Hello,

I have a 68 F100 that I am rebuilding and I am ready to put the 390 back in. When I got the truck, the front of the motor was taken off already. I have looked up enough pictures to have some idea of how the set up goes. I am adding power steering and my truck did have the AIR system which it no longer has. My first question is, Can someone give me a better idea of how this set up should be. My second question is, This AC system has been sitting dormant for at least 2 years with the compressor on the wheel well. The low pressure side has simple hose clamps. the drier cannister has them as well. Is that right? I plan to replace the hoses and probably the cannnister. What else should I do. Flush the system right? Can you guys give some ideas here?
Thanks
Ken
68 F100 390
74 Bronco 351W

 

Never "flush" an A/C system with anything!!!

The following are "standard" procedures.

First you should remove the compressor oil and replace it with new. Consult the dealer for the type and quantity. (note refrigeration oil has to be wax-free oil unlike standard oils) Whatever the recommended quantity, you only want to add 95% of that figure. (about 5% always remains inside the compressor). Do not overfill the oil level.

Next assemble the system using all new gaskets and hoses. Nothing like putting the entire system together to find that you have a leak in some awful spot to reach and it is due to a reused gasket or o-ring.

Now leak check. Simple method. Using a nitrogen bottle and a regulator, pressurize the system to 120#. Disconnect your guages from the system, install new caps on the access ports and let sit overnight. If pressure is 120# in morning move on to evacuation below.

Finding a leak...well here is a simple method... Pressurize the system back up to 120#. Using a mixture of 15% liquid joy dish soap, 10% glyceron (from local drug store) and 75% water in a spray bottle, spray all the joints and connections. Leaks will show up as bubbles that grow. If this doesn't work, more extensive equipment will be required.

Evacuation - using a vacuum pump, pull a vacuum to below 29" on your guage. Once there, leave it go for another hour. Care must be taken to close all the valves before turning off the pump or air will suck back in.

Charging should only be done under the direction of a trained professional. Using proper proceedures, purge the center hose and weigh in your charge.

Now with favorite beverage in hand, climb into your vehicle and enjoy the a/c.

Good Luck!

 

Flushing it will clear ALL the old oil and anything sticking to it, and prepare you for an R-134a conversion (much cheaper and doesn't require a license to buy it). You can get a pint of flush for ~$16 and it'll do the whole system. The flush won't interfere with the new oil or refrigerant, so don't worry about getting every drop back out. Just pour it in & blow it out with compressed air.

Most newer Ford compressors use rare low-viscosity oil (PAG 46), so be sure to use the right stuff for yours. PAG is compatible with R-134a & R-12. Newer O-rings & dessicants are compatible with both refrigerants.

You can get an inexpensive vacuum "pump" that works off your air compressor, but you need a LARGE tank so it can run above 90psi for an hour.

If you convert to R-134a, be SURE to install the new port fittings and the new refrigerant label, and a high-pressure switch is advisable. You also have to use a slightly smaller orifice tube calibrated for R-134a or you won't get satisfactory peroformance.