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Just bought myself a 1991 F250 with the IDI 7.3 in it. I love it. Its my first experience with a diesel vehicle.
My question of the day is, yesterday I was driving to town and the brake pedal got extremely hard to press all of a sudden. Coming to a normal relaxed stop takes 2 feet pressing on the pedal. I'm almost concerned I'll break the pedal off!
Is it the brake booster possibly? When the truck was off I pressed the pedal several times to get rid of any vacuum in there and held it down while starting it, and it didn't move downwards at all.
If y'all could give me some guidance, and maybe someone who has parts? That'd be awesome.
You either have a vacuum leak or more likeley your vaccum pump has failed. Diesel engines dont produce vaccum so we need a pump to run the booster, hvac controls, etc.
welcome to FTE.
i have to agree with bashby, it sounds like the vacuum pump is bad.
does the heat/vent/AC controls work, or does air only come out of the defrosters?
this is a hint that there is no vacuum, air out of the defrosters only no matter where the control is set is default position when no vacuum is present.
you need at least 17 inches vacuum for the brakes to work properly.
welcome to FTE.
i have to agree with bashby, it sounds like the vacuum pump is bad.
does the heat/vent/AC controls work, or does air only come out of the defrosters?
this is a hint that there is no vacuum, air out of the defrosters only no matter where the control is set is default position when no vacuum is present.
you need at least 17 inches vacuum for the brakes to work properly.
I do not get any air it seems on the floor, still comes out of defrost, but it comes out of the vent just fine and cuts off the defrost.
I do not know how to test for vacuum :/
sounds like the vacuum pump is shot.
start engine. step on brake pedal. it should be easy. instantly release and step on it again twice. if it gets harder first time and real hard second time vacuum pump is probably bad.
you can buy new from rockauto priced between $72 and $240, or about the same price spread from NAPA.
the new pumps do not come with a pulley though, so you will have to have the pulley pressed off your old pump and then pressed back onto the new pump.
Disconnect the line from the vacuum pump and start the engine. If you put your finger even near the line fitting, and the pump is working, you'll feel it sucking.
Your truck has v-belts, right? First thing to check is the vacuum pump belt. IIRC, even with air-conditioned trucks, it's a stand-alone belt going from the alternator down to the vac pump.
Pulley tool is usually available at the auto parts chain store as a loaner. Or it can be purchased at Harbor Freight; it's the puller/installer tool used for power steering pulleys.
So... I should have done this first, and I apologize, I looked under the hood at my alternator (because my battery light came on the same time the brake problem started - I was gonna test that later) and the belt that runs it to the fan is gone... I found a couple pieces of it scattered around. So. What size belt is that, and does it run just alternator to the fan? Or does it route to the pulley underneath the fan too? Does anyone have a belt diagram picture?
thank you tjc, that's exactly what I needed. Thanks a ton guys.
and a couple of belts is a heck of a lot cheaper than a vacuum pump!!
tighten the vacuum pump belt first, then make the alternator belt tight.
this is a long time problem with these trucks, the vacuum pump pulls at a weird angle, so if you tighten the alternator belt before the vacuum pump belt the alternator belt will loosen up real quick.
also, you will always get a lot of deflection out of the belt because there is so much empty space between the alternator and water pump pulley.
well i hope it clears up for your sake.
i know from experience that job sucks when it is 10 degrees out and snow is falling. been there and done that more than once while out plowing and the damn thing decided to throw the belts off.
i always carry 2 spare sets of belts in the trucks just for that reason.
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