Forums/Z31P/z31-repairs-forums engine-mechanical/Little to no oil pressure at idle
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cuong nguyen: (2017-02-22 06:19:04)
I have an equus electric oil pressure gauge with the stock dummy light hooked up to it.
Starting up, the oil light stays on and the gauge reads 0 or less than 10 psi. I rev the motor up to 3250 RPMs and I get 36 psi.
It's a VG33 block with a reman vg30 crank running a used turbo oil pump in my truck. Would this main bearing clearance be the main cause?
[archived image: P1030413.jpg]
I failed to check the clearances of the oil pump before installing.
[archived image: P1030502.jpg]
midian: (2017-02-22 07:15:54)
mechanical gauge or stock with sensor?
NissanXRMA: (2017-02-22 12:31:51)
Was the remanufactured crank undersized? I'm not sure with your gauge setup, but my new stock sensor will show 0 "bars" with the red low oil pressure light at idle (700rpm), and 3 "bars" on the digital gauge at 800-900rpm on my fresh rebuild, so i ignore it.
If i recall, a VG30 should be around 7psi at idle.
NissanEgg: (2017-02-22 19:20:15)
I get about 5-6 psi at hot idle and about 40-44psi at 3000rpm hot according my Prosport EVO digital gauge. When cold pressures can be as high 75psi at 3000rpm and 25psi at 1000rpm cold idle. I use 20w-50 in summer and 15w-40 in winter. All this is on a VG30ET A-series with 84T automatic oil pump. All new Nissan main and rod bearings when I built my engine. I run thicker oil due to forged Eagle rods and Wiseco pistons.
cuong nguyen: (2017-02-22 19:46:07)
The Equus oil pressure gauge is a 90* sweep and the sender allows you to hook the stock dummy light sensor wire to it.
The crank was undersized but included the correct size bearings with it or so I thought. I should have went with larger bearings to get the clearance tighter.... I figured it would be okay when I rebuilt the motor 6 years ago.
I'll bump up the weight of oil and change out the filter. I'll hook up my other mechanical oil pressure gauge and see what I get. It's a pain to down there.
I have about 600 or so miles on the rebuild and I'm fearing the worst for a mistake I could have easily avoided.
flatfoot: (2017-02-24 00:05:13)
Let me open my mouth and fan the flames.
According to an Innovate mtx-d pressure guage.
On a nice hot stock internal vg30et with easily 200k running 10/40:
at idle/700 rpm 20 psi
at 2700 rpm low 50's psi
According to the FSM for an 86 turbo I should be getting:
at idle 11psi (this is probably low enough to set your warning light off)
at 2k rpm you should be getting 43 psi
at 4k rpm you should be getting 57psi
These last two numbers bother me that you're note getting them.
Your shot of the crush gauge looks good to me. Getting out there a little bit but still within tolerances.
Now my turn to ask some questions.
Where do you have the sender for this gauge plugged in at??
If you used the stock hole in the block be aware that the oil goes from the pump through the filter to the sender.
So if your stock filter is plugged for some reason you're gonna read whatever pressure is over the amount to kick open the emergency bypass for the filter.
AKA change your filter ASAP and see if that helps.
EDIT
And while your in there make sure that little ball moves on pressure relief.
cuong nguyen: (2017-02-24 03:39:09)
Well I changed the oil and filter today and am still getting the same thing. I'm using Castrol Gtx 10w40 and some kind of parts America oil filter that I got on clearance at Rock Auto. Before the change it was a Micro guard filter. The sender is in the stock location. I don't know anywhere else to attach it.
I took some videos with my phone of the gauge reading.
I also noticed an audible clacking like knocking near the oil pump.
This whole investigation started when I was driving on the highway 65-70 mph I just heard loud valve tapping out of nowhere so I began to exit. I pulled over to stop, check for leaks and oil. Nothing. Start it back up and no more valve tapping.
I bought a jug of Rotella 15w40 to try and see if it will increase the pressure.
Really trying to avoid dropping the pan to check clearances but I might have to. Fortunately I have a lift in my truck so dropping the pan is a lot easier.
turbofedz: (2017-02-24 06:03:03)
Well this is just my opinion if this was my build,new new!! Oil pump that's just a no brainer,but that's just me good luck.
Timbo_021: (2017-02-24 09:26:11)
Bearing clearance is spot on. I'd look at your oil pump if its noisy, that's a dead give away somethings not right in there.
Also, as a rule of thumb I was taught 10psi oil pressure per 1000rpm for your average engine. Any less is no good.
cuong nguyen: (2017-02-24 15:10:10)
Well this is just my opinion if this was my build,new new!! Oil pump that's just a no brainer,but that's just me good luck.
Yeah, I totally agree with you. I did not know what I was thinking about using an old oil pump when I had rebuilt the engine.
I guess I'll order a new pump. Dreading tearing up up the front end and pulling the pan again.
