Dentside Questions

[LEB Ben]

My dentside Bronco has been sitting since about May, I drove it around last night and my dad did today...and some issues arose that I've either forgotten about, or developed while sitting.

1) Minimal stopping power, and the pedal has some resistance to begin with, but then drops to the floor. If I two foot drive and keep the rpm's up, the pedal firms up. I can never remember the difference in syptoms between MC and booster. I believe this to be a brake booster issue, correct? Braking system has had new shoes, pads, wheel cylinders, springs, calipers and MC replaced in the last 18 months...only thing not touched is the Booster. All underhood vacuum lines have been replaced in the last 18 months.


2) What is the vacuum operated plunger looking thing behind the dash that handles HVAC controls. And there's another item right behind the HVAC controls that tends to leak, what's it called? Sorry the descriptions aren't that great, but I figure there's not much back there, I just don't know what they're called.

3) While in park, idle is super high...while in gear idle is super low. Simple curb/high idle adjustments? Other possible issues?

 

[Alvin in AZ]

What resistance to ground did you get with the volt/ohmmeter?

My '75 F150 shows ~infinite between the removed positive battery
clamp and ground.

All underhood vacuum lines have been replaced in the last 18 months.

That don't mean they ain't leaking now.

But either way, bypass all that stuff inside by pulling the vacuum hose
off and plugging it along with the brake booster. If it runs good again,
hook that stuff back up one at a time.

2) What is the vacuum operated plunger looking thing behind the dash
that handles HVAC controls. And there's another item right behind the
HVAC controls that tends to leak, what's it called?

Page 36-61-10, Ben.
Volume 3 & 4 Electric & Body
I know you got the books and I know you don't like looking at 'em.

Other than the procedures, I'd read mine before the dangged pickup
showed-up at the dealership. Realized I should've ordered a 390 too. :/

3) While in park, idle is super high...while in gear idle is super low.
Simple curb/high idle adjustments? Other possible issues?

Sounds like it could be a vacuum leak to me plus a little too rich on
the idle mixture? Is your choke opening like it should?

Alvin in AZ

 

[Mil1ion]

Alvin the Bronco is a 79 ..different than 75

I just bet the PPV is rusted completely and needs replacing (Hydraulic)

Vacuum - You need to do a Brake Booster test to verify

HVAC

I presume you mean Vacuum Motors that redirect operations





3) What is the temp of the engine when this happens ?

 

[Alvin in AZ]

Alvin the Bronco is a 79 ..different than 75

Of course it's a different page number (I messed up! LOL

But was also thinking of the line drawing of the control system
with names for the parts etc. Is that in 36-61-xx still?

Alvin in AZ

 

[LEB Ben]

Dennis...

How or what is a brake booster test????

And the big control valve next to the chart is one of the items I was talking about. And the 'plunger thing' looks like one of the water valves.


3) it happens at all times...although curb idle is fine when the engine is still relatively cold and high idle has been knocked down, but once the engine raises to operating temp, curb idle almost kills the engine.

 

[Mil1ion]

The brake booster test is where the engine is shut off and you keep pressing the brake until all the vacuum has been aspirated....holding the brake pedal down you then start the engine and observe what the brake pedal does.Pushes toward you or falls to the floor

 

[Jolly Green]

The brake booster test is where the engine is shut off and you keep pressing the brake until all the vacuum has been aspirated....holding the brake pedal down you then start the engine and observe what the brake pedal does.Pushes toward you or falls to the floor

there's something I never heard before. Reps!

 

[LEB Ben]

^^^Me neither...and it's so simple even I can do it.

 

[m78]

.Pushes toward you or falls to the floor

What does either of those two outcomes mean ?

 

[Mil1ion]

This is all I can find.
I think It refers to a dash mounted booster with pipe threaded hole

 

[Mil1ion]

 

[BKW]

1973/79 F100/350 & 1978/79 Bronco w/factory A/C

What is the vacuum operated plunger looking thing behind the dash that handles HVAC controls. And there's another item right behind the HVAC controls that tends to leak, what's it called?

Sorry the descriptions aren't that great, but I figure there's not much back there.
That's what you think!

Ask, and ye shall receive...much more than you bargained for.

Factory installed integral A/C is combined with the heater. The A/C controls are in the same panel as the heater controls.

With factory A/C only: D4AZ-18495-A (replaced D1AZ-18495-A) .. Vacuum Controlled Heater Water Valve (Motorcraft YG-136) / Available from Ford.

Applications: Myriad 1971/79 Passenger Cars / 1973/96 F100/350 / 1975/2007 Econoline / 1978/96 Bronco / 1997/98 F250/350 Super Duty.

This POS valve is spliced into the inlet to heater core heater hose and is notorious for getting stuck in the closed/open, or partially either way positions.
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D5TZ-19B888-A .. A/C Vacuum Control Selector Valve Assy (Motorcraft YH-285) / Obsolete

This little charmer bolts to the backside of the A/C Heater control panel. All the vacuum hoses connect to it, it also contains the A/C compressor "kicker" switch.

When you slide the lever on the panel, this valve opens one damper door, closes another, also operates the water valve. Slide the lever to A/C, the "kicker" switch turns on the A/C.
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1977/79 F100/350 & 1978/79 Bronco: There are four damper door vacuum motors:

2) D3TZ-18A318-A .. Heat Door Vacuum Motor (Motorcraft YH-219) / Obsolete

1) D3TZ-18A318-B .. Heat/Defroster Door Vacuum Motor (Motorcraft YH-218 / Obsolete

1) D7TZ-18A318-A .. Recirculating/Fresh Air Vacuum Motor (Motorcraft YH-308) / Obsolete
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Sources for all these little charmers:

D4AZ-18495-A / Available from Ford =

MSRP: $34.46 / PARTSGUYED.COM price: $20.68.
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D5TZ-19B888-A / Obsolete =

ANTIQUE AUTO SUPPLY in Arlington TX has 1 = 817-275-2381.

GREEN SALES CO. in Cincinnati OH has 4 = 800-543-4959 / 513-731-3304.

CARPENTER NOS OBSOLETE PARTS in Concord NC has 351 = 800-476-9653.
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D3TZ-18A318-A / Obsolete =

NOS PARTS SOURCE in Olathe KS has 1 = 913-220-5746.
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D3TZ-18A318-B / Obsolete =

ANTIQUE AUTO SUPPLY in Arlington TX has 1.
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D7TZ-18A318-A =

No FoMoCo Dealer or obsolete parts vendor has any, or any other of these obsolete parts.