but because some do not see proper maintenance, issues can arise.

ls1247

iTrader: (2)

I could be wrong or maybe I just never saw them, but I've had a couple of hydro clutch cars and I don't recall ever seeing a check valve in any of those...

Of course, I never had them apart either...

ryridesmotox

Some may or may not. But the idea is to protect the integrity of the line, to keep air out when its disconnected to change the slave. The hydros in other applications use check valves or similar items to stop air and debris from entering the line when they get disconnected.

ls1247

iTrader: (2)

If it doesn't have anything to do with the function of the clutch itself, it would make it fairly unnecessary in my book. Sounds like you could do the same thing by just making sure the line stayed up right and you didn't pour the fluid out of it when you opened the line up.

Getting that valve to seat was the worst part of installing the PMC for me.

Wonder if the F-bodies and vettes have them?

edit - wonder if gm used it to make the car easier to assemble?

ryridesmotox

The valve is there on the master cylinder side to prevent fluid from escaping the master and it running dry, thereby necessitating a full bleed and flush of the system.

You're over thinking this. They did it to preserve the hydraulic system. To keep air out, contaminants out, and to keep the fluid in.

The inadequate master cylinder was more than enough to slow down the clutch activation to limit the shock on the drivetrain.

ls1247

iTrader: (2)

so basically what you just said is that it is totally useless when installing the PMC because its already dry.

Gus_Mahn

iTrader: (1)

I thought it was a delay valve to slightly low up the action of the clutch to limit shock loads, prevent drivetrain damage, and save on warranty claims.

ls1247

iTrader: (2)

Thats what the link to the BMW valve scenario in the first post is saying.

I can see what motox is saying about it keeping the fluid from dumping out when you disconnect the line to install a new clutch but, how do you keep the brake fluid from doing the same thing when you replace a brake caliper?

You leave the master cylinder lid on. If no air can enter behind the fluid, it isn't coming out for the most part.

ryridesmotox

Yea sure... But when you get a new slave have fun with the clutch fluid flowing out of the master. The idea is that the master cylinder stays, while multiple slaves change.

ryridesmotox

You don't replace calipers much in brake jobs. They are supposed to be fairly permanent items. So the system stays sealed.

Our master cylinders flow so poorly, that is where you need to look to place blame on a lazy system to reduce the drivetrain shock.

Brake fluid will still come out if you leave the lid on the master. When I dropped the cradle and rolled it out to do the bushings, the passenger brake line from the frame to the caliper has to come off. The line dripped until we plugged it. Calipers are made to stay on the line and the car for most of its life.

ls1247

iTrader: (2)

Cast iron calipers require a certain amount of maintenance and I've done my share but I've never had a manufacturer hook me up with check valves in the brake lines so the system doesn't drain. I'm thinking Gus_Mahn is more correct than we are on this one.

The PMC is plenty up to the task but we're still getting reports of notchy shifting and hard pedals so it isn't entirely the master cylinder. Its possible something else is at play here and everything else has been talked to death so why not this valve.

Gus_Mahn

iTrader: (1)

Drum brakes actually do have a residual check valve. It's there to keep 1-2psi on the lip seals so they don't leak.

philistine

iTrader: (2)

There is no check-valve in the system and the heading is incorrect. Fluid has to flow both ways. A check valve allows flow in ONE direction. I believe what you are referring to is an orifice. Orifices are used regulate pressure - you create a high pressure zone a slightly lower pressure zone along with velocity.

The large plastic adapter when removed from the slave line will close by the internal spring preventing fluid loss and foreign contaminants from entering the hydraulic line. Very common with any hydraulic lines or when you disconnected any hydraulic hose, you would spill fluid everywhere.

The MC and slave are coupled....that is just the way it is, they are both wear items and can be replaced by uncoupling them. It's convenient for clutch swaps, transmission servicing etc and you don't have worry about flooding the floor with piles of hydraulic fluid getting all over the place and getting an airbound MC.

ls1247

iTrader: (2)

Learn something everyday.

philistine

iTrader: (2)

It is however a check valve when uncoupled from the slave line.

ls1247

iTrader: (2)

Any input on this statement and did the orifice size you describe play a role in the sizing of the master cylinder?

Is it possible that this valve/orifice is also a wear item as it has moving parts?

philistine

iTrader: (2)

Absolutely it did! The sizing of the MC was critical for the application of the V1. The Tilton is a slightly larger diameter with equal stroke compared to the factory. Any larger diameter piston for the MC and it will take 2 legs to mash the clutch pedal. It was sized to move more fluid volume and pressure and also to firm the clutch pedal.

The orifice is not the limiting factor with the hydraulics - it works well with the system. It has no moving parts. It has a spring and a stem.

ls1247

iTrader: (2)

I know GM designed the clutch master and the orifice size as a matched set. I'll just have to assume that by changing one, we shouldn't have changed the other.

The orifice is designed to regulate or create a pressure but to what end? Does what Gus_Mahn say have any relevance here?

I've never seen anything with a spring that wasn't designed to move.

ryridesmotox

It doesn't move continuously. It moves once to open, once to close. You way over thing stuff dude.