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Technical I need to warm up my brakes?

Discussion in 'The Hokey Ass Message Board' started by Crazy Steve, Oct 12, 2021.

  1. Here's a weird one for the collective wisdom...

    The brakes on my avatar have all of a sudden decided not to work very well when cold. The rainy season has arrived in Washington, so the car is coming out less. Now I've owned this car for about 8 years and have had no issues with the brakes until about the last month. The brake system is typical stuff, a GM caliper/Granada rotor in front, Ford 10" drums on a 8" in the rear, 7" booster with a GM-style master.

    What's going on is the brakes don't want to stop the car when cold. I really have to step on the pedal and even then it only slows. But drive it 2-3 miles up the road and make a few stops and it's all back to normal. I've visually inspected everything, fluids up, pads/shoes are all good, don't see anything out of the ordinary. Again, this has manifested itself in just the last month... And the car is parked under cover.

    Any ideas?
  2. oldolds
    Joined: Oct 18, 2010
    Posts: 3,433


    I would suspect something with the power brake booster. Something like the fitting on the vacuum line is cracked and expands with heat and seals the crack. Or something just as odd.
  3. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230


    Replace all the friction materials, they are starting to glaze up.

    Don't go with high performance pads/shoes on a car that is seldom used . Use stock standard OEM pads /shoes and learn to deal with the brake dust.

    On our race car we used Carbon Metallic 83 compound and they could slow down from 270 kph to 70 kph in 190m [basically a 5 sec ET in deceleration]
    But they took a few laps to warm up [the 1st corner was dangerous]
    When we entered the car into hill climb events we swapped the pads for standard soft OEM car variety.

    On the street you are better off with pads/shoes that wear quickly and replace them more often.
    They stop better from cold [and you aren't on the brakes all the time]
  4. saltflats
    Joined: Aug 14, 2007
    Posts: 12,655

    from Missouri

    I had a clutch that wouldn't lock up till get some heat in it. :confused:
  5. Petejoe
    Joined: Nov 27, 2002
    Posts: 12,349

    from Zoar, Ohio

    Consider moisture in your brake system. I’d first drain it and reinstall fluid.
    Elcohaulic likes this.
  6. When ceramic brakes were something "new" I put a set on one of my cars and it would barely stop when cold, but the temperature I'm talking about cold is not something you would be experiencing. (-20* C) The point is though brake friction materials can be affected by temp. quite a bit.

    I've also seen brake boosters that didn't work well cold because the rubber diaphragm had gotten hard and wouldn't respond well to vacuum until it warmed up. Again though, some pretty cold temperatures.

    Food for thought, if nothing else. :)
    HemiDeuce and Just Gary like this.
  7. That was the first thing that came to mind, so I checked; no sign of any glazing. The pads/shoes look like standard light brown organic lining and seem to be wearing about the right amount given how much the car is driven. What it acts like more than anything else is if you've ever driven a disc-brake equipped car in a heavy downpour for distance without applying the brakes, the rotors can get coated with water. You apply the brakes and have a hard pedal/poor brakes until the pads scrape the rotor dry again. It's acting exactly like that, but there's no rain under cover....

    I should also note that this only occurs if the car has sat for 3 or more days. Once on the road, it goes back to normal quickly, I can park long enough for the brakes to cool and it'll be fine when I go home... until it sits a while again.
  8. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,239


    Drive it on gravel and make stops to check if its the front or back with the issue.
  9. It won't lock the wheels on grass when it's like this...
  10. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230


    What you describe is what glazing feels like, But also "green fade"
    In the early stages you can't visibly tell, but they are getting harder on the surface.
    When you get the brakes hot, it increases the co-efficient of friction [and also removes the outer layer which is why they are OK after a cool down period]
    Green fade is when the heat in the pads initially warming up, causes a layer of gas to get between the pad and the disc. The brakes feel really "hard" but there is no grabbing [like somebody oiled the brakes]
    After all the gases dissipate , the brakes feel normal.

    If you want to experiment [based on the fact that you should replace them anyway]
    Pull all the pads and shoes [evnen just the pads at the front] and surface them with a 40-grit flap disc .
    If you have a linisher /belt sander even better.

    Then install them and bed them in again.

    We get this phenomenon in our Falcon when towing. Especially after towing down long gradients.
    It is difficult to throw away "near new" pads all the time.
    We've had good results from cheap Chinesium Pads that simply wear away to nothing [they don't wear the discs, and only last 6 months]
  11. I agree with the glazing, but you don't necessarily need to replace anything...

    Do this first. Don't neglect the rotor/drum surfaces also.

    In my experience, this will restore your brake performance to normal.

    Sometimes it doesn't work. In some cases the pads or shoes have outgassed and glazed to the point where there is no saving them.

