Vacuum lines & motors; how do they work exactly?

[natenkiki2004]

We've all seen this:

Now, from that, I gather that when you turn on MAX A/C, the lever opens vacuum to the motor and sets the intake door to recirc mode. For someone like me, who deleted the A/C, I can't think of a situation where I would want/need that feature. It might be nice on super cold below-freezing days but looking at the dash, I don't think you can have heat and recirc mode on at the same time. Being that I'd like to tidy up the engine bay and get rid of any vacuum stuff I can (less potential for leaks) there's no reason to keep that connected is there?



What about the vacuum motor for the air intake of the engine? I don't see that often talked about here. The one that makes the intake pull air from the exhaust manifold when the engine is cold. After 24 years, how do we even know if that system works? Maybe it's stuck in that position and only pulls hot engine air? How does that system even work? That little oval thing in the top of the air box with the 2 vacuum lines going to it, does that have to get warm for that valve to close? I've thought about removing that system entirely since I installed a block heater but I'm not 100% sure yet, thought I would get opinions from you guys.

 

[vq5speed]

There are lots people who went with a cold air intake setup or tube setup and eliminated the air box are all not using that function any more. Its possible leafs could of jammed the door from fully opening or closing. I seen a video of the actual door moving under vacuum. Not sure where I saw that here or on YouTube. I think if you eliminated it it will not hurt the function of your motor. It may just take longer to warm up in really cold climates if your motor used it before.


found it
https://www.youtube.com/watch?v=oCotafjeu6U

 

[natenkiki2004]

So it looks like by default, the door is held open by spring tension. My next thought then, do the bimetal sensors ever break? Maybe I need to get a handheld vacuum pump and start testing.

Also, it looks like the outdoor/recirc blend door works opposite of what I thought; vacuum has to be applied to pull the door open so outside air comes in. Disconnecting the vacuum line that runs into the passenger side harness below the blower motor means I'll forever be recirculating cabin air. That's fine with me, more heat in the winter.

 

[vq5speed]

Well on mine I don't know where that duct is that goes to the exhaust manifold on mine. Maybe I removed it years ago when I swapped motors cause there is no ducting going near my exhaust manifold. I know I have that vacuum hose connected and assume its functioning the door as its suppose to. The warm air its suppose to get is just what ever air is down near the lower intake opening area. I haven't ever thought my engine took longer to warm up in the winter. I would have never even gave it any thought until you made this thread.

 

[natenkiki2004]

There should be a thin sheet metal cover on the passenger side exhaust manifold, you won't see the individual pipes as you do on the driver's side. That sheet metal comes to form a circle in the front of the engine, to that is supposed to be a flexible silicone hose with a coiled spring in it. That connects over to where the vacuum motor is in the intake tract. You should be able to see it from underneath the vehicle. If you removed yours, I'd suggest removing the entire vacuum line and just plug it on the vacuum manifold. One less hose in the bay, one less point for unmetered air to enter.


I guess the whole reason I started this thread was to talk about whether or not the vacuum thermostatic intake is working or not or if there's potential to harm engine performance with either a vacuum leak or always sucking in warm air from the exhaust manifold.


My thoughts have now progressed to setting up a KKM (or similar) intake but with a twist; having a hood scoop right above it. I'll start a new thread for that though as it has almost nothing to do with vacuum lines.

 

[vq5speed]

I just went out and looked I spotted where that accordion looking tube connects to the lower intake its missing. So I been just getting I guess cool air from either side when my door is closed or open.

 

[vq5speed]

My thoughts have now progressed to setting up a KKM (or similar) intake but with a twist; having a hood scoop right above it. I'll start a new thread for that though as it has almost nothing to do with vacuum lines.

I been putting together a custom intake tube for awhile. Just piecing it together this is what i have so far. If that big cone filter doesn't fit will fit the shorter one. I need few more clamps and a coupler to fit that 45 to the adapter.

 

[natenkiki2004]

That looks like the best intake I've seen anyone come up with

My issue with any non-stock intake is that 99% of them suck hot air from the engine bay. I've been wondering about adding a hood scoop to draw in cooler air to help out. Cool air + unrestricted flow should be a good combination.

