I just finished a partial brake job on a 86 240 sedan 125,000, -no ABS-

I replaced front rotors, pads and left front caliper(broke bleeder valve off) and then pressure bled entire system in order Bently lists, twice.

I now have no brakes, (pedal goes to floor), and the "Brake Failure" light is on constantly.
I checked for leaks all over system and found none.
My guess is the master cylinder, but I am confused because there were no problems prior to brake job.
My question:
Is this common? and does this point to the master, or is it a Servo/Booster problem.
How do you diagnose a bad Booster versus a bad master cylinder or is there another area I'm missing.
Also, what does bench bleeding the master mean?
I would appreciate any suggestions

Thanks
Chapster out

may i ask if your getting a good volume out of the bleeders when you open them, it should shoot out at least 2- 3 inches. if its just dribbling out, you have got air in the system and you will not get a pedal. One thing you might try first, is starting with the caliper that you replaced, fill your master cylinder all the way and open the outside bleeder, after a few minutes it should be dripping steady. close it and then open the inside matching one, after it starts dripping steady, close it and open the top one last, and wait until it starts dripping steady, make sure the master never runs dry,.After youve done this then repeat the bleed procedure for the whole system,

I am under the impression that the brake failure switch can be reset. You unplug the electrical lead and unscrew the plastic switch. There is a rod that slides to make contact when a pressure differential occurs. You need to center that rod that is now pushed one way or the other making contact. Once the rod is recentered you can reinstall the switch and attach the lead and the light should be off.

As an asside if you find that once you remove the switch there is brake fluid in this area the distribution block must be replaced. It is my understanding that you risk complete brake failure if you ignore this condition.

Randy

I think if the pedal drops to the floor it's the master cylinder seals. A "spongy" pedal (ie. not firm) would indicate air in system.

My good chap,

All the advice provided by others concurs w/my exp. w/240s up to '83 and 140s from 72-74.

Boy, I wish I'd held onto my Haynes 140 manual, gave it away to a person in need....

I mention this because of that PRESSURE DIFFERENTIAL WARNING VALVE as Haynes 240 (1994 ed.) manual calls it, see photo 8.1 of ch.9 on brakes. That device was similar though different back in the 140 days; whole braking system w/excellent redundancy was much the same as on 240s at least till ABS came along. IMHO.

Back then (w/140s), there was a part to that assembly that was user friendly, that you could unscrew which would would "reset" the valve that sticks somehow once the brake hydraulic system has been serviced. Esp. on the older beasts, eh?

Sounds to me like you did your best, perhaps find some more info before more messing w/ hydraulics and bleeding? Haynes claims this magic warning valve is "unserviceable." Though in next sentence they claim a rebuild kit is avail....

Must admit black tape over BRAKE FAILURE dash light was my solution when I last had this prob after replacing a seized caliper, as well as brake checks (STOMP ON EM), anything to assure you all is well if and when emergency arises.

Maybe just rapping gently on the press. diff. valve would reset it? A lightweight ball peen hammer sounds sensible. Could be an ordeal to replace the whole valve, but if your car isn't too rusty, might be worth it.

Keep us posted, experts are often wrong on "trivial" details like this.

Sorry for the novel, but really good info is hard to come by....

Regards,

Frank near Lake Erie
--
83 245, 81 244

Anytime you have the brake pedal travel all the way to the floor there is the possibility that the master cylinder will be rendered useless. If you think about it before the recent problem with your brakes your pedal probably didn't travel very far. The system was full of fluid and there was no air trapped in it. If you do not regularly (yearly) flush your brake system the moisture that brake fluid loves to acquire can cause oxidation in the system. This could include the bore of the master cylinder. The rubber seals that exert pressure on the fluid are easily damaged. If (for whatever reason) the pedal travels further down the bore than normal there is a chance that rust/scale that has accumulated in the system will damage the seals. They may not hold pressure after this experience.

