No brakes, pedal rock soild...

[bladerunner3]

My '91F-250 IDI has always been hot in cab in summer. Would turn heater controls to "off" to not allow any air at all to come out of vents in summer but would still be hot in cab.(truck has no A/C so just roll down windows and go fast in summer. No problem in winter, have plenty of heat. Just re ently found that a mouse had chewed the white vacuum line going into the heater box. Thie point it is in two is on the left of engine compartment. The white vacuum line is a small diameter white tube, easily seen as it is on top of some other lines going into same same heater box. Has been that way for who knows how long. Truck has always seemed hot in cab sinch I have owned it, so maybe last 5 years. I have noticed that if I brake hard and then for some reason let up and brake again that I don't always have good boost. Give it a few se conds and the boost is there again.
So the pump is probably having a hard time staying ahead of demand with the small leak. Will try to fix this problem soon and give a report on whether it helped the brakes or not.

 

[madmax401]

My pedal is rock hard and all the major components such as master cylinder,power brake booster,proportioning valve and Vaccuum Brake pump all replaced this week. Still rock hard pedal and not as spongy as before.

Low vacuum warning switch 12A182 is the only other component it could be.
No vacuum leaks anywhere .
Apparently 12A182 is no longer available thru ford or any local parts stores.
Is there a superceded part number that'll help me locate the new low vacuum warning switch ?
I don't have a vacuum gauge other than a mighty vac pump to check pressure.
Any help or advice would be much appreciated.

 

[79jasper]

Check the vacuum with the mighty-vac.
The warning switch doesn't matter, unless it's leaking. You can just plug it off.

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[madmax401]

I have also noticed that the white plastic vacuum line has been eaten or just dryrotted. The low vacuum switch looks older than dirt..... Definitely want to replace it any regardless. Any suggestions on recoupling the white vacuum by slipping rubber vacuum line over the ends ?
It didn't appear to be leaking,lacking or drawing vacuum prior to the new pump installation. Gonna check it tomorrow with a spray bottle. These brakes went while I was pulling 7 ton trailer with a vette on it (scared the crap outta me) manually slowed down by dropping down to 1st.

 

[79jasper]

That white one is for the max a.c. setting, but yes, chase it back into the harness to a good spot, slip vacuum line on.
I can't say for the vacuum switch. I'm sure there's a way to test it. Well, disconnect the hose and see if your brake light comes on.

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[madmax401]

That would certainly explain why my AC doesn't get as cold as it should and also why there's more heat in the cab than there should be unless I have all heater controlls off.
I'm goin to attempt to chase down any and all vacuum system leaks and try to measure vacuum readings somehow.
I found a part number for the : LOW VACUUM WARNING SWITCH - 12A182 (sw1794).
Called local ford dealer this morning with vin number as well as part number.
No longer available and no superceded part number,no notations,no further information available to R&R this defective component.
I ask this question..... How can ford discontinue a part and not have information on how and where to upgrade ?
I beg the tech savvy ford guru God's to answer my request and help solve my issue .
Many times I will hit a wall that after time I will eventually get around..... This wall seems to have no alternative direction :-(

 

[79jasper]

You'll have to find a used one. Post a add in the wtb section and visit the part out threads.
That white line may have a little to do with it, but I would bet your blend door is stuck.

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[madmax401]

I located 1 out of state in a warehouse. Now I'm heading to my local dealer to purchase it for me . apparently you can't just give them a credit card over the phone anymore.
I did the lip on vacuum hose test and dann near lost my lip.....we have an incredible supply of vacuum

 

[79jasper]

Well.... Could just be a bad booster. Lol

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[madmax401]

Good guess.......booster , master cyl & vacuum pump are all brand new non remans.

 

[79jasper]

And your point is?
Just search the forum about new parts.

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[madpogue]

Of all the parts you threw at it, what did you TEST?

Have you tried running a vacuum line directly from the pump to the booster, just as a test?

 

[madmax401]

No , I haven't done that .
A few months ago I replaced the proportioning valve due to the rear brakes not getting any fluid pressure master was working fine. That solved that issue. Then my pedal had great pressure initially after 1 pumps but would start creeping to the floorboard. We bled it in the shop with a snap on automatic blender machine.
Still slowly mushes to floor (hm). Then the pedal would intermittently get super hard and not stop the truck, so I just got a new master, vacuum pump and booster to upgrade everything new.
I don't have any leaks in the system...fluid or vacuum. I have more than sufficient vacuum coming off the low pressure warning switch. I'm assuming the low pressure switch might be malfunctioning. there aren't any other components to change at this point.
Spending the money on new parts is a worth while investment to insure more trouble free years of service since I'll be hauling a heavy 5th wheel Frito lay cargo trailer.
Just better safe than sorry .

 

[79jasper]

Again, there's nothing with the low vacuum warning switch to cause your issues. (You said it doesn't leak)
Your sinking pedal is rear brakes out of adjustment. You have to manually adjust them on these trucks. Heavy driving/towing even more often.
Best way is to jack the tires off the ground, and tighten until you feel a slight resistance. After awhile you'll get a feel for it.
I know you don't want to, but you need to go warranty the booster.

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[madmax401]

I have less than a thousand miles on the truck since I last pulled the dorms and adjusted the shoes to snug the drum. Did that when I changed a leaky wheel cyl.
I'll definitely recheck everything to make sure they didn't back off.
I appreciate the insight