[bruinjeeper]

Figured i'd document this and do as good a job as i can stomach in terms of a detailed write up. There are many ways to skin a cat, this is but one. I went this route because i thought it was quite cool, i like the idea of repurposing things, wanted to keep my electrical system cleaner and its been known to have the 7 piston SD models putting out up to 8-9cfm by my research. It runs quieter and can serve up a massive amount of air. By comparison, a very expensive 12 volt system can't match the CFM rating. The install is also cleaner for the most part, hugging the engine and leaving lots of peripheral space for other fun doo-dads. Seeing as how i know i will be stuck with the 4 squirrels for at least a little while yet, i figured it was worth it.

I got a hook up on two Sanden OBA compressors from a mid-late 90s Cherokee - best part was they were free and fairly clean looking from the outside. They aren't the IDEAL Sanden model to use (These are model #4691 - AFT SD-709T).

YJ Sanden A/C Compressors makes this a bit of an easier job in terms of hooking it all up. The main difference would be the cylinder head of the units. YJ's SD 709s have rear ports on the unit and they are threaded externally. My models utilize vertical ports at the top of the head with a manifold.

I ran over it back and forth which way to go about using this - you can repurpose/use the manifold in a number of ways, i chose to cut threads in the ports at 1/4 NPT - 18 and directly hook up the input and output lines directly with teflon tape. A good back up plan that i ran over with many /f12 members back and forth would be to utilize weld bugs and braze them into the ports off the valve cover directly - bypassing the manifold entirely.

First thing you're going to want to do to get the ball rolling is remove the 6 bolts at the backside of the unit holding the head onto the unit with a 13mm Socket. The head may be a little stuck on. There are two 'divots' along the edge between the cylinder head cover, it's gasket and the unit itself. You can pry it off with careful work with flathead. *BE CAREFUL. Try your best not to damage the head gasket*. Once you have cracked that, stand the unit on its pulley and pull the valve cover off. Doing this, gravity should keep any oil still within the unit in place and not making a mess (I did this in my condo lol).

Get some brake cleaner, rags and start cleaning everything up. You can separate the gaskets from the valve plate after removing the 10mm bolt and nut which keeps the valve plate assembly together. There is a gasket on either side of the plate - you can replace these if there looks like there was any corrosion on any of the internal components and the plate itself. Everything looked a little dirty, but in real good shape after a quick clean up. I was also lucky to not have any struggles removing the gaskets from the valve plate. I simply cleaned it up with layers of brake cleaner, and a light scuffing on a low speed with a wire brush at an angle in my drill. Worked out well for me.

Because your hands are kind of full for the pulley removal, it was difficult to take pictures of disassembling the front end of the unit. Your gonna need snap ring pliers, refer to photo below from the SD series manual.

I should note that the only special tools i had during the removal and re-install were snap ring pliers. I got by with ingenuity for most of the special tools displayed up there in those images. But, if you want, see below:

Once you the pulley and field coil assembly out of the way, loosen the 8 bolts holding the facia onto the front of the unit with a 10mm socket. The facia will begin pushing up as you backout the bolts on its own. It's normal, don't worry. There isn't much pressure so no worries about your safety here. Just undo those bolts and then pull straight up and Voila!

From here you grab the internal workings and try to pull straight up as a unit, you can help yourself out immensely by also pushing/guiding the piston assembly up from the bottom by the piston heads. Once that is out, give everything a nice cleaning with brake and parts cleaner and wipe it all down well. Analyze the walls and all the components closely for any gouges, scrapes, chips, warpage, damage of any kind. My unit was kick *** spotless, i cleaned up the oil residue and was good to go!

Next step is to grease everything up nicely if you're going the route i did. If not, and you will be running an inline oiler, clean up and lightly oil everything and re-assemble. I used high-heat bearing grease and slathered it everywhere as i wanted to keep it as easily maintained as possible going forward and didnt like the idea of a cheap chinese oiler or something from home cheap-o i would have to keep an eye on. A few squirts of grease out of a gun every couple months (based on usage of course) sounded like an easier and better option. The oil fill plug of my Sandn unit would be on the engine side of the compressor which is not ideal to get to so i went with a 90 degree elbow grease zerk fitting. This was used to replace the unit's oil fill plug. I retained the rubber O-ring and lock-tighted sealed the fitting in place. I got it to point as close to vertical as possible to make for easy greasing down the line.

