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I violated one of my own rules and did some non-essential maintenance to my winter car in the winter. I'm paying the price.
The car is an '88 245DL automatic, non ABS. The original problem was the brakes required too much force on the pedal for too little braking, and the pedal travelled a little too far in the process. I felt this could be either the booster, unlikely, or the master cylinder. Pumped the pedal to bleed off the vacuum, held it, and started the car. Pedal dropped noticeably so I figured, master cylinder, and replaced it.
Bled the system with my home brew vacuum bleeder. Does about 10" max vacuum or the bottle collapses. Had a little trepidation going in because of a bad experience on my '80 Mercedes which clearly didn't appreciate the vacuum bleeding method. I've only used it to exchange fluid on the Volvos. Never had to actually replace a brake component so never had to actually "bleed" the system. A good run of luck with three 240's.
Followed Bentley's prescribed bleeding ritual; rear left, front left lower, etc. Everything looked cool, but the pedal had just slightly more than the ideal travel before firming up, no power, when I was finished. Torqued all the wheels on and rolled it out of the garage and about soiled my pants. Pedal sunk nearly to the floor under power, with alarmingly poor braking at best. Dropped it into drive and rolled it right back into the garage and almost through the workbench.
With no vacuum on the booster the pedal travels a good third of a stroke before encountering spongy firmness. Can't pump it up, or maybe just ever so slightly. We're talking 20 strokes and some imagination to say it pumped up a tiny bit, maybe.
Ok. Bled it the conventional way. Pump, pump, pump, prop the board against the seat, bleed, repeat; still following Bentley's. No diff.
Got the wife in the drivers seat (Hard of hearing. Mechanically challenged. Could have made money if I'd filmed it. Amazingly nobody had to sleep on the couch! She's an angel). She pumped and I bled. I jacked up the rear of the car so air could go up. I jacked up the front so it could go the other way (down?). We ran two+ quarts of DOT 4 through this thing. No diff.
Did some reading here on the forum and ordered the Motive pressure bleeder. Hooked it up, watched my brake reservoir bulge alarmingly at twenty PSI and ran another two quarts of DOT 4 through the system. Nope. Bulged that mutha out to 25 PSI, with my eyes bulging to match. Nope. Bulged and pumped, calmly, then wildly. No dice.
Did some more forum browsing. Dumped the Motive and rigged a bottle to each rear wheel, hoses in a couple inches of fluid. Stroked the pedals with the bleeders open and watched amazing quantities of fluid index through them at high velocity with nary a bubble. Did tops and bottoms of the fronts the same way. Waste of time.
At this point, it is impossible for me to believe there is one molecule of air in this brake system.
Rigged some plugs on the new master cylinder. Firm as you could ask, with and without power. If only it were connected to some brakes!
Ok. Examined all the calipers. Must have some lost motion somewhere. Replaced the rear left; one stuck piston. Bled everything. Same #&^%!! story! Ahhhh!!!
Maybe the wrong size bores in the master cylinder? Got one for ABS or something?
Folks, I ain't no neophyte. I've done ALL my own mechanical work for thirty years. The only thing I haven't tackled (yet) is rings and pinions. But this has got me baffled and humbled.
Help.
Chuck
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posted by
someone claiming to be bobfrompittsburgh
on
Tue Feb 8 16:41 CST 2005 [ RELATED]
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i have put 100's of master cylinders on volvos. if you put a rebuilt cylinder on take it back. most are worthless. if you started with an ate,new cylinder, i have never seen a bad one. first of all, if you had any calipers off the car, you make certain that the bleeders are on the top of the calipers. you can not bleed air from the bottom. i noticed you stated that you bled top and bottom bleeders. let s assume you meant the ones in the middle of front calipers and you did not put calipers on the wrong side. there are no calipers with bottom bleeders. next,if calipers are correct, propping pedal with a stick may not work. if the stick falls when you open the bleeder and the pedal comes out while the bleeder is open, you will suck air back in. it is not absolutely neccessary to bleed in sequence and it is not neccessary to jack front or back end up higher.a pressure bleeder is not needed to do the job, but it sounds as though you have bled it enough. once you have bled all the fittings on the calipers there is no need to remove and bench bleed the master cylinder. is ther any possibility that you have a bleeder that is not sealing tight enough or that you have a switch on the junction block(on frame rail below master cylinder) leaking. a bad caliper could cause all of your problems but i would think you would get some pedal. i do not think the master was bad to start with. maybe try pumping the pedal several times until you get some pedal and hold it while someone checks for leaks. one more thing. you are aware that one section of reservoir has to be almost filled to overflowing before the other section fills, right?
bob
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A common mistake people make is to start bleeding the system (at the calipers) before clearing out the air at the top of the lines that attach to the MC.
