Brake drum temperature

Steve Owner/Technician Spokane, Washington Posted   Latest  
Question
Braking
1999 Chevrolet K1500 Suburban 5.7L (R L31) 4-spd (4L60-E)—1GNFK16RXXJ515325

Working on a 99 K1500 Suburban. I have one of those customers well all dread. Vehicle was towed in with rear brakes removed and master cylinder dry. We replaced all rear brake components and bleed the brakes. Every thing seems fine. But..........

His complaint is the brake drums are too hot. He is not towing and uses the vehicle to commute to work, some highway and some in town. I understand that braking temps will depend on driving conditions, towing, speed, and MOST IMPORTANT the nut behind the wheel. When we drive the vehicle the drums will be anywhere between 125 degrees and 210 degrees. He has check the drum temps himself and says he will see as high as 320. (yeah all customers should check brake drum temps). I have looked in Alldata and Mitchell and no where do I see a factory spec for brake drum temps. With that said I am wondering if there is a spec or should I shut the door and retire (it has crossed my mind

We have replaced drums twice, adjusted the brakes multiple times, bleed the brakes several times, and changed to shoes. Last but not least I brought in my wife's Tarot cards and did a reading. I saw dark times ahead for the next election but the cards said nothing about brakes. 

Thanks

Steve

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Tyler Technician
Olathe, Kansas
Tyler Default
 

I don't check drum temps nearly as often as disc temps, but I'm generally OK with your reading of 125 to 210. Depending on the nut behind the wheel, like you said. How are you measuring temps? Infrared temp gun? How is HE measuring temps?

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Nate Owner
Santa Cruz, California
Nate Default
 

And under what conditions - just after driving down the mountain? You could offer to have the customer accompany you on a road test and at the end of the road test, have the customer watch while you check the drum temps. But certainly don't do anything else to the vehicle until you know what the conditions are when the high temps occur.

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Gary Owner/Technician
Peck, Michigan
Gary Default
 

Rear Brake hose swelled shut? Seen it a lot on the fronts, but rarely on the rear.

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Tim Owner/Technician
Springfield, Virginia
Tim Default
 

I'm wondering why it arrived with rear brakes removed, my guess is someone adjusted the booster rod to make up for low pedal and caused the rear brake overheating. Driving in traffic with multiple brake applications does not uncover master cylinder return long enough to return shoes and brakes burn up. Mis-adjusted cruise brake cut cut out switch can cause same problem.

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Matt Educator
North Canton, Ohio
Matt Default
 

I was thinking the same thing. ABS modulator may trap pressure if a valve is hanging up too.

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David Owner/Technician
St. Albert, Alberta
David Default
 

I don't think ABS can trap pressure, only bleed back to master.

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Paul Owner
Strongsville, Ohio
Paul Default
 

What about parking brake cables, they freeze and bind up a lot around here, does customer use parking brake?

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Paul Mechanic
Harvey, Illinois
Paul Default
 

Using common sense and logic-if the metal isn't bluing from excess heat and your nose doesn't detect anything amiss, tell customer parts have a warranty and he'll be covered if an issue develops due to defects on materials/workmanship as long as you confirm and are confident no issues exist. I would request a ride along while he drives and make sure he isn't two footing it (there are some still…

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Daniel Manager
Dunedin, New Zealand
Daniel Default
 

Ask him to make a log of where he was driving and get front and rear temps. It sounds like to me, you dont really have a problem. - good luck

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Mike Technician
Salina, Kansas
Mike Default
 

Like others have posted see if the driver is riding the brake , the e brake if used not coming back off all the way. Could the rear end be low on oil bearing going out , go with the driver for a road test . At end ask them how they check the temp of drums , could it be what they are Use ing to test be bad . Have them bring it in then check it with yours or another one .

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David Owner/Technician
St. Albert, Alberta
David Default
 

Seems to me that is too hot unless he has been doing some serious stopping exercises. If his front rotors are not getting too hot at the same time, you likely have a problem. I would call anything over 225F to be hot, or more than the expected temp. due to normal stops. You need to be sure he did not contaminate the fluid accidentally giving rubber swelling issues. Master link from booster…

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

What brake components were replaced? Measuring half of a braking system is a waste of time. Without knowing what the other half is doing how can you know what to look at? If the rears are overheated and the fronts are cool, there is a brake system problem, if the rears are overheated and so are the fronts you have a driver problem or an overloaded vehicle. Stop trying to figure out the…

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Steve Owner/Technician
Spokane, Washington
Steve Default
 

Great replies but what I am really looking for is a spec on brake drum temperature. It seems there is a spec for every thing, brake drum run out, max machine, ect, ect. Brake fluid has a boiling point, Some where there must be a spec that says "This brake drum is able to with stand temperature of XXX".

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David Owner/Technician
St. Albert, Alberta
David Default
 

You are looking for something already given as good as you are going to get. There is no meaningful high end temp. spec. for our purposes. These things are made of pearlitic iron castings. How much heat can it take before "what happens" is what you seem to be asking. Melting point is likely about 2500F if you need to know. Iron as a casting does not easily make big distortions from heat, they…

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Mike Technician
Salina, Kansas
Mike Default
 

Steve, I see the problem here lol the brakes been to those adult Web places ,lol or calling the 900 phone number Look at the end of message above got to have some fun after all you and others have , been working this year Thank you and happy thanksgiving to all

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Your problem is going to be accessing the brakes to make the measurement. You can't rely on the measurement taken on the outside of the drum, there are too many variables, drum thickness, rust buildup, amount of time exposed to the heat, for example. You would have to be capable of measuring the actual brake material temperature. A lightly dragging brake can slowly heat a drum up evenly and you…

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Pat Technician
Carson, California
Pat Default
 

There is no such spec...that's like asking how long is a piece of string. Brake convert kinetic energy into heat energy. The temps you are seeing are normal....if he wants them cooler, tell him to take it easier on the brakes.

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Gary Owner/Technician
Peck, Michigan
Gary Default
 

Brake Temperatures (for trucks) Note: Temperatures indicated are at the lining/drum interface and are approximate. 550°F - 650°F Brake resin odor is present 850°F Brakes begin to smoke 1,100°F Brake oxidation occurs at parts of the brake open to air rushing by 1,250°F Drums become cherry-red internally +1,250°F Danger of run-away due to excess drum expansion And then there's brake…

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Steve Owner/Technician
Spokane, Washington
Steve Default
 

GREAT INFO!! Thank you

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Nate Owner
Santa Cruz, California
Nate Default
 

Steve, it seems funny to me how you are approaching the customer's concern. You seem to be indicating that the problem to be solved here is just the question of temperature (is 320 too hot?). Most of the responses (including my first one) are addressing what seems to me the more pertinent question: what, if anything, is wrong with the Suburban. Perhaps your original post was not written…

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Gary Owner/Technician
Peck, Michigan
Gary Default
 

Not really related to this thread but kind of interesting in regard to brakes. Thought I'd share it here. youtube​.​com/watch?v=DZ8O2t…

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Matt Educator
North Canton, Ohio
Matt Default
 

Isolation valve traps pressure

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Richard Owner
Columbus, Georgia
Richard Default
 

Forgive me, but I do not comprehend what replaced all rear brake parts means. Did you replace the backing plates or check them for wear? Were hardware kits and adjusters replaced? I am not being arrogant in asking. We frequently find the need to replace backing plates and I am in the sunny south. The rust belt guys must replace them on a very regular basis. I do agree with others that the issue…

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