 

[vq5speed]

I opened up the center under my hood scoop. There is only hot air in the engine compartment standing still idling. when the truck is moving down the road there is not much hot air around the engine. Hot air is getting sucked away out the bottom. You got air being forced in through the front the fan is pushing air over the engine. Going down the road the air in the engine compartment is not just sitting still. There is violent turbulence of air moving around being drawn out the bottom. So as air is drawn out then air must be drawn in from the front or from the top if you have an opening in the hood.

So if you think about it. For the fan to be able to pull air in through the radiator that air must escape out somewhere or it would not pull air in. It escapes out the bottom so as the hot air goes out cool air is drawn in.

 

[natenkiki2004]

That's true but the air coming off the radiator is hot, that's how it cools the coolant. Also, over by the air box there probably isn't much airflow.

I just thought... I have one of those weather sensors that do indoor/outdoor temp. Would be a neat experiment to see what the under-hood temp is over by the airbox and if it's actually significantly higher than ambient temp. That might save me cutting a hole in the hood for peace of mind.

 

[vq5speed]

The stock air intake draws its air from the bottom just inside the frame far away from the engine . So really the stock setup is already a cold air intake. I think your gain with a tube setup is less restrictive over the stock plastic intake. If you were to route the inlet say all the way out like a Snorkel. Then you get really true cold air intake. I don't know what to expect from mine. I just want to see if it does run any better with a tube and cone intake setup.

 

[natenkiki2004]

I agree, the stock is already a great cold air intake, the issue is that it's restrictive with so many bends and flexible tubing attached.

I just e-mailed KKM and got a reply pretty quickly:

Back in the early days of KKM, we tested under hood air temperatures on Ranger and Explorer models. When driving down the road, the under hood air temp will average around 4-5 degrees warmer than outside air. This can be attributed to the fact that the under hood area has plenty of fresh airflow.

It should also be noted that the vacuum operated heat damper door is notorious for leaking and drawing in hot air from the exhaust manifold stove box. All that to say that simply mounting the kit as shown on the website is much more efficient than the stock system and no other modifications are required.

4-5 degrees is a lot less than I had imagined.


*EDIT* Another reply:

All of the tests were performed back in ‘97 on our local main thoroughfares which are 35 and 45 mph in the months of April or May. If you have a lot of stop and go driving, a kit like this may not be ideal for you, but is still probably better than stock.

As for mileage, we have had all sort of good reports over the years. Some of the reports of 4mpg better mileage seem almost ridiculous, but if they had a dirty filter and leaking damper door, it would make sense. Most come in around 1 to 1.5 mpg better, not really anything worth advertising.

 

[vq5speed]

Well that was very honest replies from KKM. As I suspected there is lots of air movement under the hood when driving down the road. If you were to open the top of the hood like you wanted directly above the filter that does let hot air out when your just sitting or moving slowly. I said I opened my hood under my scoop when idling hot air pours out of the scoop opening. When moving the air is force into the scoop making the air exit the bottom. So my scoop is bring in air that has not passed through the radiator heating that air up.

 

[2stroke]

My opinion is that on the stock engine, any aftermarket air intake is a wasted cause. If you want to go to a clean-able filter, that's a completely legitimate reason, but I have yet to see any data of increased performance. No increases in gas mileage, no increase in power, at best people claim they run better. I'm not knocking guys who have put on aftermarket air intakes on, but I'm sure you would agree there are much better ways to spend money. Again, I'm talking stock engine. My b4000 came with an aftermarket air intake, and it was garbage. The filter (admittedly a knock off brand) didn't filter much of anything, and round tube just takes up space under the hood. I ripped it out and put the stock setup back in. Its about as perfect as it gets.

As for the thermostatic control valve, its easy to tell if its working. Assuming you take the tube off, you will see the flapper open when you start it on a colder morning. After a drive, it will be closed. That said, they offer next to nothing. They are there for that extra .05% increase in gas mileage over millions of vehicles. I simply unplugged mine, and capped the port on the vacuum tree. I also capped the max A/C, as I see no purpose for it.