lbq

My 98 SC300 just had the compressor replaced with a rebuilt one. After 2 days of cold air, the AC system is blowing hot air. I had it checked for leaks but could find any. The compressor is running as i hear the clutch engages every time i turn on the AC. The AC light does not blink. Pressure reading is 30/150 PSI on low/high side at 90F. However the pressure on both side stays constant even when I hit the gas. At 3000PRM the pressure is the same. What could possibly be? Compressor goes bad? clogged line? leak that I couldn't find?
Thanks in advance for all the help.

redsc400

sounds like you have a leak - bring it to a shop, have them put tracer dye in the system and search with a UV light. they will be able to find it - most of them are pinhole sized and hard to distinguish.

lbq

My mechanic did put dye in the system and checked under the hood but did not find any leak. Is it possible that the leak was at the evaporator where the expansion valve was connected to (which is behind the glove compartment)? Is there a better way to know for sure that there's a leak in the system?
Thanks

dwebb99

iTrader: (17)

Autozone rents free of charge vacume pumps and gauge sets. You could try a recharge yourself (assume you have r134) and try and look yourself for where it is leaking. AC's can be a pita tracking down leaks and $$$. Best to do what you can yourself to save on $$$ spent.

dwebb99

iTrader: (17)

BTW, the good news is that you lost most/all your freon in just several days. There's a real leak somewhere and not a slow one(i.e. takes 6 months to loose freon). Run a vacume on system to see if it holds pressure (most likely will not). Then recharge system and look VERY CLOSELY at every spot throughout the AC system for leaks/ester oil.

lbq

I''l try to look harder to find the leak. But if i had a severe leak how come the low side pressure gauge showed 30psi?

5spdSC300

iTrader: (1)

Check to see if the A/C is throwing any codes and start troubleshooting from there. The link below will show you how to run the A/C system diagnostic codes. Hope that helps

https://www.clublexus.com/forums/sho...d.php?t=294197

lbq

Thank you all for for your responses
The code was 23 which was low refrigerant. I must be leaking. I checked the join where the expansion valve is connected to the evaporator and found some light trace of yellow dye around the thread. I think that was it. I also heard constant hissing sound around the evaporator area. Is it normal that the sound was there as long as the ac is on or you should only hear it at the beginning when the ac is fist turned on?
Thanks again

dwebb99

iTrader: (17)

AC connections (at most all joints) use o-rings to seal them. You may have a old/bad o-ring. Always run you ac everyweek or two during winter months to keep those o-rings lubricated with the ester oil that is in your freon. It will help rolong the life of your o-ring seals. Changing out o-rings is a very easy diy. Your local Autozone has any o-ring that you may need. Once done, then use must vacume your ac lines and recharge system.

lbq

I think i might try to do it myself. Do I need to add oil when i do the recharge or the oil is still in the system after discharging and evacuation?

redsc400

CORRECT! thats exactly where my leak was.... it was a pinhole leak. takes about 6 hours of work to get at the evap - need to take apart most of the dash.