Almost Spun a Main Bearing...

[agni]

After finding some flakes of metal during my last oil change, I finally got around to pulling the oil pan. I plastigaged all rod bearings and visually inspected all mains. Everything looked fine, except for the #1 main (on the front side of the engine) . . .



Aside from being completely chewed up (you can see where the metal is flaking off of the side), it is warped and no longer fits snugly in the cap.

The crank journal is a bit discolored, but still smooth. So I think I'm going to try changing the bearing. I plan on doing it with the engine still in the car, so it's probably going to be a pain, but still doable I think - the top half of the bearing slides in and out easily, I am hoping the new bearing will do the same.

My question is - can I get away with just changing this one, or do I have to change all of them? Toyota sells them in sets of 2 (#1 and #4, #2 and #3); can I change just #1 and #4?

[JohnGD]

You can just change one but since these are select-fit bearings make sure to get the right ones and plastigage them. But having gone through all the trouble why not just all of them? You can use the paper clip trick - make an L out of it and put one side in the oil hole and rotate the crank to push in/out the bearing.

An alternative is a set of Clevite standard bearings. But you still have to plastigage them. I'd very oil pressure using a power drill before starting up, and use a Krikit-II belt tension gauge to install drive belts. Over-tightened belts can cause front main bearing problems.

[agni]

Went ahead and replaced just the bad one with a Sealed Power brand bearing from O'Reilly. It went in pretty easily, for which I was thankful. The others were a different story - the top halves were pretty tight fitting, and were hard to move. All of the clearances checked out within spec, so i just left them.

The paperclip trick sounds pretty clever. I'd be kind of worried about it breaking off inside of the oil hole though The main problem I encountered was initially getting the bearing into the space between the crank journal and the block. After that, it slid in pretty easily just by pushing with my finger.

Yea, it occurred to me earlier that an overtightened drive belt was probably the cause. This is supported by the fact that the top half of the bearing is in even worse condition than the bottom half. I see now where all of those shavings came from I'm definitely going to start using a tension gauge now . . . It certainly didn't occur to me that it was this crucial.



By the way, how do I use a power drill to vary the oil pressure? I was just going to remove the spark plugs and spin the crank.

[JohnGD]

Yeah, this is another confirmation why manual tensioners suck. Automatic belt tensioners cost manufacturers a little more, but many just pass that cost and multiplied on to the owners. Yours is a perfect example.

I assume you have an I4 (maybe wrongly), but if so turn the pump sprokcet with a power drill to pre-lube the system until the oil light goes out.