bearing maybe?

[vervepipes]

OK, after a bit of searching on the forum lets see what we have the noise narrowed down to.

-The previous owner thinks it's a main bearing, but I cant narrow it down using my stethoscope or by unplugging spark wires one at a time.
-Noise from water pump is normal, alternator sounds very noisy though, but running the engine without the belt for a couple of seconds shows that it's still noisy.
-The noise was bad at first, but I gave it a good shot of carb cleaner and now at idle I can barely hear it, sounds like valve chatter or a ticking exhaust leak.
-no large exhaust leak found.
-given gas from idle it begins clacking loudly.
-Took the valve cover, springs look unbroken, the valve stems that I can see look fine, cam looks good. Didnt have time to inspect the cam bearings or measure the valves.

I know this subject has been covered a lot but I cant find any post with all of what I found, especially given that I cant find the source with the stethoscope. This is a 260,000 km motor, less than what I'd expect to have serious problems at with a toyota of this vintage. BTW if it turns out to be a main bearing I'm just going to look for a 4A from a good runner to drop in as-is, given this is a free car I intend to keep the repair as cheap as possible.

[takza]

Sometimes the fuel pump will make noise...espec when cold. Best deal would be to go thru the valves and adjust them...at least to cold specs.

Should be able to tell a lower end bearing from something in the head? Though sounds travels around the block fairy well.

More likely a rod bearing than a main? Piston skirt ?

[Petros]

we should write up a procedure for this in the repair guides, it comes up often enough.

Not likely a main bearing, the connecting rod bearings will always fail first. Mains are much bigger, better lubed and have much lower stress than rod bearings. If it is a rod bearing you can isolate it by running the engine at a fast idle speed so the clacking is clearly heard, than pull each spark plug wire one at a time. If it is a rod bearing when you remove the spark from the bad one it will stop the noise. If it is not a rod bearing the clacking will not stop.

If you can determine the noise is going at half the rpm of the crank, it is from the valve train or fuel pump. If it happens once per rev with the crank, it is in the low end. Twice I had a piston skirt fail on worn engines (too much piston clearance caused piston slap, than skirt failure). It ran but made a load clacking sound, not quite a knock, when the piston would slop around in the bore with each stroke, and spark made no difference. Sometimes if the engine swallowed a screw or other object and it embeds in the piston top it can also make a knocking each time it strikes the head. Pulling the head will tell you if this the case, if bad enough you may have to replace the damage piston.

One of those inexpensive mechanics stethoscope is real helpful (I bought mine from Harbor Freight for about $10) or you can use a long screw driver pushed against your ear. This will help you isolate the location. If it is rod bearing or failed piston it will not have a precise location, but just be lower in the block area. Usually a valve train problem can be isolated with the stethoscope.

If it either a bearing or a failed piston, the engine has to come out to fix it, if it in the head or valve train you can just pull the head and have the problem corrected. It is not always necessary to pull the head to fix a valve train problem, so it is best to isolate it first. If you have to pull the head, it is best have all the valves done, and head resurfaced while you are at it. If you have to pull the engine to fix a bearing or piston problem, you would be best to rebuild the whole engine or jus replace it with a good one.

Good luck.

[vervepipes]

OK, new developement, with higher idle I can hear it's in the bottom end at the front with my trusty stethoscope, disconnecting the spark plugs doesnt affect it though. Also in today's hunting the oil pressure light illuminated...

[Petros]

It might be the oil pump lost a tooth and is "clunking" every time it goes around. Though I never heard of that happening, it is possible. See if you can isolate it to the oil pump behind the front pully on the front of the engine block.

Or you have a fully shot rod bearing and it will not hold oil pressure. Better pull the engine, with no oil pressure you could be on the verge of throwing a rod and trashing the whole engine (it can be rebuilt now, after the rod fails it becomes scrap). Usually the number 3 or 4 rod bearing goes first, they get oil starved earliest because they are furthermost from the pump, but anything is possible with an abused engine.

Good luck