HELP, please strange noise @ 40 mph.....

[whytry]

I was driving my Camaro to the Pleasanton Good Guys show this morning and after about 30 miles it all of the sudden started making a wierd noise. I describe it as a slapping sound against the fiberglass hood, but it was not that. It sounded like one of the ribs from the 12 rib Procharger belt broke and was still on the motor but enough has ripped/broke to slap the underside of the hood and it rotates...... What I have do so far:
Pulled over looked at belts (V-belt and 12 rib), both checked out ok, I saw the overflow a little loose, so I zip tied it to the radiator mount to make sure it was not loose and rattling and hitting the frame.... Got back on the road, seemed ok, began increasing speed and once again sound came back, exited freeway turned into gas station again checked, can't find anything. Checked the underside of the hood not a mark on it..... Also checked blower boost lines to see if one loose and blowing something against engine compartment and all good. Start heading home and try to go down my own checklist. I checked while driving with a maglite through the cowl hood and could not see anything flying around under the hood.
Ruled out:
Motor problems - not RPM sensative
Procharger problems - not boost sensative
That's when I made the connection between the sound and the speed. @ 40 mph in anygear, at any boost level, the sound starts, below 40 its gone. Not fading away below 40, completely gone..... As MPH increases so does the rate of the sound. Once the sound was being made I hit the brakes both hard (not locking up) and pretending like I'm coming to stoplight and it does not stop the sound until I get before 40 mph. The car does not "jump" around or "shake" when sound is being made.... By the time I got home, my wife drove along side me after I got home and she thought it sounded like it was coming from the front end passenger side, (same place I thoiught)... Any ideas for me to check? I was thinking maybe wheel bearings? I don't know what else to check. Thanks....

[Tom Welch]

maybe some of the front cooling fairing, the part under the radiator is loose. Maybe a front fenderwell or fender even. Wheel bearing will roar or grind, you will know the difference. Now that I re-read your post I am leaning toward a piece of plastic that is part of the front facia or similar part is loose and you hear it flapping.

[paul67]

Check the fan blade is not hitting the shroud , it could be as the wind going throught the grill turning the blade, over 40 it's fast enough to start it to hit the shroud also the blades do move back a forth the faster they go ie towards the rad and away from the rad .

[whytry]

OK will recheck fenders, grille, etc... On the fan, if I manually turned it on and I do not hear the sound would that defeat the potential of the fan causing the sound?

Also I did add the front plastic spoiler, and did not use the bracing on the ends that the kit comes with, I have driven it several times already without that sound but nevt for 30 miles straight at highway speeds I did not think those bolts could come loose though....

[paul67]

Yes I would think that should remove it being the fan.

[paul67]

Its not something daft as a piece of plastic under the car that you might have drove over and caught thats stuck .

[6'9"Witha69]

I once drove over some duct tape that got caught on my tire. Sounded like a slapping and was speed sensitive.
Just turning on the fan will not do it, as the suggestion was that the air flow at speed through the radiator was causing the blades to be forced back and into the shroud. Just turining it on will not yield the same comparison.
Front spoilers are flimsy. You NEED the reinforcements. I suggest removing the front spoiler or installing the reinforcements and checking again.

[whytry]

Jacked car up checked underneath and found nothing, also spun all 4 tires and nothing stuck to them either. Inner fenderwells are pretty tight, will check on the front spoiler tonight.

[whytry]

Installed the reinforcements last night on the front spoiler, and still having the same problems. Anything else?

[paul67]

Hose or cable loose under hood ? , or remove hood ask wife to sit on top of engine a drive till you hit 40 and see if she can see anything:seizure:

[Jim Nilsen]

Is the cowl weatherstrip in good condition?

[whytry]

I just replaced the cowl weatherstrip last night, I was thinking it was about 40 years old..... I will see what I can come up with tonight.

For the hoses, I think I have them all out of the way of everything. I do have the heater and A/C hoses ran through gromments in the upper part of the fenderwell behind the inner fenderwell so they are hidden, they are laying on the inner fenderwell though, I never thought that could be a problem, I will check that too.

Now how can ask her to sit out there while I drive at 40, and make it sound like it a fun thing for her..... :):):)