Engine has a whistle

jeep
wrangler

#1

Hey Fellers,

My Jeep 4.0 has developed a whistle in the engine when it is cold, and there is no accelerator being applied. The tone of the whistle changes with the amount of gas peddle you give it. Then as the engine warms up, or if I sit for a while the whistle will slowly diminish to nothing. I have looked and listened and it appears to be on the left side of the engine, but can not find the source. Can you help?

Thanks,

Bill


#2

Do you have a stock air filter setup …or aftermarket? Before I went back to OEM, my conical K&N would allow me to hear a whistle at every shift event. It could be some vacuum related problem with the EVAP:PURGE system …but I’d probably clean the AIS motor on the throttle body as my first action. That’s the port you see above the throttle plate on the throttle body.


#3

No, I have a stock set up. I have been told that it may be a leak in my exhaust gasket, but the person that told me this said it without even looking at the car so I was skeptical, and am looking for further possibilities. It is on the exhaust side of the engine, so I was incorrect in saying that it was the left side. It’s driving me nuts, because of that darn sound.


#4

It could also be the sound of an alternator on the way out. When you first start the truck, the alternator is put under high load to recharge the battery, then this tapers off as the battery gets recharged. High load could make an iffy bearing in the alternator squeal, but relax as the load drops off. I mention this because I’ve experienced it personally. The alternator in my case acted like this for more than a year before it gave me problems keeping the battery charged. After I changed it, the whistle was never heard from again.


#5

Could be an egr valve or exhaust manifold leak.


#6

could it be the gasket? MOAB Offroad implied that the gasket had a leak. But the guy didnt look at the jeep, although they are the authority in my area as far as jeeps go, I am still leary.


#7

Vacuum leak?


#8

I have a couple of updates on the whistle. I noticed today that it only started to whistle when the engines temp got up over 140, and then whistled when I depressed the clutch. the whistle is on the exhaust side of the engine. and the tone varies with the amount of accelerator that is used. I hope that this extra information is helpful in your helping me track this incessant whistle.


#9

I have a couple of updates on the whistle. I noticed today that it only started to whistle when the engines temp got up over 140, and then whistled when I depressed the clutch. the whistle is on the exhaust side of the engine. and the tone varies with the amount of accelerator that is used. I hope that this extra information is helpful in your helping me track this incessant whistle.


#10

Yes on my truck I can it play like a flute. Engine they think would need to be pulled to replace the hole in the exhaust manifold, a definitely different sound, and as there is nothing but rust where the bolts used to be our mechanics thought it was not worthwhile, The flute adjustable by engine speed they thought egr valve but not sure. Being a 93 I just have to smile live with it and hope it lasts another 4 or 5 years


#11

Try a small length of vacuum hose or the like as a stethoscope to try to pinpoint the actual location of the noise. Or you can get an actual mechanics stethoscope.