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Onboard Air Setup #4
Basically I wanted an air compressor built into my Jeep. This would allow me to put air in my tires after a trail where I aired down, use air tools (impact wrench, mainly), run air lockers in my differentials, install an air horn (sweet), and even re-seat the beads on my tires when I blow 'em.
For the best starting point, go to Brad Kilby's site at http://www.onboardair.com. You will see that I took alot of effort looking around for used parts. You can save yourself alot of time and hassle if you just buy all your parts new from Brad. Don't expect a "full kit", there's no such thing since everyone's needs are different. However, he sells most everything you'll need to build your system.

The Design
This system is based on a belt driven Air Conditioning compressor, that will be modified to compress (pump) air. First you need a suitable compressor, mounted to the engine. The air getting sucked in should be filtered to avoid contamination.
The discharge (air out) should have a check valve, to prevent back pressure on the compressor. Then from the check valve, we'll push the air thorugh an air hose into a tank. The tank will allow the system to hold a larger quantity of air.

The tank should have a safety valve on it to avoid over pressurization. It should also have a drain valve to drain any water out of the system as compressed air makes H2O.

From the tank, we will go through an air hose to the main manifold. The manifold splits the air into a pressure gauge, a pressure switch, and a quick connect fitting. The pressure switch will engage the compressor's clutch in order to keep the pressure in the tank between 95 and 125 psi. The quick connect fitting will allow us to pop on and off the air hose easily.

Notice, I don't have a coalescing filter (oil/water separator) in the system. I decided to test out how much oil spews from the compressor before adding it. I was planning on adding it before the manifod (after the tank) if it became a problem. It doesn't seem to be blowing oil now, so I don't really see a need for it. If you are planning to run sanders and such where you need dry air, I'd recommend adding it anyway.

Make Some Room
(Done a while back) Now I didn't have to do this, but I think it really helps with space in the engine bay. I hacked off the stock air filter box at the intake hose just off the accordion section. Removed the box (a couple screws), and popped on a K&N air filter (# RU-0960). Some people do this for performance or mileage reasons, but I haven't noticed anything. Anyway, I've got more space in my engine bay now, and the filter cost about $35. A cool thing is that it's not a disposable filter. You just clean it when it gets bad, so you'll save some money over buying the paper filters in the long run.

Mounting Bracket
(12/26/01) I ordered the compressor bracket and serpentine belt from Brad. I'm sure if you know how to weld, and have all the time in the world to try different setups, you could make one yourself for cheaper. But personally, I'm perfectly happy allowing Brad to do all the work! I got it for $125 at the time. The bracket will allow me to mount the compressor on the engine, and the new serpentine belt is longer so it will go around my new accessory.

(12/29/01) Then I needed a compressor. I chose to get a York brand air conditioning compressor from a junk yard for various reasons, but the basic reason is that it's cheap and reliable. I wanted to find one that was model number F210. The "F" stands for flange head, which makes life easier for finding adapters. The "2" just means that there are 2 pistons. And the "10" stands for the displacement. 10 is the biggest, but you may find 8 or even 6. The bigger the displacement, the faster air gets compressed for you.
I went to several junk yards that pull all the parts and put them in a warehouse. I was hoping that I could just walk up to the counter and pick one out. No such luck, they only had newer (90's and better) compressors, and no Yorks. I was pretty discouraged. Then I went to a junk yard where I could walk around and look at all the trashed cars myself. Bingo, I found 5 cars with Yorks in about 15 minutes!

I got my York F210 compressor out of an '83 Volvo. They all had the model number stanped right on the plate in plain view. It was very easy to get out with just a couple sockets and wrenches. You'll need a hack saw to cut the lines, but be careful, mine was still pressurized and it scared the bejesus out of me when I cut them! One or two bolts needed a slight tap with a mallet to break them free, but no big deal. They charged me $25 for the compressor, and I was on my way.

When I got home, I used about a half a can of "Gunk" engine degreaser on it to clean it up, and it worked beautifully. The York is in great shape, and has no rust (it's aluminum). I opened it up to check the pistons and crank, and they looked great. Take care to not ruin the gaskets if you open yours up, you don't want to have to replace them if you don't have to. I also spray painted the outside of the compressor with black Rustoleum paint that is rated for 1000 degrees. That should do it.

(1/2/02) Next, I needed a serpentine clutch for the compressor, as it only had a dual v-belt clutch on it. A clutch looks like a pulley, but it doesn't turn the shaft of the compressor unless it is engaged. Apply 12v to the power cord (the frame grounds it) and the clutch, well, "clutches" the shaft (basically) and drives the pistons. A clutch keeps the system from being turned on all the time.
So I went to find a used clutch. This is where it got interesting. I thought I'd save some money and find it used. GOOD LUCK! I looked EVERYWHERE for it, but it wasn't meant to be. I thought I had a couple good leads on one out of an International Truck, but that just didn't work out. I heard that you might be able to find one on an '81-'84 Mustang, but I have never seen it. The only one on a mustang I saw had an offset of about an inch or so, which made it stick out too far. Also, some people have said that they machined down thier dual v-belt pully so that the serp belt would work. If I were to do this all over again, I'd try that method first. I didn't know about that method at the time, and I ended up ordering it new from Brad for $110. Time to move on.

