Dark Fluid

[Tracey]

I've noticed the clutch master cylinder fluid is getting dark. A brief history: 2002 Lemans that I bought crashed... Replaced clutch master cylinder and fluid in December 05. I have put 2,500 miles since then. Things work fine but what causes this fluid to get so dark so quickly? (dot 4 fluid from the local auto supply) The fluid level has not changed and I have not added any since Dec. 05.

All of the fluids were fesh and none of the others have gotten dark, whats up?

I need expert advise, got any?

[Guest ratchethack]

Tracey, brake and clutch fluid should be completely changed-out yearly. The stuff is powerfully hygroscopic -- meaning it attracts water molecules -- so much so that it actually pulls water vapor directly out of the air right through clutch and brake reservoirs and flexible lines. The stuff then becomes a transport for corrosion-producing oxidation inside master and slave cylinders. If allowed, old brake fluid will entirely destroy your clutch and brake actuation systems from the inside out. The dark color is the seals in the master cylinder going into solution from attack by oxidation. Possibly, you didn't get all the old toxic fluid out last time around. Pete Roper has been known to lament that he's found stuff resembling "oysters" growing inside Guzzi brake calipers. This is an accumulation of chemical by-products from oxidation and break-down of the seals, lines, plastic reservoirs, etc. Bleed it out, my man!

 

EDIT: One more important thing! If y'er gonna bleed the system, use a can o' NEW fluid. That old can in the corner of y'er garage is likely nearly as bad as what's in y'er master cylinders. If it was old when you put it in last time, depending on HOW old, this could dramatically shorten it's service life.

[orangeokie]

I've noticed the clutch master cylinder fluid is getting dark.  A brief history:  2002 Lemans that I bought crashed... Replaced clutch master cylinder and fluid in December 05.  I have put 2,500 miles since then.  Things work fine but what causes this fluid to get so dark so quickly? (dot 4 fluid from the local auto supply) The fluid level has not changed and I have not added any since Dec. 05.

All of the fluids were fesh and none of the others have gotten dark, whats up?

I need expert advise, got any?

89488[/snapback]

 

Brembo clutch systems are notorious for dark fluid. Regardless if you change it with fresh, within a few weeks it will be dark again. I agree with RH, as does Brembo. Change it out at least once each year. If the dark color bothers you, put on some speed bleeders and change it more often.

[DeBenGuzzi]

Brembo clutch systems are notorious for dark fluid.  Regardless if you change it with fresh, within a few weeks it will be dark again.  I agree with RH, as does Brembo.  Change it out at least once each year.  If the dark color bothers you, put on some speed bleeders and change it more often.

89496[/snapback]

WHOA, so much matience. when do I get to ride again?

 

Guess I'll go buy some more DOT brake fluid and change it out.

[beauchemin]

When you start draining the old fluid, use some Methyl Hydrate to clean the system. Then start adding the new fluid. The Methyl Hydrate will make sure that all the gremlins are purged.

[DeBenGuzzi]

When you start draining the old fluid, use some Methyl Hydrate to clean the system.  Then start adding the new fluid.  The Methyl Hydrate will make sure that all the gremlins are purged.

89507[/snapback]

like this?

[Dan M]

I've noticed the clutch master cylinder fluid is getting dark.  A brief history:  2002 Lemans that I bought crashed... Replaced clutch master cylinder and fluid in December 05.  I have put 2,500 miles since then.  Things work fine but what causes this fluid to get so dark so quickly? (dot 4 fluid from the local auto supply) The fluid level has not changed and I have not added any since Dec. 05.

All of the fluids were fesh and none of the others have gotten dark, whats up?

I need expert advise, got any?

89488[/snapback]

 

 

Everything Ratchet said, Tracey.

Define "dark" though. New is clear. Slight discoloration is normal. In a about a season of riding (depending on humidity) it will darken to light "carmel", eventually it will be "coffee" colored. (way too late)

I usually change mine when I see light carmel (color not texture!) regardless of time or miles.

 

Edit: If the clutch fluid went dark sooner then either brake perhaps the reservoir cap was loose for awhile allowing air / moisture in.

[Guest Nogbad]

My clutch fluid is darker than the brake fluid. I put this down to the difference in operation between the two systems.

 

The brake largely transfers pressure and not a lot of movement of the pistons relative to the seals. The clutch hydraulics however transmit pressure and movement with the master and slave cylinders operating through virtually the entire stroke each time the clutch is operated.

 

Furthermore, the clutch is operated far more often than the brake so the amount of wear debris from the seals etc. will be greater.

 

It is therefore good advice to change the clutch fluid when it becomes darkened. However, the clutch fluid is not subject to the same thermal rigours or safety considerations so more frequent changes than the brake fluid would not be justified.

[Paul Minnaert]

brake and clutch operate exactly the same way, the cylnder from the clutch looks like a brake cylinder, and is made by grimeca. The dark clutch fluid shouldn't bother you, as long as the clutch operates normal.

[Kiwi Dave]

I'm curious.

 

Why is the brake reservoir so much larger than the clutch one?

 

Other than the obvious more reserve capacity in the brake reservoir for safety reasons, I would like to see this one shrunk to the same size as the clutch. Perhaps we would need to watch it more often, but don't we do that anyway before we go riding?

 

Welll, I'm sure you do; me?

[orangeokie]

I'm curious.

 

Why is the brake reservoir so much larger than the clutch one? 

 

Other than the obvious more reserve capacity in the brake reservoir for safety reasons, I would like to see this one shrunk to the same size as the clutch.  Perhaps we would need to watch it more often, but don't we do that anyway before we go riding?

 

Welll, I'm sure you do; me? 

89602[/snapback]

 

 

The rear brake reservoir is the same size as the clutch, as you know, so I would guess it is a "safety margin/liabilty" item as you say.

[Guest ratchethack]

Why is the brake reservoir so much larger than the clutch one? 

Smells regulatory to me. Gotta keep those buildings full o' government bureaucrats and lawyers well-paid, and make sure they can expand their budgets for next year....

 

We're lucky motorcycles were invented before government was here to protect us from 'em. If someone tried to invent them today, you KNOW it'd have less 'n a snowball's chance in Hades....

 

Rant mode off...

[Dr Gil]

I'm curious.

 

Why is the brake reservoir so much larger than the clutch one? 

 

Other than the obvious more reserve capacity in the brake reservoir for safety reasons, I would like to see this one shrunk to the same size as the clutch.  Perhaps we would need to watch it more often, but don't we do that anyway before we go riding?

 

Welll, I'm sure you do; me? 

89602[/snapback]

 

 

Might it be because the brake reservoir is working both sets of front brakes whereas the clutch and rear brake are only working single items?

[DeBenGuzzi]

Might it be because the brake reservoir is working both sets of front brakes whereas the clutch and rear brake are only working single items? 

89625[/snapback]

By george I think he's got it!!!

I almost smell a quiz point in here somewhere.

but I'm sure that the front brakes would work just fine with a smaller resivor.

[Dan M]

By george I think he's got it!!!

I almost smell a quiz point in here somewhere.

but I'm sure that the front brakes would work just fine with a smaller resivor. 

89634[/snapback]

 

They're protecting us from ourselves. The front has to supply 8 caliper pistons. Assuming no maintenance, there has to be enough fluid for the pads to wear completely out and not run the reservoir dry. The rear has to supply only 2 pistons so it needs 1/4 the fluid capacity of the front.