Bleeding power brakes. Engine "ON" ?

I recently replaced the front calipers (and rotors) on my 245 GL (I suppose that after 20 years with the same calipers, even with a Volvo you eventually have to change them [insert winking smiley])which of course means I need to bleed the system.

The last time I changed the calipers on a Volvo (long ago on a 79 245 DL) I don't recall whether it had power brakes or not but I'm pretty sure that I didn't have the engine running.

The 245 GL does have power brakes and I'm wondering whether the engine has to be running so that the power assist is "on" in order to bleed the system ?

Logic tells me "no" but sitting in the car and pumping up the pedal makes me wonder because the pedal doesn't seem to get any stiffer even though I've already gone around all of 8(?) of the bleeders screws once.

One thing that I supected might be the cause is that I didn't remove the white nylon hex-headed plug (switch ?) in the octopus-like gizmo (pressure warning valve ?) to which all the brake lines are connected.

So the second question is "Does that white nylon plug have to be removed before bleeding the system ?" (I did disconnect the wire to it, if that matters.)

In any case, thanks in advance for any wisdom (or slaps upside the head) you may have to offer.

Reply to
Eunoia Eigensinn
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Did you follow the recommnded sequence: For you car (an '85 with no ABS, I assume), it should be:

1) L.R 2) L.F - single top bleeder 3) R.F - single top bleeder 4) R.R. 5) R.F. - both lower bleeders 6) L.F. - both lower bleeders

The book doesnt say anything about bleeding the distribution block...

Although beleding brakes is USUALLY easy, following a procedure can, at times, be critical. When I first got my '79 BMW motorcycle (in

1981) I wanted to replace the brake fluid. The front was not problem (dual disc, Ate calipers). The rear was another matter (single disc- Brembo caliper). I bled the rear for over a pint of fluid (about five of six reservoir's full). Could not get them the brake come up. I took off the master cylinder and manually tested it- it shot fluid across the garage. I couldn't figure out what was wrong. I finally made a call or two, and found that the bleeder, being at the BOTTOM (!) of the caliper made it impossible to bleed them with the caliper in place. You HAD to remove the caliper, turn it UPSIDE DOWN, then it bled perfectly with two or three strokes of the pedal... :-/

"Eunoia Eigens>I recently replaced the front calipers (and rotors) on my 245 GL (I

__ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"

Reply to
Randy G.

Thanks Randy. I did follow the reommended sequence (or at least the sequence outlined in a Hanes Manual for 240s).

I think that part of the problem may also have been my helper who was pumping the pedal for me. I did my brakes one weekday afternoon and the only person around who I could enlist to help me was a neighbour's teenaged son.

I don't think I was very successful in conveying the concept of "pump up and hold till I say "release" to him. I suspect that he may have just been pushing the pedal all the way to the mat.

In any case, I'm going to try and rig up something with a stick and a bungee cord (or somesuch) so that I can do it myself.

Randy G. wrote:

Reply to
Eunoia Eigensinn

Get a clear plastic tube that fits snugly over the nozzle on the bleeder. Needs to be long enough so you can put two (~4"Ø) loops in it, wind the tube around the loops so they stay, and reach a clear quart size glass jar on the floor. Secure the end of the tube so it stays in the bottom of the jar. Then you can get in the car and pump away. The coils keep air from sucking back. Watch you don't empty the master cylinder or you'll be starting over.

Reply to
Clay

The way to do that is to just say, "down," and then later, "up." The problem with poushing it all teh way to the floor is that if the master cylinder is old, and/or the fluid has not been changed regularly, a ridge of crud, rust, and corrosion builds up in the master cylinder. It is beyond the normal range of the piston. WHen the pedal is now allowed to move all the way through its entire range because a bleeder is open, the master cylinders piston seals are now drug across that ridge and they are damaged.

Keep a close eye on the fluid level. If it drops faster than normal, the fluid will be found inside the booster and it is time for a new master cylinder.

__ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate"

Reply to
Randy G.

Yep- second this, it has worked for me.

Reply to
Jim Carriere

Take a gatorade bottle and tie a piece of string, wire or whatever around the top below the threads. Leave a foot, eighteen inches or so free beyond the top of the bottle. Find a piece of hose about a foot long that fits snugly over the bleed screw nipple (Tygon hose from the pet store (fish tank airline)works ok. Pour a little brake fluid into the bottom of the bottle. Break the bleed screw loose and immediately snug it back up. With the wrench on the bleeder connect the hose to the bleed screw. Submerge the other end of the hose in the brake fluid on the bottle. Use the string/wire to make a loop that allows the bottle to be suspended from the bleed screw and keep the hose end sibmerged. Now open the screw. Pump the brake pedal. Watch the bottle. When bubbles stop and the fluid coming out is clear, as opposed to black and nasty, that line is clear, flushed and bled. As long as the hose is connected and under water you don't have to close the valve after every pump since air can't enter the system. I use a long screwdriver to push the brake pedal so that I can look under the car and watch the bottle (bubbles).

NB. Have lots of DOT4 brake fluid on hand and keep the reservoir filled. Usually somewhere between 5-10 good, long, easy strokes will empty the one side of the reservoir. You don't want the reservoir to go dry simply because it takes a good while to refill and bleed a dry line.

You can use the sequence above or not. The factory sequence is the easiest way to fill and bleed lines if the system is empty. Since you already had fluid in the system it really doesn't matter. Just start with the longest lines first (rears).

Bob

Reply to
User

Please don't press the pedal to the floor as any ridges formed will ruin the rubbers just press as far as normal even tot he point of putting a brick or block of wood under the pedal .Slow gentle firm short strokes will allow the fluid to bled out .Make sure all parts are free and not sticking ,mainly the sliders need watching ,as other wise you are wasting your time .Fluid is cheap and washes away with water .Take your time .

Reply to
John Robertson

To clarify: take your time with the bleeding process, but once you are done don't waste time washing away spilled or splashed brake fluid. It is very bad for paint if allowed to sit. I like to spray with Simple Green, Fantastik, 409 or whatever before hosing it off just to be sure. And don't spray the brake reservoir cap - you definitely don't want to get water in the vent and contaminate your gorgeous new fluid :-)

Mike

Reply to
Michael Pardee

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