Toyo-Mama

I, too, am trouble shooting what I think it a bearing issue. It sounds just like BassinFool has described, noise-wise. I'd like to hear more about the compression testing per cylinder and working at it from the bottom end. My oil pressure plummetted after the oil filter gasket gave way. Quaker State says it was a spike in my engine causing a surge to blow the filter... I drove it for less than 2 miles before refilling with oil and replacing the filter. The noise showed up the next morning, and progressively worse (to even at idle) with 20 miles.

Am I being hasty in shopping for a rebuild? Maybe doing rod bearings from underneath would be a much better alternative...

Radyota

Toyo-Mama, sorry to say but if it's making noise at idle, chances are good that the crankshaft is scored/torn up and will need to be reground/replaced. Probably needs a new crank, set of rod and main bearings, and new seals, maybe even a oil pump at the least. It depends if the top end (cam bearing surfaces) are still good.

Sounds to me like a rod bearing starting to go. Another possibility is the wrist pin on the piston. I don't think it's a main bearing because the bottom end of this engine is stout! Bad main bearings will make a low-pitched rumbling noise, and gets louder as vehicle speed increases. They won't make noise if you rev the engine or at low engine speeds. By the way, the main bearing caps on this engine are cast as a one-piece girdle, like a Honda engine. You'd probably have to remove the front differential if you were to try to remove it with the engine in the vehicle. Good thing it isn't a main bearing noise! You could try using a heavier grade oil/oil treatment to minimize the noise/damage. Hope this helps, and good luck!

gohawks

I don't get a rumbling noise, I get a knock. And it is exactly at low engine speeds where I get the knocking. Dealer mechanic today told me he thinks it is a main bearing.

Radyota

It's all speculation right now. I was once called the speculator, because I like to try to diagnose things by sound and then see if I'm right. I've never heard a main bearing knock, or even that they knock when bad. It's possible a main bearing could've spun, and starved that rod bearing of oil making it knock, so it'll still be a rod bearing. Whatever it is, I do hope it's able to be repaired quickly and cheaply!

gohawks

Well one thing you can bank on: I have no clue! I come from a family where when my brother had a pipe burst he tried to find where to shut the water off in the breaker box!

I second that, but I have a feeling it won't be quick or cheap!

L33T35T 4Runner

this may be way off, but check your timing. i had similiar complaints about mine. Went to get a smog and failed because my timing was 20 deg. advance. set it back to normal, passed with flying colors and that sound went away.

gohawks

I'm willing to check anything, but it doens't sound like spark knock or detonation to me.

A yota mechanic on about.com and engnbldr said what I have described is exactly what main bearing failure sounds like.

Now, if this is true it begs the question of what caused it? Fatigue from 205,00 miles? I know it has been very well maintained, I have the receipts to prove it. Of course I have no way of knhowing if he ever ran low on oil or not.

Well nevertheless the thing has ran like a champ for 5,000 miles at least with this issue.