You're now ready to make sure you clean the mating surfaces really really well, especially in the groove.Make sure you line up the large o-Ring/gasket in its place where my finger is pointing below:

Now guide the piston assembly making sure the race and thin bearing which sits on it are properly placed and greased. It will take a little finagling, again utilizing the open cylinders from the bottom side to manipulate the pistons as required to get it all to slide in helps a lot! Once you have it all lined up, press it down and in place fully until it is seated on the ball. Below reveals how much clearance there should be when fully pushed down. It will take its angle as you tighten down the bolts on the facia/cover.

Tighten those 8 bolts down to ~25-28 Nm with lock tight.

Before we get the valve plate re-installed, i drilled out the weep hole circled in the first pic below and tape 1/4" x 1/4-20 and lock tighted in a grub screw (low profile). This will minimize any grease getting through and out of the compressor.

Now we're ready to put the gasket components and butterfly valves back onto the valve plate, bolt it together and stick it back onto the @$$ of that compressor and torque everything back down.

Refer to the manual instructions posted earlier up there ^, reverse everything and reinstall the field coil, snap ring, pulley wheel clutch assembly, snap ring, the shims that came on it, the facia and 14mm bolt. lock tight and torque down. Make sure the wheel spins freely with no grinding sounds and you have your compressor back together! We can now move onto the real fun stuff.
Here we have the shims pictured:

 

[bruinjeeper]

Alright.

Onto some fun stuff here. This can be done most any way you choose, so long as you use the fundamental and required components. I got all fancy on me intelligent phone photo editor so there is less typing for me. We're all visual learners right?

Of course this is completely customizable to your preference. There is one port un-used at the bottom of this manifold. I changed my mind and picked up additional air hose. I will be running it from there to a rear output. Figured i'd get this out of the way and run it back now, as i will add a tank later on down the road and it will be a quick install because of this.

I didn't want to extend crap everywhere and wants to keep it huddled together, so i had a prebent HVAC duct cap in storage and am going to utilize that as a mounting plate for the filter and manifold assembly to save space and keep a logistical tidiness to it all. I am utilizing the mounting bolts/holes for the compressor itself to keep the HVAC cap secure. I cut it to suit my needs and also found some old door edge rubber trim which i will line the sharp cut edges with to protect the hose and just for general safety whenever i am finagling around under the hood:

After some discussion, i chose to incorporate the OE Sanden Manifold into the system. With some enlightenment from fellow forum members, I arrived at this conclusion because if ever there was an issue with the compressor itself down the line, you could simply pop off the manifold and take it out (and seeing as how i have an exact replica compressor on standby, it'd be simple to clean it up and plug it back in). I figured i would give it a try to tap the Suction and Discharge ports to 1/4" - 18 NPT as this would allow me to plug my lead-in and lead-out hoses directly to the manifold without the need for additional fittings (and additional points of leakage) while saving some coin. If i failed with threading it correctly and creating a leak-free connection, i was simply going to braze in some aluminum bungs to the compressor head directly. In essence, this gives you a two method approach to get it right once. The ports themselves are odd sized and it was tough to get a good measurement on them without a digitial micrometer, something i wasn't willing to purchase at this time because like i said, if i got this wrong, i always had a fail safe plan to weld in the threaded bungs. I cut the lines, and drilled out the holes accordingly then used a 7/16ths drill bit tapped for 1/4" - 18 NPT. It seems to be okay, of course i won't know until i get the system wired up for initial testing.

Here you can see the Suction end of the system already teflon taped and installed good and tight. The threading on the Suction side didn't turn out that great truth be told, there is a small but noticeable break in it. But it seemed to thread in alright. This was due to my drill angle deflecting on me as i was coring it out. The Discharge side is what i am more concerned with, and those threads turned out solid.

So, had some time tonight to test fit everything. Then one thing lead to another and the test fit became drilling and grommeting the CAI elbow for the suction intake. 5/8" hole and grommet (O.D).

then that lead to me running the suction line to the compressor. The barbed head fits nice and tight in the grommet.

