Noise from the engine compartment shortly after AC is on

A

Ataher

Member
Location
Tripoli - Libya
In the summer, when I first turn the AC on it works perfectly, but within 30 minutes a noise starts coming from the engine compartment that gets louder when I step on the gas, it is not exactly an annoying type of noise but it is like another engine running. From the outside it is barely noticeable but when I sit in the car I can hear it clearly and it is very distinctive. Soon as I stop the AC it fades away. I tried turning the AC on previously during the winter but there was no such noise so I thought maybe it has to do with heat.

I seen many topics discussing this issue, but in all of them (the ones I read) the noise starts immediately as soon as the AC is turned on, not exactly like my case.

Any thoughts will be appreciated.



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hello ataher;
i think your description of the issue is the same as what i'm facing with the AC during hot weather and when starting the car when its still warm, did you ever solved the issue or it went away on its' own
 
I had a noise when my AC was on. It was like a clicking noise? It turned out that I just needed to reposition the in cabin filter. I would look into that.
 
The noise is still there, I never revisited the problem and I just ignored it so far.

I know it is not my clutch because the noise is not coming from there, my belts are new and I have auto tensioners so that is ok too, I tend to believe it is my AC, I can safely say that I do not have sufficient cooling, it still blows cold air and gets the temperature inside right around 25 degC when it is 40 deg outside, but it takes a bit of long time for it to do so, it is not like when I first bought it.

According to the manual, there are a few checks that I did not do yet, I need to see if there is a collapsed line, check on the high and low side pressures, and see if I need to add refrigerant and / or lubricant, and finally pull and inspect the expansion valve, all of these can generate what the manual describes as just "noise".


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If its not cooling like it was your system may need a recharge. When it's recharged new freon and lubricating oil are put into the system. It may not be a mechanical problem. I would take it to a good A/C shop for diagnosis.
 
So after I have changed the coolant recently, I have noticed a much better AC cooling, I can say that it freezes my hand off when I put it in front of the stream, this tends to happen at 2,000+ rpm, obviously when more power is delivered to the compressor.

This told me that, my problem with the whole AC thing could be just poor heat transfer overall, so after I took care of the coolant, I decided this morning to pull the radiator out, clean the fins on it and also on the condenser.

The radiator was in a really poor shape, I will post pictures when I get good connectivity, there was a lot of dirt and the fins were clogged up specially at the lower side, so I blew it with air first, then water and finally dried it up with air again. You can not believe how much crab came out of it. The contender was in a little better shape, but it had a considerable load of crab on its own, I did the same blowing on it with air, water and finally air again.

I will be test driving the car tomorrow with the AC on, I will post the outcome along with some pictures.





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Ok guys, so here are the findings after testing the car following the coolant change and radiator/condenser cleaning:

The outside temperature was 38 degC (max), I drove the car under different conditions while the AC was on: idling, accelerating, cruising at 100 mph and 140 mph.

1) At no time there was an overheating, even at high speed with AC on like what I posted in one of my earlier posts.
2) Cooling is excellent, that is what you would expect from a 310 hp engine.
3) The moaning noise it much lower now, it is still there but the sound of the engine is louder.
4) An additional rattling noise that used to kick in when the outside temperature is really high > 35 degC was completely gone, the cause was the the two AC lines (in and out of the condenser) were too close - see picture below, so I placed a rubber pad in between. This was a tip from the service manual. I put more pads in other places where I thought the lines were to close to each other or other components.

Note that I had also a grinding noise when the AC was on, but that was fixed long time ago by changing the drive belt.

As a conclusion, sitting behind the steering wheel, I know the problem (whatever it is: AC is going bad, low refrigerant pressure ... etc) is not 100% gone, but it has been reduced significantly, if it gets me through this summer I will be very grateful. Next summer will likely be another and newer FX.


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