Loud Intermittent Sheet Metal Rattle

[wbabst]

I would be scooting along, everything running fine and dandy when all of a sudden I would get a loud sheet metal rattle. It was very loud, and sounded like everything was falling apart. I would slow down and it would go away then nothing. I would pull over and hear nothing, everything looked fine, no idiot lights, everything was fine, and the car drove just as good as before. Still being worried I thought it might be something in the shroud, the would get free and pinball around inside.
Instead I think I found out what it was. Both my thermostat doors were loose. I adjusted and took it for a drive, I think that was it.

[terribleted]

Umm these should be loose (starting to open) as the thermostats start to open just after the engine starts running. They should be adjusted to be only barely closed when the engine is stone cold. That rattle is likely due to bad or missing bushings on the hinge pins for the thermostat doors. Have they been changed? Are they even there? Should be 2 nylon bushings in the doors where the rods god through them. These doors should be fully open or nearly fully open when the engine is at operating temperature.

[wbabst]

Bushings are long gone, but found the doors way out of adjustment. Not sure if this was the problem but sounds alot like what I was hearing while driving. At a certain temperature and speed the door must have fluttered causing that sound. When you are driving down the road it sounds like all hell broke loose. I will be taking the car to work tomorrow and see if I get the noise. I did a thorough undercar inspection this weekend and found a couple things but that was the only thing that made that kind of sound. I have adjusted them per the manual.

[Wagon Master]

I have always set them by pulling the rod rearward against the stop, then adusting the swivel to just slide in a fully opened door. Guess I've been setting them too tight all these years. Thanks for the info.

[terribleted]

Adjusting them should have made no difference if they are the noise as they should be hanging wide open when driving not almost closed where they can bang like in your video. If they are closed when you are out driving you have a problem like binding doors or way out of adjustment (too tight). Driving with them closed all the time will cause the engine to run hot and indeed possibly overheat. Replace the bushings they are cheap and readjust the doors.

[terribleted]

I have always set them by pulling the rod rearward against the stop, then adusting the swivel to just slide in a fully opened door. Guess I've been setting them too tight all these years. Thanks for the info.

Maybe maybe not. What you say is the procedure from the shop manual. May or may not result in door just closed when fully cold. I am not sure. I would not fully expand the repro thermostats this way to set them. They have issues with staying operational for long even without forcing them to full extension. I have seen a tech article somewhere that recommended the just closed setting and have been using it since. Seems to work. It is also fairly easy to adjust and hook up the thermostats with the rear grille in place from underneath with the lower shroud off only. I bet doing it the book way the results are similar.