If you are using this #4691 model number of the Sanden 709, there are specific 'washer gaskets' that go between the ports on the cylinder head and the Suction and Discharge manifold. If you are in Canadia where part #'s do not make sense, the below image WILL help you.

Pop those suckers onto your cleaned and smoothed out cylinder head and torque down the manifold.

The most natural run for the suction line seemed to go to the back of the engine and around and under the loom, sneaking through the vacuum connections. Probably not the most ideal spot for the connection, but that's where it's staying now. I will be covering the hose and all other hosing with wire loom.

Here's a shot of the filter/manifold setup mounted to the HVAC cap mounting spot. Nice and snug - used small nuts and bolts that i had laying around for mounting the coalescing filter, and the manifold is braced tightly to the mounting plate with an SS zip tie.

My hole saw mandrel's drill bit gave up the ghost and snapped as i went through the Poison Spyder Brawler winch bumper and so i took a 3/8", then stepped up one step and then finally finished off with a 5/8" hole through the top side. I have primered it for now just to keep the evil rust away. The hose end fit perfectly through the hole and i tensioned the quick connect on and it stays tight and strong against the hex neck on the hose. So that works out.

I added wire looming around all the air hosing, and ran the rear line from the final remaining port at the bottom of the manifold under the splash flap along the outside of the frame rails to avoid the heat from the exhaust system and utilized some of the holes along the tub channel to zip tie it in place. In the rear wheel well i passed it through the OE hole which leads into the tail light cavity in the body up through an already existent hole in the top of the wheel well behind the roll bar C pillar and out the back.

I utilized the last remaining vacant spot in my overhead switch pod for the compressor switch.

As i definitely overkilled the wiring for this thing, i will be tying it into a relay from the auxiliary accessory relay box i installed recently. Already have the relay tied into a fuse slot in one of my accessory fuse panels as well as have the relay grounded. All that's left is to run the power from that switch through the firewall grommet to my relay, then a separate wire from the relay to the pressure switch on the OBA manifold which you can see below that i have done. I tested the compressor clutch once ore by juicing it with 12v and heard it click. Good news! Essentially, this model came with its ground and its power lead tied into eachother (ground had diode to protect against backsurging?). Regardless, i separated those two wires. The wire that ran to the clutch was ran to one post on the pressure switch, and the ground wire was tied into a spot on the negative bus associated with one of my auxiliary fuse panels. I chose to loom it in tandem with the pressure switch power feed coming out of the relay box along the grill tie in rod.

If you were starting with a 4 cylinder like I am, and it didn't have A/C before hand - you're going to require a longer belt and an additional idler pulley. I had pulled one from the jeep wrecker i got the compressors from, but it was off an older AMC engine and wasn't quite the right size unfortunately - it measured out to 2.75" OD, and what we require is a 3.5" OD pulley. Picked a Dorman model up cheap on Amazon:

I heard the bushings on these aren't the best fit for our application so i will be re-using the one that came on the pulley i pulled at the wrecker.

The belt will have a 96 and 7/8" effective length. Napa canada Part below for AMC design 2.5L FI with Power Steering and A/C:

Well, after struggling for about an hour to get that 96 and 7/8" belt on, and this is with the tensioner bolt completely removed, it seems we should probably aim for a bit longer if you have the 2.5L like i do. Crazy! ~98" or a bit over that belt would have worked like a charm. What i ended up doing was removing the OEM idler pulley up top beside the thermostat housing and replacing it with the smaller 2.75" pulley i pulled at the wrecker to make it all work. Seems i didn't need to pick up that Dorman pulley displayed up there ^. Is what it is, i have a spare now. So what you want to do is take your belt off, take care of any squeaky pulleys you have now (my water/power steering pump pulley had been squeaking, so i pulled it and greased it). Despite other information, i did have to unbolt my alternator and move it a bit over in order to get some space to get a swivel head ratchet wrench (oh how i love these things) behind the pulley mounting bracket so i could torque down the 3/8" bolt i used as a make shift fix. You may need to do this also if your brackets threads are stripped or you cannot figure out the proper metric sizing bolt required like myself. SOme sources say M10x1.25x100 (i found that to be false...)

