When I leave for work in the morning and I step on the break peddle its very hard and it seams slow to stop. Then about less then a 1/4 mile the breaks go back to normal.Could this be a rear caliper sticking? Or a problem with the master break cyclinder? I replaced 4 yrs. ago all 4 calipers(rebuilt) and master break cyclinder(new).Or could it be something else causing this to happen.There arn't any leeks and the breaking is fine after that time in the morning even after the car sits for the rest of the day befor I drive home and no problems.Has anyone had this happen and what was the cause.Thanks for any help.Charlie
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85 244ti B21ft 180,000 Dawes @12psi,Airbox Mod,Magnecor 8mm wires.Allways a work in progress,but you got to love it!

After chatting with a few brick specialists that make a living with a wrench, my money is on the vacuum check valve on the face of the brake booster.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

Hi Jorrell, Thats strange,I was at the pic&pull today and I was looking at pulling the break booster and saw the check valve and decided to just take the check valve.I got a few other things that I needed for the change over to R134.I put the check valve in and I will let you know If that was the problem.I'm in South Carolina and at the time that it happens is below 60 degrees. But it's warm in the lower 70's so it hasn't happened since.Don't get me wrong but I'm fine with 70 degrees,it saves on the electric bill.Thanks for everyone's input. Charlie
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85 244ti B21ft 180,000 Dawes @12psi,Airbox Mod,Magnecor 8mm wires.Allways a work in progress,but you got to love it!

The check valve has a rubber disc in it (at least the one I tore apart), the disc had hardened, swollen, and cracked. If the check valve sticks, no vacuum makes it to the booster and you are back into the 140 series left leg pain era!

jorrell
ps. hope the new used check valve fixes the problem, replacing the booster is a (politically correct comment) very difficult. PITA comes to mind!

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!

One thing that we found contributed to this, believe it or not, was the bellows over the end of the master cylinder (between the booster and the m/c) sometimes lost its resiliency, causing stickiness when cold. 'Graunching' noise may have accompanied the symptons. Solution was to lubricate the bellows by slightly splitting the unit and spraying in a silicone type lubricant. Worked for us, and saved lots of money in replacements. Hope this helps.

You didn't mention it being cold out, and I don't know where you're located, but something similar was happening to me last winter, and I solved by simply replacing the check valve in the booster vaccuum line. Turns out it was getting stuck when the car had been sitting in the cold (like overnight).
If you haven't already ruled out the check valve, and it's cold in the morning where you are, it's worth a shot.

First thought that comes to mind is the Brake booster, as mentioned below.

I had a failing brake booster in my '79 242 that would actually stall the car when I stepped on the brakes.

I plugged up the vacuum line going into the booster until I was able to replace it. Car had a stiffer brake pedal but it still stopped fine. It was just like driving a 122.
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Formerly 'HearToTemptYou'

Thanks Guys,I'm sorry I didn't get back to your replies but I have been very bissy. I hope to go to the pic&pull this Sunday and get a break booster.Are there sertain years to get from? I have a 85 240 ti auto trans. Thanks,Charlie
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85 244ti B21ft 180,000 Dawes @12psi,Airbox Mod,Magnecor 8mm wires.Allways a work in progress,but you got to love it!

The brake booster is not working first thing. Sometimes called "morning sickness". Try stamping the brake pedal a few times with the engine idling before you begin driving. If that prevents the hard pedal feel when you do drive, then what's happening is you are freeing up the apply valve in the booster. It admits atmospheric air to provide the assist against a diaphragm that has low pressure on the other side. If it gets worse, change the booster for a good used one.

Agree, suspect the booster first.

Remove all brake pads and hardware. Replace the pads if they are significantly worn. Beyond that install new pad pins, spring plates, and cotter pins. Sounds like the pads might be dragging on rusty hardware.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!