Brake boost failure

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Feb 2, 2004 | 12:50 PM

kmans777

Thread Starter

Senior User

Joined: Feb 2003

Posts: 192

Likes: 0

From: Puyallup, Wa.

Brake boost failure

Hi guys, just lost all power assist to the brakes on my 88 Ranger. The pedal is hard and the brakes operate just the way they do with the engine not running. I found some troubleshooting tips and tried them. Check for vacuum line blockage. None. Pinch off vacuum hose to booster and check for rpm increase. None. Listen for hissing from under dash when brakes applied with engine running. None. The engine rpm does increase by about 500 when I push on the brake pedal. This I don't recall as being normal. I was having some idling problems along with a fuel pressure regulator that was bad. After changing the FPR the truck wouldn't idle once warmed up. So as a temporary fix til I had time for further troubleshooting I bumped up the idle using the adjustment screw on the throttle body. I know this is not the way to do it, but needed the truck driveable for a few days. Could this have some effect ? Also went to this site: http://www.mightyap.com/Data/gb0802.pdf. Gave me enough doubt that I didn't run out and buy a new booster. Any help appreciated.
88 Ranger XLT 2.9L 4X4 5Spd

Last edited by kmans777; Feb 2, 2004 at 12:54 PM.

Feb 2, 2004 | 07:00 PM

Dealford

Cargo Master

Joined: Aug 2003

Posts: 3,237

Likes: 3

From: Belleville, Ontario

With the idle rpm increase when the brakes are applied, sounds like the diaphram in the booster is leaking. This could also explain why the truck doesn't idle very well.