328 GTS Rattle/Resonance

I have an '89 328 GTS which has recently started to display an extemely annoying resonance/rattle which seems to eminate from somewhere near where the passenger's right ear would be. It starts at about 3000 rpm, is worst at about 3200 rpm and is completely gone by 3500 rpm and is present in all gears. It is there with the top off and on, with the passenger side window up or down, with the doors locked or unlocked. It is definitely worse with the car moving but is still present with the car stationary but revved in neutral to 3200 rpm. While in neutral, I had my girlfriend rev the motor to 3200 rpm while had my head in the engine compartment and I couldn't hear it coming from there. I removed the slats which cover the 3/4 window on that side; I have tightened every nut and bolt I could see and get my hands on in the engine compartment (near that area) and in the interior and still the damn thing resonates. It seems a little worse when accelerating through (or when the revs fall after a shift) this rpm as opposed to cruising there. Can somebody give me some hints...

 

The only thing I can think of is you are hearing something in the intake. Take the air tube leading to the air cleaner off and see if it sounds different.

Dave

 

i swear i have been hearing this in my 77 308 and my friends 79 308. i cant tell if its the exhaust or some kind of metal shielding around the gas tank on the right rear side. my a/c compressor is going to be off the car for the winter so i am hoping to poke around more. could the slats on the engine cover be loose enough to vibrate like this?

 

Seems VERY similar to a resonance my '89 328GTS (#79526) had as well. I poked and prodded and ultimately assumed it was a heat shield or some other low mass, non rotating, non critical object. Sorry, no help.

 

My 78 308 GTS did this and drove me nuts...I found the exhaust system went over a frame rail in the passenger side of the engine compartment, the heat sheild would intermittently touch the frame rail at certain rpms. Careful bending with a pry bar, improved the clearance, no more noise. Cheapest fix I had on that car.

 

good to know!

 

Thanks for all the great responses. A consensus seems to be that it is either an a/c line rubbing or an exhaust heat shield. Is it necessary to access these items from under the car or can it be done from the engine compartment?

Thanks again.

 

my brothers 328 did the same at exactly the same rpms in all gears. ill aske him how he got rid of it and post it tonight, it was not anything to do with the intakes, it was very simple to fix.

 

For the heat shield, you will need a lift.

 

I'd really like to know what he did to remedy this problem. I love the simple fixes!

Thanks.

 

definitely check a/c coolant tube on passengar side of car.
Very tight quarters there and it may be resonating against an alternator bolt.
I found replacing the rubber hose helped hold it in position (that hose tends to collapse w/ age) so it does not rub. It is gone for now. Very annoying
noise. Also check for damage. Mine was alomost worn thru and had to be re-welded.

 

I had the same problem recently. I took it over to my friend's house and put it up on the lift and removed the muffler. A heat shield had busted loose and was rattleing around. He spot-welded it in 5 minutes and no more noise problems...other than that damn ticking noise behind the fuse panel.