Hi everyone, I’ve got a persistent idle noise on my 2012 Kia Sorento D4HB (build date Jan 2012, 748,000 km) that happens all the time but gets significantly worse when fuel is low or the AC is turned on.
The loud noise occurs at idle — it disappears after ~5 minutes of idling or when driving/accelerating — and instantly returns if I switch on the AC again.
A mobile mechanic replaced my crank angle sensor (but couldn’t diagnose propely) and he believes it could be a high pressure fuel pump which is located just below the power steering pump.
While another mechanic (over the phone) thinks it’s timing chain pretentionser wear, but the noise is constant even with full fuel. I’ve already replaced all fuel injectors 100,000 km back (with second-hand parts — they work perfectly), and I also replaced the fuel pump motor 2 weeks ago —yet the problem persists. My cheap scanners show no consistent codes (previous ones vanished and not back again)
I need your help to avoid wasting money on useless parts! Since the noise is always present but spikes under low-fuel/AC conditions, it’s likely an electrical interaction during idle, not mechanical wear but i'm not sure. Key clues:
- Noise stops when driving or pressing on accelerator pedal
- AC activation instantly triggers it
- Fuel level doesn’t cause the noise but only intensifies it when fuel is very low
2012 kia sorento 4 cylinder diesel, 6 speed automatic
Engine with 748,000 km, and still original
Gearbox Transmission has around 550,000 km
Here is the video of the issue:
Video 1:
https://youtube.com/shorts/nCH_8ssWpbo?feature=share
Video 2:
https://youtube.com/shorts/l5t1X0JXhPQ?feature=share
Given the diesel engine and metric units it appears you are not in the U.S. With a few exceptions, most of us on this board are in the U.S. and that model was not sold here with a diesel engine. Thus most of us have no experience with it.
Generically, you might want to use a mechanic's stethoscope or a length of small diameter hose to pinpoint the source of the noise. The use of a hose to find engine noises is demonstrated in this video:
https://youtu.be/o8ixg87X8AM?t=356
Also, have you checked your fan belt and all belt-driven pulleys and accessories? (When the AC is turned on it stresses the entire belt system.) Performed a complete diagnostic scan for codes and data?
Also at that mileage (in real miles nearly 465,000) it's quite possible your engine is just plain wearing out and you are hearing internal engine noise due to wear.
AC activation instantly triggers it
I guess it has also something to do with the AC compressor.
Anyway you can check out this video and see if helpful
https://www.youtube.com/watch?v=oVyhsdeXS34
Scotty doesn't generally return to topics he has already answered.
AI was telling me that we have to do a system flush to make sure there is no contaminants or else it will damage the new compressor?
Why are you relying on AI? AI in its present form is notorious for giving wrong answers and hallucinating complete fiction. For example, an AI used to generate police reports here in the U.S. stated that a police officer turned into a frog:
In my case when I tested an AI "mechanic" on a problem that I had in the past and already fixed on my own car it gave a completely wrong answer as to the cause of the problem and told me I probably needed to replace a part that didn't even exist on my car.
Having said all this, in this case your AI is only giving you part of what needs to be done. When a compressor fails it contaminates the AC system with metal debris. To insure success and avoid premature failure of the replacement compressor you also need to replace the condenser, expansion valve or orifice tube, and the drier as well as flushing out the rest of the system. (You will probably find your new compressor warranty requires this.)
On vehicles where the evaporator is easily reached it's not a bad idea to replace that as well. (In general though the expansion valve or orifice tube will keep large debris out of the evaporator allowing it to be successfully flushed, unlike the condenser.)
Well, if you're anywhere near Clarksville, Tennessee, I'll analyze it free during the weekdays when I'm filming. Any mechanic with an electronic stethoscope should be able to pinpoint the noise though it makes the noise the noise can be pinpointed. Start with a better mechanic one who has equipment and knowledge of how to use it
Hi, I live in Canberra Australia so unable to come for this.
Do I also need to flush the Air con?
I found out the AC compressor is the one that's making all the noise, and the Air con doesn't give cold air anymore.
The rough idling and noise goes away when driving, or when pressing the pedal 5% during idle
The noise reduces when weather is cold and when Air con is switched off.
I bought brand new aftermarket compressor, and my mobile mechanic is coming on Wednesday to replace it
However, I then have to visit another mechanic at his workshop, to have the regas done.
AI was telling me that we have to do a system flush to make sure there is no contaminants or else it will damage the new compressor?