I was driving along and pumped the brake by accident (traffic) and almost put my head in the dash. If I pump the brakes just once they become super strong. I had no idea having just bought the truck. I just assumed that's how the brakes were. So I drove long and stepped on the brakes pretty hard and the rear tires locked up. Guess that means the front tires are doing very little braking. The dealer did tell me they flushed the brake fluid because it was contaminated and put fresh fluid in. I guess they left some air in there.
Anything special about bleeding brakes on these trucks?
Your truck ( like mine, a 2006) has a brake feature called BRAKE ASSIST.
This is an electronic assistance that enhances the pressure on the brake master cylinder as you press the pedal with your foot. In other words, it pushes down more than you do so that you have to apply very little pressure to slow down easily.
Makes sense ?
So when you pump the brakes I assume it puts the system in high alert and REALLY applies pressure and the wheels lock.
( or rather lets the ABS regulate to max braking )
Now if the rear wheels lock up, maybe you have a leak in the rear end somewhere and your drums/shoes are contaminated, I would check the drums and seals.
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Last edited by Boosted27606; 01-29-2009 at 11:04 PM.
Reason: spelling
I should clarify. The rear tires only locked when I did not pump the brakes. I just drove along normal and did one single firm press of the brakes like I had to make a quick stop.
When I do a pump on the brakes, just a quick light pump the brake pedal firms right up and gets rid of that spongy feeling and suddenly the brakes are a lot more powerful. The truck noses down a lot more too like suddenly the front brakes are working. If I do not pump first it feels like the rear brakes are doing the majority of the braking. That's why I thought perhaps the front brakes have air bubbles in the brake line, pumping will pressure the front line and cause them to work properly.
Then maybe you should bleed all brake lines ( as air will find a way to
migrate everywhere )
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If your pedal isn't spongy on initial application then it likely isn't air in the lines. However, it's not a bad idea to bleed the fronts just to make sure. Nothing special on these trucks about bleeding. If you have some clear tubing, use that so you can see if you actually get bubbles out of the front brakes. If you don't see any bubbles, you know you need to look further.
Other thing to check are front wheel bearings. A loose bearing will allow the brake rotor to wobble a little, pushing the pads apart. The initial pedal press pushes the pads back against the rotor but doesn't result in much stopping force.
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'06 Tundra AC Ltd 4x2 - Phantom Gray
'89 Porsche 944 Turbo (track car / wallet deflator)
Malcolm,
Air will not get into a system unless you have a leak or you run the master dry, another sign of a leak. It is much more likely that you simply need to clean and adjust your rear brake shoes. It is very common for the rear adjuster to fail and keep up with wear. The first time you touch your brakes you push the shoes out, then you hit the brakes again before the shoes had time to retract giving you a much higher pedal.
Now the rear locking up is not a good sign, this could be as simple a load of dust in the drum or you could have a axle seal or wheel cylinder leaking.
You need to pull the drums and look at things, if you see nothing leaking clean the brakes up with brake cleaner, lightly sand the shoes and drum surface, adjust them up and see if things aren't better. If you have leak it must be fixed and the shoes replaced.
Check out the write up here Sticking Parking Brake Bellcranks it shows how to remove the drums and how to adjust the brakes.
Mike
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“The significant problems we have cannot be solved at the same level of thinking with which we created them” (Albert Einstein) Moderator Brake Forum
Thanks for the info guys. Yes the brake pedal does feel spongy until I pump it so that lets me believe there's air in there.
MEvang, I know air won't normally just get in there but the dealer I just bought the truck from told me the brake fluid was contaminated so they flushed it and put new fluid in. That's how I suspect air got in. They never bled them properly.
Can't hurt to crawl under the back of the truck & eyeball the rear shoes. Just pull the round plug at the 3 (driver) or 9 (passenger) o'clock position & check the clearance between the shoe & the drum, without the emergency brake on. There should be enough clearance for a sheet of copier paper to fit, but not much more.
If it needs adjusting, pull the oval plug at the 12 o'clock position & use a wide, flat head screwdriver to turn the star wheel until the gap closes.
Thanks for the info guys. Yes the brake pedal does feel spongy until I pump it so that lets me believe there's air in there.
MEvang, I know air won't normally just get in there but the dealer I just bought the truck from told me the brake fluid was contaminated so they flushed it and put new fluid in. That's how I suspect air got in. They never bled them properly.
Thanks for all the tips guys.
Malcolm
Wait a minuet!!! What do they mean it was contaminated? Did they tell you how they knew this or what it was contaminated with?
I don't want to scare you but if there was anything mineral based, like ATF or power steering fluid in the brakes you goy big problems.
Mineral based fluid will attach all rubber parts and you could be experience the first signs of a major brake failure.
Mike
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“The significant problems we have cannot be solved at the same level of thinking with which we created them” (Albert Einstein) Moderator Brake Forum
Can't hurt to crawl under the back of the truck & eyeball the rear shoes. Just pull the round plug at the 3 (driver) or 9 (passenger) o'clock position & check the clearance between the shoe & the drum, without the emergency brake on. There should be enough clearance for a sheet of copier paper to fit, but not much more.
If it needs adjusting, pull the oval plug at the 12 o'clock position & use a wide, flat head screwdriver to turn the star wheel until the gap closes.
Be sure to check/adjust both sides the same.
Yup I'll take a peak for sure. They are forecasting decent weather for tomorrow so I should be able to get this done.
Malcolm, look for swelling or distortion of the rubber cap seal. This is the first sigh of oil contamination.
Mike
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“The significant problems we have cannot be solved at the same level of thinking with which we created them” (Albert Einstein) Moderator Brake Forum
Well I got to bleed the front brakes a little today. My helper got tired and didn't want to do it any more (8 year old son). Not sure if I bled enough fluid from each front wheel but the brake pedal is still spongy unless I give it one pump and then the pedal firms up.
Did not see any swollen rubber hoses or other bad things. I pulled the rubber plugs in the rear and the brake show was about a copiers thickness away from the drum. What an awesome plug btw. I never understood why my Ranger never had something like that. Although really I wish they'd just ditch drum brakes, can't stand em or working on them but that's getting off topic here
It's hard to explain but I can tell the rear brakes are doing the majority of the braking unless I pump the brakes. If anyone's ever had a vehicle with only the front or only the rear brakes working they know what I'm talking about. It's the way it behaves on braking. In my case it's the rear pulling, lack of nose dive front from brakes, press real hard and rear will lock up first (that should never happen). However one pump and they work normal, front brakes are doing the most braking force, pedal is firm, vehicle nose dives on harder braking and rear tires no longer lock first.
I'll do some more bleeding as soon as we get another nice day out.
Guess I need to bleed my brakes
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