no back brakes
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Freshman User
Joined: Jun 2002
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no back brakes
morning every one out here in computer land!!
Once again I think I did something bad. The last camping trip went totally bad, on the way home I blew a back brake line, all the fliud dripped out first stop was a surprize! anyhow I pulled over cripped the bad line off THEN put 10w30 oil in the res. got home with trailer/front brakes, replaced the line. bled the brakes (that radII) also but can't get the back brake to work fronts work fine. Did the motor oil mess up the master cylinder? The front didn't loose all its fluid. Need help once again Thanks mark
Once again I think I did something bad. The last camping trip went totally bad, on the way home I blew a back brake line, all the fliud dripped out first stop was a surprize! anyhow I pulled over cripped the bad line off THEN put 10w30 oil in the res. got home with trailer/front brakes, replaced the line. bled the brakes (that radII) also but can't get the back brake to work fronts work fine. Did the motor oil mess up the master cylinder? The front didn't loose all its fluid. Need help once again Thanks mark
Senior User
Joined: Sep 2002
Posts: 431
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From: Midwest
no back brakes
The oil should not have messed up the master cylinder. A couple of potential problems exist here however. Motor oil is thicker than brake fluid and may take more bleeding, if you have a vacuum pump it would be a good idea to use this to make sure all motor oil is out of the lines. You might also want to check that brake and the wheel cylinders. Pull the cylinders take them apart clean them real well and then reinstall them. Wheel cylinders are not that hard to rebuild. I assume since it is bleeding you don't have a plugged line so try those two choices out and if it doesn't work let us know and we will try something else.
Posting Guru
Joined: Oct 2000
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From: Southern MD
no back brakes
I remember a vehicle I once had, had the same problem. I looked in the shop manual, and there is a pin on the proportioning valve that has to be pushed when bleeding. Check the manual and see if it applies to your vehicle.
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'94 E-150 Conversion Van 4.9 / C-6 -- '89 Mustang LX 5.0
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no back brakes
How do ya know if you need a new master cylinder? I've done the graivty bleed down this morning,put all new fluid in the m/s the brakes work good for 2-3 stops than no back brakes. Could the back part of the m/c be bad? thanks mark
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From: Southern MD
no back brakes
[updated:LAST EDITED ON 29-Sep-02 AT 10:21 AM (EST)]What year truck do you have?
You used to be able to tell if you had an internal leak by putting pressure on the pedal, if the pedal went down, it was leaking. I'm not sure about the dual type cylinders.
I wouldn't think engine oil would be good for the system, I'd get it flushed out real good, then start from the basics. It's makeup is entirely different from brake fluid.
Did you check the proportioning valve for the plunger I mentioned?
-------------------------
http://easyad.net/images/94vanavitar.jpg http://www.easyad.net/images/mustang1.gif
'94 E-150 Conversion Van 4.9 / C-6 -- '89 Mustang LX 5.0
You used to be able to tell if you had an internal leak by putting pressure on the pedal, if the pedal went down, it was leaking. I'm not sure about the dual type cylinders.
I wouldn't think engine oil would be good for the system, I'd get it flushed out real good, then start from the basics. It's makeup is entirely different from brake fluid.
Did you check the proportioning valve for the plunger I mentioned?
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Freshman User
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no back brakes
van man, I have a 1994 f-150, what you just said about the pedal going down made me think, before I couldn't get back brakes the pedal would go almost to the floor with slight pressure but holding it hard the pedal would stay firm. I'll bet my inner seal have gone bad.
Thanks alot mark h
Thanks alot mark h
Elder User
Joined: Oct 2001
Posts: 750
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From: Buena Vista
no back brakes
Hey toy man, your right your master cylinder is bad.
What happened is when your rear brakes went out and your pedal went all the way to the floor, the (LIP) seal slid across a part of the bore that it hasn’t been in years, and it probably had gunk or even dirt on it. This seal going across the gunk will destroy it, and cause the symptom you have.
If you would like me to explain this more I can.
94van you’re talking about the metering valve that you have to push the pin in.
There is not one on his application, the metering valve closes pressure to the front brakes, and opens at 75-300 psi, and so the rear brakes can travel to the drum. It was mostly used on front engine rear wheel drive cars.
I can explain these in more detail if you like.
What happened is when your rear brakes went out and your pedal went all the way to the floor, the (LIP) seal slid across a part of the bore that it hasn’t been in years, and it probably had gunk or even dirt on it. This seal going across the gunk will destroy it, and cause the symptom you have.
If you would like me to explain this more I can.
94van you’re talking about the metering valve that you have to push the pin in.
There is not one on his application, the metering valve closes pressure to the front brakes, and opens at 75-300 psi, and so the rear brakes can travel to the drum. It was mostly used on front engine rear wheel drive cars.
I can explain these in more detail if you like.
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Hotshot
Joined: Aug 2002
Posts: 12,679
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From: BC, Canada
no back brakes
Oil will destroy the master cylinder, wheel cylinders and caliper seals as it causes the rubber seals to swell up. In an emergency water is better to use as brake fluid than oil. Usually if you change the fluid soon enough it wont cause any rust problems in the lines etc. The water will boil in the system though which will cause a loss of brakes so you dont want to drive far or fast with it.
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