Home » Public Forums » GMCnet » [GMCnet] Brakes going soft - How long to wait / What to do?
 [GMCnet] Brakes going soft - How long to wait / What to do? [message #322201] |
Wed, 16 August 2017 14:55  |
Olly Schmidt
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
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This morning we left Big Bear Lake and are on our way towards Los Angeles.
On the downhill on CA330 the brake pedal all of a sudden became very
soft, and braking was ... nearly non-existant. We found a nice place to
stop for a while, and I wonder, if it is okay to just let the brake
fluid cool down, or if there might be other things I should do. If cool
down, how long would be appropriate?
--
Best regards
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA
'76a Eleganza II, CA
'73 Sequoia, VA
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Best regards
Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322202 is a reply to message #322201] |
Wed, 16 August 2017 15:35  |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Oliver, if the fluid boiled and that's the issue you should be fine within an hour I'd guess. 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.
Things should have cooled by now. Be careful.
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322203 is a reply to message #322201] |
Wed, 16 August 2017 15:37 |
Olly Schmidt
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
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We have made it down to Highland, CA and are sitting now in the AutoZone parking lot.
I am still open for ideas. I don't see any fluid near the brakes. atm I can't get the top of the master brake cylinder off, but eventually will succeed.
Is there a way to determine what DOT (3,4,5) I should use, if I need to fill up? Open for all hints, tips, tricks, and suggestions 
Best regards
Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322204 is a reply to message #322203] |
Wed, 16 August 2017 15:49 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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It is most likely DOT-3 fluid. Pry the clips that hold the top off with a screw driver. Make sure to keep everything clean, and push the rubber 'gasket' back into the top of the MC.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322206 is a reply to message #322203] |
Wed, 16 August 2017 15:47 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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You shouldn't need to top it off unless there was a leak. If there was a
leak, fix that before doing anything else.
But you do need to bleed fresh brake fluid into the system to get rid of
the moisture that dropped the boiling point. Unless someone put DOT 5 brake
fluid in it (highly unlikely), use DOT 4.
Rick "or avoid long descents" Denney
On Wed, Aug 16, 2017 at 3:38 PM Peer Oliver Schmidt
wrote:
> We have made it down to Highland, CA and are sitting now in the AutoZone
> parking lot.
>
> I am still open for ideas. I don't see any fluid near the brakes. atm I
> can't get the top of the master brake cylinder off, but eventually will
> succeed.
>
> Is there a way to determine what DOT (3,4,5) I should use, if I need to
> fill up? Open for all hints, tips, tricks, and suggestions :)
> --
> Best regards
>
> Peer Oliver Schmidt
> PGP Key ID: 0x83E1C2EA
>
> '76a Eleganza II, VA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322208 is a reply to message #322201] |
Wed, 16 August 2017 15:52 |
rod utterback
Messages: 18
Registered: April 2016
Karma: 1
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Junior Member |
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Peer, just the fact that you are asking via your message is blood curdling. As they say “just what I would do”
DO NOT MOVE THE VEHICLE UNTILL IT HAS BEEN INSPECTED BY A PROFESSIONAL MECHANIC. THE LIVES OF YOUR FAMILY AND POSSIBLY SOMEONE I KNOW ARE AT RISK. Many things can be at fault. Your driving style, your brakes, traffic and weather conditions, etc. They must all be addressed BEFORE putting the vehicle back on the road. LA traffic is no place to test theories.
Please heed this warning.
Rod Utterback
1904 Felice Drive
Escondido, Ca.
From: Peer Oliver Schmidt GMC
Sent: Wednesday, August 16, 2017 12:56 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Brakes going soft - How long to wait / What to do?
This morning we left Big Bear Lake and are on our way towards Los Angeles.
On the downhill on CA330 the brake pedal all of a sudden became very
soft, and braking was ... nearly non-existant. We found a nice place to
stop for a while, and I wonder, if it is okay to just let the brake
fluid cool down, or if there might be other things I should do. If cool
down, how long would be appropriate?
--
Best regards
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA
'76a Eleganza II, CA
'73 Sequoia, VA
_______________________________________________
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322212 is a reply to message #322210] |
Wed, 16 August 2017 16:27 |
Olly Schmidt
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
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Senior Member |
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Keith,
> I prefer,
> Keith "Use the engine not the brakes on long descents" Vasilakes
that's what I have learned in driving school as well. However, 2015 or
2016, when we did Blue Ridge Mountain Parkway, I asked the same thing,
and someone mentioned that the GMC transmission guru advises different.
So today, I drove with the brake most of the time, while after getting
affected by the pedal, I moved it down to 2nd gear setting, just to be
one the safe side from my point of view. There were only something like
5-6 curves and after that the freeway.
