gohawks

Hey all. I asked this question on a site with a Toyota mechanic. Do you think he is right? Give me your opinions please.

Subject 1988 4Runner Engine Noise
Question Ted,

Thanks for helping.

I have a 1988 Toyota 4Runner with 207,000 miles. It has the 3.0 V6 with automatic transmission.

Here is my problem. Whenever the engine is warm such as after a long highway drive the engine develops a t rapping/knocking/tapping sound at low rpm at low speeds under load. The sound is duller than a pinging sound.

This sound only occurs when the engine is warm and I can only hear when accelerating from a stop at lower rpm. This sound does not occur when the motor is reved in neutral or park, just in gear. Again this sound is not present until the engine is very warm, at least 20 minutes of highway driving. It only appears when acclerating from a stop and disappears as speed increases. It seems to come from the passenger side of the engine compartment.

I checked and there are no codes stored in computer.

Any ideas on what it could be?

thank you again.


Answer This is a crankshaft bearing noise, very common on higher mileage V-6/3VZN engines, the solution is to replace the engine main bearings and while that's being done replace the rod bearings as well.

Do you 3.0 experts agree?

regularguy412

I wouldn't rule out that diagnosis. What weight motor oil are you using? If it really is the main bearings, you might switch up to a 20w-50 weight oil and see if you get any relief. The thicker oil may provide you a little more cushion. I've never owned an engine with over 200,000 miles on it, but I am about to. My 92 3.0 has 183,000+ miles on it and I'm gonna see how far she'll take me. I currently run 10w-30 weight, but am considering going up to 20w-50 around the 200,000 mile mark. There has 'got' to be wear in those bearings, by that time.

Mike in AR

gohawks

Mike, thank you as usual.

I run 10w-30 right now. So what am I looking at here if this is the case? How long will she last? How much to fix?

Thanks.

gohawks

Any other tell tale signs to pinpoint that this is definately the issue? My oil pressure seems okay, I do lose some oil between changes, nothing crazy though.

regularguy412

It'll be kinda hard to get under there and listen witha a stethoscope or long screwdriver while the engine is under load and driving down the road. You might try to see if your oil leak is coming from the bottom end of the motor. If the crank has too much play in it, it may be stressing the main seals.

Mike in AR

gohawks

I don't have a leak that is appreciable in terms of being able to actually "see" any oil leak. There are never any drips. So I don't know if I have a leak. I just figured some oil was being burned, and that resulted in a relatively normal condition of losing a quart between oil changes.

gohawks

Anyone have anymore advice or might be able to tell me some good news?

I could use some.

snap-on

I just switched to gieco and saved a bunch of money?

Bassinfool

I spun a rod bearing on my 92 3.0. The knocking noise was apparent at all revs, at any operating temperature. It sounded like an exhaust leak to me at first, then it got louder. When it was at it's peak of bad shape, it actually knocked louder & faster when the engine was down-revving(?), say between shifts (manual), but you said it doesn't happen when revving in nuetral. I'm not going to say it's not a rod bearing, but it doesn't sound anything like when mine went out. I replaced my rod bearings myself, along with completely removing & rebuilding the motor, at a cost of about $900 (including complete gasket / bearing set, having heads checked / milled, new starter, new distributor, and a few misc. tools), but I've heard of people on here doing the rod bearings / rod through the bottom of the motor, with the oil pan removed. I'd imagine that's cheaper as well as easier. Good luck & keep us updated!

gohawks

I walked right into that one didn't I!

I really don't know anything about motors so forgive me for my ignorance. Is the main bearing(s) different from rod bearings? It seems as though the mechanic believed that is was the main, and to just go ahead and replace the rod bearings as well...

I guess I'll have a mechanic look at.

Anyone have a guess as to what rod bearings/main bearing replacement would cost me???

thanks.

Bassinfool

Oh. Main bearing might make more sense than rod bearing based on your description. I don't know if you can have those done through the underside through the oil pan location. I would guess it would cost in the neighborhood of $2k-$2,500 to have it done, but that's just a guess. I'd have two or three mechanics give you best / worst case scenario prices. Sorry for the bad luck. That crap's no fun!

gohawks

I had a mechanic looking at it today. He claims it is coming from torque converter or flywheel? I really have no clue. I'm gonna take it in to a dealer Saturday to get another opinion.

Bassinfool

That sounds more likely, since you said it doesn't happen in Neutral, and didn't happen until it had warmed up. Sounds like an easier fix as well. You could get one from the wrecker & replace it yourself??

gohawks

I don't think I could put it in myself, I have a hard enough time changing the oil lol, would this be any cheaper labor wise for a mechanic compared to the bearings?

Bassinfool

I would imagine labor would have to be cheaper. I don't know for sure, but I see replacing a torque converter or flywheel being quite a bit easier than rod or main bearings. The mechanic didn't give you an estimate?

gohawks

No he didn't, this is a shall we say, shadetree mechanic (he does a little of everything with automobiles). I just dropped by his shop on my lunch hour so he could listen to it real quick, then I had to get back to work. It was his feeling that it was not a bearing/ lower end issue. I trust him for the most part to do the work, however I'm gonna have it diagnosed at the dealership this weekend (I hope I can get in).

Once I have a confirmed diagnosis I will go back to my guy to have him probably do the work. I am really anxious to find out what the problem is and at the same time dreading it.

I'll probably vomit if its a ton of $$$

fierohink

If it's a flywheel or torque converter issue you're gonna have a good bit of time in labor. For either one you're gonna need to get the trans pulled and if it's a 4x4 add an extra hour, so you're at like 6hrs minimum for a 2x or 7hrs for a 4x.

Back to the bearings... main bearings isolate the crankshaft from the engine block and rod bearings isolate the pistons from the crankshaft. Rod bearings, if caught early enough, can be done through the bottom of the motor. You drop the oilpan and take the retaining nuts off the bottom of the connecting rod and push the piston a little bit up in the cylinder. Then you pop out the two parts of the old bearing, do a plastigauge check if you want, put in the new bearing parts, and tighten everything down. Then you put the oilpan back on and fill the motor with oil and drive away.

Granted that's the cliffnotes version.

If it's main bearings you really need to pull the motor. Otherwise there really isn't any way to slip the top half of the bearing inbetween the crank and the block. You'd have to pop all the main bearing caps and drop the crank, then somehow hold the tops of the bearings in the journals while you shove the crank back up there. Not something I'd like to try. And pulling a motor really isn't that hard for a shop that does them often.

I'm not very familiar with the 3.slow's block design, but on some motors there'll be a plug in the block at each main bearing journal. If this is the case for your motor a good mechanic, not everybody thinks of this, so a good mechanic can put a sending unit and gauge at each bearing to see if any of them have different oil pressure. If the pressure varies from bearing to bearing there has to be a reason, and that reason would be wear.

gohawks

Thank you for the help, looks like I may be pretty screwed either way.

I doubt there is much chance I caught it in time. It has been this way for the entire 5,000 miles I've owned the vehicle.

Sigh, I will have a hard time sleeping, and when I wake up and remember my baby's problems the depression will start all over again.

WHORERUNNER

If you say your oil pressure is good, then it might not be the bearings because they would have more clearance to consume oil, that would drop your pressure. I would think that you would have spun a bearing if you have been driving it for 5k. Have you checked to see if anything is loose on the passenger side where you say it is heard.If it is only heard in gear, jack up the rear and give it some gas with someone underneath to get a better look at it.

gohawks

Oil pressure is okay. I hopefully will be able to get it in tomorrow and get an opinion from the dealer.

I just have no clue anymore, I was really leaning towards a bearing issue.

I guess we will see.