Today my wife was driving home in the snow in her '94 850 wagon 130k.
She was going down a hill when a dog ran into the road. She hit the brakes hard, but the road was so slippery on the downhill grade that it took her forever to stop. She said the ABS was working hard, but she was on the brakes very hard also. Dog took off when she laid on the horn.

She then noticed the ABS and TRACS lights were on and she had no more ABS or TRACS for the rest of the drive home.

Restarting the car and getting up to speed to let the ABS/TRACS do its self-check did not restore ABS/TRACS functionality nor turn off the lights.

I pulled this code (the only code there) from the A3 Socket:
4-4-2 Hydraulic modulator pump pressure low

I reset the code and the ABS light went off after the self-check when driving around the block.

Normally, when I driving/sliding, and the ABS is working hard, I don't press the brake pedal any harder because it's useless.....you're at the traction limit, no sense in putting in even more pressure. So I've never really mashed the brakes super hard for a long period of time while sliding downhill.

I took HER car for a spin on a snow covered straightaway and got up to speed and pushed on the brake pedal HARD. ABS was working hard and doing a good job of slowing me down. However, I did notice that the brake pedal continued to sink more and more and did eventually get to the floor (barely). No codes were set. From what she said, she skidded for a very long time, something I could not repeat on the flat roads near our home.

So then I tooy MY '94 850 sedan 100k out for a spin and repeated the experiment. My car did the same thing, but I got stopped before the pedal got to the floor. No codes were set.

I'm guessing that when the tires lock up, the ABS valving releases fluid in order to get the tires spinning again. The ABS pump has to kick on to make up for the released fluid, or your pedal would eventually hit the floor. When I'm hitting the pedal very hard, I'm guessing the valves are having to release so much fluid each time that the pump cannot keep up.

Has anyone else experienced this? Any thoughts? Do I need to be worried or buy a new ABS pump assembly? Thanks in advance!
--
Jason S. '94 850 turbo 203k

Hi, if you change the flex lines, be prepared to renew the left copper line as well as the joint might be not releasing due winter and salt over years.
have 2x 850-94s with this same experience.
br tapsa

I agree. Flush the brakes at a minimum. The best thing to do is to replace the front flex lines, they are quite cheap, just hard to get loose after all of these years.

You did real good in explaining and trouble shooting your problem. Thanks for the good input.

Klaus
--
Always willing to listen, just not able to take direction.

haha yes you did a great job troubleshooting and explaining the problem. Your description of the steps to reproduce were great - I don't suppose you would like a job with my company's QA department? (I'm kidding of course, I am a plebeian and unable actually offer you a job, but I wish the QA people I work with would apply your vigor to explaining the problems they see)
--
1998 V70 AWD->FWD Turbo 200k+

Start with the easy stuff.
How old is your fluid?
How old are your flex hoses?

If your fluid is more than 2 years old you need it flushed with fresh fluid. Brake fluid needs to be changed every 2 years.

If your flex lines are more than 4 or 5 years old they need to be inspected for break/tears/cracks/flexing/etc.

You could have just started boiling your brake fluid or caused a section of flex line to balloon.

--
1998 V70 AWD->FWD Turbo 200k+

Unfortunately, the fluid is less than 1 year old. I replaced it when I replaced my flex hoses as part of regular preventative maintenance.

But you make a good point....I should inspect the new hoses to make sure there isn't a structural defect. I doubt it though.....normally the brakes are solid and firm.

Thanks for your thoughts and help.
--
Jason S. '94 850 turbo & '94 850 N/A