--
Best regards
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA
'76a Eleganza II, CA
'73 Sequoia, VA
_______________________________________________
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Unsubscribe or Change List Options:
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Best regards
Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322213 is a reply to message #322203] |
Wed, 16 August 2017 16:33 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Peer Oliver Schmidt wrote on Wed, 16 August 2017 16:37We have made it down to Highland, CA and are sitting now in the AutoZone parking lot.
I am still open for ideas. I don't see any fluid near the brakes. atm I can't get the top of the master brake cylinder off, but eventually will succeed.
Is there a way to determine what DOT (3,4,5) I should use, if I need to fill up? Open for all hints, tips, tricks, and suggestions
Peer,
The DOT number of the brake fluid is substantially its boiling temperature.
If the fluid it purple (or blue depending on your vision), then it is DOT 5. Hope it is not as it is incompatible with everything. This is unlikely as it is way more expensive than either DOT 3 or 4.
You are in a Autozone lot, they sell a Valvoline DOT 3&4, you can't go wrong with that.
The things inside the master cylinder cover are just diaphragms to allow the fluid level to change with introducing air and the associated moisture.
When you say that the brakes where non-existent, was there just little or no effect or did the pedal go to the floor. These two are very different cases:
=> The brakes had less effect => That is fade, it is common to all brakes but worse for drum brakes because the drum expands away from the shoes faster than the system can accommodate. If this is the case, the brakes will be good as they were before once they have cooled.
=> The pedal went to the floor and you heart went into your throat. This is a boiling brake fluid case. Brake fluids are highly hydroscopic (they soak up water) and the water depresses the boiling point. If this is what happened, you can drive it once it is cool, but it is advised that you get the brake system flushed with new fluid as soon as you possibly can.
In both cases, it is unlikely that the brake parts were actually damaged. Therefore, cooling and maybe new fluid should do it.
Water gets into brake fluid two ways. One is around the cylinder and piston seals, it actually gets pulled in there a molecule at a time over long periods. The other way that rubber gasket/diaphragm in the top of the reservoir, they get bad with time just like all the other rubber. They are usually available on the parts pins at auto parts stores.
Am sure am glad that you are at the bottom of the hill and telling us this.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322214 is a reply to message #322208] |
Wed, 16 August 2017 16:30 |
Olly Schmidt
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
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Senior Member |
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Rod,
I appreciate your concerns. I feel confident that I have checked
everything, and all points to "just" the brake fluid overheating. I will
try to find a dependable mechanic in the LA area. If I do, I'll let them
flush the fluid. If I don't I'll find one on my way home or at home.
Thurday next week I'll drop my girls off at LAX, and will take the tour
back to the GMCs home in VA.
--
Best regards
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA
'76a Eleganza II, CA
'73 Sequoia, NH
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Best regards
Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322215 is a reply to message #322212] |
Wed, 16 August 2017 16:34 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Peer,
Whoever advised you not to use the transmission to keep your speed down was INCORRECT!
What Manny says is not to drop the transmission into Super at speeds above 45mph (I may have that number wrong, if I do someone
correct me) as it puts a high load on the trans. He says slowing down to 45 THEN putting the transmission in Super is OK.
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 7:27 AM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Brakes going soft - How long to wait / What to do?
Keith,
> I prefer,
> Keith "Use the engine not the brakes on long descents" Vasilakes
that's what I have learned in driving school as well. However, 2015 or
2016, when we did Blue Ridge Mountain Parkway, I asked the same thing,
and someone mentioned that the GMC transmission guru advises different.
So today, I drove with the brake most of the time, while after getting
affected by the pedal, I moved it down to 2nd gear setting, just to be
one the safe side from my point of view. There were only something like
5-6 curves and after that the freeway.
--
Best regards
Peer Oliver Schmidt
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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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| 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 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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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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| Re: [GMCnet] Brakes going soft - How long to wait / What to do? [message #322218 is a reply to message #322215] |
Wed, 16 August 2017 16:42 |
Olly Schmidt
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
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Senior Member |
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Rob Mueller schrieb/wrote
> What Manny says is not to drop the transmission into Super at speeds above 45mph (I may have that number wrong, if I do someone
> correct me) as it puts a high load on the trans. He says slowing down to 45 THEN putting the transmission in Super is OK.
thank you for clarifying this. Even though the number of downhill miles
went downhill dramatically today, it is good to know for the future,
when riding the 23' in the Alps (the Himalaya...)
--
Best regards
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA
'76a Eleganza II, CA
'73 Sequoia, NH
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
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Best regards
Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
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