DOT 4 brake fluid
Thread Starter
Pro
Joined: Apr 2007
Posts: 663
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From: Arvada CO
DOT 4 brake fluid
I purchased Valvoline (fully synthetic) dot 4 brake fluid for my clutch fluid change. I read Ranger's post and he did mention dot 4 was OK. My question then is there any problem changing the brake fluid in the brake resevoir with dot 4? The brake fluid cap says 'dot 3.' Does the brake fluid even have to be changed since it isnt exposed to the high temps that the clutch fluid sees? I noticed it is slightly dark, but not bad. My car is an 07 with 6000 miles.
Race Director
Joined: Jan 2005
Posts: 10,924
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From: Daytona Beach FL
I purchased Valvoline (fully synthetic) dot 4 brake fluid for my clutch fluid change. I read Ranger's post and he did mention dot 4 was OK. My question then is there any problem changing the brake fluid in the brake resevoir with dot 4? The brake fluid cap says 'dot 3.' Does the brake fluid even have to be changed since it isnt exposed to the high temps that the clutch fluid sees? I noticed it is slightly dark, but not bad. My car is an 07 with 6000 miles.
The fluid has a dry and wet boiling point specification. DOT 4 racing brake fluid has higher boiling points than DOT 3. Driving around on the street you're probably correct that the fluid in the brake system doesn't get very hot. Even an extreme panic stop probably won't heat up the fluid too much because it's not normally followed by another panic stop 20 seconds later, like you do on a race course.
However, the fluid gets extremely hot if you do auto-xing or HPDE's. DOT 3 boiling on the road course can be one of the main reasons you'd have brake problems and a good reason to go to DOT 4 fluid with a higher boiling point. Many owners flush the brake system before and after events (or even during a weekend of a hard braking event).
So....yes, DOT 4 is compatible with your DOT 3; and yes, you do need to flush your brake system once every couple years even just street driving.
Bob
CF Senior Member
Joined: Feb 2006
Posts: 23,313
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From: Tucson Arizona
You may also want to consider that when 'changing' your brake fluid (similar to Ranger's method for changing clutch fluid) with a turkey baster and bleeding your lines, you won't be able to completely flush out the old fluid. It will likely be 'good enough' but to totally flush the old fluid you will need to have the dealership use their Tech II to exercise the ABS circuits.
I changed to Motul 600 fluid previously (without any issues) but when I installed my stainless steel brake lines I had the dealership completely flush the system and replace the fluid with Motul 600.
I changed to Motul 600 fluid previously (without any issues) but when I installed my stainless steel brake lines I had the dealership completely flush the system and replace the fluid with Motul 600.
