MarcL

On the VQ35, is there a oil check valve? or some other device that regulates oil pressure?

If so, where is it located?

Thanks.

Weimar Ben

iTrader: (5)

No. Oil pressure is a function of the efficiency of the oil pump, the clearences in the engine, and the visocity of the oil. If your clearences are within spec and you're using the right oil, you should have no pressure issues.

There is a bypass valve in the oil filter which allows oil through if the filter clogs.

MarcL

There is not valve at all in the oil pump? I remember changing an oil pump in a 240 a few years ago because the valve in it was bad...

Weimar Ben

iTrader: (5)

The pump itself probably does, but these pumps don't really go bad all that often. I've put 300k miles on VQ engines and have NEVER had an oil pressure issue, nor have I heard of anyone who has.

What's the problem you're having? Low oil pressure? High oil pressure? Noises?

Weimar Ben

iTrader: (5)

The only mechanical issue I've EVER had on VQ engines is oil consumption on the 3.5. Never had any mechanical issues on the 3.0.

MarcL

A while back I lost a thrust bearing, and that took the main bearings too. I changed them out. Engine seems to be running fine since then, with about 1500 miles on it so far. No noises or anything, but the oil pressure seems low.

At idle is is under 20Lbs. Driving, with my foot off the accelerator the oil pressure comes UP a bit. as I give it more throttle, the needle starts to jump all over the place, if I give it hard throttle the pressure drops.

Last weekend I pulled the timing cover off and checked/cleaned the 2 upper timing chain tensioner, and replaced the lower one. It made no change on the oil pressure.

Weimar Ben

iTrader: (5)

20psi at idle is good. at 2000rpm, you should have around 43psi and near redline, 57psi.

If you changed out the crank bearings, I hope you did the rod bearings as well. Sounds like you have a bad oil pump.

MarcL

Yes, I did rod and main along with the thrust..

With the needle jumping all over the place, it is hard to determine the true reading. 2000 RPM with no throttle it may be 30PSI or so.. but if I mash the pedal, it drops back to 15 or so.

What would change oil pressure based on engine load?!