240 soft brakes - please help!

[AlexO]

Originally Posted by Clifford Pope

Should it push at all when not in use? Commonsense suggests to me that if your foot is off the pedal then the MC should not be being activated at all?
And if the MC is being activated slightly all the time than pads will be rubbing slightly, getting hot, causing noise, vaporising fluid, causing vapour bubbles - generally all the faults you are describing.

Second Clifford on this. Rising brake fluid (which is utterly bizarre by the way) would suggest that you're heat soaking the fluid. If the brakes are also binding all by themselves then this would support this theory. I haven't been following the full thread but if you've replaced the calipers I'd recommend checking that all the piston covers are attached properly since any small rock or bit of grit getting stuck in them will stop a piston returning and give you lots of heat and binding (that's from personal experience). This will also be evidenced by one especially hot corner after a long drive.

I'm not sure how rising fluid can suggest an air leak since any air leak in to the system must surely become a fluid leak out of the system once you pressurise it, right? If you're not getting a mushy peddle or losing fluid then it doesn't sound like a leak of any kind.

I'm by no means an expert on this but having had brake problems in the past I feel your pain. If you've replaced all the component except X, Y and Z then that might be the next place to look. I know the last time I looked at that rear bias valve on my 240 I had to wince; grotty doesn't even come close.

Hope that helps,

Alex

[Clifford Pope]

I've once had rising fluid levels in another much older car.
I was carrying a heavy load, and the handbrake cables pulled a bit even in their released position, slightly engaging the shoes. The consequence was the rear brakes got quite hot, the fluid vaporised in the pipes and displaced fluid backwards towards the MC, raising the level in the reservoir.
The brakes became spongy, but returned when it cooled down. Taking the load out restored everything to normal.

So I would say yes, something is causing the brakes to rub very slightly. The most likely culprit sounds like the servo being too tight so the MC push rod cannot fully retract.

[JDW3696]

So I bought this lovely car but the brake problem is back. They were fine until I jacked the car up and changed the wheels. Now I have no brakes

[ladytmoney]

Hi there! I am new here. Bought my first car ever a few days ago, at age 47! (Been living in NYC for 30 years). Got a used 1991 Volvo 240 and had it at the mechanic's to bring it up to speed to be road ready. I just need safe and cheap wheels, I had no idea what a great car and legacy I have stepped into. About 15 minutes after taking it fully fixed (new shocks, new coils, new exhaust system, fixed idle air control valve and a ton of wiring issues), I went to step on the brakes and the pedal went straight to the floor! I kept pumping and pumping it in disbelief as I grew closer and closer to the car in front of me, and finally the brakes starting gaining some resistance, and then worked. Needless to say, I went straight back to mechanic's. He double checked everything and it all looked good and said maybe it was air in the brake line and not to worry. Then, 5 days later, took it on a longer drive (4-5 hours of driving in total, but broken up), and then the brakes failed me in rush hour NYC highway traffic aka VERY dangerous. It's a miracle no one was killed. The brakes did NOT come right back, but did about 20+ minutes of sitting on the FDR highway with hazards on. I was told by the mechanic that I should replace the brake master cylinder with the resevoir that has the sensor for the brake fluid. Can you please advise? Thank you.

Originally Posted by morsing

Hi,

I had this problem for years with my 240 and it turned out to be the anti-squeal shims. Take them out, you don't need them...

Thanks

[Bob Meadows]

Firstly I would get a new mechanic: ~ air entering the system needs to be sorted ASAP- as you have found out!

Check the obvious first- any fluid leaks at the unions.
Master cylinder seals may be on the way out
Slave cylinder seal as above.
Servo fitted? Check the one way valve & associated pipe work.
Are the fluid levels correct (if old then change it)
Check the brake calipers on each wheel to include the pads & disks and the function of the same.

A manual is a useful guide to all the above but be systematic, the brakes are quite straight forward the obvious inspection may lead you to the solution quickly.
Good Luck.

[Stephen Edwin]

It sounds as if your car has been looked after and/or worked on by people who have not followed EXACTLY the best procedures specified by Volvo. I have followed all of this thread, and other discussions, re brakes for Volvo 240 cars. And for Volvo 240 brakes hydraulics it seems to be ESSENTIAL to follow EXACTLY the procedures specified by Volvo.

