Hi everyone

I just purchased a 2005 Dakota quad with a 4.7 with 39000 miles. When I open the hood and stand on the driver side I hear a distinct sound of a vacuum leak. I have no engine light on. I'm not sure if this is normal. It sounds like it's in the throttle body area. I moved the hoses around a bit to see if it affects the sound but no luck. It may be normal but I'm just not sure. If it is a leak it seems loud enough to give me an engine light.

Any ideas on diagnosing this. I do have a warranty but if the dealer says it's normal the will charge me a $114 diagnostic fee.

Thanks

 

Grab a can of brakeleen or propane and spray (or release the propane) near the suspected vacuum leak area, and listen for a change in RPMs. If it was a vacuum leak, you would probably notice things other than just the sound though. Because its a speed density system, the PCM doesnt care if there is a vacuum leak, therefore you wont get an engine light until something else is triggered, such as an engine light for an uncontrollable idle.

 

Ok will do. The only problem I might have is a lack of high end torque or maybe that's the way these truck run. I've only had it for three weeks.

Thanks for the info

 

Use the brake cleaner, spray it on all the vac hoses and gasket areas.
Do you have a cold air intake? sometimes the cai will have a rushing sound that can be mistaken for a vac leak.

 

No cold air just a K&N filter I just put in. Seemed to happen after that. I thought I may have mocked a hose loose. The sound is not coming from that area. Then I thought it might be where the intake hooks to the throttle body, but it seems snug.

 

The stock 4.7l dives in terms of HP and torque in the high RPMs. The power is before about 4000-4500 RPM IMO. Definetly spray something flammable in there and see what you can find. You can also get a 3ft piece of 1/2" tubing and put one end up to your ear and move the other around the engine compartment. This will narrow down where the noise is coming from.