Today I found that the braking performance is very bad on my recently acquired 1998 V70. I bought the car 6 months ago from the original owner. It has about 100K miles and the brakes were fine with excellent stopping power, short pedal travel and very solid pedal feel.

For the past 4 months the car sat outside and was not driven. I last started it in February and just drove a couple of miles, I think the brakes were OK then. The battery completely discharged in the past 7 weeks. Today I charged the battery and went for a drive. The first thing I noticed was that the brakes felt very different.

Now the brakes start to engage like they always did after short pedal travel but then the pedal sinks much further than normal and there is little ultimate stopping power. I tried a panic stop on asphalt - ABS does not engage and the car does not stop fast. I tried a panic stop on loose gravel - ABS did operate then.

I am guessing that leaving the car outside in 10-40 degree snowy weather and not driven for several months did something to the braking system. Perhaps some rust occurred in the master cylinder and seals were damaged ? Or perhaps a rubber brake hose has weakened ?

Master cylinder fluid level is normal and brake warning light stays off.

Thanks for any advice,

Mike

Thanks everyone for the comments. Here is more information:

With constant pressure the pedal sinks close to the floor then feels firm. At that point the car stops but with braking power much less than normal. The car does stop straight with hands off the steering wheel.

The brake booster is working OK: with engine off and light pressure the pedal sinks a couple of inches. Starting the engine causes the pedal to sink close to the floor.

I dont think there was much rust on the rotors and there isnt any now. The previous owner was meticulous about maintenance and the brake fluid in the master cylinder looks fresh.

The master cylinder has 2 hydraulic circuits but I dont know if it is arranged as front-rear or dual diagonal. Could an internal master cylinder leak cause the symptoms ? It feels like one master cylinder hydraulic circuit is leaking. The pedal travels until it compresses the internal spring between the primary and secondary pistons. Then the other circuit creates enough hydraulic pressure to stop the car.

I have pumped the pedal dozens of times with no change in master cylinder fluid level. If there is a fluid leak it must be internal, not at a caliper.

Mike

With the engine turned off and cold, depress the brake a couple of times. The pedal should become hard as a rock and almost no travel. If it doesn't, then you have a MC problem and need to get it repaired ASAP.
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My back feels better when I sit in a Volvo seat

Hi Klaus,

I tried the test you suggested, pushing on brake pedal with engine off. The pedal slowly sinks until it is 2-3 inches from the floor.

We have two almost identical 1998 V70s with 5 speed manual trans, one has 130K miles and the recently purchased one has 100K. I tried the same brake pedal test on the frequently driven 130K car and it is fine.

The 100K car with the brake problem was not driven all winter. It needs front end alignment and a new heater core before we can use it. The braking system was excellent last fall when I bought the car - pedal feel was even firmer than on our frequently driven 130K car.

Sitting outside for several months in snow and cold without being driven must have done something to the master cylinder. Now I wish I had started the car every week and driven a few miles. I last started it in February but only moved it from one parking spot to another.

Looks like I need a new master cylinder.

Thanks,

Mike

I have never tried replacing the seals in a MC, I have always left that to a qualified mechanic. Cold weather could have contributed to a seal coming loose.

Check Ebay for a new heater core, there is one for sale at around $50 which has been used by a lot of folks. It is an 'easy' thing to do, just have a plastic bag handy to catch antifreeze coming out of the supply tubes and there will not be any mess. Then rest your back for a day :)

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My back feels better when I sit in a Volvo seat

Hi Klaus,

I looked at the Ebay heater core - all metal instead of metal/plastic seems like a good idea. The price is so low that I wonder about quality. I would hate for it to come apart while I was on a trip.

Thanks,

Mike

At that price, buy 2! Actually, there are a LOT of 850/70 cars now using the cheap cores. No one came back and said they failed, yet.
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My back feels better when I sit in a Volvo seat

I too think it is most likely a bad master cylinder. Probably leaking internally. Sounds just like the MC on my 240 when it went bad.

I think the key symptom is that the brake pedal sinks farther than normal. Either there is a leak in a line or a caliper, there is air in the system, or the master is leaking internally. Inspection and a fluid change should eliminate the first two. When the master goes bad usually the pedal sinks with constant pressure, i.e. sitting at a stoplight, but there are other ways they fail too.

Greg

Flushing the brake fluid with DOT4+ would be my first reaction. But you have other problems. First, the 'rubber' fuel lines are only rubber coated, there is stainless steel under the rubber to keep the lines from 'expanding' under pressure. The master cylinder is probably OK, so long as there is fluid covering the seals.

Are your rotors full of rust from sitting outside? Yes, the rust does rub off when you use the brakes, but some of it collects between the pad and the rotor. The best way to get rid of the rust is to use your left foot on the brake and get the rotor hot to burn off the rust and anything else on the pads/rotor.

Because the ABS activated on loose gravel, and I am assuming that both front wheels tried to lock up, the system is in good shape.

Check for a stuck caliper piston by gently applying the brakes and loosely holding the steering wheel - the car should go straight at all times. If it tries to turn, the caliper in question would be the one opposite the direction of the turn.

You could remove the pads, clean them off with brake cleaner and both sides of the rotor also. But 'burning' in the pads by braking should also 'clean' them.
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My back feels better when I sit in a Volvo seat

When cars sit for a while, things stick. First, push on brake pedal (car running), does the pedal go down, then stop moving or continue to head to the floor. If it stops, the MC may be OK, heading to the floor suggests a failing/failed MC. These units are generally very reliable, but that is with an occasional fluid flush, 15 years of black brake fluid may be too much.

I would see if the brake pads are stuck. Start with the front since it does most of stopping, lift car onto stands and simply take pads out, clean up edges so that they can move in the calipers when you depress the brake pedal, reinstall, pump pedal a few times to set pads, and see what happens (on a safe street). This will happen to my 940 if it sits a while.