notkrap

I'm changing/DIY my A/C compressor with a new denso. Lexus told me 1.54 lbs of R-134a goes into the low side after vacuuming it down, but I'm trying to find out how much PAG oil to insert and what type.
Some youtube videos have 4oz being poured directly in the comressor. Any advise?

Also, if anyone has ALLDATA type instructions for a compressor change, I'd be grateful.

I'm planning on changing the compressor and o-rings, dessicant bag, & expansion valve.
Am I missing anything?

notkrap

BTW, 2004 LS430, front A/C only w/ 148K
Found this site which states 22-24 ozs R-134a, & PAG 46 but no amount
http://www.techchoiceparts.com/refri...pacities/lexus

Viper6

AC charge amount you need is noted under hood on a sticker for your model... Manual says for single AC unit 22.93 +/- 1.76oz

there is a formula in the manual... (oil capacity inside new compressor is 130 +/- 15cc) - (oil remaining in old compressor) = (amount of oil you need remove from new compressor before install). Basically any oil residing in the old compressor should be removed from oil filled replacement compressor to maintain constant level. I guess lexus OEM comporessors come with this 130cc factory fill so you have to drain them off before install.

if your new compressor has no oil in it, just add an amount equal to what you recovered from the old compressor and that should ensure the system stays level.

Manual says use ND-OIL 8 or equivelent... not sure how that cross references to the PAG oil grades...

LScowboyLS

The oil charge on the label under the hood is for the entire system. The system's oil charge is distributed at various points in the system, including not only the compressor, but the condenser, the evaporator and the dryer as well.

So in order to to get the system oil charge correct, the system would need to be flushed of the old oil, which should be done anyway in the event of a compressor change. The preferred flushing solvent according to Nippon Denso is Kwik-Solv.

A good analogy is that there is similarly no way to to accurately charge a vehicle's A/C system with the correct amount of refrigerant, without evacuating the system and weighing in the refrigerant charge, any other method is a guess.


the problem with this method is that if the system has ever had a refrigerant leak (or has one currently), the oil that was lost via the refrigerant leak is now unaccounted for and missing in the new replacement scenario

Viper6

Agreed, good point. When I had mine hooked to a pro machine it measured how much was taken out in the vacuum draw down process (i did 30 minutes of vacuum) and they just simply added an equal amount of new oil back in with the refrigerant charge (by weight of course). flushing an AC system is beyond my abilities/DIY interest levels.

If I were the basic guy at home trying to do this and system had no leak except when I removed the old compressor, I'd add equal amount of oil removed with new compressor like manual describes and then take it to a place that could do the vacuum and recharge per OEM specs... otherwise you gotta have the vacuum ability at home through gauges so you can switch to recharge coolant without introducing air to system after the purge, blah blah blah... just pay someone $150 to do the evac/recharge perfectly so you preserve your new components!

My $.02

LScowboyLS

something else people who try to do their own, as well as most shops, miss, is the fact that the evacuation process itself can remove oil that is critical to your system, especially depending on where the service ports are vs. where the oil is in the system

PS - a little too much oil is better than too little

notkrap

Thanks for the feedback!
I'm trying to decide whether or not to proceed without replacing the expansion valve, just replacing the compressor and the drier bag. Apparently the whole dash has to come off to replace the expansion valve. Parts wise I'm at $450 . Just shopping around, a mechanic said he's do compressor, drier, flush & recharge for$425, & add $500 to also do the expansion valve.

LScowboyLS

the dash does not have to come off, but there is far more work to replace the expansion valve than the rest of the compressor job entails - it is approximately the same labor as replacing the evaporator - I am wondering why your compressor is out in the first place, if the system is left alone and no bozos work on it when it is not necessary, the LS430's NipponDenso compressor should last at least 250K miles.

if the compressor is being replaced due to wear or burnout, then the expansion valve should definitely be replaced - if the compressor is being replaced due to a body or shaft seal leak, or a defective clutch or clutch coil, then no expansion valve replacement is necessary or advised.

notkrap

Had a leak last year & compressor stopped and added 20 oz of A/C cocktail and worked ok. Started getting warm a week ago and added another 20 oz and a day later the compressor seized. It was noisey for several months, plus the car is black on black and was originally a Miami car before I bought it, so the compressor was well used.

LScowboyLS

A/C cocktail?

I hope you didn't add anything besides pure 134a refrigerant, or that may very well be what killed your compressor

A/C systems actually last longer the more they are used

notkrap

Yep. I chumped myself. Used the ole'can of A/C Pro from PepBoys. Lasted for a year, but I'm a gambling man and it probably helped choke it out.

notkrap

Wound up taking the LS430 to a mechanic and he replaced the compressor and desiccant bag , leaving the expansion valve alone. I know it was a gamble, but being so far behind the dash meant another $500. Roll the dice, please.
Vacuuming it down, all o-rings were leaking and he had to change them too.
Charged $425
So I got it all done under $900 and Johnson Lexus wanted $2500