Technics

Just today I noticed a low pitched whine coming from the engine. It's most audible when the engine RPM's are going down after giving the car some gas. It's almost like a mechanical humming sound. It only happens when the a/c is operating. It doesn't sound like a belt at all.

I had been running the a/c aroud town this past weekend when the temps were 95 degrees+ looking for a new apt. A lot of stop and go driving.

What do you guys think? Compressor on it's way out? Low refrigerant?

Aristo300

It almost sounds like the car has a low charge of freon.......... does the output change with RPMs?

Technics

If you mean as far as the A/C getting cold then yes. Around town at low RPMs the A/C is not that cold. At sustained speeds on the highway it's much colder.

Is that what you mean?

SC400TT

iTrader: (4)

Check the power steering pump reservoir just to be sure...It whines if there is a PS fluid leak in the system...

Ryan

Technics

Checked PS fluid and it's topped off with no leaks. Maybe I'm losing my mind but I've never heard this noise when the A/C was on before. Do you guys hear anything simular when you rev your engine? A rurrrrring sound?

As far as the refrigerant being low - the car is ten years old. A Lexus tech suggested the car MUST have a leak in order for the freon to be low. Is that true? If there were no leaks in the system the level of freon would stay the same for a decade?? I would assume after all that time it would have to be low in some way.

p.hase

i have exactly the same whining sound at 42mph only when A/C is on. not at 41 and not at 43.

i recharged and converted my A/C system lately and i am glad i have done it!

Aristo300

Well I got my compressor/clutch replaced, and the system recharged..... the dealership is telling me that there is a leak coming from the expansion valve & that the evaporator could possible be going out.... so I don't know what to think. The car cools fine.. as long as the car is running at normal temps and your crusing. From a standstill the air doesn't get very cold. Anyone have any advice?

JJG2005

Slightly off topic, but when I went to convert and recharge my AC, I had a complete 0 rating of Freon in my system. Is it possible that I just ran out (safe to refill with r134 instead now since it's empty?) or I'm thinking there is a BIG leak somewhere? The seller of my car told me that it was working last year and he thought it probably needed to be recharged.

groovinSc3

i was about to make a thread until i saw this one. mine's just started about 3 weeks ago. it works when it wants to. when it works its really cold but then it'll stop working. i have no clue. maybe the clutch thingy?

lex400sc

I had that same sound for years but the "ruuur"ing was intermittent and went away every time after about 10 sec of running so i thought nothing of it. I don't know if it's related but my psp has been leaking too and just killed my alternator. If SC400T is correct, that would explain it...

Technics

Hmmm, mine is consistent. It's directly related to engine RPM's (as RPM's increase, so does the noise) so I'm thinking maybe it has something to do with one of the belts?

nextlevelcoupe

iTrader: (1)

i have a whine as well, but mine has been diagnosed as a tensioner pulley (very easy to miss)
- it's in the path of the drivebelt..my bearing is worn, and gives of the same sound as mentioned in this post. i went crazy trying to locate this sound by myself ,but i had an ex-lexus mechanic who know these cars very well take the pulley out spin it, and voila! problem localized!!