On Board Air (OBA) Question

I think I have decided to convert my AC on my 90 XJ to an OBA system. I have read a bunch of threads and believe I have a firm grip on what to do. I know most guys use an inline tool oiler/fogger/lubricator to lube the compressor, but I have seen at least 2 builds where they T'ed into the the ventilation on the valve cover instead of using an inline oiler.



I'm seeking opinions on whether the engine oil vapor floating around in the valve cover would provide enough lubrication to oil the compressor. I like the idea of not needing to worry about filling the oiler, but I just can't find much info on it.

Has anybody tried this? If not, whatta you guys think?

I'm pretty sure that would be enough. I converted the compressor on my old 91. I would pour a little oil in the intake every few months when I thought of it. After 4 years, I pulled the compressor out and installed it in a YJ. I continued to oil it rarely and used it on the YJ for 4 more years. It was still working when I sold the YJ so I don't think they need much lubrication.

raptor314 said:

I think I have decided to convert my AC on my 90 XJ to an OBA system. I have read a bunch of threads and believe I have a firm grip on what to do. I know most guys use an inline tool oiler/fogger/lubricator to lube the compressor, but I have seen at least 2 builds where they T'ed into the the ventilation on the valve cover instead of using an inline oiler.


I'm seeking opinions on whether the engine oil vapor floating around in the valve cover would provide enough lubrication to oil the compressor. I like the idea of not needing to worry about filling the oiler, but I just can't find much info on it.

Has anybody tried this? If not, whatta you guys think?

Click to expand...

I'm pretty sure compressor oil is not used/bad engine oil...

Thanks jeepingben. Did you add compressor oil or regular motor oil? I doubt that it matters much.

PhotoJared, I'm not sure what you're trying to say. Not to use compressor oil or the oil vapor from valve cover? Can you explain?

Anybody else try this?

I doubt I bought compressor oil. It was definately motor oil sometimes, probably all the time. A used compressor from the JY or a part out is so cheap, you should just try what you proposed and report back if it blows up.

I doubt the system pictured above worked very well for providing oil to the compressor, unless that motor had tons of piston ring blowby.... In which case thered be A LOT of crap (combustion gasses, carbon buildup) going to the compressor...

I'm not positive, but I think that area should be filled with oily mist from the rockers splashing around. Normally, fresh air would be pulled into the valve cover there. The idea shown in the picture would be that if you were running the compressor, it would pull air from the valve cover instead of pulling it from the airbox. Maybe a restricter plate would need to be added between the airbox and the T? The compressor is meant to be lubricated by PAG oil and I don't know how this differs from compressor oil. My experience is that the compressor will survive a long time when lubricated occasionally with clean motor oil. A compressor converted to OBA has a pretty easy life compared to one running for hours at a time pushing refregerant around. This is why you are likely to get away with abusing it like this for years.

There's two ways to look at this.
Compressors use oil from either the lubricant in the freon (Sanderson types) or more traditionally in a separate reserve (York).
If you want to us your Sanderson style compressor as an oba set up you have to decide how long you want it to last. Since you no longer will have the freon and it's lubricant in the system you have to get it from somewhere. I suppose you could run it with NO oil... but the results would be about like draining your vehicle's motor and going on a road trip with out it.
Then when you decide you don't like that idea you kinda have to choose between dedicated oil for the compressor or using off gas oil from the valve cover.
Up to you.
Are you the cheap (thrifty) kind of guy who buys the cheapest oil possible for your truck and doesn't care? Are you someone who believes a quality oil is legit and changing it at regular intervals is your way of life?
CAN you run the Sanderson off vent line oil? Sure. How long? Who knows.
Is it better to provide the Sanderson with oil specific to its design, compatible with anything (tools,lockers,etc) it may find its way into? I'd say yes but that's your call.

I am running an inline air tool oiler on mine and fill it with air tool oil. Have used it for a little over a year now with zero problems. It really doesn't use as much oil as you think it would.

raptor314 said:

I think I have decided to convert my AC on my 90 XJ to an OBA system. I have read a bunch of threads and believe I have a firm grip on what to do. I know most guys use an inline tool oiler/fogger/lubricator to lube the compressor, but I have seen at least 2 builds where they T'ed into the the ventilation on the valve cover instead of using an inline oiler.

I'm seeking opinions on whether the engine oil vapor floating around in the valve cover would provide enough lubrication to oil the compressor. I like the idea of not needing to worry about filling the oiler, but I just can't find much info on it.

Has anybody tried this? If not, whatta you guys think?

Click to expand...

That looks like a really bad setup to me. In particular, that is the intake side of the CCV, so it is supposed to be drawing air into the valve cover through that tube. The only time any oil would be in there is if the rear outlet was blocked off and combustion gasses had to escape through the inlet. At which point you'd be filling your compressor with engine junk--gasoline, carbon fumes, etc.

I would not try to use the outlet tube either, for the reason above, lots of unwanted crap in there.

ehall said:

That looks like a really bad setup to me. In particular, that is the intake side of the CCV, so it is supposed to be drawing air into the valve cover through that tube. The only time any oil would be in there is if the rear outlet was blocked off and combustion gasses had to escape through the inlet. At which point you'd be filling your compressor with engine junk--gasoline, carbon fumes, etc.

I would not try to use the outlet tube either, for the reason above, lots of unwanted crap in there.

Click to expand...

Are you sure on this being the intake side? I thought this vented to the airbox to run the shit air from the CCV through the air filter and then back through the engine. I'm probly wrong...

If it's the intake for fresh air, where would the exhaust side of the CCV for the shit air? Probly a dumb question...

The basic flow is air gets sucked through the air box filter, through the valve cover, and into the intake manifold. This way the combustion gasses in the block get drawn into the cylinders for disposal. The intake manifold is under negative pressure (vacuum) all the time, so its always trying to pull air through. The front hose is on the filtered side of the air box so that contaminants don't get into the engine.

If the rear elbow gets clogged up, the vacuum will get blocked off and the gasses will have to expand and escape through some other path--usually the forward elbow to the air box filter is the path of least resistance. If that gets blocked up somehow, the gasses will start blowing out the sides of teh oil pan gasket or the valve cover gasket or wherever is the least resistance.

That makes more sense than my misiformed understanding. You're right, there shouldn't be much if any oil there. Looks like I'll be using an inline oiler...

I'm not in a position to look at mine, but is there a line that I could T into going to intake manifold? Would that be feasible?

You don't want the combustion gasses in your compressor