Certainly follow the good suggestions in the previous posts but be open to the fact that your master cylinder may need replaced.

Bench bleeding involves evacuating all the air from a new master cylinder before attaching the brake lines to it. Many new master cylinders come with a bench bleeding kit (if it doesn't they are available for purchase). It has fittings that screw into the line ports on the MC and lengths of rubber hoses that attach to the fittings and are then routed to the reservoir. With fluid in the new master cylinder you push the plunger into the bore to pump fluid and air out of the MC and back into the reservoir. The air is expelled to the surface of the fluid and when you release the plunger it draws back only fluid (and no air). Repeating this operation until the fluid being pushed back into the reservoir stops exhibiting air insures that you have eliminated all the air from the MC and it is ready for installation. At that point you merely bolt it in place and one at a time remove the fittings from the port and install the brake line. "Bench bleeding" can actually be done with the master cylinder in place and using the brake pedal for activating the plunger in the bore but the fittings and hoses must be in place as described.

Randy

2 things:
1, it's easy to get the wrong caliper on the wrong side. This happens usually when you're replacing both. They are very similar- make sure the bleeder screws point the same direction as the one you removed. If they're opposite, you've got the opposite side there. You'll *never* get it properly bled. I have received wrong calipers in factory boxes before- don't assume they're right, compare and be certain.
2, the brake distribution block / brake failure light switch block is usually very unhappy when you bleed old brakes on these cars. I do whatever I can to avoid breaking lines or fiddling with the system in any way. It's possible the only fix is going to be to buy a new block. Air gets trapped in them and the switch seems to get stuck over to one side. OR something along those lines. Pressure bleeding is usually the way to fix it, but it wouldn't be the first one to fail during a bleeding attempt.
Make sure you're following the brake bleeding order correctly. It's a complex system, and it's essential that it's done in the right order. It's unique to Volvo's double-triangle brake system.
Start over bleeding the system and see if it makes any difference when you do it in the correct order. Good luck!
--
Rob Bareiss, New London CT ::: '86 244DL- 215K, 87 244DL- 230K, 88 744GLE- 198K, 91 244 180K

A couple of thoughts....

1.) It is not uncomon of have "no pedal" following even minor brake work. Whenever I merely press the caliper pistons back into their bores each time I remove the wheels for womething (just a PM thing I do) it takes several pumpings on the brake pedal to restore function

2.) It is less likely the pressure bleeding would have failed your booster (MC). If you said you used manual bleeding by stomping on the brake pedal to bleed, then, yes, you might have caused that problem

3.) A replacement caliper takes successive bleedings to remove all the air. Three or four attempts is not unusual. Also, try tapping on the caliper with a rubber of plastic mallet as you bleed. This untrapps tiny air bubbles still clinging to the insides (credit this idea to Don Foster)

4.) The brake failure warning light is likely coming from an imbalance in the combination block switch below the MC on the frame. Check the FAQ for this topic. I believe the remedy is listed there.

5.) If you bled the MC resevoir bottle empty, you introduced air into the MC. Then that is your problem. Bleed the MC.
--
1989 740Ti 1986 240DL 1984 244GL

First of all, thanks for all the advice I really appreciate it.

There was also a loss of fluid through a bleeder valve that wasn't quite tight enough when I was first trying to loosen all the valves which drained the master cyclinder, would this have allowed air into the MC itself that
couldn't be bled out through the regular process? sorry for the run-onnnn.

There are a couple of things I'm am considering:

1) rebleeding system while banging/tapping on the new caliper,
and again, I am following the bentley manual for order.
2) remove and bleed MC in case air was introduced to it.
3) purchasing new master and more fluid to have on hand.

Is there a visual after removing the master that would show that it is bad/ like leaking fluid?

This is when I seem to have endless ?s and have trouble sorting it all out,
bear with my Bent Brain folks
Thanks again
Chapster out