ive had a metallic rattle that happens on startup as well as when coasting.

it can be rather loud at startup, and seems to lessen or go away after sitting a bit. it can come and go when in park.

if im coasting downhill and it is making the rattle noise, a touch of throttle makes it go away. i can even apply a bit of brake, and touch the throttle and make the noise go off and on.

another interesting clue, sometimes when coasting downhill going into neutral makes it stop. back in drive and it comes right back. interestingly that does not seem to make it come and go when at a stop.

any guesses?

 

Exhaust pipe rattling against something? That's what mine was last week. The sound happened basically in the same scenarios as you described. I originally thought the sound was coming from the engine, but then tracked it back to the tail pipe rubbing against a bolt on the rear shocks. I bottomed out the tailpipe a while back and I guess I bent it enough for it to sit against the rear shock bolt, but only during random driving situations. I found the rattle by walking around and shaking everything that would move... When I grabbed the tail pipe it made the sound.

 

^ my guess is exhaust, too. Maybe a shield or hanger is loose

 

Rattles are hard to find. I had one up front (driver's side) that was a captive bolt rattling in the frame. It was near the ACE pipes. I can't figure what it was for as nothing was attached. Being captive, I couldn't get it out, but I wedged some duct tape around it and it's better.

 

Mine had that.
Solution.
get steel rope.
Tie it to the tail pipe

Then to the light stand at a Target store.
The big cement base.

Then low range.
Pull ahead and let the rope yank the pile straight.

Someone had rear ended my Discovery II before I owned it
and they had hit the end of the exhaust pipe and pushed it back.

Where the curve goes over the rear axle there is a bolt where it hits.
Check it out.

 

finally getting back to this with some more information. i went through the exhaust system and found some potential rattle spots and got everything sorted, rattle persists. i saw a good amount of rust on the frame which bothered me so i have been doing some heavy grinding and anti rust treatments, things are under control now.

back to the rattle. spent some time poking around. clearly a bearing style metallic rattle coming from the front of engine, around accessories. perhaps lower pulleys as it seems louder from underneath?

again evidence is it rattles at startup. it will quiet down after a few minutes just leaving it in park and sitting. then when driving off it will start up again with a touch of throttle, then under constant throttle it goes away only to come back under coasting deceleration.

idler pulleys or tensioner or water pump? ive read they can all cause a bearing style rattle. ive also read you can simply pull the belt and run the car for a couple minutes keeping an eye on temps to prove its something on the accessory drive. recommended?

 

any feedback on running "beltless" as a test?

 

One of your cats is toast. All that's left is probably a nugget of what used to be the catalyst substrate.

 

decent guess but its been ruled out.

i pulled the belt off and fired it up and it was silent. i had a viscous fan, both idler pulleys, and the tensioner. i replaced all, put on a new belt, and still got the rattling noise.

while the belt was off i felt the tiniest tick while turning the water pump. the ace pump took a good amount of effort to turn, but seemed smooth. fairly certain its the water pump, i have a spare so will tackle that soon.

anyone know of a good write up or able to point me to a page in the rave? seems like 9ish bolts, and hose clamp, and its off. reverse with a new gasket to pop it back on. reuse the pulley, 3 bolts for that on and off. i would have gone ahead and done it with the rest but wasnt in the mood for the coolant refill and bleed.

 

I too suggest the starting beltless to eliminate belted accessories, quick and easy