1994 Grand Prix 3.1 Liter Brakes

1lasttime
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1994 Grand Prix 3.1 Liter Brakes

Unread post by 1lasttime » Thu Sep 05, 2013 9:21 pm

I really hope someone can assist me, here.

My car has had the rear brake pads, calipers and rotors replaced. I bled out all the old brake fluid without running the master cylinder dry. Now for the problem... my car sits... a lot. It doesnt really get driven, yet as i have had a few other issues which i have been fixing. I went to take it for a test drive and the brakes are REALLY tight. They build pressure without pumping the peddle. If i press the peddle, there is barely any play. I can open a bleeder valve and fluid will spray out and all the pressure is gone, but if it sits for a day or so, the pressure is back. This is without my car being started. I have checked the brake booster for a valve leak, and there isnt one.

Again this is a 1994 Grand Prix 3.1 liter SFI

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carriedi
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by carriedi » Fri Sep 06, 2013 11:24 pm

which bleeder screw do you open to release the built up pressure? If you open a different bleeder screw do it do the same thing? You may have a damaged brake hose. sometimes they collapse on the inside holding pressure to the caliper the feed. Does this happen to all four bleeders or just one? Does your car have ABS? it says it was optional for your year and model. It should also have diagonal braking. So if you have pressure holding in the system it should be tied to LF/RR or RF/LR. If it only hangs up on one wheel it's probably the hose.
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by 1lasttime » Sat Sep 07, 2013 11:02 am

carriedi wrote:which bleeder screw do you open to release the built up pressure? If you open a different bleeder screw do it do the same thing? You may have a damaged brake hose. sometimes they collapse on the inside holding pressure to the caliper the feed. Does this happen to all four bleeders or just one? Does your car have ABS? it says it was optional for your year and model. It should also have diagonal braking. So if you have pressure holding in the system it should be tied to LF/RR or RF/LR. If it only hangs up on one wheel it's probably the hose.
I have released the pressure from the driver front and rear. It does not have ABS. I have seen where it can be the booster or the master cylinder, but the symptom of all brakes locking up isnt there. Its just the rear getting really tight.

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carriedi
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by carriedi » Sat Sep 07, 2013 3:35 pm

I am still a little unclear what you mean. So you have released the pressure by opening the bleeder on the LF and the LR? Both the front and rear had a pressure build up? Did you check the right side? Did you check the LF and it had pressure and you released the pressure and then went to the LR and it had pressure after you released the pressure from the front? Or was it done at different times?

Here's the thing, the master cylinder has ports built into it to allow the pressure to return to the master when the pedal is returned to the normal position. When you step on the brake pedal these ports are closed to allow pressure to build up and go to the brakes. If you have a pressure build up it should be because there is something not allowing the fluid to return to the master. Things that affect this are like the master not returning all the way back, contaminated brake fluid that is damaging the rubber components, damaged brake hoses that may have been pinched closed during a brake installation to keep the lines from leaking, wrong master that is made for drum brake so it has a check valve for drum brakes to mention a few.

However, this will not cause a brake fluid pressure build up over time. It causes a brake fluid pressure retention from the last time you stepped on the brake pedal. Are you saying the after you bleed off the pressure and do not press on the brake pedal a few days later you have a pressure build up again? Like it's building up pressure over time?
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1lasttime
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by 1lasttime » Sat Sep 07, 2013 4:08 pm

carriedi wrote:
However, this will not cause a brake fluid pressure build up over time. It causes a brake fluid pressure retention from the last time you stepped on the brake pedal. Are you saying the after you bleed off the pressure and do not press on the brake pedal a few days later you have a pressure build up again? Like it's building up pressure over time?
^ that last part is exactly what i am saying. The bleeding was done at separate times. Yes i did the Lr the first time it happened, the next time it was the Lf. Fluid sprayed out. The master cylinder isnt showing any signs of pressure being built up when it is.

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carriedi
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by carriedi » Sat Sep 07, 2013 7:57 pm

ok, the next time it feels like there is pressure causing the brakes to drag don't touch the bleeder screws. crack the line at the master cylinder and let some fluid seep out.. If you have pressure at the master you have lessened the area you have to check. Now you know the master is not letting the fluid back. But if you don't have pressure at the master where the line connects, you just have some gravity fluid seepage, then check the bleeder screws. If you have pressure at the bleeder after you checked it at the master, then you have a brake hose problem. (most likely)

brake fluid is made so that it's properties won't allow for it to expand under normal conditions. It must expand to build up pressure if no other action has been acted upon it. Dot 3 brake fluid boils at 400F so it shouldn't be expanding. If your brake fluid has been contaminated with anything besides dot3 then the seals in the master may expand from the contaminated fluid and close off the return port. It's just a possibility. I have seen many examples of brake fluid contamination. Seals and boots can swell up more than double their original size.
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by 1lasttime » Sat Sep 07, 2013 8:49 pm

Awesome! I will definitely do this. Thank you for your time! :)

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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by 1lasttime » Sun Sep 15, 2013 6:42 pm

carriedi wrote:ok, the next time it feels like there is pressure causing the brakes to drag don't touch the bleeder screws. crack the line at the master cylinder and let some fluid seep out.. If you have pressure at the master you have lessened the area you have to check. Now you know the master is not letting the fluid back. But if you don't have pressure at the master where the line connects, you just have some gravity fluid seepage, then check the bleeder screws. If you have pressure at the bleeder after you checked it at the master, then you have a brake hose problem. (most likely)

brake fluid is made so that it's properties won't allow for it to expand under normal conditions. It must expand to build up pressure if no other action has been acted upon it. Dot 3 brake fluid boils at 400F so it shouldn't be expanding. If your brake fluid has been contaminated with anything besides dot3 then the seals in the master may expand from the contaminated fluid and close off the return port. It's just a possibility. I have seen many examples of brake fluid contamination. Seals and boots can swell up more than double their original size.

Okay, I did as you suggested and there was pressure between the master ans the lines. I bought a new master, bench bled it until there was only fluid in the clear tubes, no air was being pushed into the reservoir. I placed it onto the car and removed the bleeder parts and put on the brake lines one by one. Went to bleed the brakes and there seems to be air in the master still? I am at wits end and i dont know what i could have done wrong if anything? Can someone tell me the process from square one? Starting with the master?

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carriedi
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Re: 1994 Grand Prix 3.1 Liter Brakes

Unread post by carriedi » Mon Sep 16, 2013 12:42 am

you can use the tubes that come with most masters to bench bleed them. Run the tubes so that they are under the fluid level inside the master. Pump the master slowly all the way from stop to stop until you have a few strokes that have just fluid and no bubbles. OR, toy can put in plugs onto the ports instead of the lines and pump the master and watch the bubbles that come back through the port inside the reservoir until the master won't compress because all the air has been bled out. Then install on the car.

Now, when you said there seems to still be air in the master, what makes you think that? You see air bubbles? Spongy pedal? Air out of the bleeder screws when bleeding?
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