MarcL

Hey guys; I am having low oil pressure issues on my VQ35 swap (VQ30 timing/oil pan) and looking for some advice. Here is my story-

About a year ago, the thrust washers fell out of the engine. Not sure why. It happened at high RPM so I suspected maybe the oil was too thin. In an effort to save the engine, I changed the bearings in it (Rod, Main, and thrust) and put it back together. Since then, the engine always ran with very low oil pressure. When it failed again a few weeks ago, it was clearly from lack of oil. Every wear surface was scored, and one of the rod bearings got so hot it could not be removed from the crank shaft. That rod/piston broke and came through the side of the oil pan.

The new (junkyard, supposed to have 20K on it) VQ35 is in the car now, and I swapped the VQ30 bits from the old one on to the new one. Oil pressure is still very low once the engine gets warmed up. I took it for a short drive this evening (first time with this engine) and was concerned such that I left it back at the shop. When I say low oil pressure, it is maybe 10PSI at 2500 RPM, and seems to drop when I accelerate in a high gear, and come back up when I take my foot of the pedal with it still in gear. It is as if the oil pressure drops under load. If I just goose the throttle in neutral, the oil pressure does come up (50PSI range).

Just going by process of elimination, I'd have to think the problem is in one of the parts I swapped over. The oil pan I had to replace because the old one was broken. So, the entire timing cover and it's content are all that is left to focus on. I think I changed the main timing chain tensioner in the past year thinking it may be the cause of the oil pressure (cheap one from Rock Auto- which may be part of the problem too). I did not change the other 2, but there was debris in them from when the bearings failed last year. I cleaned them out, but that may not have been good enough?

I am at a loss, and not looking forward to pulling the engine apart again.. Do you guys have any ideas what to look for?

Thanks

Maximeltman

iTrader: (11)

Did you replace all the o-rings when you swapped the 3.0 upper oil pan? If they are holding pressure at idle or when you only goose it, they might be deformed or flattened, allowing oil to leak out under continuous demand but able to hold it at idle.. I certainly may be wrong here. Also the thrust washers hold the crankshaft from having too much end play so when these went bad, the oil pump might have been damaged. Just throwing it out there.

MarcL

Thanks for the response. I used the O rings than came with the new engine. They looked OK, and I put a dab of RTV on them too.

On the old engine, I did change the oil pump thinking the same thing but it made no difference. This "new" engine came with an oil pump too.

I may try to change the oil to something thicker. Maybe 5W-40, see if that helps. I also see recommendations to use 0W-40 on forced induction, so I guess it can't hurt.

MaxPR0908

iTrader: (4)

Why are you using 40 wheight ? If you want to built pressure Use 5w-20 or ow -20... But 40 is to heavy for this motor..

Also, i guess that you have a oil pressure gauge to know the psi.. So, you have check the line of the oil pressure gauge??

MarcL

I am using an electronic oil pressure gage on the dashboard. I confirmed it is (for the most part) accurate with a mechanical gage. I am reading it using a brass "T" fitting where the oil pressure switch is.

Right now, I have 5W-20 in the engine (wanted to run with a thinner oil for a few miles just to clean it out).. But, I don't understand the theory behind thicker oil = lower pressure? That seems backward. Can you explain?

For sure, the oil pressure drops as the engine heats up (oil gets thinner).

L36

iTrader: (4)

Do you see any leaks or spots on the engine where oil might leak? Check the timing cover area really well. Might be those seals that you reused.

MarcL

The front timing cover did not seem to have any seals/rings. For all this time I had been installing it with just RTV.

Oil pan, and back timing cover had some O rings. and the water pump too. Did I maybe miss some that should be installed?

Engine oil is VERY clean right now, I need to look for the shinyness on the dipstick when I check the level. Right now it may be difficult to see any leaks, unless it hits the ground. But- Will check it again this weekend.

Thanks for all the advice. Keep it coming!

MarcL

Just had a thought- Could a problem with the oil cooler cause this issue? I think I re-used the oil cooler from the "bad" engine... Maybe it is clogged with crap, and causing a bypass to open?

MarcL

Today I pulled the oil filter to change the cooler. The oil that came out (only 10 miles driven) was filled with bits of silver/copper metal. Did not look good.

I drained all of the oil, dropped the pan, cleaned it, put it all back together with 5W-40 oil. No improvement at all. So, the cooler and oil are not the problem.

Are there any mechanical parts inside the timing covers? Hidden somewhere? something that would be causing the low oil pressure?

Thanks

MarcL

Another thought- The (disconnected) solenoids for the variable cams also came from the "old" motor.. Maybe a long shot, but could those cause this problem?

Maximeltman

iTrader: (11)

You said there were no o-rings on the front timing cover, I think that is correct, depending on what you consider the front timing cover. The rear timing cover has I think two (2) o-rings, for the oil galleries. Upper oil pan has two as well...
The inactive solenoids could be the issue...do you have a pic of the open timing cover to post up?

MarcL

Yup.. I remember the 2 rings on the back timing cover, as well as the 2 on the upper oil pan. I am pretty sure they were installed... If one was missing, I would expect to see the low pressure even when the engine is cold. no?

As for the timing cover photo, I don't think I have any.. What would you be looking to see? I have had it off so many times, I may remember what you are looking for. The solenoids can be replaced without removing the cover.

MarcL

Photos, as requested..

Inspecting the VQ35 cover, it looks like those holes in the head that are exposed with the VQ35 cover FEED the intake cams with oil. How does oil get up there with those paths missing from the VQ30 cover?

L36

iTrader: (4)

Im pretty sure it has to do with the VQ30 rear timing cover. The VQ35 rear timing cover has a passage way that interconnects the oil return with the main oil line in the middle of the block. I don't know the layout of the VQ30 RTC but i think that might be your problem.
See the circled lines that im talking about.

cardana24

iTrader: (81)

Are you sure your oil pan is not dented? I had a problem with low oil pressure on my VE30 swap. It turns out my oil pan was dented a little bit not giving enough clearance for the oil pick up to pull enough oil (I forget if the vq35 pick up is the same style). Just throwing that out there. Good luck.