Hello there. Looking for some advice on my 2007 G35 sedan. Car has 155,000 miles, and I'm thinking about doing a track day. I'm a bit concerned about spinning a rod bearing on an engine that old. I tried doing a search and didn't find much on rod bearing replacement. Has anyone done this is preventive maintenance? How tough is it to get to the rod bearings? I don't mind pulling the pan, windage tray, and stud girdle, is there more to it than that? How tough is it to get to the oil pan which seems to be protected by an aluminum plate.

All comments are appreciated!

 

Spinning a bearing is mostly due to insufficient oiling of the bearing not simply because of mileage. Replacing the bearing with a new one requires a break-in time because you are putting a completely smooth bearing up against an unfinished and worn surface. Personally I wouldn't recommend trying to simply replace bearings like that, sure you can match the color codes and use the same bearing thicknesses that were used on initial install but you're still working with rings and all other internal components that have 155k on them. It's a lot of time invested for only replacing about 20% of the actual wearable components.

Do you suspect the motor has excessive bearing wear? Is there noise?

The disassembly entails most of the front end suspension, starter, transmission lower bolts, etc, use a support bar to hold the engine because the crossmember has to go, lower/upper pan aren't really difficult.

Frankly I think this is a complete waste of time, if it's that big of a concern then replace the motor, rebuild the existing motor, etc. I haven't torn the bottom off of an HR motor so I can't be much help about specifics like exhaust getting in the way or anything. I assume it's just the oil pickup and oil baffle on the inside like the DE but not totally sure.

Stud girdle IS the crank main bolts, removing it will free the crankshaft.

You're sure to get various opinions on the matter.

 

In the BMW world, replacing rod bearings is standard preventative maintenance. The S54 (I6 from the E46 M3) and S65 (V8 from E9x M3) are notorious for excessive wear well before 100k miles. Fortunately, this is not the case for our engines, but it's worth having your oil analyzed (I use BlackStone Labs), which will tell you if you have excessive lead in your used oil (indicating bearing wear).

 

I've got experience with rod bearings that agrees with the BMW comment.

Unfortunately I spun a bearing at a track day. The car had 165k on it. I may have gotten the oil too hot, which would obviously be a problem (accidently left the AC on and went out on the track).

I had changed bearings on an identical engine at about 165k; the engine was not showing any signs of bearing problems, but the bearings were showing some copper, so there would have been excessive clearance. I changed the bearings, the engine now has 285k on it. Changing the bearings really smoothed out the engine btw.

It sounds like rod bearings are not much of a problem with this car, but I also don't see much talk of track days. Just started looking at the 370z forum, did not see much there either.

Anyone ever take an engine apart and see rod bearings worn down to the copper?

Also sounds like a major project to get to the rod bearings. That's unfortunate.

 

Google something like "rod bearing wear indicators" and you'll probably find a lot of pictures, smooth and even wear across the width of the bearing down to the copper is basically bearings that wore normally but need replacement. It's not often I've disassembled a higher mileage motor and didn't find worn bearings, that only happens on (EDIT) low mile kabooms and such. The only one that comes to mind was a 2000 Audi A4 non-turbo my brother had, tore the motor apart at a little over 200k and the bearings were in excellent shape, rings were shot but the bearings had hardly any wear. It was a slow turd of a motor and he did all the oil changes on interval so it wasn't unexpected.