Freaky brake problem this morning

Qyota

Qyota

New member
OK, this has me slightly concerned. I've had my T4R for two weeks, and this is the first time it's done this. I hop in this morning to head to work. It's 1 degree F. I back out of my driveway in reverse, slow to a stop, click it into drive and head out. I slow at the next intersection, and the following (these are rolling stops, not complete stops). Then, I need to make a stop at a T-intersection. However, the brake pedal is HARD. I can't depress it. I press harder, but quickly realize it ain't movin'. Luckily I'm only going about 10mph, and I pull up the E-brake and shift into neutral. No one behind me, thankfully.

So, I try to pump the brake while sitting there (stunned), and it finally comes back to "normal". I reverse a little bit and slow to a stop. Then I go forward and begin my day over again, as if nothing happened.

What the? Any ideas on this. I'd hate for this to happen in real traffic, or with my wife driving with the kid in the back.

Master cylinder issue? I really don't know where to start.

Thanks much,
Q
 
Did any warning lights come on on the dash?

That has happened to me a few times after I floor it out of intersections. Power brakes and steering lock up.

Freaky.
 
I have never had such a problem.


but I live in southern California so...


yeah lol it's the cold alright


I have practiced many a scenario where my brakes were to fail.


If you shift to first, no matter what gear you're in, the car shifts down for you without going past redline.


so basically, shove the shift lever all the way back, wait for it to get to first gear and yank that e-brake! and if the e-brake is gone, shove it into neutral then park.


or a tree will stop ya even betteR!
 
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Whoa! I'm surprised more of you aren't concerned! I know it's a good thing to have an emergency plan, but I believe it's best to prevent the problem from happening in the first place.

I've never had a cold-related brake issue. I've owned lots of cars, and lived in MN and WI my entire life. I can't solely blame the cold on this...is the brake booster the most likely culprit?

Mmmm, that sum***** is about $350! Fack
 
I wouldnt worry about it to much...mine does this too when it's really cold outside and I just ride the brakes a little to warm up the fluid.
 
Mine did this too, 2 days ago when we went on a trip to Edmonton, it was -24 degrees celsius. I guess, give the pedal a few courtesy pumps before starting off.
 
I lived in PA when I had my '90 SR5 and most of the lifetime of my '00 SR5 and I never experienced that. What's very strange about your scenarios is that the brakes seem to start out fine but you lose the power assist at some point afterward. Is it possible that there's moisture in your brake lines that's momentarily causing a blockage and then finally lets loose?

I've been on other Toyota forums and this one is new to me. If that had happened to me it would scare the crap out of me. I think I'd flush the brake lines pronto to see if that stops it.
 
yeah i had this happen to me all the time on cold mornings with my old 99 runner, when i lived in keystone.

Just let the truck warm up a few minutes BEFORE you drive in the cold, and besides you should be doing that anyways, its bad for your car to drive it on cold fluids. Bottom line, use your brain and let it warm up and you will be fine.
 
So according to the thread that was posted in the link, replace the check valve? Mine has not done this yet (nor my other 2 4Runners). First time actually hearing of this problem. Hopefully, the check valve solves it for you guys.
 
Yup, I'm going to investigate the check valve, as it's definitely not a problem I want to experience again.

00Spork -- Actually, letting a car warm up by idling isn't very good for the engine...and actually takes longer for it to reach operating temp. Idling also doesn't warm up the transmission. And, how does idling in the driveway warm up the brake fluid? The best way to warm up a car is to drive it (nicely). But thanks for telling me to use my brain!

Nuke -- yeah, the brakes were fine for the first 2 or 3 "slow downs", then locked up on the first "real stop". That's what concerns me. I will start with the check valve and go from there. The funny thing is, the booster looks pretty new already...so hopefully it's OK.
 
i additionally suffer this issue on ice cold montana days... if it's in the 5 or lower range (30- once this year). i have been doing a few pumps prior to take off and warming the runner for at least 10 minutes. the pedal will let you know when it's ready. make your wife aware of the situation for when she drives. mine won't even step near my runner since she traded her camry for the IS300.
 
Did any of you get this fixed? More I think about it, the more I think it is moisture in the brake lines that freeze overnight and only unthaw after a while. Maybe a brake system flush would take care of it.
 
Since it has warmed up a tad around here, I haven't had the problem. But I will be doing a total brake job this spring.

On my brake booster, the check valve is integrated into the booster housing, where the vacuum line comes in...it isn't a separate device on the firewall as mentioned earlier. So, I'm not 100% sure I can just replace the check valve.

Having said that, the booster looks original, so it might be time to replace everything (Booster, M/C, rotors, pads, fluid). For peace of mind, at least.
 
p nut said:
Did any of you get this fixed? More I think about it, the more I think it is moisture in the brake lines that freeze overnight and only unthaw after a while. Maybe a brake system flush would take care of it.
Click to expand...

Since it stopped now it has warmed up, p nut is probably right about the moisture in the lines. Why don't you flush the system and put in new fluid. It you have any little pores in seals or lines the brake fliud can be ruined in no time.

Plus, you wouldn't want the fluid to boil in the spring or summer during hard braking when you least expect it. Cheap insurance.
 
A few things could be happening. For the pedal to be really hard and then work again tells me that there may be some kind of blockage which later went away. Brake fluid is very hydroscopic, meaning, it loves and absorbs water. You could have some water in the fluid which froze due to the cold weather and blocked something. For it to now work and then go back to normal is weird.

Depressing the pedal pushes a cylinder in the brake master cylinder which provides the pressure for the brake system. You could have something mechanically loose in the system which is giving a bind of some kind as well.

When was the last time you had your brake fluid flushed and replaced with new fluid? You may want to do that if it's been a while. This will make sure at least that part works well. The water (if any) absorbed in it could be freezing in the cold weather. Your brake fluid reservoir could also have dirt in it which is clogging something. A full flush will clear any of this.

Check also to make sure your calipers and pads are not binding. I don't think this is it since if one is binding, the other 3 will still work well. Your hard pedal makes me think it's a fluid/master cylinder issue.

Good luck and let me know how it turns out.
 
Reviving an old thread here, I just had this exact issue but I live in AZ, so the cold is out on the one. The brakes work fine, then randomly they are SOLID! I give it a few pushes, mostly out of fear of not being able to stop, and then they come back. I just have the brakes done 6-8 months ago. I was thinking MC before I jumped on here, hope its not that. I am your basic DIY mechanic, but when it comes to brakes i use the professionals..
 
Brake booster more than likely. Check though to make sure your rears are adjusted properly and the cylinders are OK so that the shoes don't lock the drum.
 
I have the same problem - sometimes when I apply my brakes the pedal is as hard as a rock and wont move without extream pressure, but it happens at random and it is NOT related to cold mornings in my case, it is only 50 - 60F here right now and it is happening in the afternoons when it is nice and warm.

I subsequently flushed the brake fluid and bled the brakes to get any air out. But the problem is still occurring at random. Any suggestions? Can anyone tell me how to check the vacume lines? Is there a way to check / test the check valve or should I just replace it?

Thanks guys!
 
I cleaned out my check valve and that fixed the problem.
The check valve gets stuck (froze, rust, dirt, what ever)
This last winter it was around -20deg F and had the problem in the morning. The vacuum from the engine is not creating a suction on the booster to give you that normal pedal feeling. The hose that attaches to the booster has a check valve in between te two held on by a 10mm iirc screw and bracket.

So when this happens you still have brakes but no power brakes. Just mash on the pedel and you will slow down/stop.

Look into the check valve, iirc it's about a $60 part. From the dealer.
 
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