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#1 |
Registered User
Join Date: Jun 2009
Location: san francisco, ca (east bay)
Posts: 674
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Long Downhill Brake Fade!
1973 Suburban 1500
350/350 Had the truck for about a year, took the family on some deserted back road and encountered a very steep and long down hill. This, on the brakes for 15 mins, going really slow, steep, winding one lane road. At some point my brakes overheated, and I got massive pedal fade. I stopped and the rotors/calipers were smoking a bit. I think to myself, "I'm going to fix this! Having your brakes disappear sucks!" (several months later) Replaced: * New pads * Front Brake hoses (rubber) * Master Cylinder * Brake Booster (did not seem to be keeping pressure) * Front Rotors * New fluid (also did wheel bearings in front, and tie rods, etc.) I did not touch rear brakes, which show about 1/3 left on the pads. THEN, I took the Burb out camping again, and came down a steep slow downhill, and YEP. It happened again. Brakes get hot, fade, and I lose pedal. (It felt like I lost power assist. It would stop but I had to really put some force on it.) What am I doing wrong here? I really want this thing to have brakes that I can trust you know? Thanks! |
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#2 |
Registered User
Join Date: Apr 2010
Location: Guntersville Alabama
Posts: 1,073
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Re: Long Downhill Brake Fade!
My guess would be if your riding the brakes that long and hard you are most likely loosing the rear brakes first . Drum brakes do not like heat . Once they get hot and loose there braking power the fronts are really having to work hard .
You would benefit from a drilled and slotted front rotor . They get rid of the gasses from the heat build up under the pad and help to get rid of some of the heat . Most wont see benefits from a drilled and slotted rotor because they never put them to use for what they are designed to do . It sounds like you could definitely use them . You could also convert the rear to disk and do the same on the rear to get rid of most of the drum brake fade . Just do your research on that conversion to get matching components . My biggest deal on my conversion was getting a master cylinder that worked with my setup to have good peddle travel and feel . |
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#3 |
Registered User
Join Date: Jun 2011
Location: Baytown TX
Posts: 2,219
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Re: Long Downhill Brake Fade!
How slow were you going down the hill? If you would have down shifted to second gear the engine could have taken some of the load off the brakes.
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John 82 Chevy Silverado 350ci/TH350 ![]() |
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#4 |
Registered User
Join Date: Jun 2009
Location: san francisco, ca (east bay)
Posts: 674
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Re: Long Downhill Brake Fade!
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#5 |
Robert Olson Transport
![]() Join Date: Oct 2002
Location: recent transplant to NC USA
Posts: 20,288
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Re: Long Downhill Brake Fade!
are the rears properly adjusted?
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Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!! |
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#6 |
Registered User
Join Date: Jul 2010
Location: MD
Posts: 1,937
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Re: Long Downhill Brake Fade!
My advice would be to drive differently to avoid heat soak. Slow in pulses with short periods of little to no brake pressure in between. This skill is essential when using 4-wheel drums on long hills and works for disks too.
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#8 | |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,194
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Re: Long Downhill Brake Fade!
Quote:
K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
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#9 |
Registered User
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,540
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Re: Long Downhill Brake Fade!
Heavy suburban + several hundred pounds of family + several hundred pounds of camping stuff is hard to stop. One thing that can help if you have AC is to run the AC even if you have to set the temp control on hot to keep the compressor from kicking off. The extra drag from that large compressor will help the engine slow the vehicle. Be sure you disconnect the AC idle solenoid if equipped. Make sure your engine idle is proper. A too fast idle will decrease engine braking.
Since the brakes last about 15 minutes before fading, the best, safest and cheapest answer is to take scenic rest stops every 8 to 10 minutes. |
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#10 |
Registered User
Join Date: May 2015
Location: Montana
Posts: 3,696
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Re: Long Downhill Brake Fade!
Wow - I've never had any trouble with Chevy disk brakes fading. We had a 1977 C-10 Suburban in Colorado but it had a four speed manual.
Are you pulling a trailer too ???
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Current/past Chevy/GMC trucks: 1958 Chevy C-60; 1965 GMC C-50; 1965 Chevy C-10; 1971 Chevy K-10; 1973 Chevy K-20; 1976 GMC C-20; 1977 Chevy C-10 Suburban; 1980 Chevy K-10; 1989 Chevy K1500; 1991 GMC V1500 Suburban; 2016 Chevy K2500 HD Other vehicles: 1988 Jeep XJ; 2011 Toyota 4Runner |
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#11 |
Registered User
Join Date: Jun 2009
Location: san francisco, ca (east bay)
Posts: 674
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Re: Long Downhill Brake Fade!
Thanks for the replies everyone.
( Heat Soak ) Yes I believe that the brakes are getting hot and boiling the fluid, which is why the pedal “fades”. ( Rear brakes adjusted properly? ) This I need to check. So far this is the most compelling test to make. It would explain why the fronts get overly hot. For what it’s worth the parking brake does work, which I assume is a sign that the rears should be doing something (or are capable of it!). ( Drive differently ) I was going very slowly and in no way did I feel like I was over taxing the brakes. I feel like they should have been able to handle the relatively mild load I put on them. I believe there is something wrong here, and it’s not safe! ( trailer ) Nope and I’m pretty much not going to tow anything with the brakes like this. |
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#12 |
Registered User
![]() Join Date: Jul 2014
Location: Sherwood, Oregon
Posts: 974
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Re: Long Downhill Brake Fade!
