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Pedal-less braking

My 2001 Honda CR-V seems to seize up randomly. I can be driving on the highway and suddenly the car will not go over 40mph. If I keep driving, the car will return to normal after a couple of minutes. I first thought it was not changing into 4th gear, but the transmission guy said no. Took it to a Honda specialist who said it was the transmisssion. Took it back to the transmission guy who again said it’s not the transmission and guessed it was brakes. A shop replaced the calipers and hoses. The fix worked 6 months. When the grabbing started again I would pull over and pump the brakes, which would release the grabbing. I took it back to the brake guy who replaced the master cylinder. Now the brakes scrape and gurgle. From outside the car they squeak. this feels like its in the front. There are no codes suggesting the ABS system is faulty, but I don’t understand what signals would cause intermittent braking. I’m not confident the master cylinder is the solution. Any suggestions?

"I first thought it was not changing into 4th gear, but the transmission guy said no."

If this is genuinely the way it seemed, and if that’s still your sense, try this: can you determine by sound or by the tachometer (if you have one), if the engine seems to be turning too fast? If that is the case, then you may be right that it is not shifting properly. It’s possible that you are in “limp mode” which happens when some problem occurs in the electronics, and normal engine and transmission behavior is altered in order to allow you to “limp” to a shop for repair. There are electronics in the transmission and engine which might alter the shifting, and you’d need to have codes scanned.

Or it could be related to the brakes as you have been told. Who knows? Apparently NOT the shops you have consulted thus far. You may need a different local independent shop, one recommended by people you know.

there are no codes so the mechanic who did the calipers and master cylinder thought the ABS would not be the problem. If the problem were the transmission, why would the problem be once a week, then after a few weeks, once a day, and then to several times a day? Seems like a false signal is making something seize. I don’t understand how the master cylinder would cause the intermittent signal, but then I’m not mechanical! Why would there be no codes? Could the code generator be malfunctioning?

One experience I had was that the speed sensor in the transmission had accumulated a coating on it which barely allowed it to read what it was designed to read. It worked correctly sometimes, other times not. I managed to drive 1000 miles from southern Arizona to central California with it working properly most of the time, but occasionally it would hold the transmission in a lower gear. It was a cheap fix, a $35 part which I changed myself in 20 minutes, after a transmission shop scanned for transmission specific codes. I was told that simply cleaning the sensor would probably solve the problem, but I reasoned that since I was going to have to pull it out regardless, I’d replace the sensor which had about 100,000 miles on it.

You may have something similar, or something entirely different. Others here may have better suggestions for you, I hope they do.

You may have needed the brake work regardless, but then, why the recent odd noises? I’d return and ask for an explanation on the noises, and expect the shop to make it right since you paid them to work on your brakes. Good luck and report back what happens.

I think you should try to isolate the basic problem, that is, whether car speed is limited because the brakes are grabbing or dragging, or because the transmission is not shifting (check your engine speed), or if it’s neither of these. Do you have a tachometer? If yes, then what is the RPM when this problem occurs? (would be something like 2000 or 3000 revolutions per minute or thereabouts). If the engine is far above that when you have the speed limitation, then I’d guess it’s related to your transmission not shifting as it should. If the RPMs are around 2000 or less, it’s probably not the transmission, but something entirely different. But please try to narrow down the symptoms. You might also try revving the engine gently while parked to see if it is restricted without moving. If it won’t rev freely, then it’s not the brakes, or the transmission, but a very different root cause.

The more detail you can provide about the symptoms, the more likely you’ll get a useful answer.

One quick way to determine if it is the transmission or brakes, if it is safe to do so, when this happens, shift into neutral and see how fast your car stops. If it stops suddenly, then its the brakes, if it coasts for awhile, then the problem is elsewhere.

Thanks for the comments. I will try to make these observations the next time it happens. No problems in the last few days since the master cylinder replacement, but I wasn’t convinced by the mechanics reasons for replacing the MC. I did call 4 or 5 other shops to ask how they would think about the problem. None of them even suggested isolating it to a system, transmission, ABS, etc. No codes, no ideas!

Since pumping the brakes would release the grabbing, I would have looked at the brake booster. The booster is a canister with a diaphragm in it that helps you push the rod that operates the piston in the master cylinder. When the brakes are not applied there should have equal vacuum on the front and rear of the diaphragm. When the brakes are applied, a valve system reatricts the vacuum to only the front of the diaphragm and vents the back of the diaphragm to ambient. If the rod is misadjusted or the valve is not properly operating, the vacuum pulling on the front of the diaphragm can slowly apply the brakes. Page 2 of the attached document shows a cutaway drawing of a booster.
http://tijil.org/Scion_Docs/Scion_06_misc_docs/2007sciontc_ncf%20Folder/brake.pdf

You can test for this by disconnecting and clamping the vacuum line to the booster. The brakes will be hard, so expect that, but if that stops them from self-applying, than the problem is a defective booster or a misadjusted rod.

See how it goes with the new MC. It is possible (even highly likely) that when installing the MC they adjusted the rod and inadvertantly corrected the problem. If it’s fixed, enjoy.

One other check - when it starts acting up, drive for a bit then pull off into a parking lot and (VERY CAREFULLY) see if one or more of the wheels is unusually hot. If so, that points to brakes.

My kid was driving my car (no abs) and he called and said it was pulling/dragging severely. Nough for him to pull over. And he is a lead foot. I took him to get, walk around car. Check tires? Inspect all wheels for packed snow, funny smells. He did. Starting driving and said it seemed ok. Or better? Did not have any more issues. Never did find out issue. Never had weird brake wear or any sort of trans issues.

Start a thread and we’ll be happy to see if we can help you. Hijacking this one will only get the answers all mixed up.