Clutch Fluid Spec.
Discussion
woody said:
Hi guy's,
I'm probably being a bit thick.
I've looked in the bible and the handbook and can't find what spec fluid I need for the clutch.
Any suggestions?
Cheers
Chris
Use brake fluid. Personally I use DOT5.1 because thats what I use for the brakes, but as it doesn't get very hot DOT3/4 will do.
Z
Z
When you say DOT 5 I assume you really mean DOT 5.1. This is fully compatible with DOT 3 and DOT 4 but with a higher temperature rating (not that this particularly matters for clutch fluid). This stuff is readily available in the shops.
DOT 5 is completely different. It is the work of the devil, don't be tempted to use it under any circumstances. It is not compatible with the other standards (DOT 3, DOT4, DOT5.1) and if you change to it you will need to flush the entire system out and replace all the seals. It is not hygroscopic, which means water entering your hydraulic system will separate out and collect in odd corners, this can cause all sorts of problems. Fortunately it is far harder to get hold of and you would probably have to go to a motorsport specialist.
DOT 5 is completely different. It is the work of the devil, don't be tempted to use it under any circumstances. It is not compatible with the other standards (DOT 3, DOT4, DOT5.1) and if you change to it you will need to flush the entire system out and replace all the seals. It is not hygroscopic, which means water entering your hydraulic system will separate out and collect in odd corners, this can cause all sorts of problems. Fortunately it is far harder to get hold of and you would probably have to go to a motorsport specialist.
as discussed dot 5 is not mixable with 3 or 4
5.1 is
5 still has a much higher boiling point but yep new seals should be used
5 is usually for brakes
interesting about 5 not being hydroscopic because when we got it mixed up through stupidity and added it to a system with 4 already in the lines on the race bike it seemed to absorb atmospheric humidity and boiled like mad the next week end - or at least that's what we assumed happened - you might be right and what actually happened was that water separated out in the calipers where we couldn't see it
most unpleasant coming up to the hair pin at cadwell and finding the lever coming back to the bar
stick to 4 for the clutch and all will be fine
reb
5.1 is
5 still has a much higher boiling point but yep new seals should be used
5 is usually for brakes
interesting about 5 not being hydroscopic because when we got it mixed up through stupidity and added it to a system with 4 already in the lines on the race bike it seemed to absorb atmospheric humidity and boiled like mad the next week end - or at least that's what we assumed happened - you might be right and what actually happened was that water separated out in the calipers where we couldn't see it
most unpleasant coming up to the hair pin at cadwell and finding the lever coming back to the bar
stick to 4 for the clutch and all will be fine
reb
GreenV8S said
"This is fully compatible with DOT 3 and DOT 4 but with a higher temperature rating (not that this particularly matters for clutch fluid)."
The clutch fluid in my S2 was black with a ton of soot in the bottom of the reservoir, which definately shows heat is a problem. I have now replaced it with Dot 5.1.
I have only just bought the car so I dont know what the previous owner has been doing. It does mention in the Steve Heath manual that clutch bleeding is a constant requirement especially with track days.
Al
"This is fully compatible with DOT 3 and DOT 4 but with a higher temperature rating (not that this particularly matters for clutch fluid)."
The clutch fluid in my S2 was black with a ton of soot in the bottom of the reservoir, which definately shows heat is a problem. I have now replaced it with Dot 5.1.
I have only just bought the car so I dont know what the previous owner has been doing. It does mention in the Steve Heath manual that clutch bleeding is a constant requirement especially with track days.
Al
Modern DOT3 , DOT4 and 5.1 fluids are glycol based and there is no naturally occurring source of glycol, so by default they are all synthetic. The idea that you cannot mix DOT3, DOT4 and 5.1 is not true. You cannot mix them with DOT5 which is silicon based, but the others will be ok to mix. Be aware that mixing of brake fluid will produce a fluid that has characteristics nearer to the worst performing fluid in the mix. So, if you mix 5.1 and 3 chances are the boiling point will be nearer DOT3. This is also true of when you bleed your brakes, you need to remove all of the old fluid to ensure you get the best performance out of the new.
DOT5.1 has a higher boiling point because greater control over the size (polydispersity) of the glycol chains has been achieved in this fluid. This achieves the optimum boiling point / viscosity characteristics for brake fluid. Achieving narrow polydispersity in the manufacture of glycols is exceptionally difficult and therefore more expensive.
I also doubt very much that the deposits you saw in the fluid were soot, more likely is that they were small particles of oxidised material and broken down particles of your seals drawn into the reservoir.
Z
DOT5.1 has a higher boiling point because greater control over the size (polydispersity) of the glycol chains has been achieved in this fluid. This achieves the optimum boiling point / viscosity characteristics for brake fluid. Achieving narrow polydispersity in the manufacture of glycols is exceptionally difficult and therefore more expensive.
I also doubt very much that the deposits you saw in the fluid were soot, more likely is that they were small particles of oxidised material and broken down particles of your seals drawn into the reservoir.
Z
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