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Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322216 is a reply to message #322205] Wed, 16 August 2017 16:29 Go to previous messageGo to previous message
USAussie is currently offline  USAussie   United States
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma:
Senior Member
Peer,

I have read all the comments made regarding your brakes and you suffered a case of brake fade. I agree that is unlikely that you
have DOT 5 in your GMC. There are two ways you MIGHT be able to tell if you do:

1) DOT 5 brake fluid is purple in color, however, if the fluid has been in the master cylinder a long time it may not be purple.

Tiny URL: http://tinyurl.com/yaguemc7

Full URL:
https://www.google.com.au/search?q=dot+4+brake+fluid+color&rlz=1C1NHXL_enAU731AU731&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKE wjM3uH
B09zVAhWIf7wKHQkQBNAQsAQIMQ&biw=1280&bih=629&dpr=1.5#imgrc=2UIQdIXE8dm8KM:

2) Smell - buy a bottle of DOT 4 open it and smell it, then extract a small amount of the brake fluid from your master cylinder - if
they smell the same you've got your answer, however, once again if the fluid has been in the master cylinder a long time it may not
smell the same.

Additional FAQ courtesy of Google:

Q: What is the difference between DOT 3 and DOT 4 brake fluid?

A: DOT4 brake fluid has a higher boiling point than DOT3, making the fluid less likely to boil. ... Dot 3, 4, and 5.1 are glycol
ether based. They are compatible, but like motor oils, you should use the recommended or higher grade fluid. Dot 4 and 5.1 also have
borate ester to handle higher temperatures.

A: Can you mix DOT 3 and 4 brake fluid?

DOT3 and DOT4 brake fluids are compatible to mix together. But do not mix with DOT 5 as it is silicone based and NOT compatible with
glycol ether based brake fluid.

Since you made it to the AutoZone store in Highland, CA I assume your brakes returned after cooling down. I would suggest you
contact Miguel Mendez of MGM GMC 909-982-7747 http://mgmgmc.com/ in Montclair, CA (approximately 45 minutes from Highland, CA) and
have him flush and replace the bake fluid. If he can get ATE Typ 200 it has the highest dry and wet boiling points.
http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p41972-ate-brake-fluid.html - note where it's made.

Unfortunately Super Blue is no longer available the DOT banned it's use because it was blue and might be confused with purple
silicone brake fluid. Then they created DOT 5.1 which is glycol ether based brake fluid which wouldn't be confused with DOT 5
silicone brake fluid. As the saying goes; "I'm from the government here to help." ;-)

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of Peer Oliver Schmidt GMC
Sent: Thursday, August 17, 2017 6:40 AM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Brakes going soft - How long to wait / What to do?

Thanks Hal.
> Be sure to check the brake fluid level at the master
> cylinder and look for any leaks around all of the brake cylinders at each wheel, front and rear.

is there any way I can determine what kind of brake fluid I have?

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, NH


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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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