'87 Ford Ranger - Repeated brake booster failure

[dfinn]

Hey folks - new guy here.

I've got a 1987 Ranger - 2.9L, 5spd, Electronic 4WD, Ext. Cab, shortbed. The track has an aftermarket second fuel tank. Bought it a few months back, because the body (even though a little dinged up) was nearly rust free, and the frame was excellent for a New England truck of it's vintage.

Here's my issue:

I have replaced the brake-booster three times in the past two months, and the booster failed on me again tonight. Some specifics:

The booster that was in the truck when I bought it (May) seemed older -- like it was either the original, or an OEM from some time back.

When it failed, there was a great deal of fluid in the booster, but not brake fluid (the brake reservoir was fine). Actually, it smelled like gas.

i replaced it with a reman booster from the local NAPA auto parts.

That booster failed in about three weeks.

I then took the truck to a friend's service shop, and he replaced the replacement (lifetime warranty is a good thing).

THAT booster failed in about two weeks.

My friend replaced the booster again, making sure to adjust the booster rod, and check things out all over.

That was two weeks ago, and the booster has failed again, tonight.

(...and the folks who heard me at the time, well, they knew I wasn't happy...)

So, I'm wondering a few things:

- How could gasoline get into the booster in the first place?
- Could it be causing the booster to continuously fail?
- Could it be a bad install of the second fuel tank?

i don't use the original tank - the second one seems to be the one that's connected to the fuel system, and the gas gauge.

Your thoughts, comments, would be appreciated.

Thanks!

- Finn, Massachusetts

 

[Hopman]

Finn, welcome to TRS.

This is baffeling me. Where in Mass are you? I'm from NH but am doing a temp gig in Westford next week.

Okay we know this:

- The booster smells like gas an NOT brake fluid.
- Your truck has killed THREE of them since May.
- There's an aux fuel tank.

I could be wrong, but I'm guessing that SOMEHOW gas is getting into the brake line (be it crossed lines from the old tank or something more nutty) and killing the booster.

This may sound like a stupid question on my part, but when was the last time the brake system was flushed? If I recall, doesn't brake fluid get corrosive over time?

The other option is that you've just had a string of bad boosters.

 

[kunar]

yeah i would be vary suspicious about that fuel setup too... any sign of fuel going through the vacuum line? any fuel leaks elsewhere?

even if the brake fluid was bad for whatever reason, it shouldnt come in contact with the inside of the booster. are you losing brake fluid?

 

[TimV]

Sounds like you have fuel coming through your vacuum line into the booster. Gas will make the rubber diaphragm in the booster expand, and ruin it. Theres only one vacuum line that runs to the booster. Now you just have to figure out how gas is getting into it.

 

[adsm08]

Your fuel pressure regulator has failed.

It's a vacuum actuated diaphragm that provides a signal that is directly related to the engine's throttle position. Since one side is open the the fuel rail and the other side is open to the vac system, when it breaks you get gas in the vac system, and the brake booster. Gas does a number on the rubber in the brake booster.

 

[kunar]

Your fuel pressure regulator has failed.

It's a vacuum actuated diaphragm that provides a signal that is directly related to the engine's throttle position. Since one side is open the the fuel rail and the other side is open to the vac system, when it breaks you get gas in the vac system, and the brake booster. Gas does a number on the rubber in the brake booster.

thats a very good point, although that much fuel going into the engine should make it run pretty bad....

the sure fire way to check is to pull the vacuum line off of the fuel pressure regulator (bolted to the fuel rail, i believe its on the drivers side near the back)

if it has failed, there will be gas in the line. if its dry, its good.

 

[adsm08]

I agree that you'd probably see some sort of driveability issue, but if that much fuel is running into the vac system it may be keeping pressure in the right spot.

The thing is though, there really isn't another available answer. There is no other spot that the two systems touch, and there is really only one automotive fluid that smells like gas, and that's gas.

 

[LIMA BEAN]

Your fuel pressure regulator has failed.

It's a vacuum actuated diaphragm that provides a signal that is directly related to the engine's throttle position. Since one side is open the the fuel rail and the other side is open to the vac system, when it breaks you get gas in the vac system, and the brake booster. Gas does a number on the rubber in the brake booster.

Yep mine did the same thing.

 

[gwaii]

Your fuel pressure regulator has failed.

It's a vacuum actuated diaphragm that provides a signal that is directly related to the engine's throttle position. Since one side is open the the fuel rail and the other side is open to the vac system, when it breaks you get gas in the vac system, and the brake booster. Gas does a number on the rubber in the brake booster.

i'm in with this camp.makes sense.

 

[dfinn]

Re/ '87 Ford Ranger - Repeated brake booster failure

Hey -

Thanks to ALL of you for your thought.

Hopman: I'm in Western Mass, towards Erving on the north (route 2) side of the state.

Kunan: No signs of brake-fluid loss -- the fluid reservoir seems to be right up to snuff, seems to contain only brake fluid (by the texture and smell), and has been since this adventure began.

Tim V: Agreed -- The more I thought about it, the more that some sort of fuel/vacuum crossover made sense.

Adsm08, Lima and Gwaii: Thanks for the support on Adsm08's strong finger pointing to the problem. This makes sense for a few reasons:

The engine doesn' really run all that well; and
I haven't been losing brake fluid or fuel (still getting about 23 mpg, actually).

I'll be putting the truck on the lift in the morning, and checking the entire fuel-delivery system, including the fuel-pressure regulator.

Thanks for the input, and I'll follow up tomorrow.

- Doug.

 

[TimV]

Since everyone is pointing to the regulator, it would probably be a good idea to change it anyways. Also, I would suggest changing your oil at the same time, since there is a good chance it is also fouled with fuel.

 

[Hopman]

Finn, you're a little far out for me to be of any use.

Even if I may not have had the right answer, maybe I put somebody on the right track.

It is ALWAYS our pleasure to help another Ranger owner. Better to have asked the question and confirm what you thought that not to ask it and make something totally FUBAR.

 

[superds]

Your fuel pressure regulator has failed.

It's a vacuum actuated diaphragm that provides a signal that is directly related to the engine's throttle position. Since one side is open the the fuel rail and the other side is open to the vac system, when it breaks you get gas in the vac system, and the brake booster. Gas does a number on the rubber in the brake booster.

I agree 100%. I replaced my fuel pressure regulator after replacing my brake booster twice in a month. Problem solved. Brake booster has lasted 3+ years now.