2003 F250 6.0L

This has been going on all winter and I think I know what it is, but I don't know...
Depending on temp my engine will start squealing, very high pitched, after 2,000 RPM. If it's cold it start around 2300 RPM. If it's hot, it start earlier, sometimes right at 2,000 RPM. We had a nice hot day recently and had my son hold the RPMs right where it was squealing while I tried to narrow it down. It's one of those noises that comes from everywhere and it's high pitched so a mechanics stethoscope does nothing. I leaned over the engine, grabbed the intake boot that goes from the filter box to the turbo and it stopped...It didn't come back until this morning. The connecting bands are tight, but that doesn't mean there isn't a leak. I wouldn't think this part of the intake would be under pressure from boost as it's before the turbo. Could the suction from the turbo kicking up at that RPM be causing a strong enough vacuum to create a high pitched squeal?

 

You have a gauge on the air filter outlet that tells you if you have a vacuum or not. It is called the "Filter-Minder" gauge, and it shows if the air filter is plugged.

That said, IMO you have something else going on. I would install a pressure gauge on the degas bottle.

 

Can you recommend a gauge?

 

For the vacuum or for the degas pressure?

You can tee in a relatively inexpensive manual gauge for the degas pressure - tee into the small vapor line from the radiator.

 

The degas bottle is what I was referring to. So plug the return line and hook the vacuum gauge up to the nipple it was connected to? I assume that positive pressure is bad?

 

You do not want to plug any hose. You TEE into the hose and put a pressure gauge on the tee.

You are NOT using a vacuum gauge here. The degas bottle sees up to 15-16 psi of pressure, so you need a gauge that goes to AT LEAST 20 psi.

Do not cut the existing vent hose.
Remove the small vent hose from the degas bottle (the one that comes from the top of the radiator).
Insert one straight side of a tee into the end of that vent hose and then clamp it (you will need to clamp all hose connections to each barbed fittings).
Then use some new hose (say 4-6 inches of hose) to re-connect this vent hose to the degas bottle (ie - connect the new hose to the other straight side of the tee, and then to the degas bottle).
Then use a small piece of hose to connect the 90 degree side of the tee to a second barbed fitting - this second barbed fitting must have threads that your pressure gauge can screw into.

ATM I do not recall the size of the vent hose, 3/8 maybe?
Get the hose at a local Auto Parts store. Home Depot or a True Value will have the barbed fittings you need. First you need to pick out a pressure gauge you will use and what threads it will have on the end of it. I buy my pressure gauges from Grainger. You should get a gauge than can withstand at least 250 *F (but just for a few tests at least get one rated for 200*F). Usually you would want 1/8" or 1/4" male NPT end on your pressure gauge.

https://www.homedepot.com/p/Everbilt...3099/300862702

For a pressure gauge, something like this:

https://www.grainger.com/product/Ind...e-Gauge-18C747

Barbed to NPT fitting:

https://www.lowes.com/pd/B-K-3-8-in-...ing/1000504941

 

Ok, once I get that setup, what I am looking for here? What pressure level indicates a problem?

 

The cap vents around 15-16 psi. If you reach that pressure, then the sound you hear is likely to be the cap venting pressure. Most likely source of this (if you have it) is a leaking head gasket.

 

Good to know. I'll report back when I get this figured out.

 

You could very well have an exhaust leak or a Charge Air leak as well, but people usually look for those before posting.

 

Like I said, I've tried narrowing this noise down, but it sounds like it's coming from everywhere under the hood.

 

I had already assumed that you had already looked diligently .................

 

Any possibility it could be the belt? I had an ongoing issue with the belt slipping on the fan pulley, causing a high-pitched squeal at higher rpm's. A new tensioner finally fixed it for me.

 

I thought about that, but it doesn't sound like belt slippage. Plus, I replaced the tensioner last year.

 

I had a similar problem, and a new tensioner did NOT help, I ended up having to replace the water pump pulley. The old was glazed and super shiny.
But I was able to narrow it down to the belt slipping with the use of Torque Pro. I set the the FAN speed PID and everytime the fan speed hit 2000 rpm the squeal would, Wil for lack of a better word, squeal.