Thread: awkward tapping coming from motor...

Just noticed this on the way home from the local mckay d’s last night. I hear a metallic tapping sound coming somewhere either behind the motor(against the firewall) or inside the motor itself. The tapping sound does not go faster if I apply the throttle. also FWIW theres another sound that doesnt seem to be normal at idle. it kinda sounds like how whenever you would turn the car on when cold and if you have a CAI and the IAC valve stays open for a bit you hear that 'whooosh'-ing sound, well thats kinda what i hear when the car's at normal temp and its not coming from the CAI/TB side either.

Car doesn’t slow down if I go into PE mode I notice no misfires while applying gas. Oil doesn’t seem to be contaminated with coolant. Does not sound like a lifter tick. Im gonna pull the plugs and see if the gap’s been changed/damaged. Last Friday I noticed I got the P0300 code for random misfires, but that’s like the 3rd occurrence since I had the VS cam installed since this past march. Aside from the lil race from this past Friday, I get no knock, if any 1-2* of random blips with the 3.1”. I did notice the car was having louder lifter tick ever since I switched to 5W-30a few weeks ago, but I don’t know if its coincidence or not as i did not hear the loud lifter tick since that specific night. I always been using Mobil 5000 10W-30 and this last oil change I used Mobil 5000 5W-30.

One idea is an exhaust leak, yet again, on the rear header, however I installed a new felpro aluminum gasket not long ago. another is a broken flex on the downpipe? Give me some ideas on what to check first on the outside of the motor then once I cant find anything, give me some more advice on what to check if it’s a possible internal issue please. Like stated, im gonna pull the plugs later to see how they are as well as look underneath the car and such. Thanks in advance.

thanks for the reply. i'll def check if theres anything touching the rear header or not. i dont have any heat shields since im running the pacesetters, unless you meant the heat shields that came with the stock manifolds? i do have an electric oil pressure gauge, but for some reason its not working at the moment. its at 0psi but every once in a while it'll randomly flicker back and forth which i believe may be a loose wire r a bad ground somewhere. i already double-checked and tightened the sensor ground, so im thinking i have a tear on the wire as its running through the passenger firewall and the metal frame.

YouTube - gtp knock

what could it be? some say rod bearings going out others say flexplate. i revved the car around the 58second mark.

To be honest, when I heard it, the first thing that popped in my mind was the flexplate. Have you taken the inspection cover off and checked to see if its cracked or maybe a bolt loose or gone?

I noticed that when you idled the motor higher, I didnt hear the sound then.

TDC has some good suggestions as well. Hope that helps.

yea a friend suggested the flexplate as well, but when i stuck a long screwdriver on the drivers side where the heads meet the lower end of the block, i can hear the sound more immensely. since the car's gonna be parked, and just for the sake of it, how would i check if the flexplate is cracked? i know i'd have to jack the car and pull the cover off, but then what?

im in the process of demodding the car as im really fid up and tired of her lil quirts to be honest... :-(

Jack car up, take cover off, and slowly turn crank looking for cracks in flex plate.

Originally Posted by Sabrewings

slowly turn crank looking for cracks in flex plate.

dumb question, but how do i crank it over slowly?

Put a larger (1/2" drive) ratchet on the crank bolt and turn in a tightening direction.

no accessory belt right? the crank bolts on the harmonic balancer right? ^_^;

You can do it with the accessory belt. Yep, crank bolt is on the crank pulley (harmonic balancer).

remove your spark plugs so it's easier to crank the motor by hand. Put a 15/16" socket and a ratchet on the crank pulley and turn it.

It doesn't sound like rod knock......sounds more like something is rattling around.

I have a mechanics stethoscope you can use to help pin-point the sound.....as long as clean your ears really well before using it. :-P

Originally Posted by DuBob

I have a mechanics stethoscope you can use to help pin-point the sound.....as long as clean your ears really well before using it. :-P

Ummmmm, EWWWWWWWW

Originally Posted by TDCRacing

If theres an easy way to put a ratchet on the crank bolt and turn it with a ratchet without dismantling your car let me know. I know it cant be done from the top.

Don't you have to take the pass wheel off?

I dont think so, you can get to it from underneath without taking the wheel off and since you gotta be under there anyway to inspect the flexplate, it may all work out well.

I've done it on an SS with a breaker bar through the top.