Possible Rod Knock but...

[criz067]

So for the past 3 years, when it's cooler outside, my car has started with a very loud metal rattle/knocking sound. I have always just turned it off and turned it back once or twice and it goes away until the next time the car is started when completely cool.

Now, a couple of days ago, that sound became permanent. Restarting no longer helps. Also, restarting a warm car does not get the sound to go away. I've listened to knocking online and it sounds like a rod knock. However, I pulled each plug wire individually as is commonly suggested when diagnosing knocks and the sound never changed. The sound is very loud at idle and seems to vary but not disappear with differing RPMs. The car has sufficient oil that has been changed regularly.

So I am left wondering what the problem is. Does anyone have any ideas?

Thanks

[Ivory8g]

hmmm was the car ever run low on oil in or before those passed 3 years? that is the number one cause of a spun bearing. pull the oil filter and cut it open with a can opener or with the special tool from autozone or your local auto store. look for metallic flakes. or you can pull the oil pan and check the rods for movement. since removing the spark plugs doesnt quiet the sound all of the rods are probably moving.

[criz067]

I'm not aware of it running low in or before those 3 years nor recently. I have been the owner of the car for 5 years. I have a magnetic oil drain plug that I check when I change the oil and there hasn't been metal on the magnet. What else could it be that is that loud if it is not "rod knock"? The sound is coming from the pully side of the block.

[Ivory8g]

no metal is a good thing. honestly I would still pull the pan. check the rods for movement by hand. this is going to be a process of elimination.

[Galanttuner10]

Check the lifters. On my 7g I had a similar noise and it would come and go then stayed. One of my lifters showed abnormal wear and needed replacing.

[criz067]

Thanks I'll have to find time to do that.

BUT, right this instant, the car sounds fairly good. It doesn't make sense! I've almost forgot what good sounded like. There are some minor ticking that was normal right now.

I've been driving the car for about a week now while considering replacing the car since it has 240k on it and the entire week it sounded terrible and embarrassingly loud. But on the way home from work it stopped making that sound. If it was rod knock could it just stop? Now it's only been about 20 minutes of driving but it just baffles me that it stopped! I don't doubt there is still something wrong of course but if I was confused before then I really am now.

Any other ideas?

[cntrylvr79]

rod knock doesn't just disappear, it gets worse. The magnetic plug may not help. I'd have to check to be surebut I don't believe the rod bearings are made of a magnetic material. Does the sound change a lot with rpm? I'd lean more toward failed or failing hydraulic lifters especially with that kind of mileage.