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Re: [GMCnet] Brakes and brake fluid [message #64282 is a reply to message #64274]

Sat, 14 November 2009 19:26

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma:

Senior Member

Les,

Since you didn't disassemble brake system in the Audi and it worked OK then
the old adage of "you can't argue with success" is apropos.

I wonder if it would be a better to blow all the Dot 4 out; flush the system
with denatured alcohol, blow it out again, and then fill it with clean Dot
5.

HOWEVER, I think the "best practice" would be to take the whole thing to
bits and clean everything then change over to Dot 5!

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Les Burt
Sent: Sunday, 15 November 2009 11:30 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Brakes and brake fluid

Rob,
The very first car in my fleet to receive the DOT 5 was my father's Audi
5000. We did a 5 minute flush using the DOT 5 and the pedal pump bleeding
procedure, unaware of the fact that DOT 5 is bad for creating & holding air
bubbles. We got a mediocre pedal initially but it got better after a few
days. We eventually did a second bleeding procedure several weeks later with
a pressure bleeder and the car ran for many years like that without any
problems. The brake system was not dismantled and cleaned, The lines were
not flushed, and the hydraulic components had been in service since the car
was new. I certainly would not do that now with the knowledge I have gained,
but the car didn't suffer any from the way in which we did the conversion.
This was the car in which we noticed the improvement in rear brake
sensitivity during severe cold operation (-20 and colder) We had done the
conversion over Xmas so we had a good feel of the before and after with no
other changes to the braking system.

During a lengthy discussion with the engineer at Cartel many years ago, I
asked about what happens to the two fluids when mixed together. The engineer
said that the old fluid would just puddle in the lowest points of the system
and be somewhat harmless other than to hold moisture and potentially cause
corrosion at those points. The two fluids would not intermix. He said that
the best method was always to do a thorough cleaning and refurbish of the
hydraulic system prior to using DOT 5 silicone fluid.

If you wanted to just dump the old fluid and add DOT 5 without dis-assembly
& cleaning, the engineer recommended a thorough flush of the system first
using fresh, clean DOT 4. This ensured that whatever DOT 4 fluid remaining
in the system after a DOT 5 conversion would contain a very low moisture
content and be relatively harmless.

Les Burt
Montreal

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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[Message index]

		Brakes and brake fluid By: Harry on Fri, 13 November 2009 15:16
		Re: [GMCnet] Brakes and brake fluid By: Gary Casey on Sat, 14 November 2009 11:56
		Re: [GMCnet] Brakes and brake fluid By: USAussie on Sat, 14 November 2009 13:57
		Re: [GMCnet] Brakes and brake fluid By: Duce Apocalypse on Sat, 14 November 2009 18:10
		Re: Brakes and brake fluid By: JohnL455 on Sat, 14 November 2009 15:49
		Re: Brakes and brake fluid By: GeorgeRud on Sat, 14 November 2009 16:01
		Re: [GMCnet] Brakes and brake fluid By: GMC_LES on Sat, 14 November 2009 17:48
		Re: [GMCnet] Brakes and brake fluid By: USAussie on Sat, 14 November 2009 17:55
		Re: [GMCnet] Brakes and brake fluid By: GMC_LES on Sat, 14 November 2009 18:29
		Re: [GMCnet] Brakes and brake fluid By: GMC_LES on Sat, 14 November 2009 18:36
		Re: [GMCnet] Brakes and brake fluid By: USAussie on Sat, 14 November 2009 19:26
		Re: [GMCnet] Brakes and brake fluid By: Harry on Sat, 14 November 2009 19:44
		Re: [GMCnet] Brakes and brake fluid By: GMC_LES on Sat, 14 November 2009 21:35
		Re: [GMCnet] Brakes and brake fluid By: roy1 on Sat, 14 November 2009 18:55
		Re: [GMCnet] Brakes and brake fluid By: Gary Casey on Sun, 15 November 2009 06:21
		Re: [GMCnet] Brakes and brake fluid By: USAussie on Sun, 15 November 2009 07:03
		Re: [GMCnet] Brakes and brake fluid By: midlf on Sun, 15 November 2009 07:55
		Re: [GMCnet] Brakes and brake fluid By: Matt Colie on Sun, 15 November 2009 11:41
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		Re: [GMCnet] Timing chain By: Charles on Sun, 15 November 2009 08:57
		Re: [GMCnet] Timing chain By: USAussie on Sun, 15 November 2009 06:35
		Re: Brakes and brake fluid By: GeorgeRud on Sat, 14 November 2009 18:45
		Re: Brakes and brake fluid By: GeorgeRud on Sat, 14 November 2009 21:31

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