As air "floats" it will tend to bubble up through the brake fluid as the fluid is being pulled from the system via the calipers. So you end up with fresh fluid in the system but air still at the top by the MC.
What should be done first is clear out the air in the MC and upper line before proceeding to the bleed. Ie. First get peddle to firm up, indicating no air in upper lines, then bleed.
Before you pull the MC to bench bleed, try this:
1. Get something that will block the pedal in the down position eg. wife.
2. Crack open lines at MC exit.
3. Depress brake pedal and block it in the down position.
4. Tighten lines.
5. Release pedal.
6. Check for pedal firmness. If firm then air is out. If not, repeat from step 2.
Basically you're pushing air (and fluid) out at the crack on step 3 and replacing it with fluid in step 5.
Shouldn't take more than a couple of cycles, will save you from bench bleeding and you won't have to re-bleed the brakes (as there's already fresh fluid in the system).
Brake fluid softens paint so rinse away any spills.
--
1980 245 Canadian B21A with SU carb and M46 trans
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Thanks for the suggestion Trev29. I'll give it a shot when following up on everyone else's tonight.
Air in those vertical lines was a concern of mine, and the rubber lines looping up around the struts to feed the front calipers. Through this ordeal, however, I have determined brake fluid is viscous enough to carry air downward with a fair amount of authority.
I rigged some clear tubes to run down to my bleed bottles by hanging them over jack stands. The ID of the tubes is much larger than the brake lines, so velocity is much lower. Despite that, even large air bubbles essentially indexed in one direction, heading right for the bottles with virtually no hint of floating up between strokes of the pedal.
FYI, it took three strokes to completely clear a large gob of air through the rear left bleed that resulted when I, in my enthusiasm, forgot to keep track of the reservoir level with my wife pumping away.
I made this discovery inadvertently at a point when Maria and I were getting substantially out of sync on the holding of the pedal and the closing of the bleeder.
Chuck
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BENCH BLEED THE MASTER CYL. I've been through the same thing in the past until i was clued in.Nice slow strokes with a long screwdriver until you see no air bubbles pass through the CLEAR PLASTIC TUBING. Much luck,B.G.
--
'78 244DL, 278k '83 245Ti 246k, '89 760Ti 180K,'86 245DL 320k
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You give me hope. We'll see tonight. Promised the wife I'd get the network back up last night.
Chuck
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Bleed the master cylinder,Then the brakes in order as you are shown in the repair book.If no brakes after that then my guess is a bad master cylinder.
I've put 3 on before I got a good one before. If brake booster is bad you will hear it from inside the car a whoose sound fairly loud.That is a broken seal on the vacumn in it.You are doing every thing right it's just a bad part.Haven't you heard the old saying (third time is the charm)
Don't give up.
Thanks
Rodney
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Thanks Rodney,
That's always a thought in the back of my mind. If it were an American car, or a rebuild, it would be an actual suspicion. One would like to think a brand new ATE would be a bit more trustworthy, but...
Chuck
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Hello Chuck; I just went through the same thing about a month ago. About tore what little is left of my hair out, until I did the procedure that Prater suggests about the master self bleed. Once all the air was out, it did fine. My old way of pump and hold with a helper, just would not get all the air out.
--
'94 940 150k, '86 240 170k, '72 142 KIA, '70 144 KIA, '69 144 RIP
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Hello Sumerduckman and Prater, and thanks for responding.
No, I did not do a "bench bleed" or equivalent. I've always had some kind of philosophical objection to that. Don't know why. I did, however, buy some spare brake lines a couple of days ago with just that procedure in mind. Because I got such a firm pedal when I plugged the MC I abandoned the thought, but with what you two have told me I'll give it a try.
Chuck
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Chuck - Sounds like due diligence to me. I know you plugged the MC and it held firm. This may be a shot in the dark, but did you bleed the MC? I always do that (thanks to a tip from BB). I just cut a brake line in half and bend the tubing so that each piece runs from an outlet port, up and into the reservoir. Make sure tubing ends dip below the surface of the fluid in the reservoir. Make sure no metal shavings from the cut remain on the tubing ends.
