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.

 

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... :-/

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

 

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.

 

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.

 

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"

 

Yep- second this, it has worked for me.

 

<snip>

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

 

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 .

 

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