Diagnosing a power brake booster problem
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Mountain Pass
Joined: Jan 2003
Posts: 102
Likes: 1
Diagnosing a power brake booster problem
Hi all,
I suspect I already know the answer to my question, but I'm gonna post it here anyway, 'coz I've always had good luck here with people guiding me right to the problem.
I got my 1990 F250 4.4, 7.3l IDI home tonight, and noticed that the brakes were suddenly a lot of work. It would stop, but needed a lot of foot effort. My immediate thought was that it might be my vaccuum pump - I had replaced it six months before, and I know that the rebuilds can be "touchy".
I pulled a vaccum line off (from some sort of switch, not sure what that is...), and hooked it up to a guage. 5inches of vacuum @ idle, climbing up to around 10 at revs. Hitting the brakes would immediately drop the vacuum right down to about zero. I let the vacuum build up again, switched off the engine, and the vacuum stayed the same. Hitting the brakes would immediately drop the vacuum to zero.
So, sounds pretty likely I need a new brake booster, but I thought I'd post here to see if there is any more diagnosis I can do just to be sure...
Thanks,
Chris.
I suspect I already know the answer to my question, but I'm gonna post it here anyway, 'coz I've always had good luck here with people guiding me right to the problem.
I got my 1990 F250 4.4, 7.3l IDI home tonight, and noticed that the brakes were suddenly a lot of work. It would stop, but needed a lot of foot effort. My immediate thought was that it might be my vaccuum pump - I had replaced it six months before, and I know that the rebuilds can be "touchy".
I pulled a vaccum line off (from some sort of switch, not sure what that is...), and hooked it up to a guage. 5inches of vacuum @ idle, climbing up to around 10 at revs. Hitting the brakes would immediately drop the vacuum right down to about zero. I let the vacuum build up again, switched off the engine, and the vacuum stayed the same. Hitting the brakes would immediately drop the vacuum to zero.
So, sounds pretty likely I need a new brake booster, but I thought I'd post here to see if there is any more diagnosis I can do just to be sure...
Thanks,
Chris.
Post Fiend
Joined: Nov 2004
Posts: 5,638
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From: Manitoba
Thread Starter
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Mountain Pass
Joined: Jan 2003
Posts: 102
Likes: 1
Thank you!!!! So I did the Vacc test, and indeed, it was the vaccum pump that was dying. Don't you hate it when new parts die after six months...
So, I picked up a new one ($125, because I couldn't find my
receipt for the last one), swapped the brackets and pulley (10mm socket need for the brackets, and a GM power-steering pully puller/installer for the pulley), bolted it on and started her up, Vacuum was straight up to 25 inches. buttoned everything up, and the brakes are now fine.
Thanks again, this website has saved me so much time and money!
Regards,
Chris.
So, I picked up a new one ($125, because I couldn't find my
receipt for the last one), swapped the brackets and pulley (10mm socket need for the brackets, and a GM power-steering pully puller/installer for the pulley), bolted it on and started her up, Vacuum was straight up to 25 inches. buttoned everything up, and the brakes are now fine.
Thanks again, this website has saved me so much time and money!
Regards,
Chris.
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