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Old 04-06-2001, 06:01 PM   #1
Scooby Newbie
Member#: 5540
Join Date: Apr 2001
Post "Clutch Fluid"

My car: 98 RS
My question: Are there any negatives to replacing the standard Subaru DOT 3 "clutch fluid" (brake fluid really) with DOT 4? My fluid seems to be overheating during drives of any length and the pedal looses all resistace. The guys at my service department said this was the only possible problem/fix, but they werent sure the stock clutch is able to "accept" anything besides the standard fluid. Maybe a dumb question, but I wanted to make sure. Thanks
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Old 04-06-2001, 06:05 PM   #2
Member#: 67
Join Date: Jul 1999
Chapter/Region: SCIC
Location: San Diego, CA
1999 Outlasting
the competition.


that was one of the first things i did to my car. i changed all the fluids to some good Motul dot 4 fluid
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Old 04-06-2001, 06:06 PM   #3
Scooby Newbie
Member#: 554
Join Date: Nov 1999
Location: Darien, CT, USA
2002 Subaru WRX S/W
Aspen White


...My 1998 RS used to do the same thing on warm and humid days. I solved the problem very easily. I purchased a WRX.

(I had TOO MANY problems with the RS!)
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Old 04-06-2001, 06:08 PM   #4
Bottom Feeder
Scooby Specialist
Member#: 2808
Join Date: Nov 2000
Chapter/Region: MAIC
Location: Occupied Virginia

Where the heck did you go to get this diagnosis? I can't imagine what toture you would have to inflict onto your car in order to overheat the clutch fluid. I've heard of racebikes boiling brake fluid, but a car overheating clutch fluid... geezus.
Get a second opinion somewhere else.
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Old 04-06-2001, 08:36 PM   #5
Scooby Newbie
Member#: 2643
Join Date: Oct 2000
Location: Woodbridge, VA, USA
2001 2.5 RS


Go ahead and change it to DOT 4. The manual says you can use either or.

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Old 04-06-2001, 11:13 PM   #6
Scooby Specialist
Member#: 420
Join Date: Oct 1999
Chapter/Region: SCIC
Location: The LBC, CA, USA
2001 Cr-V


I did the same as Kartboy I noticed when my clutch pedal got all "funny" Disengaging only at the furthers travel of the pedal, low pedal position, sticking, etc. I put in the Motul and prob Solved.
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Old 04-07-2001, 04:53 AM   #7
Scooby Newbie
Member#: 4101
Join Date: Feb 2001
Location: Minneapolis
2000 Impreza


Yes, Use DOT4 synth-brake fluid and read this...

Good Luck
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Old 04-07-2001, 03:17 PM   #8
Scooby Specialist
Member#: 5563
Join Date: Apr 2001
Chapter/Region: NESIC
05 OBXT 00 RS-T 05 STI


It is not a good idea to change to DOT 4 because the seals in the clutch resivior and in the slave cylinder are not compatiable with the DOT 4 fluid. The seals will swell over time and begin to leak.
I have never heard of clutch fluid getting hot enough to fail.
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Old 04-07-2001, 06:58 PM   #9
Scooby Newbie
Member#: 4577
Join Date: Mar 2001
Location: Victoria, British Columbia
1998 2.5RS
Black Diamond Pearl


Hey Void!

I'm trying to sort the same problem with my car (98 RS). Funny thing is that I'm on my fifth clutch (warranty replacement to try and cure shudder) and the first three shuddered but didn't have the problem under discussion. #4 - no shudder but....

I'm tuned in with interest!!
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Old 04-08-2001, 04:04 AM   #10
Scooby Newbie
Member#: 4101
Join Date: Feb 2001
Location: Minneapolis
2000 Impreza


In my 2000rs manual page 10-29 it says use dot 3 or DOT 4! The only time when you can't use dot 3 or 4 is when you use silicone DOT 5 brake fluid. Call a dealer or any dealership for any car and ask. Synthetic fluid DOT 4 will not boil as fast and will not cause harm to the seals.
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Old 04-08-2001, 04:42 AM   #11
Scooby Specialist
Member#: 2817
Join Date: Nov 2000
Location: NYC and Troy, NY
2001 Impreza 2.5RS



This dude is correct. You can use DOT3 or DOT4 fluid for brake or clutch. I have used Valvoline DOT4 synthetics many times in different vehicles.

You cannot use DOT5. That's only for Corvettes and other fast cars (I think).
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Old 04-09-2001, 12:51 AM   #12
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Member#: 5410
Join Date: Apr 2001
Location: Stillwater, NY
2008 BMW 335XI


Replace the gearbox fluid and the rear diff fluid to synthetic. I`ve never had a problem with over heating but I have had a problem with hard gear changes in winter and really sloppy ones in summer.
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