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O.K. Fello Brickers
My drivers side right rear rotor was extremely hot, so much so that when I touched it, it burnt my finger. Also on the way home I was hearing some squeeking which I had not heard before, and when I slowed down to 20 miles an hour I could feel a whooble. (warped rotor?)
I checked all other rotors the same time and they were all cool. So, I thought I would do my first ever rotor and pad replacement. I got the car up on jacks and took off the wheels and was going to compare the two wheels, the hot one vs the not hot one, and hopefully see a difference. But they look pretty much the same. The only thing I noticed was that the hot rotor seemed to have some uneven wear.
I have read all the faq's but I need a little help with the basic understanding of how they should look to begin with. All I got from the faqs was how to replace everything.
How much brake pad should I be looking at? It looks like there is 1/8" to 1/4" of pad left. Most importantly, on both wheels it look like the pads are up against the rotors. I would assume I should see daylight between the rotors and the pads if the brakes are not on. Am I right? Or do they ride so close you can hardly tell?
Does your emergency brake, if it stuck keep your pads against your rotors?
So I am ready to do my brake job but maybe I don't need to, maybe the ebrake is stuck.
Thanks for your help, I don't mind doing the work, I am trying to avoid the $500 mechanic bill.
Paul
94 940
91 940 SE Turbo
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If your master cylinder(MC) is original then you will want to put a brick or a short piece of a 2x4 UNDER the brake pedal to prevent the piston in the MC from traveling too far and tearing the rubber diaphram. That area is not usually traveled and rust develops. When the rusted area of the piston travels past the rubber diaphram, it will tear the inner ring of the seal causing "blow by" when braking, giving you a soft pedal and poor stopping performance.
The other is to make sure you use a FLARE NUT wrench for the copper lines going to the caliper. Don't try to use a regular open end wrench on the soft fittings.
You may want to soak the fittings with penetrant first for a couple of days before attempting to crack loose the fittings.
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Good points, both.
I would also add the bleed valves should be opened with a 6 point box wrench. They, too, are soft and small enough that a 12 pt. box or crescent wrench can round them over.
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It does sound like you may have a warped rotor possibly due to malfunctioning caliper. (uneven wear).
1/8, 1/4 inch of pad left, replace them, and NO, you cannot replace just one pad or one wheel, well you could in a pinch--but they should be done by axle, do all front, do all back.
NO,no daylight between piston rotor and pad, they touch lightly.
Volvo emergency brakes are inside the rotors and have separate shoes, they don't engage the regular pads.
Just cap, or pinch the brake line once you have removed the caliper, the idea is for air not to get sucked in the line, and don't press the pedal whatever you do--you'll have to bleed the brake line at least on the side of caliper replacement after all is installed. And you can replace the calipers one at the time, same with the rotors...
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"Just cap, or pinch the brake line once you have removed the caliper, the idea is for air not to get sucked in the line, and don't press the pedal whatever you do--you'll have to bleed the brake line at least on the side of caliper replacement after all is installed."
Just reinforcing Hovonogila's tips below (which I neglected to read first).
The Volvo Green Book brake manual for 700/900 says (for caliper replacement) to press the brake pedal to the floor, with caliper bleeder open to catch expelled fluid, and block pedal down till new caliper is in place. This prevents any more fluid from leaving the MC as long s pedal is down. Then connect and bleed that caliper.
[This works for 200 series too, but pedal only needs to be depressed about 1" to 2" on pre-ABS cars.]
This method eliminates the need to pinch or clamp brake hoses, a method that is not advocated by industry spokesmen:
BIG 3 BRAKE SYMPOSIUM 2002, by Larry Carley
(excerpted clamping comments)
• GENERAL MOTORS PRESENTATION, Russ Dobson - GM Service Operations, Warren Tech Center
>CLAMPING BRAKE HOSES? GM says NEVER! Risk of damaging hose too great.
• FORD PRESENTATION, Garrett Van Camp & Chris Oakwood
>CLAMPING BRAKE HOSES? Ford does not recommend clamping hoses. . . This may damage the hose and increase the risk of hose failure.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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You can clamp off the rubberized brake line to the caliper (there are special clamps for this....forceps might cut...careful) or you can depress the brake pedal to the floor and block it off with the front end of the seat and a small stick. This will close off the pistons in the master cylinder and not allow the reservoir to drain. I did this when I changed mine and it worked perfectly.
This is not a simple change out the pads procedure...changing a caliper and bleeding brakes is more involved. Make sure you note the caliper piston size before you go to buy a rebuilt or replacement. It's stamped on the caliper....assuming you need one, and I think it's likely you do.
And you cannot replace the pads and rotors on one side without doing the other. This is 'brakes 101'. No shortcuts when it comes to brakes and tires. When you gotta stop, you gotta stop!!
"Removing Caliper and Installing a Rebuilt Caliper. The only difficulty installing a caliper is likely to come from corroded brake pipe or line fittings. See the notes below for tips. To keep fluid from escaping the master cylinder with a brake line open: 1) Disconnect battery negative (or pull relevant fuse) to keep brake lights off. 2)Connect a bleeder hose to the caliper (hose routed to waste container). 3) Open the bleeder, then slowly press the brake pedal to the floor and block it there till you are finished. 4) Slowly press the caliper piston back to expell as much fluid from caliper as possible. 5) Close bleeder and remove caliper for bench work."
