Replace Dot5 with Dot3

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Mar 29, 2009 | 02:57 PM

VictoriaVette

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Pro

Joined: Feb 2007

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From: Victoria VA

Replace Dot5 with Dot3

I know you are not suppose to mix dot5 with any other brake fluid but can the system be flushed to replace it with dot3? Anyone ever do this?

Mar 29, 2009 | 04:47 PM

Roughrider

Melting Slicks

Joined: Mar 2007

Posts: 2,100

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From: Frederick Maryland

There's no reason why not but you have to make sure you completely flush the old fluid out and make it's it's dry before adding new fluid. The procedure should be the same as replacing Dot 3 with Dot 5 as the reverse.

You just want to make sure all vestiges of the old fluid are purged completely. Rebuilding the calipers with new seals would be a good thing as well.

Mar 29, 2009 | 05:12 PM

Bond007

Racer

Joined: Jul 2000

Posts: 416

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From: Iron Mountain,Michigan

VictoriaVette,
Why on earth would you want to go back after going through
the process of replacing 3 with 5????

Mar 29, 2009 | 06:15 PM

Bee Jay

Safety Car

Joined: Nov 2005

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From: Lompoc, CA. Santa Barbara County

Quote:

Originally Posted by VictoriaVette

I know you are not suppose to mix dot5 with any other brake fluid but can the system be flushed to replace it with dot3? Anyone ever do this?

I had this done about 20 years ago. I think they flushed the system with alchohol to get rid of the DOT 5, before refilling with DOT 4. That DOT5 was bad news, mostly for concourse weenies, not for any high performance driving. I run synthetic DOT4 now.
Bee Jay

Mar 29, 2009 | 08:17 PM

VictoriaVette

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From: Victoria VA

It sound like it will be more costly than to just keep my Dot5. I owner of my 77 put new calipers and master cylinder on it and started using Dot5. I need to bleed the brakes and Dot5 is very costly in it self but I guess I'll keep it. Thanks for the replies.

Mar 29, 2009 | 08:35 PM

Bee Jay

Safety Car

Joined: Nov 2005

Posts: 3,960

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From: Lompoc, CA. Santa Barbara County

Quote:

Originally Posted by VictoriaVette

Your sig has dual exhaust, rpm manifold, aluminum heads, and a cam. I bet you drive your car hard and fast occasionally. I like to drive mountain and canyon roads. Every once in a while you have to haul it down from superlegal speeds to 15mph for a hairpin or three. The silicone would get spongier on me as the day wore on. Other than that, Dot 5 was great, and back in the day, we all put in Dot 5 to save our precious factory brakes from corosion. When you upgrade to Wilwoods or stainless sleeves, that would be a good time to get rid of the sillycon. Your results may vary.
Bee Jay

Mar 30, 2009 | 10:08 AM

Crash80

Drifting

Joined: Apr 2003

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From: Castle Hills Texas

So....what would happen if DOT 5 and DOT 3 were mixed? Just curious....

Mar 30, 2009 | 10:18 AM

Roughrider

Melting Slicks

Joined: Mar 2007

Posts: 2,100

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From: Frederick Maryland

Quote:

Originally Posted by Crash80

So....what would happen if DOT 5 and DOT 3 were mixed? Just curious....

The two types are not compatible. You'll end up with a cloudy mess in the brake lines and lots of air bubbles that won't bleed out. The car will end up with very mushy brakes that defy correction until completely flushed.