NissanEgg: (2017-02-24 18:06:30)
You can check the relief valve of the oil pump to make sure it isn't hung open from debris or sludge. It's the part of the oil pump with the very large bolt head. Take that off and inspect the spring and sealing ends of the valve. You can raise oil pressure by putting a washer or shim under the spring to raise opening pressure of the valve.
But since it's a used pump you could open up the backside of and inspecting the gears to see if they are excessively worn. I'd do that after replacing with a new one just to see what is really going on inside.
cuong nguyen: (2017-02-25 00:48:11)
I ordered a new one with gaskets just in case.
Do you think it is possible to replace the main bearings and rod bearings with the crank still in the engine?
flatfoot: (2017-02-25 02:48:10)
About 90% sure swapping the bearings without pulling the crank is a no go. Think about it.
You've got a clam shell bearing with a top half above the crank and the bottom below it.
Now being able to replace them with the engine block in the vehicle. I won't swear you cann't do it if you remove the cross member underneath the motor.
Not something I'd do, but you might be able to do it.
cuong nguyen: (2017-02-25 03:46:16)
Once I get under it I'll see what I'm working with again. In my head I'm thinking I could "spin" the bearing to get the old out and put in the new after I created more clearance. That part is the unknown. The girdle secures the mains while the oil pump and rear main seal seal the ends of the crank. If it's possible as such I wonder if I'll get an accurate measurement of clearance with the weight of the crank and such on the girdle.
NissanEgg: (2017-02-25 17:39:09)
It is possible to replace main bearings in the vehicle, but a royal PITA.
I have had to redo several #1 main bearings on 09-13 Maxima under warranty due to worn upper half of bearing causing a faint knock. The tool that Nissan has you make is take a cotter pin and make it into a T and insert into the oil hole of the crank. Then you rotate the crank gently with the T-shaped cotter pin to push the upper bearing half out. And then use the same cotter pin to push the new bearing half in by turning crank the opposite way.
DO NOT DO THIS UNLESS YOU HAVE THE MECHANICAL SKILL TO DO THIS WITHOUT DAMAGING CRANK OR BEARINGS.
cuong nguyen: (2017-02-26 02:25:45)
Thanks NissanEgg!
88sinZ: (2017-02-26 03:33:13)
new oil pump, no question. pack that bitch full of moly lube too
Ski300zx: (2017-02-26 11:18:53)
you can change all the bearings with the motor in the car. cross member will have to be removed, as will the oil pan obv. take all the drive belts off. support the front of the crank with a screw jack. take down the main bearing girdle, and use a small screw driver to push the bearing out of the upper journal. slide the new one in, making sure the notch is correct. same thing with the rod bearings.
cuong nguyen: (2017-03-01 04:06:01)
I fugged up.
Well Things just get worse as I tear apart more. I inspected the bearings for 3-6. I didn't have time to check 1-2. I'll do that tomorrow and pull the girdle off to inspect the mains.
The bearings on #6 is the worse so far. When I pulled the bearing cap, it just feels out. Same with its opposite end.
So is it salvageable? Tips to try and save it? the rods are 0.25 undersized and the crank is 0.50 undersized. [archived image: 20170228_162948.jpg]
[archived image: 20170228_173851.jpg]
It looks like the chamfer for the oil holes are digging into the bearings on the journals.
[archived image: 20170228_170444.jpg]
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[archived image: 20170228_172315.jpg]
The only decent one of the 4 I checked. This is number 4 too oddly. [archived image: 20170228_171306.jpg]
NissanXRMA: (2017-03-01 15:12:39)
I believe there are service limits in the "EM" section of the FSM for connecting rod and crankshaft reworking limits.
cuong nguyen: (2017-03-01 15:50:17)
I believe there are service limits in the "EM" section of the FSM for connecting rod and crankshaft reworking limits.
I'm aware of that. I'm going to try to see if I can get to the mains before I go any further. I'm trying to avoid having to pull the motor and transmission out again.
cuong nguyen: (2017-03-01 23:31:08)
Pulled the girdle off today but forgot to check 1 and 2 rod bearings.
[archived image: 20170301_163547.jpg]
[archived image: 20170301_163554.jpg]
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Timbo_021: (2017-03-02 11:03:10)
From lack of oil pressure I'd say. You might have a chance if you get a new oil pump and new bearings? But the crank will have scores on the journals so hard to say what will happen really.
ralph50: (2017-03-02 19:14:42)
Damn. Looks rough. Looks like you spun metal all over the place. Your cylinders are probably scored as well. You might be able to just polish the crank and hopefully hone the cylinders.
Try to get pick of the cylinder walls.
Worse case scenario is a new block and cut the crank again etc.
At this point only a machine shop will be able to tell you for sure. Hard to diag from the key board.
IDK what your goals or budget are but keep us posted.
Best of Luck
cuong nguyen: (2017-03-02 23:01:06)
I think the block is OK. Can't see the bores until I pull the crank out. I only get less than an hour each day to mess with the motor and I'm trying to get a lot done before the baby comes.
I checked rod 1 and 2 bearings. 2 shows oil starvation and looks actually decent.