--
I'm stuck on Volvo and Volvo's stuck on me....
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Ted;
Ok so I got it. Both sets of pads, But if i clamp the brake line with some forcips do I still need to bleed the brake line. Ok if i do. Just trying to save myself a step and cost of bleed tank.
Tx
Paul
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"Pinching" the hose is getting some bad rap, but the idea is NOT to crush it, and I can see where the official line would be to avoid this, what with the liablities and excessive muscle in many "techs"...
As far as bleeding, don't despair, it's easy. We are not talking about bleeding the whole system, just that caliper (as long as you don't lose too much fluid, and I don't think you will). Once you are done just have a helper slowly step on the brake pedal until it can go no further while you have the bleed valve open: fluid will be coming out. Once the pedal is to the floor, tighten the bleed valve; let pedal come back up. Repeat the procedure until the fluid coming out has no air bubbles and comes out solid (likely about 3 times). You may want to attach a short hose to the bleeder niple and submerge it into a small jar with fluid while doing this (reccomended) as then there is less chance of air being sucked up accidentally back into the system, and is neater.
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Ok
I am slow but I'm getting it. Thanks for all your help. So one more question. This bleed valve, where is it? Also do disconeect the old caliper then bleed with brake pedal or hook up the new caliper then bleed.
Paul
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hook up caliper, then bleed
Hydraulics 101 -
1) The pressure piston pushes the fluid out to the caliper piston thereby moving it and the pads thereby grabbing the rotor.
2) When the pedal is released, the pads loosen up and the fluid returns to the master cylinder.
3) If the pads travel a sufficient amount, they will not return all the way to where they started (first depressions after replacement & to a much smaller extent over time when wear occurs) and some fluid from the master cylinder reservoir replaces the "void" of the fluid that has permanently moved into the caliper.
4)If air is in the line/caliper, it will first compress, thereby limiting the amount of movement in the caliper. This requires more pedal movement to apply sufficient pressure to the pad/rotors (soft & low pedal).
5) When you replace a caliper, there will be SOME air in the line/caliper which needs to be flushed out before it migrates into the system (which it will, count on it).
6) Air will migrate to high points in the system so bleed valves are located at the top of the caliper reservoirs and at the master cylinder.
7) I like to bleed the entire system when I do a brake job to get fresh fluid in there. I start at the Master Cylinder then go to the furthest (passenger/rear) caliper next, working my way in closer to the MC once the line clears out of old fluid (driver/rear, pass./frt, drv/frt.). I replace the lost fluid in the MC after each wheel. You do NOT want to push air into the lines from the MC especially with ABS!
I apologize for the lengthy post but it seemed you were new to this and could use some pointers.
Bob K
1994 945T - 260K
1988 244 - 310K
1984 242 - 140K
1994 F150 - 306K
1968 GT500KR - under resto
various Benzes as well - all over 120K
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Paul....me thinks you might have a bad caliper....stuck piston.
No biggie to change...if you are comfortable with brake fluid. You'll have to block the brake pedal to the floor and get a rebuilt caliper and bleed the line.
Then the pads and the rotor.....
--
I'm stuck on Volvo and Volvo's stuck on me....
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Hovon;
I had been thinking about that same thing after reading all the facts. Fcp Groton has a rebuilt caliper pre loaded with pads new pins etc, for 54.99. Not bad and rotor for 30.00. Also a brake bleeder just like a garden chemical sprayer. So whats this business with a brick on the the bricks brake pedal. Can I just break the line and plug it with something then just quickly reattach the line to the new caliper? Also since there is about 1/4 inch of pad on the other wheel do you think i can get by with just changing the one side?
Thinking of buying a v 90 it will be my fourth volvo. They can be some trouble but the minute I get inside I feel good.
Paul
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Dear Paul,
May this find you well. Let's deal with the important stuff first: the "V" in "Volvo" should always be capitalized!!!
More seriously, if you follow the procedure set forth by Hovonogila (and it's good he doesn't have a gila, as gila monsters are venomous creatures) and affirmed by lucid (he is, very much so), you won't have to bleed anything. You will have to top-up the brake fluid reservoir, by whatever amount comes out of the bleeder.
No special vessel is needed to catch the brake fluid expelled, when the pedal is depressed. Any plastic, metal, or glass container will do, so long as it won't easily fall over. Do not get brake fluid on painted surfaces: it will damage the paint.
Be advised: brake fluid attracts humidity, so don't leave the container open for a second longer than needed. Also, fluid from a partly-filled container should only be used, if you know for certain that the container was promptly and tightly capped. If you have any doubt at all, buy a fresh container. Brake fluid, that has been exposed to air, will decrease braking power. The water will become steam at the high temperatures, generated by heavy braking.
Clamping brake hoses not only is unwise, on 940s (at least post -1992), it is futile. The front hoses have a flexible steel shell (under the plastic coating). The steel shell keeps the hose from being damaged and from bulging under pressure.
I doubt you can compress these hoses enough to stop air from entering the line. If you can compress it enough, you've ruined the brake hose: the crushed steel will prevent the rubber hose from opening up, once you remove the pressure.
Hope this helps.
Yours faithfully,
Spook
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