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Hi all,
I could really use some help, so if anyone has some suggestions I would appreciate it.
Problem: 1994 940 Turbo was pulling hard to the right. I jacked it up and had my son hit the brakes while spinning each front tire. The right tire stopped immediately. The left tire kept spinning as he pressed the brakes.
I assumed both calipers should be replaced, so I ordered a set. I swapped out the left (non-working caliper) first. I also changed the caliper flexible brake line.
Once changed, I could not get any brake fluid to bleed from the freshly replaced caliper. I ended up doing all kinds of things to try to determine why. Here is what I have determined so far.
1. The line from the ABS block to the caliper is clear of obstruction, fluid flows easily through it.
2. I disconnected all lines from the ABS. Fluid flows easily from the master cylinder lines to the ABS block.
3. There seems to be excessive restriction through the ABS. With my turkey baster, I can pump fluid from the line at the non-working caliper back through the ABS although it seems a bit restrictive. I was able to pump fresh fluid through it until clear. The original fluid was fairly dirty looking.
When I connected everything back up, nothing will come out the line going to the caliper. Even when I take the caliper line and put a lot of suction on it while pumping the brakes - not a drop.
I assume I have a problem with the ABS assembly or the master cylinder or both. I just assumed the problem was the caliper originally. but I suppose that was wrong. Since the right front caliper works, I have to assume I need to change the ABS assembly.
FYI, I have not ever removed lines from the ABS so I don't know if it is supposed to be restrictive or not. Please advise. I would have assumed that it would not be restrictive during normal operation.
Thanks for any tips. I am trying to fix my sons car to save him some money. Looks like I got myself into a mess this time.
Thanks,
Randy
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Dear rduke411,
Hope you're well. I can't recall a post reporting a total cut-off of brake fluid flow to a caliper.
To begin to analyze what might be wrong, please identify the location of key parts, e.g., driver-side of engine bay, passenger-side of engine bay, and describe the shape of the part. This will help to make clear what part of the system to which you refer.
For example, is the "ABS block" a small steel tube-like item, on the same side of the engine bay as is the master cylinder, but below the master cylinder? Or, is the "ABS block" a large part, with a flat, aluminum-color top?
If by "ABS block" you refer to the ABS hydraulic unit (a part with a flat, aluminum-color top) I'd not remove any lines running to the ABS hydraulic unit. I cannot recall any post reporting a problem with this unit. Allowing air into the ABS hyrdraulic unit will lead to major problems.
What OBD codes, if any, have been set? When the engine is started, does the ABS light come on and stay on? Or, after start-up, does the ABS light go out, along with the other warning lights?
Hope this helps.
Yours faithfully,
Spook
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Hi Spook,
Thanks for the reply. Sorry about my incorrect terminology. The lines I disconnected were from the ABS hydraulic modulator as you suspected. I sort of figured it was bad to disconnect those lines, but I was stuck on this problem and needed a way to isolate the blockage.
I ran another quick test. I had my wife get in the car and pump the brakes while I bled the line from the good front caliper. It pumped out brake fluid freely. I believe the master cylinder line to the ABS modulator feeds both of the front calipers from one of the lines. That being the case, it appears that the only possible fault would be in the ABS Hydraulic modulator itself.
I was kind of surprised to find almost no mention of problems with this device. The only thing I can think of is that maybe my son hit the brakes and on of the solenoids got stuck when it kicked in due to crud build up. Unfortunately this part appears to be very expensive.
Let me know your thoughts.
Thanks
Randy
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Dear rduke411,
Hope you're well. I second trichard's suggestion: get a replacement from a salvage yard. These units are heavy, so ask that the supplier use a USPS medium-size flat-rate box (up to 70 pounds to any US address, for $12.35).
The job's hard part may be purging air from the system. I'd suggest having on-hand at least two quarts of DOT4+ brake fluid.
I'll try to carve-out time to read the Volvo Tech Manual covering replacement of the hydraulic unit and presumably explain how to purge air from the lines.
Hope this helps.
Yours faithfully,
Spook
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Hey Spook,
I got a used ABS hydraulic modulator for $125. The brakes are working just fine now. I replaced that part and the front calipers, rotors, and pads. It is stopping nice and smooth. I was able to get most of the air out of the modulator by placing the assembly flat on the ground with the open connections pointing straight up. It turns out the old brake lines fit those connections so used them and a syringe to force fluid into the part. Lots of bubbles came out. I left the hoses on the bottom two connections so the fluid would not drain out when I was installing it. After that I attached the top brake lines first so the fluid did not drain much when I removed the temporary hoses that were in the bottom hole. I attached the bottom two lines last. That seemed to work out OK doing it that way.
I can't believe I was so unlucky to have that part fail. Even the salvage place said they hardly get any calls for it.
Unfortunately, now I have a leaking water pump, so I guess that is my next job.
Randy
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Dear rduke411,
Hope you're well. Great news and glad to hear things are back to normal.
Your description as to how you replaced the hydraulic modulator should go into the FAQs. While these units rarely fail, having a step-by-step process will - at some point - be very useful.
Thanks for posting with the outcome.
Yours faithfully,
Spook
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Jay's suggestion is always most appropriate. If you want to edit the remarks (which I already picked up) and send them to me for the FAQ, great.
Steve
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See the 700/900 "FAQ" at the menu bar top screen left side.
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The only thing I can think to add is that the ABS unit is self-bleeding, as far as I know. At least it is on the 700 series. I couldn't see them eliminating that option in a later series. The step to bleed it is "activate the ABS system several times".
Thanks for posting the solution!
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Steve,
To answer your previous question, the brake fluid had not been flushed since I bought the car for my son around 2004. It did not appear to have any solid trash in it but it was pretty nasty looking and certainly could have contributed to the failure.
My son does not have the money or the mechanical skills to do this work on his own so he has not maintained the car properly.
Also, I would agree with your assessment that I may have not bled all the air out. It seems to be working at the moment, but I am thinking there could still be some air in the recirculation pump area. If you know how to activate it please let me know. I was thinking it is turned on briefly when starting the car, but that may be wrong. If air is in the pump area, the only way to get it out is to recirculate it into the system such that it can then be flushed out the normal way by bleeding. At least that is what I figure, but I am a novice at this. Still I am happy with the outcome, the labor charge for this repair would have been quite high for sure. The online help here is great.
regards,
Randy
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Had you flushed fluid regularly? Any reason for corrosion or dirt in the ABS system?
--
See the 700/900 "FAQ" at the menu bar top screen left side.
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Hey guys thanks for the info. I think I will try the salvage places like you suggested. I was so sure it was just a caliper, it really blew my mind when I could not get any brake fluid to it. I will let you guys know what happens.
Thanks
Randy
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never heard of one failing before. find a used one at a junk yard.
they almost never sell them because they don't break so the cost will be small
this yard in south carolina http://www.carguts.com/ shows dozen abs pumps listed at a cost of 14.95 each.
even with shipping its dirt cheap.
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never heard of one failing before. find a used one at a junk yard.
they almost never sell them because they don't break so the cost will be small
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