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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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 Posted: Sat Apr 07, 2007 10:13 am Post subject: Dumb Question |
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Maybe this should be obvious but what is the difference between DOT 3 and DOT 4 brake fluid? Being DOT 4 is synthetic, is it better for small leaks?
7osh
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87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
PORSCHE pisses excellence... |
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71vdubturbo
Joined: 28 Nov 2006
Posts: 75
Location: Rolla, Missouri
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| Posted: Sat Apr 07, 2007 10:41 am Post subject: |
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No question is dumb. I pulled this from www.shotimes.com/SHO3brakefluid.html.
| Quote: | Lets look at what the DOT ratings mean. The table below shows the MINIMUM wet and dry boiling points for DOT 2, 3, 4, and 5 brake fluid in degrees fahrenheit.
------------------DOT 2 DOT 3 DOT 4 DOT 5
Dry Boiling point 374 401 446 500
Wet boiling point N/A 284 311 356
The DOT 2 spec is for drum brakes and is obsolete. If you have any DOT 2 in your garage, throw it away! DOT 5 is for silicone brake fluid. Silicone brake fluid (DOT 5) should be avoided because it is not compatible with regular brake fluid, it is hard to pour without introducing bubbles and thus results in soft pedal feel, and moisture still gets into your system and will pool in low areas like your calipers and encourage rapid corrosion. STAY AWAY!
That leaves DOT 3 and DOT 4 fluids. These fluids are compatible with each other and may be interchanged or mixed with no ill effects. |
I know the table turned out weird but you get the picture.
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1977 Porsche 924 - going away...
2001 Audi S4 - 2.7T, Tip |
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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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| Posted: Sat Apr 07, 2007 10:49 am Post subject: |
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Hmm, tha's interesting. I guess you learn something everyday, the reason I ask tho is because for some reason I am loosing a small amount of fluid somewhere and haven't quite figured out where it's coming from. I was hoping that if I put DOT 4 in instead of DOT 3 it would help but that doesn't seem to be the case. Thanks for your help 71vdubturbo. 
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87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
PORSCHE pisses excellence... |
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Paul
Joined: 02 Nov 2002
Posts: 9491
Location: Southeast Wisconsin
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| Posted: Sat Apr 07, 2007 12:27 pm Post subject: |
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Common places are the clutch master or slave cylinders and the brake master cylinder leaking fluid into the power brake unit. (Usually causes missing paint on the booster underneath the master cylinder.)
Leaks do not go away, find the leak and fix it. Also completely flush your brake fluid every 2 years.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy. |
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Sat Apr 07, 2007 12:32 pm Post subject: |
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The clutch master cylinder shares brake fluid from the brake fluid reservoir, so it could be leaking from the clutch slave cylinder down below - next to the starter.
If it is leaking there, some of the fluid will get into the starter solenoid + attact moisture there since the fluids (except the silicone DOT5) are hygroscopic. -So, service both the starter solenoid and clutch slave cyl if you find it leaking there (the starter solenoid may only need disassembly and cleaning).
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"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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| Posted: Sat Apr 07, 2007 11:50 pm Post subject: |
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Well, I haven't seen anything leaking from the top of the engine area, but one of these days I'm going to jack the car up and take a good look underneath it and see if I can where the leak is comming from. Thanks for the advise guys.
7osh
_________________
87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
PORSCHE pisses excellence... |
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