Problems replacing brake fluid..need help please...

593 Views 9 Replies 6 Participants Last post by maclafm, Nov 16, 2010

zucker

Discussion Starter · Nov 14, 2010

Trying to replace dirty old brake fluid but having problems pumping the old stuff out of the caliper bleed screws. First of all I had a heck of a time getting the cap off the BMC resevior. The rubber gasket was stuck on and all wrinkled up under the cap. Big channel locks did the job but the rubber gasket is no longer attached to the cap??? Hope I can find a new cap.
I used a turkey baster to remove as much of the old fluid as possible being careful to leave enough at the bottom as not to let air in. Anyway, I proceded to bleed the RR using the traditional pump the pedal and losen the caliper bleeder screw method. The first couple of times netted plenty of fluid out but then no more fluid would come out. Yes the resevior remained full. Realizing afterwards that I should have started with the LR first I moved over and tried to bleed that side but no fluid would come out at all.
Brake pedal just goes to the floor without much resistance. I put everything back together and went for a test drive and now my once very good brakes have been reduced down to very little at the floor. My buddy thinks it might the the BMC but it was working fine before...Any suggestions? How can I bleed the system if no fluid will come out??? The bleed screws were opened all the way up and still no fluid.

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salvadoran300zx

· #2 · Nov 14, 2010

what year is it again? some 90 models had some bleeder screws on the ABS pump...

second, make sure you have closed all other screws with some fluid on the threads to ensure 0 leaks.

and fluid should come out once the pedal is depressed.

I'd recommend attaching some clear 1/8" hose to the bleeder screw and leave it open and pump away. That should show you the air bubbles on the fluid as it is coming out.

but if no fluid is coming out, that just means there's air somewhere and the order in which you bleed them has never been an issue to me before

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zucker

Discussion Starter · #3 · Nov 15, 2010

Thanks for the reply. It's a 91' 2 + 2 w/167k miles. UPDATE: I drove her to work this AM and the brakes wouldn't work until almost at the floor and very soft. After 15 mins or so the brakes came back and were very strong at the top again almost to where it felt like they were applying themselves when coming to a stop as I could let off them and when coasting they would stop the car without any pressure on the brake pedal. So, when cold they are soft and at the bottom of the pedal and once hot, after driving for a while, they work super good, too good.
So, when I got home I tried bleeding them again when everything was still hot and still only a very little bit of brake fluid will come out of the bleed screw. The brake pedal was very firm and remained at the top, it didn't want to go to the floor. I pressed very hard and it would not go to the floor. Yesterday when attempting to bleed a cold system the pedal was easy to smash to the floor as it had no resistance. So i'm thinking that I may have water/air in the lines that expands when hot but I can't figure out why I can't get a good flow of brake fluid to come out of the bleed screws when bleeding.

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Cuis-Z

· #4 · Nov 15, 2010

That's really strange. It sounds like you may have some type of obstruction in a line(s). You may want to verify that each wheel can spin freely with no brakes applied.

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salvadoran300zx

· #5 · Nov 15, 2010

try this then, get again a clear hose to attach to the bleeders open them and let the car sit with the bleeders open and the hoses on a can. pump until there is no more fluid on your reservoir and start from zero once more.

I can understand some contamination on the lines, but most likely you are just being impatient or not opening the bleeders enough. Ask me how I know about being impatient when it comes to brakes :

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4-EZT

· #6 · Nov 15, 2010

i agree with Sal. I replaced the old lines with SS lines and did them all at once. I bled the car dry. I filled the res with new and per FSM bled the brakes. I know Lum doesn't like the "one man bleed screws" but i dig em MUCH. Waaaaaaay easier.

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Cuis-Z

· #7 · Nov 16, 2010

I want one of these;
Linkage

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zucker

Discussion Starter · #8 · Nov 16, 2010

Those are sweet but I think my BMC is toast and is not letting the fluid pass from the reservoir down the lines to the bleeders. May try a BMC rebuild kit.

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Billy The Kid

· #9 · Nov 16, 2010

If I remember right last time I did it I had the best results by putting the car up on jack stands and bleed the breaks (RR, LR, RF, LF, ABS-R, and ABS-F) while car is running. Only pump 3 times and check fluid.

NOTE: This works great for bleeding clutch also.

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maclafm

· #10 · Nov 16, 2010

I know that when you are trying to bleed them cold that the pedel goes to the floor, but are you pumping them to build up pressure?? When you drive it for a while, the pressure in the lines does not equalize as fast as you use the breaks resulting in the improvement in feel as you drive. So, when you bleed them, make sure you pump the pedal 3 or 4 times to make sure you have a LOT of pressure in the lines and THEN crack the bleeder screw with the pedel depressed. btw if it is a master cylinder problem, youre probably better off just getting a new one. A new master cylinder is $80 more than a rebuild kit, but I'd rather save the time rebuilding it and be certain that it's going to work when it's supposed to. The last thing you want to be cheep on is your brakes!

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