This thread illustrates how far things can go wrong if good mechanics do whatever they would do on other cars. Especially if they then make more mistakes trying to solve the problem.

Bob has given you excellent advice. And. There seem to be three little things in particular.
1. There is a sequence for bleeding the brakes. It really matters not just the sequence of wheels, but the sequence of the individual bleed nipples..
2. Jacking up the rear of the car for bleeding the brakes. So that air bubble(s) do not form or lodge in a particular place in the brake system.
3. Specific installation procedure for the master cylinder. See Nick'e explanation in this thread.

If the brakes have been messed up you could find a Volvo 240 specialist and spend possibly a lot of money. Sorry but that is my honest assessment of what is probably the situation.

There are people in this forum who can give you seriously good specific advice. They might say that a problem like this is VERY difficult to diagnose without having the car available to work on themselves.

Bottom line. As you have said, you need SAFE and cheap wheels. Whatever happens, all the best to you. And welcome to the forum




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[Othen]

Originally Posted by ladytmoney

Hi there! I am new here. Bought my first car ever a few days ago, at age 47! (Been living in NYC for 30 years). Got a used 1991 Volvo 240 and had it at the mechanic's to bring it up to speed to be road ready. I just need safe and cheap wheels, I had no idea what a great car and legacy I have stepped into. About 15 minutes after taking it fully fixed (new shocks, new coils, new exhaust system, fixed idle air control valve and a ton of wiring issues), I went to step on the brakes and the pedal went straight to the floor! I kept pumping and pumping it in disbelief as I grew closer and closer to the car in front of me, and finally the brakes starting gaining some resistance, and then worked. Needless to say, I went straight back to mechanic's. He double checked everything and it all looked good and said maybe it was air in the brake line and not to worry. Then, 5 days later, took it on a longer drive (4-5 hours of driving in total, but broken up), and then the brakes failed me in rush hour NYC highway traffic aka VERY dangerous. It's a miracle no one was killed. The brakes did NOT come right back, but did about 20+ minutes of sitting on the FDR highway with hazards on. I was told by the mechanic that I should replace the brake master cylinder with the resevoir that has the sensor for the brake fluid. Can you please advise? Thank you.

Good morn and welcome to the forum,

I'm sorry to hear your new wheels have turned out to be neither cheap nor safe.

There is nothing specific to Volvo regarding the brakes on your motor car, all cars with hydraulic systems do much the same so any workshop should be able to sort it, or even better do it yourself (it is a good idea to gain some understanding of the motor car).

Like Bob said above, be methodical. Do the simplest and cheapest things first before you start changing expensive parts, so bleed the brakes (it could be some trapped air). This is cheap - get yourself a vacuum pump (cost about $15) and a quart of DOT4 (cost about $15), it will take about an hour on your motor car and may well show up any leaks. After that just check through all the stuff Bob mentioned - Volvo 240s are really simple cars, that is a good thing when trying to fix them.

Good fortune,

Alan

[Clifford Pope]

Have I got this right - the brake pedal appears firm and the brakes initially work well, but after a few minutes of running they suddenly fail, and the pedal goes to the flooor? No fluid has been lost, and after the car has cooled down the brakes work again?

If that is the correct scenario then that considerably limits the possibilities:

1) The pads are rubbing at one of the wheels, causing the disk and caliper to get hot. This vapourises the fluid, and gives the effect of having bubbles as if it needs bleeding.
Check the wheel hubs - is any getting hot?
2) Internal seal leakage inside the master cylinder. This causes the fluid to bypass internally - no fluid loss, but no brake pressure either.

There might be other causes, but those are the two I know. The second one is very common, and it seems almost inevitable after the pedal has been pressed beyond its normal range of movement, eg when bleeding.

[Stephen Edwin]

Originally Posted by Stephen Edwin

....

This thread illustrates how far things can go wrong if good mechanics do whatever they would do on other cars. Especially if they then make more mistakes trying to solve the problem.




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I could not have put it better myself.




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[Triple-S]

I was told (by the next owner) that my 740 rears had the same problem as Clifford's first suggestion, so he replaced the caliper. The wheels did get hot shortly before selling, but cooled down after the dog-walk and all was fine again. However, it may have been flex-pipe internal collapse which caused the pads to stick on - new owner moved away just after, so can't ask.

P