gohawks

Take a deep breath this could get long, but I'll post for future reference for anyone else that has the same problem.

My 1988 4Runner with the 3.0 3vze motor developed a slight knock. This knock was specific to the motor being hot (i.e. warm, thin oil) and only at low rpm under load. It had been this way since I bought it. Initially I thought it was noisy valves or something and ignored it.

Eventually I thought more and more about the knocking sound and decided I had better investigate. I got lots and lots of theories about what it might be. I took it to a Toyota dealership and they listened and thought it was main bearing knock. They said they'd pull the motor and put a new short block in for $5000. I took it to another mechanic who swore there was no way it was a main bearing and diagnosed it as excessive clearance in the oil pump, he was full of crap and screwed me out of money.

I finally found a 30 year Toyota Master Tech online who answers questions. I gave him my symptoms and without hesistation he said: excessive clearance in the front main bearing. He drives a 4Runner with the same motor and said that this happened in his at 180,000 miles.

Now for the cure. This tech advised me to do the following. I'm not saying it is right, just what he did and advised me to do. He did it and has gone another 60000 trouble free miles to date.

Replace the front main bearing with a #5 main bearing (think Toyota select fit bearings). Then go one size up for the remainder of the main bearings and rod bearings.

He initially advised that this could be done via the oil pan w/out dropping the transmission, although he himself pulled his motor. Only later did he recall that the transmission does have to be dropped to access the main bearings (some dispute about this, I'll take his word for it and it is what mechanic had to do).

I picked it up today and drove it and hour and a half home. Got the oil good and hot obviously and the moment arrived to give it some gas from a stop to see if the knocking had subsided.......indeed it is gone for the time being.

The Toyota tech I corresponded with said this was a somewhat common issue with high mileage motors in the Toyota 3vzn family (again this is disputed by some, although there are others on this forum that have had the same symptoms)

Was it the right decision? Time will tell I guess. I did my homework BIG TIME. I could not do the work myself, I had to tell a mechanic exactly what I wanted done as they thought I was full of it, and they work on a fair amount of Yotas.

I have the bearings and if I get time will post pics. I could get into more of the platigauged clearances and blah blah blah, but I'm gonna go drive my 4Runner. I haven't been with her for two weeks!

CoedNaked

Thanks for the input!

Yoda

Glad you got it back and it seems to have worked.

gohawks

Seems to have solved it for now anyway. Unfortunately they didn't seem to have adjusted the throttle cable correctly upon reinstalling the transmission (rough engagement when put in gear) , so its probably going to have to go back again.

...but it doesn't knock anymore!

4mydogs

Very interesting. If a Toyota Master Tech (how'd you find him?) knows it to be so, why aren't stealership shops sharing the info? Or is that a dumb question . . .

Glad it seems to have worked for you, and hope to hear from you after some thousands of miles that all is still well.

snap-on

so what did the "from the bottom" bearing fix end up costing? (were you the one with the story about the shop that quoted one (low) price but wanted to jack it up after they figured out they were going to have to drop the tranny to do the work?

anyway good to hear its running again!

gohawks

I don't know the answer to that. I just know that two different Techs I found that answer questions on online sites gave me the same answer: Replace the front main bearing with a #5 size bearing and go up one size for the rest (the were all #3's for me before that).


Well it ended up being pretty pricey. ~$1300

That being said I paid a premium for Toyota bearings. They are EXPENSIVE. But I was told it was best to do it this way for my circumstances. Strap can get them much cheaper than I got them for but the mechanic wanted to deal with someone else.

I also had the rear main seal replaced, which needed to be done, as well as all rod/main bearings replaced as well as thrust washers.

I'm not saying it was the best thing to do, just what I did with the information and money that I had at the time.

I'm fully aware that I could have rebuilt it for cheaper if I could do the work myself, however that was not an option. Purchasing a reman was not an option either because of R&R cost.

In the end maybe I should have pulled the motor for what it ended up costing, but I did what I thought was best given my circumstances.