Compressor Installation

  • Disconnect the negative battery cable and the alternator
  • Remove the serpentine belt
  • Remove the alternator and the stock bracket
  • Remove the pully from the tension arm. Warning! This requires a Torx 40 bit to get this out, and it is VERY soft. I almost stripped it! It's OK if you end up drilling it out, because you won't need it with the new hardware. Thanks Brad!
  • Put on the new bracket, then the pully, then the alternator.
  • Put in the York, you'll have to bend the A/C lines out of the way if you have them, no biggie.
  • Put on the new serpentine belt
  • Hook up the alternator, I had to pull more wire from the harness, no big deal.
  • Hook up the battery and start her up!
  • You may need to go back and adjust the belt tension after you drive it a bit, mine was a little loose.

Make sure you have some oil in the compressor. Just take out the bolt on either side of the York, and pour some in. I used 10W-30 motor oil, and it seems to work just fine. You'll only need about 12oz., don't fill it to the top of the fill hole! You can make a curved dipstick out of a coat hangar to check the level periodically. It was hard for me to see the level, so I just used a long zip-tie, which bends when you push it in there. it works great, you'll want the oil to come up about an inch and a half. Check out http://ccicompressor.com for alot of great info on York compressors. Make sure you look at the on-line service manual (section one).

Shopping list from Grainger:
5X781 3/8" Check Valve $11.99
5B419 Pressure Switch $15.40
5Z665 1/2" Filter/Silencer $14.50
5A709 150psi Asme Safety Valve $6.23
1X754 160 psi Pressure Gauge $3.18

Shopping list from www.airhosereels.com:
1/4" x 1/8" Reducer (2) $0.99ea
1/4" Plug (4) $0.36ea
1/4" Hex Nipple $0.51
1/2" Coupling $1.89
3 In 1 Flat Air Manifold $5.95
3/8" Hose x 1/4" Male barb (3) $0.61ea
3/8" Hose x 3/8" Male barb $0.80

Shopping list from B.W. Rogers (company in Columbus):
B6404-8-8 SAE-NPT adapter $5.70
B6404-10-8 SAE-NPT adapter $3.47
22ft Push Loc hose rated 200deg $22.00

Shopping list from Napa:
Bulk electrical wire $4.29
20 Amp fuse holder and fuses $2.49
20 Amp toggle switch $3.00


Yup, there's alot of different parts there. Basically you need to draw out your whole system, looking at what size and type of fittings and adapters you need. It's a little tricky and requires alot of planning, but I did it with no parts left over. The toughest part for me to find was the SAE-NPT adapters. The flanges that came with my York are SAE, and the rest of my system is NPT. You can save yourself some hassle, and just buy new NPT flanges from Brad.

Dry fit eveything to make sure you have the right sizes. When you're ready, make sure you use plumbing tape or goop so you won't have as many air leaks. I was careful, and I still had a small leak.

Install the Switch
(2/3/02) I zip tied the main manifold (with the pressure switch and gauge) in the engine bay as a temorary hold. I also attached the intake filter to the compressor suction, and then the check valve to the compressor discharge. Then, I drilled a small hole in the fuse box where I mounted the master switch. I found a 12v power source, and then wired the master switch and the pressure switch to the clutch. I will rewire the master switch some other day to a 'switched' source, so that if the engine is off, the clutch will not get power. That would be a good safeguard against accidentally leaving the clutch engaged, and draining the battery.

Tank Installation and Plumbing
(2/10/02) I installed the air tank (2.5 gallon from Summit Racing for $39) under the body between the frame rails with a couple bolts and washers. Then I just added the push-on hoses between the tank and the exhaust manifold on the compressor, and the tank and the main manifold. The hoses are routed inside the transfer case shield to get them up and out of the way.
Put the plugs, drain valve, check valve, and hose barbs on the tank before you install it underneath, though. It's just alot easier to work on the tank without it being mounted.

Wow, those push on hoses are hard to get on dry, I coated the barbs with 3-in-1 oil and they went on much better. I started up the compressor again, and everything worked until, CHUNK! the clutch stopped! I cut the power and popped the top off the compressor to look inside. A screw had come loose from the valve head and jammed the piston. Ugh. The only real damage was to the screw luckily. I just bought a new screw ($0.07) at the hardware store. If you don't take your compressor totally apart like I did, then this will probably not happen to you. I guess I just didn't tighten it up enough when I put it back together. My bad.

Final Work
(2/15/02) Ok, the new screws are in the compressor valve assembly, along with some lock nuts. The heads of the screws are not quite as flat as the originals, but they work fine. I just get a little ticking noise now (it's the pistons tapping the screw heads). It is so close to being correct that I don't think any damage will result. If I'm wrong, I'll just have to pick up another compressor head at the junk yard.
Wow, this compressor is sweet! It fills up that 2.5 gallon tank in seconds! I got about 50' of hose with quick connect fittings, and an air chuck. It works beatifully.

Wrap up
Total project cost: $405.72 including the K&N filter
Not bad for a compressor that is as powerful as the $800+ models, with the added benefit that I have air on the trails! Having to buy a new clutch instead of finding a used one put me $100 more than I wanted, but I'm still happy. This was a fun project!

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 Information Courtesy Of:  http://www.ohiomurals.com/jeepin/oba.htm