    The only option then is to replace them.
  12. Mr48chev
    Joined: Dec 28, 2007
    Posts: 34,356


    You may actually be having to burn a light surface rust off the disks. I drove one of my ot rigs home from my moms where I had it stored last night and as it has sat down there about six months the first couple of stops were a little wonky. I only had to drive a quarter mile so I may have to make a few more trial stops after I get the radiator swapped before I turn my wife loose in it.
    SS327 and '28phonebooth like this.
  13. mrspeedyt
    Joined: Sep 26, 2009
    Posts: 1,006


    bottom line. run the cheap shit.
    winduptoy likes this.
  14. @Mr48chev may be onto something... I had an OT pickup that spent its off-hours in the driveway, on the outside, looking in at its much older sibling. During the rainy season (September through August in SW Washington every year but this year!) if it sat for more than a couple days the rotors would get a thin layer of rust that had to get knocked off before braking seemed normal. About three applications of the brakes was enough to scrub the disks clean. It didn't take much humidity to cause it.
  15. I could buy into this except that the problem is when the brakes are stone-cold, not 'heating up'.

    This also makes sense, except that parking/storage conditions have been the same the whole time over the years... so why now? But I do live in a somewhat humid climate even when it doesn't rain (running water in my back yard), so will give this a closer look.
    loudbang likes this.
  16. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,213


    The drum and rotor surfaces are rusting and the first few stops will remove it..

    Do you have self adjusters, if so, I would manually adjust them. Self adjusters usually don't get the shoes close enough to the drum..

    If you ever got oil or grease on the linings, it would cause the brakes to be sticky.. I usually put real cheap masking tape on the linings before installed. The cheap stuff doesn't leave anything on the shoes..

    I've been using these Porterfield shoes and pads. They have a real nice street compound.. Stops are very smooth, quiet and confident.... Best brakes I ever had... This is on a 69 el Camino with the stock power disc/drum brakes...

    :: #1 Race Specialist in The World :: � (
  17. Budget36
    Joined: Nov 29, 2014
    Posts: 13,600


    Stick your finger in the bottom of the reservoir, wipe the bottom, see if it’s dark.
    If nothing else I made you put your finger in it;)
    SS327, 2Blue2 and VANDENPLAS like this.
  18. Cheap shoes / drums / pads / rotors ?

    rusting over night ?

    bad master ?

    I have seen this with brembo brakes that need to be heated up before they stopped well, I’m somewhat confident you don’t have racing brakes on your car !
  19. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,239


    try the E brake to see if it holds cold
  20. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 1,017

    Glenn Thoreson
    from SW Wyoming

    I've had problems with lining materials that absorb atmospheric moisture and do all kinds of crazy things until they get warmed up good. I lived a mile out of Northport, WA in 1980 and know what humidity can do. I don't think you can depend much on brand name brake parts anymore. Everything is coming from overseas. My '42 Ford has all new brake components and it does funny stuff when it's first used on humid mornings (30%). So who knows?
  21. gene-koning
    Joined: Oct 28, 2016
    Posts: 4,293


    Replace the front brake pads.

    I suspect that after 8 years in the Pacific Northwest humidity, the pad material has aged enough to start to absorb some moisture that needs to be dried out of them before they work properly. When you use them daily, they don't get the chance to absorb the moisture enough to cause a problem. As the pads get older, the length of time that passes before the pads can enough moisture to effect the braking will probably be reduced. The disc brake pads are more susceptible to absorb the moisture because they are out in the open more then the shoes inside of the drums are. The rear brake drums are protecting the rear shoes from the moisture, but those too may be absorbing moisture to some extent. I suspect the rear shoes will take a longer time before the moisture absorbing will effect them, and that effect would disappear more quickly because the shoes have more surface area in contact with the drums and would dry out faster.

    The light surface rust may also contribute to the problem, but I suspect the moisture in the pads is what you are feeling now. Gene
    VANDENPLAS and Blues4U like this.
  22. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230


    The moment you use the brakes they are heating up from cold [brakes turn kinetic energy into heat]
    you want the pads to wear down a tiny bit whenever you use the brakes, not harden the surface.

    I doubt if it is rust because you can't hear them and they are usually quite "grabby" [rusty discs or drums make an awful grinding sound when you first use the brakes [and are silent the next time you use them]

    Hit your pads with a flap disc [or throw some 2nd hand pads into it, and try it]
    The first thing you should always consider is new pads/shoes. Pads do all sorts of crazy things ,like wear on an angle [so brake dust gets trapped] etc.
    Last edited: Oct 14, 2021
    Blues4U likes this.
  23. 31 Coupe
    Joined: Feb 25, 2008
    Posts: 402

    31 Coupe

    57 Fargo likes this.
  24. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 794

    from 94577

    If the car is sedately driven then it simply could be that the pads/shoes need to be re-bed in again.
    When you brake it's not brake material and iron rotor/drum that are normally interacting. A transferred layer of brake material is bedded onto the surface of the iron rotor/drum. That transferred brake materiel layer and the brake pad/shoe material are the two friction surfaces. This is how a vehicle stops, through friction.

