Bluestar

Hey I replaced my ac compressor in my 98 4.0 about a year and a half maybe two years ago. Recently it just started making this high pitch humming sound on and off. The ac seems to still work fine. Should I be worried about this? Anyone knows what it is let me know thanks.

93gc40

Sounds like it is low on oil.... If it were mine I would have it evacuated and refiled.

Mr. Langley

I agree. I had mine replaced as well and i made sure he flushed and refilled oil cause I had it happen on a previous car where they didnt fill enough oil and it made strange sounds.

djb383

From what I've read, the amount of oil in the system is very important.....a little to much, it won't cool properly, too little means inadequate lubrication. Did u completely empty the replacement compressor before installing and do u remember how much oil u added back to the compressor?

Bluestar

I dont remember exactly how much oil I put in but when I bought it I asked and put in the amount of oil and refrigerant the guy at the autoparts store told me to. So my best bet is draining it and refilling it with new oil and refrigerant?

Mr. Langley

It has to be vaccumed as well.

djb383

IIRC, the a/c system on a '98 takes 8.1 ozs of oil. The problem is, there's always some old oil remaining in the system.....but how much is the million dollar ? Any time a compressor is replaced, the accumulator/dryer and orifice tube/liquid line should also be replaced because they are both filters. If not replaced, shrapnel from the old compressor will likely migrate from the old dryer and/or orifice tube and eventually destroy the new compressor. Once the evap and condenser have been flushed (old oil removed) and new parts installed, the correct amount of oil can be added (1/2 to new dryer and 1/2 to new compressor) to the system. It's important to drain any oil out of a new compressor before installation......and yes, a vacuum must be pulled prior to refrigerant charge.

Bluestar

Alright one last thing. How much refrigerant does it take? Thanks fot the help everyone I appreciate it.

djb383

A '98 takes 8.1 ozs of oil, system total.