Hey yall thanks in advance for finding this thread I appreciate any suggestions.
I have a very odd problem with my k2500 5.7l with ac on I cant keep cool averaging 240 now I have done everything I can think of. I live in houston so its hot and ac is a must. I have replaced the ac compressor, ac condensor, orifice Tube. I charged it appropriately (vaccumm system, check for leaks, oil to spec, r134 to spec). I did not change the evaporator (Iinsert "doh") that being said I first started this whole fiasco when I noticed horrible noises when ac was on (sounded like a pulley bearing destroyed or something rattling somethin awefull) so I replaced the above listed ac components. After replacing said components the noise was still there (also note that the motor drops about 100rpm or so at idle with ac on and also has a noticable shake to it). The noise sounded like it was coming from power steering pump so I replace the pump pressure line and pulley. Did a complete flush on the rack. Noise was still there all the while I cannot keep this motor cool. For some reason it seems like the ac is just too much for the motor to handle (I know this is not the case 13k on rebuild even compression port matched intake milled heads mild cam etc etc.). Just today I did a complete coolant flush, changed thermo stat out (180degrees) checked water pump, checked for mixing of oil and coolant (none) added new coolant and a bottle of water wetter. About a week ago I installed an additional electric fan as a puller not a pusher. With electric fan on the original fan going and ac on im still at 240 degrees. At stop lights the ac blows warm and temp goes to 240 and sometimes 250 but never 250 when on highway at about 75mph it drops to 215-220. I have cleaned fins on radiator evaporator and trans cooler, no difference. Please help im on my last bit of patience. Thanks kahlen, also if you have any suggestions feel free to email me as well kahlenkoch23@gmail.com

 

Excuse my typo towards the end its suppose to say it goes to 240 and sometimes 250 but never 260

 

Ok, I just copied this list from a previous thread I replied to...
You may have already considered/resolved some of these issues.

Possible causes of an Overheat:

Thermostat not opening fully,
Dirty Cooling System heavy dirt deposits in engine,
Radiator clogged (internal/external), excessive Tube repair/closure,
Hoses deteriorating inside/collapsing, blocking flow,
Improper Coolant Mix,
Captured Air in Engine,
Combustion Gas Leak into Cooling System,
Engine Timing set excessively in advance,
Fuel Mixture too lean,
Bad Water Pump,
Belt slipping,
Air Flow blocked in frontal Air Ram, (forward of Radiator)
Incorrect information from temperature sensor/gauge,
Shroud missing/improperly set to fan position,
Bad Thematic Clutch on Fan,
Heater bypassed with hose loop,
Excessive temperature contribution from Automatic Transmission, via Radiator Capsule,
Bad Radiator Cap, if there isany loss of Coolant.

Think any of these may be the cause ?

 

Ive checked pretty much everything on that list except timing. I have an afr guage on it and it rarely leans out. It will go rich when I hammer it and when I let off it will lean out to 15.8 for a very short time than back to 14.2. As for coolant leaks I pressure tested everything. Tested the rad cap. No fuel smell in coolant. Pressure test came back normal. Coolant has a conservative 5050 mix with water wetter. The only time it overheats is with the ac on. Yesterday I did notice the belt slip once with the ac on but a quick push of the off button and it went back to normal. I know that it has something to do with the ac being on thats when the problems occur. I just cant determine why or what causes it. The only thing I can think of doing is replacing the entire ac system but cant afford for that to not be the solution. Like previously stated the ac system is new except for the evaporator and hoses.