Knock / Rattle after valve spring replacement uggh

[Gbody5]

Engine has 54K miles, not a racer, well maintained, just replaced the valve springs with the heavy duty ones, 100#. Engine ran fine for 20 minutes or so while I bled the brakes, then after I drove 5 miles and came to a stop I hear a rattle/knock. It's only at idle, goes away as soon as I build rpm. Does not do it until engine has warmed up, cold start no noise. Could it be carbon that has broke loose? If it were a bearing I would think it gets worse at RPM.

Thanks for any tips or ideas,

MT

 

[MAK507]

Any way you can record it and upload?


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[EVIL]

Subscribed

D

 

[dank GN]

How are your lifters ? How are the cam loves ?

 

[Gbody5]

Runs fine, actually more responsive with the new springs, cam and lifter are all stock. Just this crazy knock. I'll pick it up Monday and try to get a video.

 

[cj92345]

broken new spring?

 

[PSID6]

It's probably not valve train related at all. The way you described the noise, sounds similar to a problem I chased for a long time. The aluminum bracket on the drivers side head was loose and would only make noise at idle. Might be worth it to check it out.

 

[Ttype6]

Torque converter bolts?
Generator hitting A/C compressor?

 

[Pronto]

Did you pull the covers and take a look? Maybe a plastic button broke...

 

[Gbody5]

It's probably not valve train related at all. The way you described the noise, sounds similar to a problem I chased for a long time. The aluminum bracket on the drivers side head was loose and would only make noise at idle. Might be worth it to check it out.

Thanks, will check it out!

 

[Gbody5]

Torque converter bolts?
Generator hitting A/C compressor?

Checked the TC bolts, all tight, never been off lol, thanks

 

[TLIMITED]

Could be cam sensor.Put your finger on cam sensor cap and see if you feel the tap or knock.Had one do this not long ago.

 

[Gbody5]

OK, so I'm leaning towards a cracked Flex Plate or maybe something in the Trans Pump, hoping the former. The noise does not come in for 15 or 20 minutes after cold start when only idling. If I drive it it comes in sooner. And is very temperature sensitive. The hotter it is outside and the more you drive the worse it gets, but again only at idle. As soon as you touch the gas pedal it disappears.

 

[MAK507]

Mine was doing that, and the sound became a louder clunking sound like beating on metallic drums lol. It was the cracked flex plate. The shop replaced it, and I told him it had to be SFI approved flex plate... He said "I'll take care of it."

Sound came back again [emoji23]

Too bad for him


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[Ttype6]

OK, so I'm leaning towards a cracked Flex Plate or maybe something in the Trans Pump, hoping the former. The noise does not come in for 15 or 20 minutes after cold start when only idling. If I drive it it comes in sooner. And is very temperature sensitive. The hotter it is outside and the more you drive the worse it gets, but again only at idle. As soon as you touch the gas pedal it disappears.

Remove the torque converter bolts and push the converter toward the trans and start the engine.

 

[Gbody5]

Will do! I already started looking at new Flex Plates, Turbo Buicks forum had a thread recommending Full Throttle Speed SFI External Balanced, interestingly enough at FTS they showed customers who bought the Flex Plate also bought valve springs. Wondering if I maybe had a hair line crack and did not know it and the new valve springs changed the engine harmonics enough to extend the crack and/or the additional flex is causing the knock???

 

[TURBOELKY]

I recently had a cracked flex plate in my el Camino. You would hear it on start up, you would hear it at idle, sometimes at certain rpm's, best thing to do is get under the car and look.

 

[earlbrown]

Disconnecting the TC bolts is a quick and easy way to eliminate the transmission as a culprit. Plus with the plate free, you can give it the ring test.


I almost wonder if you have low oil pressure at idle and the weak stock springs didn't have enough ass to collapse the lifter. With greater spring pressure there's a chance you have just a smidge more play and it's audible.


Does the oil idiot light work at KOEO?

 

[Wahoo]

My car has the same problem, it should have stock valve springs, but the engine has 94k miles.

Cold start no noise, has 60/70psi oil pressure.

Warm it up idling, giving a little gas gere and there,but no noise no matter how l9bg it idles warm.

After driving it for a few miles getting in the gas just a little bit, maybe hitting 5psi of boost, i get a knock from that point on, its only slight. I can hear it coming from under the car. Ive been under the car with it making the noise and it seems to be bottom end. I cant feel any thuds on the floor of the car.

Then when i shut the car off and let it cool down, abd start it up cold, again no noise.

I have 15psi warm idle oil pressure.

 

[Wahoo]

My car has the same problem, it should have stock valve springs, but the engine has 94k miles.

Cold start no noise, has 60/70psi oil pressure.

Warm it up idling, giving a little gas gere and there,but no noise no matter how l9bg it idles warm.

After driving it for a few miles getting in the gas just a little bit, maybe hitting 5psi of boost, i get a knock from that point on, its only slight. I can hear it coming from under the car. Ive been under the car with it making the noise and it seems to be bottom end. I cant feel any thuds on the floor of the car.

Then when i shut the car off and let it cool down, abd start it up cold, again no noise.

I have 15psi warm idle oil pressure.