ALL brake fluid has a limited life span, hence the small cans.
Brake fluid is measured in terms of dry and wet, dry being right out of the can and wet being at a 3.7% water content at the boiling point. I have always used Silicone Brake Fluid. It operates well at higher temps (takes more heat to cause it to boil). However, the higher the temp rating the more hygroscopic sensitive it becomes (sensitive to water contamination). All brake fluid has water in it by design, again, 3.7% is one of the the measuring specs. Helps absorb heat. So finding a good silicone brake fluid with a reasonable hygroscopic sensitivity, would give you a lot of improvement over what you are doing now. However, that being said, silicone fluid has a tendency to trap air, so bleeding the brakes regularly is not a bad idea. On the whole, replacing any brake fluid annually is highly recommended. There was a relatively recent development of a non-silicone brake fluid that had all the positive characteristics of silicone (same minimum boiling points wet and dry, but didn't have the air trapping issues.) Here is a good article that really explains it in detail and is an easy read. Should give you a great place to plan any changes you need to make. Granted, it's from Down Under, but brakes are brakes... for the most part... ![]() http://www.rdabrakes.com.au/page/TB04.aspx
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#13 |
driving is in my blood
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,720
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Re: Long Downhill Brake Fade!
edited
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-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me. |
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#14 |
I know the pieces fit
Join Date: Nov 2007
Location: MONTGOMERY, AL
Posts: 5,523
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Re: Long Downhill Brake Fade!
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#15 |
Registered User
Join Date: Jun 2009
Location: san francisco, ca (east bay)
Posts: 674
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Re: Long Downhill Brake Fade!
So I pulled the rear drums off, and it seems that the rears were really not engaging.
I adjusted them and the brakes feel WAY Better, I think that solves this mystery! Not sure why the auto adjusters were not working. Brakes only have about 1/3 life left, and the adjuster screw was pretty dirty. Cleaned it up and all, but I will be replacing the shoes before too long. So far so good! Thanks all for the replies! |
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#16 |
Registered User
Join Date: Jul 2010
Location: MD
Posts: 1,937
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Re: Long Downhill Brake Fade!
Glad you figured it out.
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#17 | |
Registered User
Join Date: May 2015
Location: Montana
Posts: 3,696
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Re: Long Downhill Brake Fade!
Quote:
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__________________
Current/past Chevy/GMC trucks: 1958 Chevy C-60; 1965 GMC C-50; 1965 Chevy C-10; 1971 Chevy K-10; 1973 Chevy K-20; 1976 GMC C-20; 1977 Chevy C-10 Suburban; 1980 Chevy K-10; 1989 Chevy K1500; 1991 GMC V1500 Suburban; 2016 Chevy K2500 HD Other vehicles: 1988 Jeep XJ; 2011 Toyota 4Runner |
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#18 | |
Registered User
Join Date: Jun 2009
Location: san francisco, ca (east bay)
Posts: 674
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Re: Long Downhill Brake Fade!
Quote:
The Shoes are about 25% left, so I'm thinking it's due for a full re-do. Much better now. Thanks again all! |
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#19 |
Registered User
Join Date: Jun 2009
Location: san francisco, ca (east bay)
Posts: 674
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Re: Long Downhill Brake Fade!
So I'm reviving this thread because I'm still not happy with the brakes on this thing.
Here is what I have done: 1. New Brake Booster 2. New Master 3. New Rubber Lines Front 4. New Rubber Lines Rear 5. New Rear Cylinders, spring kit and shoes 6. New Front Calipers (yes) and pad And yet, they feel is largely the same. Emergency Braking (simulated): Press real hard, and at some point you get a hard pedal. Feels like it takes WAY to long to stop. Rears don't lock up even going down a steep hill. (all my other trucks this was easy to do) Couple of weeks ago I was out in the sierras doing some 4x4-ing. At one point it felt like I lost my power brake boost, I was trying to turn around on a hill and had to push really hard to get the monster to stop. At this point, I was convinced that my engine was not producing enough vacuum to operate the Power Brake Booster, so I bought a gauge and plugged in the vacuum gauge right where the booster connects and got something like 18". Is it possible that under some conditions I'm not making enough vacuum? ( planning on putting new heads on it ) I'm at a loss and want better brakes. What do I do next? Thanks, --Nick ![]() |
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#20 |
Registered User
Join Date: Dec 2014
Location: Northern California
Posts: 422
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Re: Long Downhill Brake Fade!
What really made the biggest difference for me was converting to hydroboost. With 4 wheel discs you could stab the pedal and it would instantly lock up the 36 inch tires. Is the truck 4 wheel drive? If so, I'm not aware of much for front brake upgrades.
Did you replace the check valve when you replaced the booster? Could there be an internal problem in the proportioning valve? Is there a load sensing valve on the rear brakes? Just a few thoughts of things to check. |
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