From this thread; http://forums.maxima.org/all-motor/637852-oil-pump.html

This weekend I was able to replace the Rod, Main, and Thrust bearings in the VQ35 without dropping the crankshaft.

We also found that one of the oil-squirter things that shoot oil in to the cylinders had been broken by the thrust washer that was destroyed. I pulled one from the last engine I blew, and was also able to install that without dropping the crankshaft.

Lots of metal in the oil pan, and the main bearings were in real bad shame. The rod's were not as bad.. The thrust washers were destroyed.

With everything bolted back in place, to the torque specs in the manual, the crank seems harder to spin by hand. It has me a little concerned, but we re-checked everything (after spinning it by hand, we dropped the main caps again to inspect) and nothing obvious is wrong. At this point, I can only hope for the best.

Now that I think about it, I used the torque procedure in my VQ30 manual. Is it the same for the VQ35? I hope so.. because the oil pan is back on already..

 

wait...how did you change the main bearings without dropping the crankshaft???? there's no way to do that...you may be able to change the ones that go on the main cap but not the ones that go on the block....i think we have found the problem

 

They roll in and out.. I just used a soft tool to push on one end, and it rolled out the other end.

I have done this before on other engines (not Nissan) and it has worked fine.

 

What size main bearings did you use? Also, how can you clean all the metal out of the oil channels without disassembling the bottom end? The fact the mains were shot means there is garbage in the exact places you don't want it for the new ones - in the channels, and if you were only able to clean the caps since you slide the bearings in, there's gotta be debris underneath the mains that's throwing off/tightening up the tolerances.

 

Standard bearings. At least that is what I ordered, but I will double check the box now that you mention it.

I blew compressed air through while the bearings were out. I realize it is not the optimum thing to do, but I am trying to salvage this motor without tearing it down all the way.

The act of rolling the bearing in would likely push out any debris in there too.

 

Did you put the caps back axactly how they came off? Location and orientation? The crankshaft bore is machined with the caps torqued down, and is not exactly centered. Hence the proper orientation.
Did you use the same size bearings as the ones you removed? If so it will be tighter than before you disassembled, but still looser that original. Did you use some spray cleaner and compressed air at least, to clean out any metal from the bearing saddles?

Personally, I see nothing wrong with this method. Especially considering the next cheapest alternative is a wrecking yard motor. I've done this before, working in a German import shop.

 

I used "standard" size bearings, and blew it out with compressed air when the bearings were out.

The caps all went back the same way they came out. Same order, and orientation.

My concern is still that it seems harder to turn than I would expect it to.. Using a old style torque wrench, it is 80-100Lbs of force to get it to turn with no spark plugs installed. As compared to the "parts motor" I have, which I can turn with one hand on the front pulley (although, the timing chain has been removed from this engine).

At this point, I am going to put it all back together and hope for the best. I will take the spring out of the blower bypass valve so hopefully the boost will never come up. Run it like that for a few hundred miles, and see what happens.

 

Did you lubricate the surface(that touches the crank) of the bearing? Preferably with some red assembly lube (clear bottle at discount), or just oil.

 

I soaked the bearings in regular engine oil for a few min.. They went in "wet".

 

There are 15 different "standard" size main bearings. You choose the size (grade) based on stampings on the top of the block and on one of the crankshaft counterweights.

Also you should not put oil on the surface of the main bearings that contact the block journals. Likewise you should not put oil on the portion of the rod bearings that contact the rod.

At the very least I would look at the EM section of the 2007 FSM and find the locations of the stampings to determine the proper size of bearings needed. Look at page EM-130.

 

When I ordered the bearings, my only options was "standard, 1 over, 2 over".

 

http://www.courtesyparts.com/kb_search_result.php?keywords=[12207]+\%28a34&cPath=2668_2669_2670_2678

Where did you order your main bearings from? There are also multiple sizes for the rod bearings.

 

Good luck getting your bearings from courtesy I've had some on order for a bout a week now.

 

Did you get ACL bearings? If you got OEM Nissan bearings, you had to measure the crank and block, OR see the laser printing on the block which tells you as well, to buy the correct size. If you still have a chance, just drop the crank, why do all that work and end up with a broken engine again. specially if the old bearings were real beat up, you dont know if the crank is worn out or anything.

Also, when I built my engine i did alot of reading and research, I always saw that you never put oil on the back part of the bearings (surface that lays on the block and caps), you only want to lube the surface that touches the crank.

Now, since you say you dipped the whole bearing in oil, this means there is a layer of oil between the bearing and the surface of the block and caps, which will make the clearance (bearing to crank) tighter (since bearings are not making 100% contact), therefore result would be a hard crank to turn, as well as possible spun bearing upon startup. This is most likely the case, so if you still do not want to drop the crank, then I would take out the bearings again, dry the surface on the block and the caps, then only put lube with your finger on the surface that touches the crank, and reinstall.

 

Rock Auto.
DNJ ENGINE COMPONENTS Part # MB632

 

If the thrust bearing looks like that of an air cooled VW, there are four important measurements.
-journal size
-bore size
-distance between crank flanges
-thickness of block webbing/cap
This bearing might be the cause of your extra drag.

 

No option for thrust bearing size.. just the one.

Drag increased as the caps were tightened down, making me think it is the main bearings, not thrust.

FWIW, the rod bearings were change too (using the same method- soaking them in oil first), and they did not impact the drag.

 

The rod bearing clearance might be more than what the mains have, so having a layer of oil behind the bearing might not affect as much. But definitely I would take the main bearings back out, dry the surface on block and caps, then only wet the inner part of the bearing, leaving the back dry. I bet it will provide a smoother and easier rotation.

 

Extra work to pull it all apart again, but maybe I will give that a shot.

 

And where would it go if it did?

Why not just pull the crank so you can drop it in and see it spin freely without the rods before you keep going? Changing the main/thrust bearings introduces enough tolerance variables, adding dirt and an improper install sequence isn't going to help anything.

 

Engine is back together, I have about 25 miles on it so far.. Hopefully it will last.

 

It would push right out to the opposite side you started from, where you could easily wipe it away or spray with brake cleaner.

Probably because he doesnt want to pull the motor, remove the timing, and heads and pull the piston/rods. I think the idea here is just to fix what broke, and extend the life of the motor, where most people would scrap the engine and swap in a wrecking yard engine. TBH, I would have just replaced the thrust bearing and left the rest alone.

Might not be your preferred method, but it is an option, and was even taught at the technical college I attended. I would have been more thorough cleaning and more conservative with the lube, but in all, well done.

 

I would keep the RPM down and not put a lot of load on it for awhile. with the lube on the backside of the bearings, and eccesive force to turn it over, I would fear a spun bearing. How is it starting? Does the starter labor excessively?

 

I cranked it for a while with the plugs out, to get the oil pressure up.. Put the plugs in, and it started right up. I let it run for about 10 min, then shut it down.

At that point, I tried to spin the engine by hand again, and it required much less force.

The starter had no problem spinning the engine over (It is a Porsche starter unit, so the torque may be higher than the regular Nissan starter).

 

there is nothing wrong with the roll in method for installing the bearings, but as said before by others they should go in dry on the back side, and lubed where the crank journals contact, and it wouldn't have hurt to pull the crank and do some measuring.

best of luck to you

 

FWIW, I have 1000 miles on the car now. I am a bit concerned with the oil pressure (it is a tad lower than I would expect, but I did switch to synthetic which may be part of the reason). Taking on an longer trip this weekend, so thanks for the good luck wishes!