The brakes on my '95 850 @ 145K have me worried. The pedal is immediately going "toward" the floor, then braking requires a LOT of effort. Pumping does not change the pedal pressure.

The previous owner had the ABS pump unit replaced after complaints of a "spongy pedal". This had been taken in several times with the complaint before the part was electively replaced. This was a dealer-replaced unit at $1500 plus < 40K ago.

It is a weird feeling that could go either way. I've had master cyl's go out and they generally could be pumped up. This can't. But, if it is the ABS pump unit, why does it go to the floor? Shouldn't a failure there just cause hard braking with no pedal drop? The pedal drops immediately...it doesn't 'leak down'. I'm at a loss. Either part is very expensive on this 850.

I love this car and want to keep it, but it is a second car. I have put a lot into it, including a full suspension rebuild, engine mounts, timing belt, rotors, etc. I do all the work myself, as I did on my 740. It runs like a champ except for a few rattles. I can't afford to throw a lot of cash at it, yet I can't sell it very well with the brakes like this.

Am I cursed or am I missing something small and obvious?

Thanks in advance.

Tom

One of the small and obvious things is the check valve on the vacuum line going to the booster. Use a pair of vice grips to gently pinch off the line and see if the lack of vacuum has any effect. If no change, remove the check valve and replace it.
Having the cap loose will not introduce a lot of water to the system. Brake fluid does not get circulated like PS fluid and any moisture should remain in the reservior.
If this car is a 5 speed, check the hydraulic pump for the clutch.
Bleeding the brakes is a good idea. Check the brake caliper springs and make sure they are touching the back of the pads, improper placement of the spring will also create the same feel you have now.
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My name is Klaus and I am a Volvoholic.

Thanks for your help so far. Here is what I found:

The reservoir cap was loose...barely threaded on. Air and humidity has freely entered the reservoir for several months. I suspect this was the effort of an oil change monkey. (I know, I know...but life is busy. I freely admit that I don't spend all my spare time checking EVERYTHING under my hood and changing my own oil. I'm at a point where I literally don't trust anyone to touch my car...sad what this country has come to.)

Secondly, engine off, the pedal falls the same distance as engine on, with little discernable difference. The feel & sound is a bit different with vacuum, but the distance is the same. It is difficult to tell if I am getting any pressure built up by pumping up the pedal. It feels like there there is some but that might be mental projection. It is certainly not pronounced, engine on or off.

I haven't had a chance to drive her much since my original post.

With that cap loose I'd say it's time for a flush with some Super Blue...just gotta find the time. I suppose until that is accomplished and I can verify a bled system with new fluid it's gonna be tough to diagnose any further, huh?

Time, time, time.

Regards,
Tom

Hey Tom....

Where do you live and what color is your Volvo? I just don't want to be anywhere near you when your out testing the brakes on the car.

If your peddle goes to the floor, that would seem to indicate to me that you have a giant air bubble in the system somewhere or perhaps one got into the mastercylinder. In any case, I once was replacing a front brake line, and all the fluid drained out of the master cylinder. I had the car towed to the dealer and they had to use a power bleed unit to get the peddle back. You might just want to let someone else figure this one out.

There's proper fluid type, proper fluid level, contaminated fluid, brake bleeding, OBD codes, master cylinder, brake booster, booster connections, calipers sticking, etc. Some of these are easy to check. You'll get better replies than this one, but you could post back with your check list of things you've been able to rule out.
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'97 855na, Mobil 1, K&N, various IPD's and eBay's

You are correct, the abs pump should not cause this problem. But I have a few questions:

When did this start happening? Did you do anything to the brakes? With the engine off, can you pump up the brake pedal? With the pedal pumped up and still pushing on the pedal, does it sink when you turn the engine on? The brake fluid reservior is full and the pads are not worn down to the 3mm mark?
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My name is Klaus and I am a Volvoholic.