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Re: [GMCnet] Brakes and brake fluid [message #64307 is a reply to message #64279] Sun, 15 November 2009 06:21 Go to previous messageGo to previous message
Gary Casey is currently offline  Gary Casey   United States
Messages: 448
Registered: September 2009
Karma:
Senior Member
Just another anecdote: Way back when (my long term memory still functions :-) I remember that GM was planning to go to DOT5. Reason was the high cold viscosity of DOT3 degraded brake response in the north country. Then they found out that if they filled the system in the same building as they painted they couldn't get a good paint job. Subsequently, all silicone products were banned from the final assembly plants. No WD-40 allowed. In our plant we didn't paint, but we filled sensors with silicone fluid. To get rid of the water and air we conditioned the oil at a few millitorr (almost a perfect vacuum and one that took many thousands of dollars of vacuum pumps to accomplish) for 24 hours. I don't know if the story about the GM plants is true, but after a few years of using silicone all our floors were pretty slippery and we had to use special cleaning processes for safety reasons. Silicone gets everywhere.
Ron is right, if you get vapor in the system the brakes go to zero in a flash. As someone said, they "cease to function properly." I'm not going to be driving if the temperature is below 0F, so I think I'll go out and just bleed my brakes using DOT4. As I understand it, one of the benefits of the glycerine-based fluid is that it tends to distribute the water through the system, avoiding any water pockets in the wheel cylinders. The bad news is that it absorbs water - the good news is that it absorbs water.
Gary



________________________________
From: roy keen <roynpaula@charter.net>
To: gmclist@temp.gmcnet.org
Sent: Sat, November 14, 2009 5:55:07 PM
Subject: Re: [GMCnet] Brakes and brake fluid



I have been using dot 5 in my street rods for 30 years. It keeps everything real nice inside. I don't worry about rusted wheel cylinders anymore like I did with dot 3. I converted the GMC to dot 5 just by flushing the old fluid out with new dot 5. It was OK for a few years but then I had problems on steep mountain grades (brake pedal went to the floor when the brakes got hot). If you are running dot 5 in the GMC I would change it just like dot3 as it will wind up with water pockets in the system and if that happens you will loose your brakes at the worst possible time. It is a lot less expensive to change dot 3 or 4 every couple of years. If you never get the dot 5 hot it will be OK like in my street rods.
Roy
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