Help!! Ihave a 2003 1500 ram van with the 5.2 magnum. Bought used with24k on the odometer. Right from the start I've been plagued by a high pitch whistle that only occurs in the cold weather. Whistle is intermittent and can occur at any speed, and doesn't matter if engine is up to temp or not. Give it a little more or less throttle and the noise goes away. ( will fade in or out like an air whistle being throttled by a 1/4 turn ball valve) Whistle almost always appears while maintaining a steady speed. Tried disconnecting all the vac lines and plugging them at the manifold - still whistles.( even tried it with brake booster disconnected and capped - scary! ) Changed throttle body and gasket, tried driving with air cleaner assembly off, checked for restricted exhaust, cleaned IAC, tried unlit propane torch trick around manifold, T.B.,& vac lines. Checked intake manifold for oil on the plate- it was pretty clean, not surprised as I wasn't using any oil.Took the van to my local garage, they did a "smoke test" and found no vac leaks, did a test drive with the scanner hooked up and everything checked out normal. Convinced it was a vac leak , I installed a vac gauge- @100 KMH it only runs about 10" Take it out of O.D. and the vac runs 18" to 20" and I'm getting about 18MPG. With the O.D. on with the lower vac reading I get 12 to 14 MPG. Out of desperation I took it to the dealership (now at 58K). After checking it out, they told me the whistle was the PCV valve and hose, but the engine had so much blow-by, they were going to change the motor under warranty. ( excess blow-by without oil consumption?) Was told no motors were available in the system,I'd have to wait awhile. While I waited (about a month) I tried driving the van with the PCV valve removed and the line capped- made no difference-still whistled. When I got the call the motor was in, I was told it was a 2 day job ( sounded about right) 1 month later I got my van back just as the weather was warming up so it didn't whistle at this time. This is after they installed a re-man factory short block, new water pump, serpentine belt and clutch fan. Now it's cold again and the whistle is driving me nuts, and I don't always remember to disengage the O.D. so the mileage really sucks. ( I was told by the dealership the overdrive can't be defeated without opening up the tranny and then I'd have to ignore the check engine light) On a side note, when in overdrive and maintaining a constant speed ( by foot or cruise) the heater controls will only switch modes once or twice , then won't work until you back off on the throttle to bring the vac up again ( the vac reservoir must be not leaking) If the van is driven out of O.D., the heater controls all work properly. I'm all out of ideas and really flustered.I've talked to anyone who'll listen , both backyard and proffesional mechanics who are all stumped-nobody seems to have an answer for me. Anybody out there with an answer ?

 

My dads 5.p would whistle but only at certain speeds or engine load. It was the air intake or where/how it mounted to the throttle body. Have you taken yours off and driven without it a short distance to see if thats where yours is coming from?

 

Thanks for responding- tried driving with air cleaner assembly off- still whistled. About the only thing I havn't tried is driving with the engine cover/hump removed , too much noise and cold to be much help pinpointing the source. It's -18 C here this morning.

 

I have a constant whistling coming from my engine. I found the source to be a leak on the valve cover around the breather cleaner.

 

To me it sounds like there's either a dead spot in the TPS or the MAP sensor is leaking.

 

The whistle is intermittent- may not whistle at all on a 50 mile trip, next time it might whistle thru a 20 mile stretch. The breather on the valve cover was cleaned before I tried driving with the air cleaner off. When I changed the throttle body, it came off of a 5.2 that didn't whistle and it was swapped in as an assembly with the IAC, TPS, and MAP (yes, I used a new gasket). If the original MAP was leaking, wouldn't it have shown up with the propane test?

 

I had a good vacuum leak I could hear, and see the crack, but when I dowsed it with propane, it did not change the engine note enough for it to be a valid method for finding the leak. Perhaps with older carb's engines it works better than one with multiple sensors helping to control the A/F ratio.

Try the 3 foot length of garden hose to your ear, the other end around different parts of the engine to find the source of the whistle.

 

I know my first post is a long one, but I wanted to be as detailed as possible in what had been checked and could be eliminated. Whistle only occurs when driving in cold weather.Vac at idle @22". Whistle still ocurred with ALL vac lines disconnected and the manifold vac ports plugged. When the dealership installed the short block, all new gaskets were used- problem persists

 

Mine has a slight whistle sound as well BUT only on cold mornings where the ambient temperature is around or below 35 degrees AND engine is at same temperature. I believe both our vans are getting the whistling sound from the IAC motor as the air goes past it and its port. When the air is that cold the PCM will give the injectors a little more fuel and close down the IAC more than on warmer days or with a warmed up engine.

On your HVAC system check/replace the one way check valve on the right side of the intake manifold and the line going to the vacuum bulb behind the passenger headlamp.

 

The whistle I'm talking about is LOUD- pedestrians stop and look around and animals run for cover. You didn't mention if your whistle goes away when your engine gets up to operating temp, mine doesn't. I'm assuming the check valve to the vac reservoir is okay since the hvac controls will operate air damper once or twice for quite some time after shutting down the engine. The IAC on my original T.B. was cleaned , and it whistled with the second T.B. assembly I tried . I also tried disconnecting the vac line for the HVAC and plugging the manifold port- still whistled . Any other ideas?