[archived image: 20170302_161944.jpg]
[archived image: 20170302_162034.jpg]
Rod 2 bearings
[archived image: 20170302_161244.jpg]
I am thinking if I polish the journals, I should be ok. Any significant nicks should just hold oil as the polishing should get rid of the high peaks to keep it from chewing through the bearings.
ralph50: (2017-03-03 11:56:47)
Something similar happened to me. I let my Z sit for 15 years and the turbo bearings disintegrated and fell into the oil pan. I spun metal everywhere and the oil pan looked like yours. The engine was fully built so I tried to save as much as I could but I ended up with new bored block and cut crank. The camshafts had to be polished.
Congrats on the baby but it might be better to deal with this now than when the kid is crawling around, shiting, puking, sneezing, coughing etc. LOL
cuong nguyen: (2017-03-03 16:23:11)
Something similar happened to me. I let my Z sit for 15 years and the turbo bearings disintegrated and fell into the oil pan. I spun metal everywhere and the oil pan looked like yours. The engine was fully built so I tried to save as much as I could but I ended up with new bored block and cut crank. The camshafts had to be polished.
Congrats on the baby but it might be better to deal with this now than when the kid is crawling around, shiting, puking, sneezing, coughing etc. LOL
Fugggg. That does not sound good for me. Haha. How severe did the bores and camshafts look? My bores are +0.75.
I'D be at max available undersized bearings and rods if I re-grind the crank.
I've got too much money in this thing to throw away lol.
ralph50: (2017-03-03 18:40:17)
The cylinder walls on my block were too scratched up so I needed a new block. I have Wiseco 30 over pistons. My crank had to be cut 50 under. It was lot of $ when all was said and done but I think/hope I did it the right way.
I was able to save the pistons, rods, heads, cams and crank. The only reason I did so was because it was balanced, ported and all after market.
As a rule of thumb if you can feel it with your finger its too much.
Don't mean to freak you out but at the very least inspect it.
I had less metal in the pan than you
cuong nguyen: (2017-03-03 22:40:18)
Ffffffffffffff.
cuong nguyen: (2017-03-15 13:48:58)
It looks like my oil pump was the main culprit.
The screws for the back plate took no effort to come off. Opening up, I could see the backing and the gears were cutting grooves.
[archived image: 20170314_175328.jpg]
[archived image: 20170314_175345.jpg]
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88sinZ: (2017-03-18 01:32:52)
glad to see the follow up, as i went through your pics the bearings look fine and low wear - that matte finish is a sacrificial layer. Those flakes and bearing surfaces would indicate some other component failure.
Unfortunately if that FOD makes it's way to the pan you're basically F'd, it'd be assumed it's drain back best case scenario
You want to have clean threads (no oil/dirt) on the oil pump screws and use an impact screwdriver to secure the screws. These screws should not be able to break torque by hand.
cuong nguyen: (2017-03-18 04:16:15)
glad to see the follow up, as i went through your pics the bearings look fine and low wear - that matte finish is a sacrificial layer. Those flakes and bearing surfaces would indicate some other component failure.
Unfortunately if that FOD makes it's way to the pan you're basically F'd, it'd be assumed it's drain back best case scenario
You want to have clean threads (no oil/dirt) on the oil pump screws and use an impact screwdriver to secure the screws. These screws should not be able to break torque by hand.
I'm going to see if I can scrape up all tha stuff at the bottom of the pan and figure what it is. I should have done a compression test prior to disassembly.
Does anyone have pictures or know of the rockers are bushed?
I plan on dropping the crank at machine shop to see if the journals measure out.
I found a quest/villager crankshaft local that's new and now I am wondering if it's the same crank so I can use as a backup option.
cuong nguyen: (2017-03-21 23:00:21)
Well, had the crank polished and I'm going to slap it back in with fresh bearings and shoot for the best.
Any suggestions as to how to clean out the oil passages in the crankshaft?
It should be interesting trying to plastigage all this under the truck.
cuong nguyen: (2017-09-06 18:31:30)
Well, I went ahead got the crank grounded to the next size available a while back and finally got some time to tackle this again. I thought a could muscle the lower end from below the truck but I was kidding myself.
I'm going to pull the front axle out to get more room to work under there and use a jack to suspend the crank to bolt it in place and get some rough measurements with plastigage. A bore gauge would have been great to have....
cuong nguyen: (2017-09-07 14:09:47)
Decided to just suspend the crank and girdle in place using some cinch straps which worked out great and saved me some time. The clearance I got from the rods bearings were ok. Most were at about 0.038mm.
My mains are what I am concerned with. 1 & 4 had clearances of about 0.051mm and 2 & 3 had clearances of about 0.076 mm. I am not sure is it because I'm torqueing it upside down and not getting an accurate torque due to the weight. The limit is 0.090 so I'm still okay just on the far loose of clearances.
88sinZ: (2018-01-21 07:56:55)
its been a while, and i hope your results were in your favor - those limits are in FSM spec's