I recently installed a new longblock in a disco I purchased with a blown motor. The engine runs great. However, when accelerating from a stop or cruising at about 25% throttle, I get a very high pitched whistle/whine. If I'm driving at about 45 mph on flat ground and applying just enough throttle to maintain speed, the whine is quite audible. But if I let off the throttle, it immediately goes away.

I've replaced the air filter box and intake elbow b/c they were both cracked, but that didn't stop the whine. Is it possible that I could have an upper and/or lower intake air leak that would whine like that? My idle is also a bit rough, so that also makes me wonder if I have some sort of leak that would contribute to the rough idle.

Thanks in advance,
Bryan

 

the rough idle you mentioned leads me to believe it's a vacuum leak. try to spray carb cleaner around the manifold seals, see if you can get the intake to suck it in. if there is a leak it should suck the carb cleaner and start to sputter.

I'm not sure of another way to check for vacuum short of in-lining a gauge.

 

I was wondering if you could do something like that. Will it sputter or increase rpm?

 

Depending on your spray, it should increase RPM. But, either way, you will notice a difference if it enters.

 

un-lit propane torch is another source....
sometimes listening to taget areas thru a short piece of hose works.

 

I thought it would make the engine sputter. Regardless, SuperSport is correct you will know the difference once you get the spray to that sweet spot.

 

I have a 2003 discovery SE7, I have the same issue, the vehicle whistles when under acceleration. It does not whistle when I lift off the accelerator. Please tell me if you ever resolved your issue and if so what was the result? Thx

 

Me too. Trying to sort out a whine.