Engine knock, no oil leak or loss on 1999 GMC Suburban 1500?
Wife came to pick me up at the airport, she has spent the last few months in Reno with my kids to try and help them "adjust" to college living. In reality, I think its her that needs the "adjusting" to not having her "babies" around.
Anyway, she comes to pick me up and I hear a knocking sound from the car. I ask when this started happening and I get the "I don't know" answer. Its fairly noticeable, so I'm lost how she couldn't hear it, even while driving.
Took the car into a local shop up here (don't know any of the shops) and they said they weren't sure what the sound was. Might have to pull the engine out and apart. That's going to cost about what the car is worth, so no.
I thought maybe a lifter, as when I checked the oil, it was low. After topping off the oil though, same sound still.
So I tried draining some of the oil and putting in a cleaner/lubricant called Sea Foam (I know, everyone is going to hate me for this). Then drained all the oil and replaced it and the filter. Still, same sound.
The knock seems to be tied almost directly to the rpms of the engine, except for one case. When you let off the accelerator, the knock speeds up excessively, then slows back down to match the rpms of the engine. So is this a valve issue then? And if so, wouldn't you think a local shop would diagnose this fairly quickly? Also, when driving, if under a heavier load, such as climbing a hill, the knock seems to lessen, almost to where I can't notice it.
Was thinking maybe trying a complete engine flush, but I've heard that can create more issues than it solves.
Also, knock seems to come from one side (passenger) more than the other.
Any direction is appreciated.