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I'm having an issue with my brakes. Just replaced front calipers. Upon completion, power bled the whole system. But now, when i start the car, i have a soft SOFT pedal--afraid to depress too far for the MC seals. When the engine is off, after a few pumps, I have a stiff pedal.
What gives? not sure how to diagnose. There doesn't appear to be a leak anywhere--from what I can tell as the reservoir is still full. it possible there's air in the MC? or air in the brake lines? or something worse?
Thanks!
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Can't believe I'm still having trouble with this. I did the rear calipers this summer and it was a cinch! Here's where I'm at. I replaced a mis-manufactured caliper with a correct one (this time I slightly depressed the pedal to prevent fluid loss). I cannot detect any leaks anywhere and the fluid level is staying constant. But I'm still having a soft pedal after bleeding.
Couple things I'm wondering:
1. As i stated, i didn't bench bleed the MC but I am using a pressure bleeder. I ran about 20 oz of brake fluid through the 8 bleed screws. maybe I still haven't bled long enough? I let bubble-free fluid drain from each bleedscrew for 60-90 seconds after last bubble. I thought I read a suggestion on the board about pumping the pedal (slightly) during the pressure bleed to expel any air in the MC (which i didn't do), but are there thoughts on that approach?
2. Is the MC shot? I would be surprised as its only 6mo old. and I purposely avoided pedal bleeding to save it.
3. Finally, I just want to make sure I got the brake lines hooked up correctly on the passenger side. One line was stuck to the caliper, so I unscrewed one line from the caliper and the stuck line from the rubber brake hose, then was able to feed a box wrench down the stuck line to the fitting at the caliper. Now I'm wondering if I didn't get the feeds mixed up on installation--reversing the lines to the upper and lower caliper fittings. So can someone verify the correct way to attach the brake lines on a 240? Right now, I have the FORWARD RUBBER line attached to the LOWER caliper mounting.
I've got an appointment for Monday to have the shop take a look at it. I've basically admitted defeat, but thought I'd throw it out there for one last attempt at it this weekend.
Thanks to all for your insight!
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We've seen this problem with manufactured calipers.
Look at the top of each caliper. If you see a punch-mark or "dimple" on the OUTER half, it's wrong. A good one will have each half marked for matching on the bottom.
Also, if you let the fluid run out while calipers were off, the rears need bleeding too.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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Thanks so much for your help. this is EXACTLY what the issue is. Mismatched caliper. So frustrating! Now, i get to duke it out with the supplier. I'm hoping they'll install the new, correct one for me. We'll see.
Appreciate all of the quick, cogent responses.
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Glad you found it.
Let us know the source. NAPA, Ray-Loc is one I know of. I always check at the counter before leaving.
I don't gamble much with online sources anymore. NAPA may be chancy but I don't have to ship the core back.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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The manufacturer was Morse. I usually by stuff from FCP, but didn't want to ship those heavy cores back. Got burned. I bought them at a parts/service center called VIP in Maine - not sure if its national or not.
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You might want to print this and take it to Morse with the screwed up caliper.
If they have any good ones in house, the 2 dimples on the bottom will prove your case.
1 — In the Girling 4-piston calipers (pre ABS), the fluid passage for the two upper cylinders is basically an inverted U, with ONE common bleeder at the high point.
The lower cylinder fluid passage forms an upright U, with bleeders at each of the TWO high points.
2 — Rebuilders sometimes get the INNER and OUTER caliper halves mismatched. That is, a Left Side INNER half, where the lines attach, could have a Right Side OUTER half mated to it — but that OUTER half will be upside down.
3 — The reversal is not obvious because the two lower bleeders are centered on the caliper body. However, Girling punch-marks the bottom of each caliper half with a "dimple" next to the joint during factory assembly . So a dimple on the TOP of an OUTER caliper half means a mismatch.
4 — Such a caliper will have:
a) A redundant (outer) bleeder from the two upper cylinders
b) No bleeder outlet for the Lower-outer cylinder
What looks like the Lower-outer bleeder actually now leads upward to the top bleeder. This means that fluid pumped into the upper inlet port can come out two bleeders: the normal upper one and the now redundant outer one.
And when you think you are bleeding both lower cylinders, the outer one actually has no bleeder. It's dead-ended where the outer bleeder would normally be. This means that a successful, air-free bleed operation is impossible, on the RR-RF lower-LF lower circuit.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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I guess I was right with you as I already printed out your exact verbage from another thread you posed on! I'm going to bring it in with me tomorrow. Now, my only worry is the part that is coming in will be incorrect as well. Then they'll REALLY look at me like I'm crazy. But maybe my old cores will be convincing enough.
Again, I can't tell you how valuable this information was. I would probably be on my tenth liter of brake fluid trying to bleed that car had it not been for this. So, thank you much!
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I guess I was right with you as I already printed out your exact verbage from another thread you posed on! I'm going to bring it in with me tomorrow. Now, my only worry is the part that is coming in will be incorrect as well. Then they'll REALLY look at me like I'm crazy. But maybe my old cores will be convincing enough.
Again, I can't tell you how valuable this information was. I would probably be on my tenth liter of brake fluid trying to bleed that car had it not been for this. So, thank you much!
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I'm at work, so i haven't been able to check for mismatched calipers yet. But, i was curious about the Master Cylinder. If the brake lines were disconnected at the calipers, and enough fluid drained out to introduce air into the MC, is it possible there is still air trapped in the MC (requiring a bench bleed) or would the trapped air be expelled during a power bleed of the entire system.
Just trying to troubleshoot, though i should probably wait until I have full information on those calipers.
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"If the brake lines were disconnected at the calipers, and enough fluid drained out to introduce air into the MC, is it possible there is still air trapped in the MC (requiring a bench bleed) or would the trapped air be expelled during a power bleed of the entire system."
I don't think a bench bleed is called for at this point, since your power bleed would have pushed any air out of the MC and into the lines. The question is, did you bleed long enough to completely expel that air via the caliper bleeders?
I guess you might bleed some more, hoping to see some bubbles that are not quite ready to come out yet.
If you have to take any calipers off again, you can prevent MC fluid loss from any/all open brake line(s) by blocking the brake pedal depressed before you start. It only takes an inch or two on the pre-ABS 240s like yours.
I made a wooden prop that hooks to the bottom edge of the pedal and bears against the 240 seat adjuster bar. It's handy for checking brake lights too. But remember to disconnect the battery or pull a fuse to keep brake lights off while the pedal prop is in place.
EDIT: If there IS still air in the system I think it's most likely in one or both of the rear lines.
The shorter front caliper lines are probably OK.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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I've also improved my luck by slightly elevating the rear of the car when bleeding my brakes.
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Yep, i bled the entire system, front and rears. I will look for the dimple at the top. Oye! how upsetting - those took so long to get back onto the car...the thought of doing it again...yikes!
Thanks!
Shane
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"Just replaced front calipers."
This has been the frustration of many a Brickster. Are you absolutely certain you have the calipers correctly mounted L/R? If you're not, take a look at the positions of the three bleeders in the picture below. This is how it should look:
Erling.
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My 240 Page
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Thanks for the picture. Yes, i made sure the calipers were correctly mounted with the top bleeder screw pointing toward the inside.
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did you bleed the brakes using all the bleeder screws on the calipers? maybe your master cylinder is on it's way out?
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Yes, i bled all bleeder screws with a power bleeder in the order from the manual. and the master cylinder is about 6 months old - destroyed the last one during an "uninformed pedal bleeding" fiasco-hence, the power bleeder and new MC.
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