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Severe Knocking .....Is My Motor Toast???

fastmvr

fastmvr

New member
I am starting to feel like I have bought a lemon.... Not long after I bought my 2004 GTP Comp G....one owner....always dealer serviced....100K miles, I had a catastrophic failure while my wife was driving (first time she drove it.....also the last time she drove it)....I believed it to be a LIM gasket failure so I tore down the motor to the required level and replaced everything that could be replaced....including the "elbows".....car ran great for about 6K miles....then the gremlins associated with the ABS/Wheel Sensors/Computer started up....still sorting that one out. A couple of weeks ago while getting on the interstate....full tilt boogie....white smoke in my rearview mirror....tow home....the new plastic (why plastic??) elbow has busted....coolant pouring from that....easy enough to replace since I have been here before. I never throw away removed....assumed to be good parts from a car so I dig in my GTP bin and locate the original elbow that I had removed and replaced from my LIM gasket project.....and what do you know....it is cracked.....don't know how I missed that the first time but that totally explained the original failure while my wife was driving. So, it's been a couple of weeks of event free driving (except for the ABS, Traction Control, Stability Control, Tire Pressure, Variable Assist Steering gremlins) until Thursday.....as I am accelerating.....loud knocking from the engine bay......NOT GOOD! I come off the gas and the loud knocking goes away.......on the gas....there it is. So, I baby her home.....slow acceleration to prevent the knocking. It sounds like a broken valve spring but this morning, I tried to isolate exactly where it is coming from and I can't.......then I remembered reading something about the "anti-knock sensor" or something like that for SC motors....is it possible that this terrible knocking is actually just the sysmptom of a bad sensor?? I am really at a loss of how to proceed from here......this is my daily driver and I am starting to feel like I made a poor selection.
 


Posting a video will help out a lot. The knock sensors just retard the timing so you don't blow your motor they don't make any noise.
 
should have bought the aluminum elbows there is a thread with the part number for them they are made by dorman.
the white smoke would usually signify a coolant leak into your engine and it burning off but if your coolant light is not coming on it is most likely a small leak
the knocking is the worst sound you can get but hopefully its nothing too bad if you wanna start at the worst and work backwards I'd say have a compression test done
this will let you know if your pistons have chipped.

also is there a chance you may have installed you LIM improperly and it is leaking?

Vid will help diagnose if you can get the sound as clear as possible
 
the new metal elbows just came out weeks ago.

post a vid, that will help out a ton.

you could have any number of things wrong that would make a knocking sound, but they all differ from bad part to part.


some easy to fix, others = a dead engine.
 
The help elbows either aluminum or plastic are still not the right ones to use. They aren't as fat as the gm ones and will not fit in the holes.spend the $20 at the dealer and get the correct elbows. Secondly if you're burning coolant out of the exhaust it has made its way into the engine and most likely wiped out a bearing. Pull the oil dipstick and see if the oil looks like yoo-hoo, if it does you're gonna need a short block.
 
Okay....sorry for such a long post to start the thread.....I must have been "venting"... LIM gasket fix worked out perfectly (thanks to the video) and with the last elbow replacement I no longer am burning coolant. Everything has been running smoothly since the last elbow replacement.....about 500 miles ago......but the knocking just showed up out of the blue....I will do a video and post it in a little bit. Thanks everyone.
 


that kinda sounds fatal...if you post another vid but do a quick rev of the engine and let drop back to idle, if you hear the knock like bouncing in the rpm drop after the rev, id say spun bearing.
 
im kind of new on here but is it possible that it could be a cracked flywheel? Ive read about it on here but i have never seen it in person. Im sure someone else with more knowledge than myself will get on and help you ! good luck.
 


flex knocks at idle and goes away with rpm, usually..

im thinking its, a rod bearing top of the list, then maybe a broken spring in the head.

thats why a rev vid is needed.

also a oil pressure test will tell you a lot. you can rent one if you dont have one. you remove the oil pressure sensor by the oil filter, and then put the pressure gauge in its place. then start the car to see the oil pressure. if its low you got a spun bearing.
 
last time i tested mine it was @ 50 psi cold start,(idle) up to 60-70 if getting on it.

warm @ idle should be no lower then 20 psi.
 


Thanks Scottydoggs.....I kinda knew that in my gut....hard to forget that sound from many years ago on my '72 Firebird Formula 350.....back then...it just meant getting a 400......now, I am not sure which direction I should go.....what do you recommend? If I'm going to spend the money anyway.....what would you do?
 
your bottom end has let go as they say. you need a new engine.

that knocking is your rod bouncing around on the crank. when the rpm's drop, its just clanks inside the engine at a different tone.


you can get under the car and put your ear to the oil pan, it should be real loud under there.
 
Cheap way is just drop in another block. Upto you and your budget. Most upgrade internals if they have the cash and the time while it's out.
 
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