strange rattle at 4000rpm

[rebuild4g63]

I have a 95 gst for starters. I got the car with a bad rod bearing. I had them replaced. I also have put about 2,000 bucks into various other parts of the engine to bring it up to par. When I am cruising along about 4,000 rpm there is a loud constant rattle until I either let off the gas or excelerate, then it dissapears. Note the noise has been like this the whole time I have had the car.
Thanks in advance

 

[TSiAWD666]

I'm guessing either the crank pulley has separated or your exhaust heatshields, the ones that bolt to the car above the exhaust, have their nut loose.

 

[rebuild4g63]

Can't be that. I have torn this car apart more then once and replaced most things. The heat sheild isn't it cause I don't have the top one on at the moment and just put the bottom one back on. hmm .... It sounds kinda like a bearing. Its only irritating because I don't wan't something to blow up and leave me stranded . It has been making this sound for about 5,000 miles so far. I have replaced all my timing belt bearings and a/c belt bearing in search of a fix. boo

 

[TSiAWD666]

You're referring to the ones on the exhaust manifold and turbine/o2, but I'm referring to the ones under the car.

 

[rebuild4g63]

I will check it out but unlikely. It doesn't sound like that kind of rattle.

 

[jessesgsx]

Lmk if you figure it out, I have the same damn noise and have rubilt the complete bottom end and swapped out the lifter/rockers.. Only thing I could think of is the balance shaft bearings but those are gone on mine also.. It sounds like its in the intake manifold on mine, but there is nothing to make that noise there.. So idk anymore.. Very frustrated with it.

 

[jessesgsx]

Well I have swapped everything besides the pistons/rods so the only thing I can think of is the wrist pins, but I have tried the trick of pulling the plug wire while running so there is no load and that makes no difference on any cylinder.. :/

 

[rebuild4g63]

I think it has something to do in the timing belt area or maybe the a/c compressor. still haven't narrowed it down completely

 

[blueboost68]

Mine did the same thing at 3200 it was the timing belt tensioner.