Another possibility, of course is a bad MC. I know what a PITA the bleed sequence is, but you may want to swap the old MC back in to make sure you didn't receive a bum part.
If anything else occurs to me I'll add to the thread. In the meantime, good luck...
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Thanks Prater, here and above.
Would have posted a reply sooner but apparently the brickboard went down for a bit while I was typing away this morning?
Putting the old MC back in circuit was on yesterday's agenda, but I dropped the idea when plugging the new one resulted in such a firm pedal.
I should clarify here, FYI. I was going to cut a couple of plugs on the lathe, but couldn't find the proper thread bolt to start from (anyone know what thread these things are?). Can't thread metric on my lathe, plus I was worried about narfing up the part of the bore the double flare would seal against.
Instead, I got a new brake line, cut it in half as short as I could and still flare it for some 37° fittings, about 2". The intent was to bleed the two tubes by cracking the flare fittings, but I stuck them on and pumped and it was so firm I just fired up the car and tried it with power. Still very nice feel. Not alarmingly firm, if you know what I mean, but just right.
Just wanted to pass along the info that with two 2.5" long "plugs", including brake lines and fittings, presumably full of air (since I made no attempt to bleed them) the pedal felt great. I guess that 5" of air in the lines must represent something close to the displaced volume of the caliper pistons as they actuate the pistons?
Anyhow, putting the old MC back on is still in the plan if your bleeding suggestion doesn't bear fruit.
Something I picked up on the forum regarding that. If you hold the pedal down enough to cover the ports from the reservoir, i.e. board against seat, you don't drool brake fluid all over while disconnecting fittings from the MC.
Now, why didn't I think of that about 30 years ago? (I hope everybody else isn't saying, yah, why didn't you?)
Chuck
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Chuck,
Found it interesting you tested the feel of 5" of air, still finding the pedal equivalent of being blocked solid. The plugs I use are made as you have, except cut as close to the nut as practical and filled with solder. I use one at a time to try to determine which of the two systems is causing the sponginess.
In a recent experience, not saying it can be applied to yours, I had a rock-solid firm pedal with both ports plugged, yet the master was definitely a dud further down the bore. But this symptom, unlike yours, is typical master sinking-pedal, not just too much pedal. I guess my point is, the response may be different depending on where in the bore the pedal moves the piston. Just would not expect this on a new master.
I do make a practice of bench bleeding, observing the amount pulled back when you release the spring in the master makes it an easier job if the bench bleed lines are as short and direct as possible. But I would have guessed you pushed enough through your system already to get the air all the way through, somewhere around 1/2 liter.
--
Art Benstein near Baltimore
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Hello Art,
My original plan when buying the brake lines for plugs was to cut them short and TIG the end, but then I thought, how will I bleed them? I assumed at that point that we're talking some rather small quantities of air. I described my setup to share my surprise the system could have that much air in it and still feel quite firm, although I don't think it felt as firm as I would expect if blocked solid right at the bottom of the port.
I considered testing one system at a time but couldn't picture how they would interact. For instance, if you have a slug of air in one, and the other is bled perfectly, what would allow the pedal to drop enough to compress the air when the bled system would presumably stop it dead early in the stroke?
I was musing about this as my wife was letting me know how much the pedal dropped while doing the old pump and bleed. Sometimes it dropped very little. Others, a fair bit. Eventually started alternating systems to coax more travel out of the pedal, thinking maybe we weren't displacing air at the end of the stroke, although I really prefer not to get there even with a new MC. I thought the pedal drop should reveal which system has the problem if I could just understand what's happening.
I too would think I put enough fluid through there to suck up every scrap of air, especially with the velocity I was getting bleeding both systems simultaneously, but I hope I'm wrong and that bleeding the MC is the magic bullet.
I have avoided bench bleeding in the past due to the mess while hooking the drooling pig up to the brake lines. I always viewed a master cylinder swap as a wonderful opportunity to exchange the fluid too, so what's a little extra air. May have to modify my opinions, especially having learned of holding the pedal down a bit to block the ports and stop the drooling.
Could you clarify that last paragraph, observing the amount pulled back when you release the spring?
Thanks, Chuck
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Hi Chuck,
I did understand what you were saying about the length of the tubing used for the plugs and thought your observations most interesting. The idea that much length of tubing with air could feel fairly firm makes you wonder where all the air is when it turns out much spongier.