    What happens if the car is sedately driven or the brakes are lightly used, not much heat, then the rotor/drum can eventually be wiped clean(machined) of the transfer layer by the cold pads/shoes. Stopping power is reduced. What then happens is excessive brake pressure is needed as braking is relying on merely the clamp/expansion pressure of the caliper/wheel cylinders to slow/stop the vehicle, not friction. This will also cause excess wear on the cast iron. Not good

    I would advise re-bedding the pads/shoes.
    Find a safe area, best would be a straight section of desolate highway during the non commute hours, get up to ~60MPH, aggressively slow down to about 10MPH and then get back up to speed. You don't want tire lockup. Do not stop. Brake like on a short offramp.
    Do this ~10X. Depending on how much heat and how much material has been transferred the brakes may begin to judder. This may happen on the 5-7 attempt. That is the heat and transfer of brake material to the cast iron.
    Keep going.
    By the 8-9th brake event the pedal should have reduced or no judder. Go until the juddering is gone(if there ever was any juddering). Like when glazing a cake the spatula is the pad/shoe, need to transfer that layer of material evenly, too hard there are dips/valleys, too soft and there are lumps. Same with brakes a nice even transfer of material to the rotor/drum. Too hard or soft and uneven layer of brake material will cause juddering/shuddering/jerking.

    After the last brake event, drive the car at speed without stopping for ~20-30mins to allow the brakes to cool down evenly. If the vehicle is stopped with the brakes hot a large uneven layer of brake material will be transferred to the rotor/drum and that will cause pulling/slipping/juddering during normal braking. At best the procedure will have to be redone, at worst a hard spot will be created known as cementite. There is no fixing this, only rotor/drum replacement is the option.

    EDIT: This procedure is best used on semi-metallic pads/shoes.
    NAO(organic) materials will usually transfer material quickly and usually do not require as aggressive a bed in procedure. NAOs will bite good when cold, better when warmed up, but will absolutely fade if you get aggressive.
    Semi-metallics require a decent bed-in but are not prone to pad fade, the more aggressive you brake the more aggressive they bite. = more fun.
    Ceramics, I personally despise, they may not dust but the material doesn't have any changing characteristics. Cold they bite OK, warm they bite OK, hot they bite OK. It's very linear in non-linear events.
    *This is merely about brake pad/shoe material, not the various carbon ceramic or carbon-carbon rotors that are available on OT vehicles*
    Last edited: Oct 14, 2021
  25. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,393

    from illinois

    Our 12 year old , 35000 mile DD sits outside 24/7 rotors rust up & make all sorts of nasty noises. never have felt any loss of braking performance , hopped in it & drove 2600 mile round trip a couple years ago without incident .......I think you have a hydraulic or booster problem ..
  26. I think some are making this out as worse than it really is. Let me recap this...

    The problem is mostly confined to my yard and long community driveway. The first time this happened I had just started the car and was pulling it out from under cover. The choke is on fast idle so the RPM is up some, I dropped it into gear and nearly hit one of my other cars when it didn't want to stop, so that spooked me. Now when driving out from my place, it's slightly uphill for roughly 1/2 mile and I'm going slow (15 MPH or less) due to the dirt/gravel/potholed nature of the driveway in an attempt to keep the worst of the mud/dust off my car so there's no speed or braking involved until I hit the paved county road (3/4 mile). There's no need to stop there as there's no driveways. The first stop sign on the pavement is another mile or so, speed is up about 40 MPH by now. At that stop, the brakes are either back to normal or at least working better. Drive another mile and it's like it never happened...

    Where the car is parked it's impossible to look at the rotors until I move it (I have 5-spoke mags), so I'll definitely check for rust/moisture next time I pull it out (without using the brakes). But virtually every car we own has disc brakes at least in the front (well, except for the '60 Sunliner, but it's not being driven currently), all sit outside and at least one isn't driven any more than the coupe and this hasn't been an issue with those.
  27. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 794

    from 94577

    Did the pedal feel harder(booster issues) than normal?
    If not but the car moved I would suspect that your brakes are relying on clamp load rather than friction.
    When the brakes gets a bit of heat in them they grab better, but not ideal.
    Might want to verify the rear drum self adjusters are working as well.
    If the more you drive/brake the better the braking is that is more likely heat related. If the brakes are stone cold they won't bite if there isn't a proper transfer layer of brake material to the discs/drum.

    Even two or three quick 60>10MPH slow downs to get some heat and a transfer layer the brakes will work much better.
    You can't overbed in pad material, it's an easy/quick test.

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