FICMrepair

I am in the process of bringing my old 91 LS400 back to life with/for my son via a new timing belt/water pump and all that goes with it. Before I started, I knew that the A/C was out - I was planning on hitting that next, hoping that all I had was a leak somewhere.

Now with the motor fully apart, I see that my compressor pulley is noisy when I manually turn it. So...minimally I need a new compressor - AGAIN (this one is the 3rd one on the vehicle and it was installed not 30k ago, even if it WAS eight years ago). I have no idea what is causing my continued A/C woes.

To minimize the chances of future issues for my son, I am planning on evacuating the system, pulling the compressor, inspecting the liquid line (even though it, too, has been replaced previously), and flushing the liquid line and the evaporator core.

Then, I would pop in the Denso compressor, along with a new filter drier, expansion valve, and condensor before adding in the oil and recharging the system.

I am considering sticking with the R12 since the system was designed for that originally, but that is a whole different conversation.

Anything I've missed? Any idea why I have been going through compressors like candy? She's only got 180k on her....

Ed

RA40

iTrader: (6)

Welcome to Club Lexus.

I believe you'll do well with a quality Denso compressor. I'd had similar A/C woes with another car and short of the blower motor and the tech clearing the evaporator, everything else had been replaced. Following that, the A/C was golden till the car was sold some 5 years later. I blew so much $ on annual fixes but that was my error in using a tech that "saved me money". Well, learning that the "lifetime warranted" compressors were a lifetime of continued replacement.

LScowboyLS

The NipponDenso A/C system in the LS series is perhaps the most reliable A/C system ever put on a passenger vehicle. A/C failure is as rare as transmission or engine failures on this car and usually caused by some bonehead "servicing" the A/C when it should almost always be left alone.

If it is actually the compressor pulley making the noise, then compressor itself is likely fine - you just need a new compressor pulley, these are available separately from the compressor itself.

only if the compressor itself internally is making noise do you need to replace it and flush the system, and if this is the case, it will become an involved repair because during compressor breakdown or burnout, metal and other byproduct from acid damage internally will collect at the tightest choke-point in the system (the expansion valve which is located inside the evaporator case) and this will need to be removed and cleaned and the flushing done without the expansion valve installed as it is not possible to flush through the expansion valve.

just make sure to have the system properly evacuated and to add the appropriate amount of compressor oil to the system since you have broken the refrigerant seal - proper o-rings and correct type and weight of refrigerant must be used as well - I would stick with original NipponDenso parts, to insure the legendary reliability continues.

Remember the golden rule: there is no way to accurately charge an A/C system other than weighing in the charge. Anyone who thinks they can charge an A/C system accurately by way of gauge reading is out of kilter with science and foolhardy and basically just employing a guess. Over or undercharging your A/C system is not good from your compressor. Undercharging results in poor lubrication and overcharging creates excessive head (high side) pressure.

FICMrepair

I've had two LS's and with each have experienced a MYRIAD of A/C issues (even if everything else was rock solid) - three compressors on this one, two on the last one, bad liquid lines, bad expansion valves, etc. All work except the very first compressor was done at the dealer at a typically $1500 price tag per occurrence. It got old.

What started this particular round of maintenance was a bad fan idler pulley/bracket (so I figured we'd just do the timing belt, water pump, seals, etc since we were in there), but the A/C had stopped working long before for reasons I never made the time to investigate. Hearing the noise out of the pulley was a surprise when I first pulled everything apart, but I know that that is not at all likely related to the fact that it doesn't blow cold.

Of course, now that this particular car is on its third compressor, I have to think something else is causing my continued A/C issues. My guess is that the system hasn't benefited from the thorough flush and evac that it should have seen with several A/C services.

I didn't know that you could get the pulley separately (that's good info - thanks!), but it seems that the OE option there is in the ballpark of a brand new compressor and all ($200 for the pulley vs $322 for a complete Denso compressor on Amazon). Since I want to flush the system out component by component anyway (and therefore need to open it regardless), I'll just go ahead with a new compressor to hit the magic reset button on that front - the $122 is worth it to me.

I saw another post by you, LScowboyLS, in which you were suggesting the benefit of sticking with R12 - pretty compelling. I can get a brand new recovery machine for $150, but would still need to source a recovery tank. I already own the gauge set and have the refrigerant - very tempting indeed.

I see that the expansion valve is located in the evaporator case, but don't know what is involved in pulling it yet. I've seen some claim that it can be R&R'ed in an hour, but am skeptical.

I'm also looking at installing an in-line filter in the liquid line - something like http://www.auto-air-compressor.com/In_Line_Filter.html.

Thanks for all the suggestions!!

LScowboyLS

if you don't recover the R-12, I won't tell anyone!

FICMrepair

Too funny. I now own the recovery machine - just have to find a source for the recovery tank now. I have to admit, though, that the true purpose of the recovery tank is to just allow me to re-introduce the R12 back into the system for when next time something breaks in the system - not exactly batting 1000 with this system thus far...

denverdog

this may not be your problem, but one way to keep a compressor going longer is to run it for 10-15 minutes each month during the winter, just to keep the seals oiled. all you need is one day of 40-45 degrees.

FICMrepair

I've always done that with all my cars, but have never had as many A/C issues as with this one. I think that the condenser may actually be my true issue as the prior owner had a front end collision that was supposedly repaired but now that the radiator is out I see that the condenser looks bent in about 3/4" in the middle - just enough to potentially be letting floaties into the system. I'm not looking forward to changing that bad boy out as I understand that the bumper has to come off. Joy.

LScowboyLS

very good advice and keep in mind, you don't have to freeze to do this, I turn up the heat and am toasty warm while lubricating my A/C system (you are heating up the air conditioned air before it comes out) - this is also a great way to clear out humidity or fogged windows on very damp winter days - a dehumidifier is actually just a small air conditioner!

LScowboyLS

yes, something very bad was done in the history of this A/C system - LS400 often goes 15 or more years with NO A/C service at all, and even after that only needs a light shot of refrigerant to replenish what has permeated through the hoses naturally (not a true leak)

As an A/C specialist for over 30 years, I cannot think of a more bulletproof reliable A/C system than LS400/430/460