The pull back during bench bleeding is something I believe happens because the bleed tubes are arranged higher than the reservoir. When I connected them, the master was dry. Then, adding fluid to the reservoir first, I would push the plunger with a screwdriver, but because the fluid would find its own level when replenishing the space ahead of the piston seal, the space would not fill up completely against the weight of the fluid pushed higher than the reservoir in the bleed lines. Not enough fluid could be contained ahead of the seal to completely fill the bleed lines until it was pumped a number of times and bubbles patiently allowed to surface while the piston was held fully in.
I think, simply cracking the fittings to allow gravity to fill the space ahead of the seals would cure this, but as you note, it is messy, bench or in the car. Just a small amount of travel puts the seal beyond the opening to the reservoir. But while connecting a pre-bled master, I don't block the pedal, quickly swapping the bleeder adapter for the car's connections, pile of rags in place to protect the paint. I am thinking this will exclude the most air.
Using one blocking plug at a time may not be such a good idea given the normal state of the o-rings in the pressure differential sensor. Also, as you note, the secondary circuit at the front of the master is equalized by that strong spring between the two pistons, so blocking the primary would, I guess, prevent any travel in the secondary. Counting on some give in a connected primary circuit must be the reason the procedures suggest first bleeding the three caliper spaces served by the secondary. Then the spring would allow continued bleeding of the primary circuit. But using a pressure bleeder, all that is moot.
--
Art Benstein near Baltimore
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Art,
Ok. Now I understand the pull back. Also, to save a few steps I was originally planning on bleeding the MC in situ, hanging off the booster, but after reading your suggestions it occurs to me that actual bench bleeding may move the pistons further down the bore than the pedal would, and with better feel to boot. So maybe I'll pull it off the booster and clamp it in the vice. I'll try it in place first.
At the same time I think I'll play around with plugging the ports one at a time with the other open back to the reservoir just to see how the two systems handle the equivalent of a total failure of the other, without concerns of how the differential sensor might feel about all of that. I think you had a good point there.
I'll post back tonight or tomorrow and let folks know what I learn. We may as well benefit a little for all my travail. Got the wife's spare 240 to get around in so the time element doesn't have it's normal authority. She's being pretty generous because I have to replace all the metal that holds (or used to hold, more accurately) the lower driver's door hinge, soon. Sob. And SOB!
Chuck
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I am having a similar problem with an 86 240 - bought this car as a project and the brake reservor was empty. I replaced rear pads and rotors - have the same IPD big motive brake bleeder and used it on my 850s with no problem. Previous owner records show the brake distribution block was replaced 15K ago ( I have an new one sitting here ) bled car first time with original MC and bad results - low pedal and poor braking. Replaced the master cyc and still got no better results. Had a front left caliper with a broken bleeder (top) so I got a rebuilt caliper for 45 and replaced and bled again - not better....hmmmm. Much cursing and tool throwing. Took off mc to look at seal on the booster and adjusted the push rod on the booster/ A bit better. Looked at page 25 of IPD catalog and saw the booster check valve on the page - they fail! My pedal is very firm with car off but sinks with car on, but still brakes well. That should be a boost problem. I am now convinced it is the check valve, booster or a wild guess of the front rubber brakes that can bulge. I have ruled out a defective new master cyc because this one is behaving the same as the old one (which means the mc I replaced and caliper I replaced were ok - so I blew $100 there). I have bled four times and know the the thing is bled correctly - have consulted in the Volvo problem solver, bentley, IPD catalog tips and 700 FAQs. I think mine is boost - does your pedal react the same (too much travel with car off) - I am pretty I am on the bad boost path! Not sure on yours, but I have been POed at previous owner for not maintaining brakes - plus, I have to replace the ignition switch - with car off and pedal pushed - brake lights come on, but so do all idiot lights and demist switch. With car on, brake lights stay lit all the time - already replaced bulb out sensor, but the big clue is the car keeps running for 20 seconds with key out - gotta be ignition switch - another 57 for a Volvo switch ro 20 for aftermarket - I went Volvo due to a bad experience replacing a 740 ignition switch a year ago - aftermarket broke immediately! I feel your pain!
