Hey everyone, I did post this over on the build thread, figuring some builders may have the answer, but didn't get a respose. I thought that I should probably post it here also, and hope for the best.
I've got a 2000 LS400 in which the timing belt slipped and a couple of things were broken. Several bent valves and a piston head slapped hard enough to need replacement.
Here's where the problem comes in. It's on the driver's side of the motor, and it appears I can buy a new one, BUT, the advertisements suggest there are different pistons for this motor.
"Drivers side, passenger side, Mark 1, 2, or 3 pistions" etc. What the heck? Different pistons for the same motor?

So the car sits in the shop now for over a month, waiting for a piston. And I've got no clue which one to buy. There are no markings on the old one.

Would anybody have run in to this problem before, or possibly bought a piston(s) for this year engine and not had a problem? I'm at my wit's end on this one. Thanks, Steve.

 

Steve it seems like the simple answer would be to talk to the Lexus Service Mgr. and find out how they are id'ed.... he should know, or know how to find out.

 

I was sure hoping one of the guys would know the answer off the top of their head, and avoid the call.

 

I hadn't thought of that, makes sense. Mine is on the driver's side.

Now just need to figure out the Mark 1,2, and 3. Which wouldn't explain when considering there are four on each side. Weird.

 

one might be (zero) un marked, then 1,2,& 3..

 

???? The offset will not be on the right side on one bank and the left side on the other bank. So what did you mean mirror images? Unless its for valve clearance.

 

Just go to the parts counter and tell them which piston you need.

 

Okay, so it appears that Lexus made three pistons for the 2000 LS400 motor (and possibly other years also). According to my research, the reason behind the Mark 1, Mark 2, or Mark 3 choice is that the piston choice at the factory depended on the quality of the block machining. The factory chose the piston most suited to the machining.

While newer pistons had an "L" or a "R" prominent next to the pin, along with the number 1, 2, or 3 next to it, the 2000 did not. All it has is an L or R, to designate which side of the engine the piston fit.

So I looked once again at my damaged, driver's side piston. The "L" is there, but the Mark number was nearly obliterated on the top of the piston by a valve. But the bottom leg of the 2 was there.

And of course it's the most expensive to replace.

So there it is. If you find yourself looking for an explanation as to why there are multiple pistons for your engine, perhaps this will help. Take it easy.