Hey all,

I have an 88 or 89 240 wagon. I've owned it for about 12 years and it's got about 140k miles. Last summer my "brake failure" light came on. Braking was fine, and then the light went off. Last week, the "brake failure" light came on again, but now the braking was very weak, in a scary way. I was able to get home though. A few hours later I started the car again, and the light was off, and the braking was more normal. Either way it seems like something needs attention.

I checked the brake fluid and it's not low, so I don't expect it's been leaking at all (which would also mean probably no air in the line). I've never touched the brake system, aside from replacing pads. I don't know how the volvo braking system works, but it does feel like when I had to replace the master cylinder seals on an old motorcycle disk brake system... pedal goes all the way down, but not much braking power. Can anyone give me an idea of what could be going on? According to a few quick google searches, it could be a shot master cylinder. In which case a new one would need to be fitted, and the system bled. Does this sound about right? I'm not sure I want to dig into this myself for lack of work space and mess. Is this something that any old brake shop could tackle or do I need to take it to a Volvo specialist due to my car's age? The reason I ask is I live in a high-rent area, and there aren't many Volvo mechanics, the ones that exist are VERY pricey.

Thanks!

 

You may have a bad brake master cylinder If the pedal is sinking towards the floor. It's a dual master cylinder setup, one piston sends fluid to both front wheels and one rear (if your car does not have ABS) and the other piston sends fluid to both front wheels and the other rear wheel.

The brake failure light switch - is a simple sliding piston that's connected between the two branches of the hydraulic system. If there is more pressure in one side - the piston slides over, and grounds the brake failure light. Take your foot off the brake - the piston is spring loaded and moves back to the middle position turning the light off. (at least that's how it is supposed to work) It is common to replace the "brake junction block" (that the switch is in) at the same time as the master cylinder. The junction block has rubber orings that can leak with old age also.

If you flush the hydraulic system every 2 years the master cylinders will last much longer.

 

Thanks for the reply. Yes, it certainly sounds like the master cylinder, and your description of how the brake failure light works seems to match the symptoms as well-- weak braking from only one piston working properly, tripping the failure light.

I searched online and it seems master cylinder replacement is fairly straight forward, but the labor intensive part is bleeding the system. I'll need to purchase a power bleeder. From there it seems like you just need to bleed each caliper separately. For the "shade tree" mechanic, can I do one caliper at a time, without jacking the car up entirely and removing all four wheels simultaneously? It seems for one person an easy job, you pressurize the system, hook up the caliper, and when you untwist the bleed nipple, the pressurized system does the bleeding for you. Correct? When no more air comes out you just tighten the nipple and move on to the next caliper, right?

If I don't have any fluid leaks, is there any reason I may have to replace the brake lines?

Finally, any tips on where to buy a new master cylinder, or perhaps, where to AVOID buying one? I'd like to buy one that will not fail. Would this item do the job? - https://www.ipdusa.com/products/1650...8111006-126021

Thanks!

 

For the first 30 years of my career I did not have a pressure bleeder - so my shop has installed hundreds of master cylinders/hydraulic components without one. A helper is needed to depress the pedal to force the fluid out. Open bleeder screw, depress pedal, close bleeder, release pedal, repeat. It would be best to have all wheels off, sometimes you have to go back to a caliper. Brake fluid is heavier than air - so if the system flows freely you can actually gravity bleed a hydraulic system! The last couple of cars I flushed systems on by myself I used a hand held vacuum pump, (a mityvac) and sucked the fluid from the calipers/slave cylinder. So a pressure bleeder is really nice (unless it pops off and sprays brake fluid everywhere!) but not absolutely needed.
When you first install the master cylinder, leave the pipes slightly loose at the master cylinder. The idea is to get all the air out of the master before is gets pushed into the brake lines. Fill the master and the air in the master will all bleed out of the pipes. You will have to "tickle" the brake pedal. Barely depress the pedal a few times to convince the air bubbles to leave the master. I would never not flush the system while installing a new master - but you can easily end up with a hard pedal (no air in the system) without bleeding the wheels.

Try to buy the oem brand of master - if still available.

 

Alright, I bought a new master cylinder, power bleeder, and some fluid from IPD. I have no leaking in my brake system, so I opted to leave the junction box as-is.

Can anyone tell me the size of the flare nuts so I can avoid buying too many of the wrong wrench? My guess is either 10mm or 12mm, but that could be entirely wrong.

Thanks!

 

7/16 or 11mm

 

Got it! Thank you!