Bob Weber
Hamilton, Ohio
60 Volvos since 1979
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Bob,
Thanks for your view. I tried to look into adjusting the push rod somewhere during all this but, unless I overlooked it, I could find no reference to any procedure or specs in Bentley, Haynes, or the Volvo factory manuals (yah, blew a big load of $'s and got Volvo's. Not worth the money if anyone is considering it, and that's hard for me to say. I'm an incurable documentation freak).
For a number of reasons I don't think rod adjustment is more than a minor contributer, but I'd be interested in the procedure and recommended free play.
>My pedal is very firm with car off but sinks with car on,
>but still brakes well.
The first half matches my problem, fairly firm with no vacuum, sinks with the car running. But I have lousy brakes.
>does your pedal react the same (too much travel with car off)...
Pedal is firm with slightly too much travel with the car off. Waaayyy too much with it running.
The booster has been in the back of my mind throughout this ordeal but, again, I think it's not the root cause since the original (and it was original at 152K) MC was fairly firm and now I have nearly no pedal at all.
I'd like to know how your issue turns out. Might be related. First item for me, I think, is the bench bleed suggested above.
Chuck
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I may have missed something here, but if you did a lot of pedal-bleeding with your wife, I'd say that was equivalent to bench-bleeding the MC.
Except that what (if any) air that may have been in the MC got pushed out, as in bench-bleeding, but into the lines—and hopefully purged. Seems unlikely there could still be any air in the MC.
As for the pedal dropping when the booster comes into play—I've never understood the mechanics of it, but that IS the test for a good booster,as I think you mentioned.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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Bruce,
How bench bleeding might clear out air that conventional bleeding was unable to has been quite a topic of conversation among the guys I work with, most of them fairly capable wielders of the wrench.
If it were not for having seen it suggested in the forum so many times by people who appear to be knowledgeable I would tend to dismiss it. Assuming they're correct (and I sure hope that's true at this point), the only thing I can figure is that the smaller bore piston in the MC, I think they refer to it as the primary, has its port tapped on the center line of the bore, so maybe a pocket of air could get hung up at the very end above the port and you just can't build up enough turbulence to entrain it with the whole system downstream.
Regarding the pedal dropping when the booster sees some vacuum, I assume the calipers always have a bit of play in them and the added assistance of a fair amount of diaphragm area just takes up the slack enough to feel it at the pedal.
I also do not understand (blush) how these master cylinders work. The piston I would think was the primary is the secondary. How they work in conjunction, and with two bore ID's, I just can't figure out with the single poor cross sectional drawing I have, in Bentley's. I am (understandably, I think) reluctant to take apart the old one at this point to determine how they're put together.
For the present, I will gladly dispense with the theoretical and trade it on some practical results in the form of my brakes working. Later, I intend to understand what the deal is and would invite anyone with some insights to share them.
Chuck
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Chuck,
FWIW, I recently put a new MC on a '93 245 I was prepping for my daughter, after getting what seemed like a too low/soft pedal after a bleed-flush..
I decided to try "bench-bleding" it on the car, by installing it with bleed pipes and clear vinyl tubes arranged to be seen from in the car.
After lots of pumps and no more bubbles seen, I propped the pedal, removed the bleed pipes, loosely connected the main lines, removed the prop, and let each fitting do a bit of "gravity drooling" before tightening.
Then I pressure bled again, using Ate Amber this time to be sure of a complete fluid change. (I had just previously flushed old fluid with Ate Blue.)
Truth be told, I didn't do a road test (no plates, sub-zero, and salty road slop). Pedal did feel better and my drawers survived a brief driveway test unshat in.
Later my daughter said brakes felt fine on a 6-mile run to the store before heading back to MV, Mass. Since the '87 245 she left behind has a nice firm pedal & brakes, I take it that she noted no alarming difference.
I pressure-bleed using the Mity-Vac pressure port connected to a modified MC cap, with a vac/pressure gauge tee'd into the pressure hose. Use about 12 to 16 psi. Does not take as much rez replenishment as you might think. Complete flush (complete defined by new color fluid at each bleeder) takes maybe 3/4 of a liter can at the most.
P.S. I believe I introduced the pedal-propping thing here about 1 1/2 years ago. I just had to spread the gospel after learning of it from a Norwegian Volvo specialist about 8 tears before. (Recently learned that the ABS MC reqiores full-pedal propping, per Volvo greenbook.)
P.P.S. Don't feel you have to respond to this unless you have a question. I can see that you have a full plate.
Press on (pun intended) regardless,
Bruce
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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