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last week my heater core went out and started shooting coolant into my floor as i was pulling into the driveway. i parked it, it did not overheat or anything, and it sat this week as i took my scooter out instead to work.

so i have fixed the heater core, now i go to start the engine and hear this HORRIFIC knocking noise. i still have oil pressure, but just in case i put a few quarts in. it seems to run fine otherwise, but it sounds like a spun bearing/rod knock. loses a bit of power in overdrive. at highway speed it starts squealing like a loose belt.

I never heard of an engine going from running fine to dying? especially a 3800! BTW it is not the harmonic balancer i am familar with that noise.

I have seen videos with Buicks and other vehicles with rod knocks and they are always hard to start and that is if they do. they die very soon after putting them into gear and taking off. also seen this at junkyards. they will hardly make it half a mile before the big BLAMMO and die.

in my car it fires right up, no noise until after it idles up. put it into gear it takes off normal, but when it hits overdrive this insane squeal coupled with a pulsing and loss of power. drop down to third the squeal is gone but the knocking is very loud but it runs normal. i'm at a loss. it hasn't been that long since i took it twenty miles one way and twenty miles back to the grocery, the only thing i know that happened is the heater core exploded (got steam all up inside and coolant spraying out the floor vents) right as i was pulling into my driveway. i had it parked since then.

Could be a bearing in the alternator as I've known that to be mistaken for an engine knock but you'll definitely know when it's knocking. Plus the motor will go rather quickly when a rod spins. From what I understand you said your oil pressure was good so that kind of confirms it. I'd check the pulley's and such before I'd having a eulogy for your 3800

all i know is it sounds horrible. would an alternator cause a sudden loss of power at highway speed? i just took it to get dinner, about 5 miles and it still starts and runs fine otherwise (runs fine at low speed, and i'm afraid of going faster than 45 until i know what it is)

it does not labor at all turning over, turns over fine. it idles fine, no misfire, so all my pistons are turning, no oil leak or loss of coolant either.

oil pressure is at around 60PSi cold and is around 45 warm. but man does it sound bad. i'm taking it home and parking it until i know the cause. all i did was bypass the heater core with a hose loop and i doubt highly that would do any damage.

Yeah for a time i worked at the same junkyard i got this car from, we had great fun blowing up bad motors. they hardly made it a half mile before going out for good. one good run-up of RPMs and BLAM!

I just find it hard to believe that an engine that was fine a few days ago suddenly is rod knocking. but that is what it sounds like.

a YouTube video with the exact same noise. not sure what it is though, but not sure how it came out of nowhere either.
https://www.youtube.com/watch?v=wE5TiVMpLv4

this one is more accurate, complete with squealing:
https://www.youtube.com/watch?v=k7eZfwDoaIk

Well the next step is to do a compression test as that can be a way to diagnose what's going on. If you have access to the equipment or have a buddy that can do the test, I'd suggest that. Start there

Check the oil - look for sparkles under a good light

oil is black on the stick but normal otherwise. no problems turning over. i think going five miles or so would tell me something, but it still runs. i'm lost on this one. i'm taking it home later and parking it until i know what the problem is.

I have no misfire that i know of, normal oil pressure, no loss of oil, no loss of coolant, no smoke out the rear. it's not LIMs again, it's not water pump, and as far as i know it's not a pulley. can an engine develop rod knock out of nowhere just by sitting a few days?

Pull the belt off and see if the noise is still there.

opened the hood again and it is not knocking but it is squeaking. sound is definitely coming from the place where the transmission connects to the engine, if that helps.

has to be the TC. soon as i get to 45-47, you feel it lock in, instant blood-curdling squeal and loss of power. drop to third, runs fine. the knock went away, not sure what that was.

all i know is some moron was riding my bumper and i got angry and floored it, then i lost power for a second at 5,000 rpm, then slowed down (thought i hit the rev limiter) smelled some coolant odor (would later be the heater core letting go) then the first instance of the overdrive squeal. at the time i thought i had blown a coolant hose near the belt and it got wet. apparently i killed my TC. it seems fine if i never use overdrive.

The parameters you are seeing when the knock and racket start sound about right for when the Torque Converter Clutch tries to apply. If you have a mind to try and lock it out to see if that is the root cause of the power loss, Pin "C" on the transmission harness connector is the TCC apply solenoid. If you have the tools to work with the harness connector, you can temporarily take pin C out of the connector shell and tape it off. That way the ECM cannot command the torque converter clutch to apply. There may be other ways to lock it out (IIRC there is also a pair of contacts in the brake pedal switch the removes power to the TCC solenoid when the pedal is depressed.)

Alternatively, if you have a scan tool, one of the parameters you can watch is the TCC when driving. If the racket starts as soon as the TCC signal turns on, then you absolutely know that's where the problem is.

And as always, check for vac signal to the transmission modulator...it uses engine vac to control the line pressure from the pump within the transmission to make all those servos work.

My 92 Regal just did this same thing. Drained the oil and a lot of metal flakes in the oil. Engine locks up after 15 minutes of running, but starts up when its cold.