Thumping Sound

Hey gang,

Okay so I put everything back together on the 84 gt. now I pulled her out of the garage today and timed her and she was purring like a kitten.....after about 5 minutes I was hearing a deep thumping sound like: metal on metal.....at first I thought it was maybe my exhaust but when I looked it was okay.....so I gave it some throttle and the thumping was consistent with the acceleration of the motor.

My question is WHAT THE HELL IS IT!.....

I changed the pullies and put on some underdrive, but that was about all I have done to the car.

Could the underdrive be causing the crank to go out of whack and make it thump....or the harmonic balancer...how do I test this....my neighbour is guessing that it might be a connecting rod.......

I need some advice people!!!!

Thanks for everything

Rick

Reply to
Rick
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Did you install headers? I had a similar experience when I put headers on my 93 LX and found that the motor mounts were a little weak. Installed new mounts and all has been well for years now. Use a floor jack under the oil pan to a little pressure under the motor. Just a slight lift will cause the sound to go away if it is sagging motor mounts.

Reply to
James

I did install headers last year and that never made that sound. The only thng I changed this year was the carb, intake, and put on some underdrive pullies! I will take off the pullies and crank her over to see if the noise goes away..

I will check back tomorrow to see if anyone else has any ideas..... also my buddy told me to put a screwdriver or long pipe on the oil pan and then put my ear to it to listen and see if I hear the thumping....if I do, then it means that it is something internal....which I hope not!

I will keep you guys posted!

Thanks Rick

1984 Gt..."first time Owner/Mechanic, trying his best"

Reply to
Rick

You say the frequency of the sound increases with engine idle... sound internal to me.

This is a really basic question: Are you sure all of your fluid levels are topped off. like oil?

Reply to
Ray Reynolds

All fluids were topped up and checked!

Reply to
Rick
** All fluids were topped up and checked!

A suggestion to help isolate the problem: remove the accessory drive belt(s). If you still hear thumping, the problem is with the engine and/or transmission. If the thumping goes away, it is one of the accessories. Reinstall belts one at a time to isolate the problem.

You mentioned that you just installed a set of UD pullies. If you pull the belts to perform this test, also remove the crankshaft UD pulley. If you hear nothing, then re-install only that pulley. If you then hear the thumping sound, the problem is the crankshaft pulley.

If the problem ends up being that UD crankshaft pulley, you'd best fix it yesterday, or it will eat the bearings and seals very quickly.

-JD

________________________________________________________ | | | 1998 Laser Red GT RAMFM Member Since 1998 | | M-5400-A Suspension http:/207.13.104.8/users/jdadams || Subframe Connectors & Seat Bracing, Strut Tower Brace || 4-point K-frame Brace, Tremec T-45 & OEM 3.27:1 Gears ||________________________________________________________|

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JD Adams

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SonicMonkey

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