F-150 low on coolant - common causes?

Hi all,
just got back from looking at the F-150 that I posted about earlier...
good: straight, rust free body, only surface rust on frame and
driveshaft. Could easily be detailed underneath in a couple weekends. Only cosmetic issue is a slightly tweaked rear bumper, apparently caused by towing a trailer from the step bumper and not having a proper receiver hitch installed.
meh: lots of oil leaks, although it was still full of oil. All fluids seem to be old, and I think it needs new front shocks and probably wheel bearings (slight hum from front end, although that might be the tires, which were a little low from sitting for several months. Also a rattle, but the leading arm bushings looked OK at a visual, although obviously since I was laying on the ground looking at it with my trusty Mag-Lite I couldn't jack it up and wiggle stuff.) Transmission a little slow to engage from a cold start at ~30 degrees F, but it did engage solidly. At about 130K miles I definitely think it's due for a full fluid change and bearing repack at a minimum. However, I have tools, and am used to the "barn car" change/regrease drill.
bad: A/C is inop, my guess is that all the freon leaked out of the receiver/dryer as it is pretty rusty and there's some very minor oil spotting on the inner fender below it. Also, and this is why I didn't come home with a title in my pocket, the radiator was only about half full.
So what in the experience of those familiar with these vehicles is the common cause of coolant loss? Water pump? Head gasket? Other? This is a 300ci straight six, 93 model year. Also, is it possible that it is too cold for the A/C to engage? Is there some kind of low temp interlock?
Oh- one more question comes to mind. The oil pressure gauge was solidly in the middle even after I let the engine get a little warm (I only drove it around the block a couple times because I didn't want to get it real hot with the coolant so low) I assume this is good, but is this a gauge, or an idiot light with a needle?
I'm kinda half-assed tempted to offer to pay to have the coolant issue checked out, because I still like the truck. For 14 years old, it looks damn good albeit plain, and I'd rather have a straight rust free body than lots of accessories to break - I'm just looking for a good, basic work truck.
any opinions appreciated... I know I'm being picky about a 14 year old beater truck, but the truth is I already have three cars that are giving me fits, and the whole purpose of this exercise is to get something that doesn't need any major work.
thanks,
nate
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The 300 I6 is a tough engine... my friend's van when it loses coolant it's from the hose to the back heater. Of course an F150 isn't going to have that. But from what I know of the engine, I would guess there is a leak in a hose or the radiator.

Not in any ford I have experience with. I've run the AC in winter and the compressor has engaged as I recall. It should also engage with defrost as well.

Is it one of those that reads N O R M A L on it? Then it should be somewhere around R M and yes, it could be just an idiot light with a needle, '93 was close to when they started going to the idiot needle but I don't know exactly what model years for which models.
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wrote:

Reading from this side I would keep looking. That slow to engage trans will probably be a "don't engage no more" trans pretty soon. All the leaks and old fluids sounds like a vehicle that has not seen proper maintenance. If they can't even bother to fill the radiator to try to sell it I would wonder how often they bothered to change the oil....
I don't know that particular system but on many it is possible for the a/c not to kick on when it is below freezing. I would expect it would have kicked on once the under hood temp came up though. You can get a pressure tester that looks like a tire tester at the parts store for close to nothing. It should work well enough to let you know if the system is empty or not.
Oil pressure gauge is just an idiot light with a needle on that model I do believe. Were it an actual gauge you would have seen some difference in oil pressure as it warmed up.
Steve B.
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"Nate Nagel"

This truck sounds like an overworked piece of crap owned by morons. I'd keep looking.
Consider paying a little more up front in order to save on maint. later. 14 yrs is pretty ancient.
- D
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