Once that's done, finagle that belt on and tension it. I use my eyeball test and try to tension it enough so that it cannot deflect .5" either way. Now admire that longer belt as you let it idle for some time to ensure nothing goes wrong. Longer is better :thumbsup: #sizematters.

We're almost ready to power it up!

I did, and got nothing. Nothing reading on the gauge, no leaks... was dumbfounded as the compressor was working its quite magic. Then i looked to the back of the manifold and realized i crossed the Discharge and Suction ports. So i flipped the input and output around and PRESTO! Holy smokes this thing puts out a lot of air! quickly! and QUIETLY! WOW!

Final shots of lay out! Enjoy the breeze folks! :thumbsup:

EDITED UPDATE 2021:
The system has been going strong with no leaks. I added in a tank, more so for a locker. I was totally satisfied with the tire fill-up time.

 

[bruinjeeper]

I have reserved the first 3 posts for a future revisit.... I started the thread now as I do have a question before I commence.

I was thinking it would be neater/tidier to tie the air input into my Airaid CAI. Via bung or splice into the PCV line.

In all I have read, I haven't seen it done this way and would like to know if there is a specific rationale to it. Yes ... no... why or why not?

I plan to have this be a detailed write up in Hope's it can become a sticky to replace our pictureless version of the same mod.

 

[bobracing]

Seen it done, not so much on CAI but old school carb air cleaners but filtered air is filtered air.
Wouldn’t do the PCV, have a chance of gasses getting back down in the tires and eventually collect oil in there too.

As for what I used, just happen to find an air compressor filter/housing with a NPT fitting at the local Ranch & Home.

The stock intake hose has AL ends. Used PVC and epoxied it to the AL tube. This adapted it to a NPT which the compressor filter housing fit. Intake side is cooler than the output so wasn’t worried about the heat.

Output side has steel lines, seal welded that to a pipe coupler.
Also drilled open the compressor output as biggest I could without getting into the threads trying for more flow and cooler temps, no way to tell if it worked or not.

 

[bruinjeeper]

Makes sense... and good call.

I'll rethink this air filtration part of it. Just want it as tidy as possible. Everything else pretty much figured out as I want it.

 

[jbolty]

Makes sense... and good call.

I'll rethink this air filtration part of it. Just want it as tidy as possible. Everything else pretty much figured out as I want it.

I put some random filter on mine and a few months ago changed it expecting it to be full of desert dust but it wasn't. I run the lockers off it but really it hardly ever kicks on except when I'm stopped so I guess it pulls in mostly clean air.

 

[jsawduste]

Please allow me to share my experience with a Kilby York based OBA.


The 210 compressor, mounted on its side with all the latest air oil separators. No matter what I could not get a clean oil less output. After talking with the compressor manufacture engineering dept. Ended up throwing the whole setup away and going CO2.


The Tech guy at the manufacture was very familiar with the Jeep OBA system. In fact he even new Brad Kilby personally. That said you cannot tilt a York compressor more than 35* and control the crankcase oil from entering the airstream.


Understand your using a Sanden. Don't know how its lubricated but do consider the air output and whether you can keep it oil less. Balancing beads for instance don't like oil. Nor did my kids air mattress at the beach.

 

[1project2many]

Compressor intake connected to engine intake is a good solution and is used by commercial vehicles with OBA for kneel suspension. Air system dryer/purge can be important if in an area with high average relative humidity. Glad you've decided not to try York compressor. I have lots of experience with York style compressor designed and built specifically for small transit bus OBA and would not recommend this compressor design.

 

[bruinjeeper]

Compressor intake connected to engine intake is a good solution and is used by commercial vehicles with OBA for kneel suspension.

Think I will hole saw it closer up to the inlet of the CAI and bung it accordingly.

Think it will give it a very clean finish. The only issue I can foresee is the distance as the intake would be on the opposite end of the engine bay from where the compressor mounts.

Edit: on 2nd thought, closer by the Intake opening would be a shorter run.... and an easier run to boot.

 

[jbolty]

Please allow me to share my experience with a Kilby York based OBA.

