URGENT! Pressure sensor leaking! - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

T_Terror · 08-19-2004, 07:13

HELP! After enduring 2 weeks off fixing siezed calipers and twisted brake lines, ive got it all done. Today i was bleeding the brakes and did the rears, then i moved to the front and noticed that brake fluid was squirting out of the pressure sensor from the master cylinder. Please help, i can ALMOST drive my car again and just need to fix this nigling problem. I got a replacement from the wreckers and it does the same thing. ANyone?

Heres a pic to understnd waht teh hell im going on about. Ive disconnected the plug since its getting soaked in brake fluid.

T_Terror · 08-19-2004, 07:15

Oh yeah, its not the seal thats the problem,the fluid is squirting out from in between the 2 poles that connect to the plug+wires.

gordon451 · 08-19-2004, 07:26

Don't waste any more time or money -- go directly to your fave brake place & buy a new or recon master cylinder.

They are not difficult to replace, but be careful if using a recon unit -- make sure it's got a warranty!

If you work cleanly, you shouldn't need to do any more than a top bleed.

T_Terror · 08-19-2004, 19:39

IM sure its some problem with sensor. I replaced the sensor with a tapered screw and that fixed the problem but now i dont have brake lights. Id sy its too much effort replacing the entire master cylinder if the problem lies with a small pressure sensor.

Dellboy999 · 08-19-2004, 20:14

Yeah just replace the pressure sesnsor, if you have to do another bleed of brakes, then bite the bullet and get a re-con master cylinder.

gordon451 · 08-19-2004, 20:57

Well, you're right about the pressure sensor. Your problem is not only what part is stuffed, but why it's stuffed. Is it the cylinder wall? Or the piston has collapsed? The fact that you get exactly the same problem after fitting a used master cylider from the wrecker should be telling you something.

Here's why you don't replace any part of it: it is more expensive, takes more time, and does NOT account for wear in other parts of the unit.

If it's too much effort replacing the entire master cylinder -- a 10 minute job -- then perhaps you need to consider your future on the road. What's that "... saver lubrication system" beside your booster? I'll bet that took a lot more than 10 minutes to install -- and it almost certainly cost more to buy. Get your priorities right, before you kill somebody.

Stooping quickly and straightly is infinitely more important than hosing off ricers or commodes -- there is NOTHING more embarrassing than leaving the other bloke in your rubber smoke and then arsending the truck at the next lights, or T-boning somebody through the red.

T_Terror · 08-19-2004, 22:04

Sorry i dont think i explained my self properly before.

The master cylinder is working fine im getting brake pressure, the problem is with the little plastic plug that acts as a pressure sensor. I can replace the master cylinder no worries, but if the problem is limited to the little plastic screw bit that ive circled then id say its overkill to replace the whole master cylinder assembly.

I know brakes are the most important part of a car so im making sure i do it right. It seems like a simple plug-n-play job but obviously something is not right.

Thanks for your replies

gordon451 · 08-20-2004, 04:57

OK. See if I've got this straight:

You step on the brake pedal, you have pressure -- that is, the pedal stays UP -- but fluid sprays/dribbles out by the sensor switch.

Silly question: Do you REEEELLY have pressure? Or does the pedal start sinking, e v e r so s l o w l y to the floor?

I should say that I had the same problem on my XF -- exactly the same cylinder ass'y -- but I had very little pressure, the car was almost undrivable. The fluid was coming out of exactly the same place, all over the exhaust manifold.

Now it is important to understand that -- no matter what people wish to believe -- if fluid leaks out of a master cylinder, you do NOT have proper pressure in the system.

The cause in this case is either the pressure cyinder has been scored, or (more likely) the pressure piston has collapsed. It is not worth trying to fix the piston assemby, because you don't know what shape the rest of the master cylinder is in, and it's a bitch of a job anyway. I don't normally like replacing entire assemblies, but in this case I make an exception. Like I said, stopping is very important to me -- especially if I have been bending the law.

So it might look as though I haven't heard a word you said. But fluid leaking out the pressure sensor tells me straight up that you don't have pressure. It's just the way these things work.

gordon451 · 08-20-2004, 05:02

Oh yes. You say you replaced the sensor with a tapered screw and that fixed the problem.

I rest my case.

T_Terror · 08-20-2004, 08:45

SO you're saying that its leaking BECAUSE there is inadequate pressure?

The tapered screw is a temporary fix since the brake lights run off the pressure sensor. Do you think if i bled all the brakes and and had pressure back to normal and then swapped a replacement sensor then id fix the prob? (Obviously id have to rebleed again)?

Sorry, but this one really has me and anyone else stumped. Thanks Gordon 451