Got a bit of a problem on my truck. Need a replacement part and don’t know what it is called. Early 70’s Ford 302 V8. The engine intake air temperature is regulated by a vacuum motor which controls a flap in the air cleaner ass’y. The flap opens and closes to adjust the proportion of cold and air heated by the exhaust manifold. It’s done to reduce emissions on cold starts and make the engine warm up faster. The vacuum source comes directly from the intake manifold, and the hose goes to a small “unknown-named gadget” (UKG) on the underside of the air cleaner, and from there another hose to the flap-controlling vacuum motor itself. That UKG is what I need.
I’ve always thought the UKG was just a pass-through, and the vacuum motor itself had a temperature sensor. But looking at the UKG, I can see that it is some kind of bi-metal strip and is probably what regulates the amount of vacuum to the vacuum motor. Anyway, that UKG is leaking vacuum for some reason and causing a lean idle mixture and poor idling.
Anybody know what the UKG is called? If I can’t source a replacement, do you think it is fixable? Any ideas for a work-a-round?
This is what the vacuum motor looks like
This is sort of what the unknown named gadget looks like
Unless you live in Alaska…I would simply delete that thing… No engine wants to inhale hot air…pretty much ever. If it fails in a certain manner you will be inhaling hot air all the time which is bad.
Me? I would circumvent this device all together and block or pinch off the vacume feed to the vacuum dashpots…you will never know its missing but your engine will thank you and make more power (in theory) when it can inhale cooler more dense air…
The internal diaphragm cracks on those vacuum dashpots and or the TVS leaks which allows vacuum to be drawn constantly after that thus leaning out your mixture.
Like I said…unless you have seriously cold temps to deal with…and I’m talking freezing and below…just block off and disable that system…and remove the hose that connects the shield surrounding the exhaust manifold to air cleaner. This has been done since this systems inception…in fact Im surprised whenever I see them hooked up.
Now if you are shooting to please judges at a concours…ignore my suggestion. But in the real world those systems are deleted more than they are repaired.
OH YES…to answer your question ? TVS…Thermal Vacuum Switch. See below…enjoy
Another function of these was to prevent carburetor icing which, believe it or not, could occur when the ambient temperature was as high as 40 degrees f.
Warm air is a good thing during warm up on cars with carbs, helps vaporize the fuel. Once warm, it shuts off, no harm done. But I see many cars without them. Being in San Jose, you’ll probably be fine. If you were somewhere with cold winters, it might be worth fixing.
In the way-back machine . . .
Ford number D4ZZ-9E607-A yellow , or DOZZ-9E607-B blue.
Air cleanr , air tempurature sensor.
I have a 2004 LMC Truck catalog # 47-1340 . .BUT . . I don’t see that part number in their online cat anymore . .yikes.
If you still want to replace it . .
Three Ford dealers show n.o.s. D4ZZ-9E607-A on hand.
Parker Ford, Parker SD, 605-297-4851
B.F.White mtr co, Stanton TX, 432-756-3321
Kahoka motor co, Kahoka MO, 660-727-2181
My 2 Cents has a good point; it helps to prevent carburetor icing and I’ve also seen icing (bad icing) with temps in the mid 30s range. It doesn’t have to hit 32 or below to ice up.
Back in the day of carbureted Subarus their air cleaner housings had a flip lever on the snout. It was marked “Winter” and “Summer”.
On the winter setting it would allow warm air off the exhaust header to travel through a tube and into the air cleaner housing to prevent icing. It also aided cold weather driveability.
On the summer setting it would close off the warm air and help to prevent vapor lock.
Excellent info. Sounds like I can just bypass that gadget for now and leave that flap full open to cold air intake since summer is on the way. The NOS info posted by @“ken green” is great, thanks to all.
Edit: In case you are wondering, Ford’s name for that part – based on the info in the Ford forums link above – seems to be the “cold weather modulator” or CWM.