The 210 compressor, mounted on its side with all the latest air oil separators. No matter what I could not get a clean oil less output. After talking with the compressor manufacture engineering dept. Ended up throwing the whole setup away and going CO2.

The Tech guy at the manufacture was very familiar with the Jeep OBA system. In fact he even new Brad Kilby personally. That said you cannot tilt a York compressor more than 35* and control the crankcase oil from entering the airstream.

Understand your using a Sanden. Don't know how its lubricated but do consider the air output and whether you can keep it oil less. Balancing beads for instance don't like oil. Nor did my kids air mattress at the beach.

I run gear oil in my york and it cut down the blow by about 80%

 

[jbolty]

side note. Thanks for starting this write up. At some point when it's done I can remove all the extra chit chat or move it to a new thread.

 

[letitloose06]

I've been running my Sanden OBA conversion for around 10 years now. I'm using a cheap crankcase vent filter on the inlet side.

With my compressor I replaced the oil fill plug on the side of the housing with a grease fitting and grease it with high temp grease every now and then. I took the end off the compressor and blocked off a small port to reduce the amount of grease that comes through. I found the idea from here. The guy is using a 5 piston SD508 compressor, but the construction of the SD709 compressor used on the YJ is similar.

Make sure you run a heat resistant hose for the first 2-3 feet from the compressor outlet. Normal air hose will melt if you work the compressor hard.

 

[DRLExpress]

Thanks for starting this thread. Been wanting to do this for a while.

 

[NHfireLJ]

Same as letitloose Works great... Make sure a check valve on compressor out...

 

[TSEJEEPERS]

Same here. As far as grease or oil getting into the air.
I run my air to the tank first then through all the other stuff. The only thing between the tank and the compressor is a check valve.
This cools the air and helps get the grease and oil out of the air.

 

[bruinjeeper]

Will be running braided stainless out of the compressor... 10" run. I have heard this would be better... if it melts... it melts and a quick re-tool would be in order.

I was looking into opening up the compressor and greasing...along with capping it off with a zerk.

 

[bruinjeeper]

Same as letitloose Works great... Make sure a check valve on compressor out...

Wait... directly at the compressor fitting? Was going to run that further down the line... before or after the filter. Good question... what would be ideal here?

 

[Awesome]

Wait... directly at the compressor fitting? Was going to run that further down the line... before or after the filter. Good question... what would be ideal here?

It doesn't matter. I put mine just before the air/oil separator. I use a combination checkvalve/pressure release. I can't remember what the dang things are called.

Basically this: https://www.grainger.com/product/CDI-CONTROL-DEVICES-Brass-Unloader-Check-Valve-4X996

EDIT: I still don't really get why people use the Sanden. They can't run non-stop like a York without burning up. If you don't use it for air tools I guess it'd be ok.

 

[bruinjeeper]

It doesn't matter. I put mine just before the air/oil separator. I use a combination checkvalve/pressure release. I can't remember what the dang things are called.

Basically this: https://www.grainger.com/product/CDI-CONTROL-DEVICES-Brass-Unloader-Check-Valve-4X996

EDIT: I still don't really get why people use the Sanden. They can't run non-stop like a York without burning up. If you don't use it for air tools I guess it'd be ok.

...cost i would assume.

Also, will only be used for inflation jobs here and there... eventually when a tank gets added into the system, lockers.

 

[1project2many]

Good question... what would be ideal here?

If you start a compressor without head pressure it greatly reduces shock load. IMO it's best to place the valve further down the line. The small volume contained in the line between compressor and valve act as cushion when the compressor is engaged. But practically speaking the valve can be anywhere. The OE system cycles on and off with high side pressure all day long.

EDIT: I still don't really get why people use the Sanden. They can't run non-stop like a York without burning up. If you don't use it for air tools I guess it'd be ok.

Most York compressors really aren't made to be used for air. The piston only has a single compression ring, no oil ring to control oil blowby. And they don't have any means for cooling if used at 100% duty cycle. In an OE A/C application oil circulates with the refrigerant and heat is drawn out at the evaporator. There's also no filter to clean contaminants out of the oil as wear occurs. This compressor is a redesigned York that will work as an air compressor.