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Discussion Starter · #1 ·
So today I was in manual mode and decided to do a little down shifting as I approach a red light. As I was braking and down shifting from 3rd to 2nd, my brake pedal became extremely hard and pushing it more made it really hard and I couldn't apply more braking power. When the car stopped, I released the pedal, then gave it 5 secs, then pressed it again all the way and it felt normal. WTF?

It's happened before when I did the same thing (downshifting) and its getting worse. Funny that I was going to go to the track last month. This issue would've probably ended me up in the side wall.

Could it be my master cylinder? Bad brake lines? Bad calipers? Fluid is clear yellow and seems fine. I checked the brake lines when I installed the suspension and went over the entire car and gave it a checkup as we finished up 3 weeks ago.

Thanks in advance!


 

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With engine off, press brake pedal until it becomes hard. Releases vacuum.
Then turn on ignition and press brake for a moment. You should hear a buzzing sound from the engine compartment near the air filter housing. If not, then you might have an issue with the vacuum pump.
 

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Discussion Starter · #3 ·
With engine off, press brake pedal until it becomes hard. Releases vacuum.
Then turn on ignition and press brake for a moment. You should hear a buzzing sound from the engine compartment near the air filter housing. If not, then you might have an issue with the vacuum pump.
I will try that today, thank you! I hope that's the problem, don't want to deal with anything worse. Where is this part located in the engine bay? Is it easy to access?
 

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If it doesnt buzz, it's not necessarily the pumps fault. Might also be the vacuum switch.
Its somewhere between the airbox and firewall.
Looks like this:

 

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It could also be a leak in the vacuum lines connecting brake booster, pump, etc.
 

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Also could be the much-discussed "Ice Mode" problem. For whatever reason, some conditions put the braking system into a mode where the pedal becomes extremely hard and braking is reduced similar to when the system thinks it is on ice. There are lots of threads about it, but no confirmed fix as far as I am aware. I used to get it all the time on my old commute in the same exact place. For me, it would occur braking on an uphill after pulling away from a stop sign to make a left turn.

As you found, releasing the pedal fully and reapplying the brakes clears the issue.
 

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When you are fighting the ABS it may be what you describe as ice-mode. As someone who has finally had some opportunity to play in the ice and snow, when you want to press the pedal to the floor but there is no grip between the tires and the road it will keep you from pushing the pedal as far as you normally could.

In this case there are several valves and solenoids between the intake manifold so make sure all are in good shape and operational. If you have access to VIDA its also worth a scan to see if the car already knows whats up.
 

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Yup, I will third that. Sounds like "ice-mode". Pedal stiffens up, can't slow down, your brain goes "OH SH*T", then you pump the brakes or let off and brake again and it sorts it out. I used to get it a few times on the way to work. No one seems to know how to fix that. It only has happened to me in cold months so I suspect it is something to do with temperature, but not sure.
 

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It's happened to me once in 110k miles, warm weather, evening, braking slightly, release, then hard pedal. Luckily I was familiar with the Ice-Mode concept, so I released and reapplied and it was normal. It's a ghost in the machine.
 

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Leave it to the Swedes to come up with a dedicated "ice mode," haha.
 

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Discussion Starter · #11 ·
See that's the thing, this has happened to me multiple times in different weather and temperature. I have a Vida unit coming in soon so I'll need to learn how to use it.

Sent from my HTC One_M8 using Tapatalk
 

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Happened with me several times, also in different weather conditions. No DTCs logged. Never heard of the 'ice mode' so far. First happened front of a junction after coming up pretty fast (100km/h) from a long uphill drive. Nearly s*** into my pants, that I won't be able to stop at all. Released the pedal and everything was back to normal for the second press. btw good to know about this hidden 'feature', however I still believe it is bloody dangerous and will freak out most drivers including myself....
 

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I dont buy this being normal "mode". Where is this literature explaining ice mode?
 

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Discussion Starter · #14 ·
I tried the instructions you told me, don't know what sound to look for.
 

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I tried the instructions you told me, don't know what sound to look for.

If you pump the brakes then hold your foot on the pedal with the ignition off (key out) until stiff, then with your foot still on the pedal turn to accessory II you should hear a buzzing and the pedal should drop.

When in accessory II if you press the brake pedal do you hear a buzzing coming from the engine compartment? If not then I'd look into the vacuum pump or control circuit as it's supposed to maintain vacuum to the brake booster when the engine is not producing enough vacuum.
 

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Sorry, couldn't resist... :D

 

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This hard pedal/"ice mode" issue is brought up every couple of years on here.

The recommendation from VCNA was to take it to your local Volvo retailer and try to have them diagnose. Apparently they should have been made aware of this potential issue from VCNA: Link to Ask VCNA thread from 2009
 

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I was having multiple daily occurrences of "ice mode." My front strut mounts were shot, I had them replaced, the problem went away.

I think the ABS controller/computer is getting confused by any movement or play in the front suspension, and applying the ABS. This is what the pedal felt like to me.
 

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Discussion Starter · #19 ·

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Private video.

You did excactly like i said and didnt hear no sound, then i would proceed to check vacuum pump coil. Measure resistance at the plug.
 
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