Strange Whining / Squealing 5.0 EFI

[BroncoinAlaska]

Bronco Info:
5.0 Mustang EFI
Explorer 5.0 Serpentine (New Alternator, Tensioners, AC Compressor, rebuilt Lee's PS Pump, new belt)
GT40 tubular intake

Just started getting a whine/squeal that varies with engine speed. Went out and got a new Gates serpentine belt and installed it. When coming to a stop light the squeal slows and stops after sitting at the light for a while. This varies and sometimes the squeal/whine is always present it even persists for a couple of seconds after the engine is shut off. What could the whine/squeal be? Vacuum leak? AC compressor? Why would the bronco still squeal/whine after the engine is shut off?

 

[hucklburry rev2]

I don't know why it would stills squeel. If you want to check the pulleys/bearings you could, with engine off, spray one (lets say idler pulley bearing) with something like wd40. Use the red straw and try to just get the center of the pulley, you don't want to lube the belt/running surface.

Start the engine and see if it went away. If not, shut her down and try the next pulley. If you make it through all of them and nothing changes, I don't know whats next.

The wd40 would be a temp fix, the noise will come back if it does go away initially.

 

[Broncobowsher]

If it is making the noise after the engine stops, it can't be the belt.
Chance it could be a whistle from the intake, that can take a second or two to fill with air after the engine stops. Does it only happen at closed throttle?

 

[BroncoBernie]

Sound

I have the same sound that I have been trying to figure out I think it comes from the throttle plate. I have gt40 tubular to with bbk cold air intake with bbk throttle body. The sound continues after engine is shut off for like 1 or 2 seconds. Hope some of this helps.

 

[ScanmanSteven]

I have to agree with Broncobowsher that if it happens after you shut it off it can't be the belt. I vote vacuum but if you have hydraboost it could be that although once the pump stops so does the pressure. So vacuum leak could be the power booster having a leak. If you don't have a stethascope, get one from HF and try to isolate noise to help narrow it down. Good luck.

 

[Voodoo21]

Staying tuned, I have the same issue!

 

[BroncoinAlaska]

Really do not think the squeal/whine is coming from the belt. I am leaning towards vacuume leak. The only thing I have changed lately is switching from a K/N filter breather on my valve covers to a fitted oil filler cap. The throttle cable was contacting my K/N breather filter on the passenger side valve cover.

What is the best way to check for a vacuum leak?
Carb Cleaner? Soapy Water Spray Bottle?

 

[hardwork]

take your s belt off (you can run the engine with-out it for a couple min ) the engine will be Much quieter especialy without any fan wind noise) listen with a piece of hose held to your ear for your squeal while quickly moving the open end of the hose around the manifold aria . it will sound Very loud when you get close to the noise . Note a stethoscope with the sensor removed so you are listening with an open hose works even better (if you have one).

 

[ransil]

Really do not think the squeal/whine is coming from the belt. I am leaning towards vacuume leak. The only thing I have changed lately is switching from a K/N filter breather on my valve covers to a fitted oil filler cap. The throttle cable was contacting my K/N breather filter on the passenger side valve cover.

What is the best way to check for a vacuum leak?
Carb Cleaner? Soapy Water Spray Bottle?

best way to check for a vacuum leak is a smoke machine, google home made one cause the the professional one arent cheap.

EFI ( mass air) should have sealed valve covers

 

[Sledneck]

My EFI motor had the same whining after a few minutes of engine operation. I had the PCV connected, but did not vent the valve covers back to the throttle body. This would pull a vacuum in the engine, and cause a lot of noise. You could hear the vacuum release after the engine was shut off. Once a added the valve cover vent, the noise stopped.

You mention you changed the filter on the valve covers to a oil cap when the noise started. Are you still venting the valve covers? If using mass air EFI, it should be vented using metered air, but have seen many people just use a filter.

 

[Matt_brianna]

I had the. Same thing on my 89 mustang. The pcv valve behind the intake had popped out, so i pushed it back in. Then i replaced it to stop the whinning/whistling.

 

[Ourobos]

If a closed PCV system, you MUST Vent he valve cover back to the throttle body as mentioned.

Also aftermarket throttle bodies for the 5.0s are notorious for that exact thing. You can drill a 1/8" pilot hole in the throttle blade that might help.