Low Oil Pressure

[menfou]

Hello,

I had 30PSI at idle and cold engine
I had 45PSI between 3000-8000rpm


I changed the stock oil pressure sender, I put a new oil pressure sender (VDO) and a VDO oil pressure gauge, and I had the same values, 30psi at idle with my engine cold, 45psi between 3000-8000rpm.
I try 0w40, mobil1 5w40, Motul 300v 15w50 oil and the same problem.

I rebuilt the engine with SOS oil pump, all gasket are new.
And I have the same problem as before
I changed the valve spring, but not the relief valve.

Where is my problem ???

 

[goldNSX]

Didn't you find mud in the oil when you disassembled the engine?

 

[menfou]

Yes I had mud.

 

[Larry Bastanza]

When you changed the valve spring was the valve itself free to move in the bore? When you opened the bolt for the spring and removed it, did the valve slide out easily?

Regards,
LarryB

 

[menfou]

I didnt check the valve, it's because this morning I ordered a new valve.
This weekend I will change my valve

 

[menfou]

On the oil sandwich adaptor, I have 95psi at idle and cold engine.
But I need to rebuild my engine again, I forgot to bush my rods, I am a idiot

 

[angus]

At least you are an funny idiot.

 

[RYU]

menfou - did changing the valve fix your low oil pressure problem? i'm in the midst of diagnosing my low oil pressure problem (.5-.75 bar @ idle, <= 4 5k+ rpm, but every so often it spikes to 2 bar @ idle and 5-6bar at 5k+) during normal operating temps. I was curious on your fix since I was about to go down the usual checklist which is to replace the sending unit first.

 

[DutchBlackNsx]

menfou - did changing the valve fix your low oil pressure problem? i'm in the midst of diagnosing my low oil pressure problem (.5-.75 bar @ idle, <= 4 5k+ rpm, but every so often it spikes to 2 bar @ idle and 5-6bar at 5k+) during normal operating temps. I was curious on your fix since I was about to go down the usual checklist which is to replace the sending unit first.

Its scary, i know all about it, but most nsx's do this. Been down this route many years ago, never fixed it.
I got another engine, which does the same. I actualy did a survey here on prime about. Search, and read.

 

[pgilliam1]

My oil pressure reading on my guage is never the same even under similiar circumstances. I believe Acura had a recall on these gauges and sending units on the early models. Common problem, but if you've changed the guage and sending unit to non OEM and still have the issue, I'm tempted to leave mine as is. If you find a fix, let us know.

 

[Daedalus]

My oil pressure reading on my guage is never the same even under similiar circumstances.

Exactly. The factory oil gauges are unreliable. It's often never clear to me that people are actually checking their oil pressure with a REAL gauge before reporting problems. That's part of proper diagnosis, which is better than just swapping parts.

 

[nis350]

Exactly. The factory oil gauges are unreliable. It's often never clear to me that people are actually checking their oil pressure with a REAL gauge before reporting problems. That's part of proper diagnosis, which is better than just swapping parts.

I read that it is the pressure gauge rather than the actual oil pressure is the real issue? So that engine should be fine if the issue is just the accuracy of the oil gauge.

 

[FXMDBilly]

I read that it is the pressure gauge rather than the actual oil pressure is the real issue? So that engine should be fine if the issue is just the accuracy of the oil gauge.

On a track, oil pressure itself can be an issue due to oil starvation.

 

[pgilliam1]

On a track, oil pressure itself can be an issue due to oil starvation.

I have never heard of this being a problem in the NSX. With as much track time as these cars get you'd think it would be mentioned here because it would lead to major engine failures. Maybe I'm out of the loop? A dry sump oiler would be nice though!

 

[Honcho]

I think the issue has more to do with power-modified cars. The stock oiling system was designed for a 270hp car and works just fine. Increasing the engine power results in faster speeds, which results on higher lateral G loads on the car in turns- especially long, fast sweepers. These higher G's could slosh the oil in the pan beyond the ability of the pickup to draw oil, resulting in oil starvation. There have been documented issues with this, which usually involve some sort of scuff on the #4 (I think?) bearing.

But, with a stock car, I don't see any need for additional oiling system mods. As you said, there are plenty of folks here who have hundreds or thousands of track miles on their stock NSX without any problems.

If it were my car, anything beyond the basic I/H/E would include a baffled oil pan as insurance. Any sort of forced induction on top of that and I would add an Accusump as well. Of course, dry sump would be best.

I have never heard of this being a problem in the NSX. With as much track time as these cars get you'd think it would be mentioned here because it would lead to major engine failures. Maybe I'm out of the loop? A dry sump oiler would be nice though!

 

[menfou]

Hi,
My engine works fine for 5 years with 0 issue, but always 30psi@idle and 45psi between 3000-8000RPM(read on the front head location).
SOS oil pump
SOS oil pan baffle
New valve spring pump

Since April 2014 I have VTEC problem on track only, I thought the problem was my new oil Mobil 5w60, but I have exactly the same problem with Mobil 5w40.
I have the problem only with those conditions : Oil temps > 230°F + long right corner.(40-45PSI on my VDO oil pressure gauge)
I changed everything except head oil restrictor.
I ordered a new oil pressure gauge, to check vtec oil pressure, I hope to measure the pressure this weekend.

 

[ftuhy]

OK, I'm confused a little. Page 8-6 of the shop manual (for 1995-96) specifies >10 psi at idle and >50 psi at 3000 rpm. You are 5 psi low at 3000 rpm, but higher than the minimum at idle. And that 5 psi could possibly be due to test gauge accuracy. What oil pressures were you expecting?

If there really is a problem, it still sounds like oil starvation is the issue.

But note that on a totally stock engine going perfectly straight, oil pressure drops noticeably when V-TEC kicks in. At least in section 8 of the manual, I could not find an oil pressure spec with V-TEC activated. But in the V-TEC section is does say pressure at the V-TEC solenoid should be greater than 57 psi (4 kg/cm2).

For one reference point, on my car (totally stock), the OEM in-dash gauge drops to about 3.5 when V-TEC kicks in, runs at about 4.5 at 3000 rpm and at 1 to 2 at idle.

 

[Mac Attack]

To be clear, is your question that you are now having problems with VTEC while it has worked fine the past five years? Same oil viscosity, same oil temperature, same track... basically same conditions?

Why are you running 60W oil? Did you increase bearing clearances when you did your engine rebuild?

Did you ever check to see if your oil pump bypass plunger slid freely in the bore like Larry suggested?

 

[Old Guy]

Hi,

Since April 2014 I have VTEC problem on track only, I thought the problem was my new oil Mobil 5w60, but I have exactly the same problem with Mobil 5w40.

There was a thread some time ago (can't remember which sub forum) which included a discussion related to problems associated with the use of heavier weight oils in the NSX (and later model Honda engines). I can't remember all the details; however, the gist seemed to be that with the tight clearances in the stock engine, the higher viscosity associated with the heavy weight oils created a problem with adequate flow (also increased drag and power loss). I seem to remember some related discussion about problems getting adequate flow / pressure to get reliable VTEC activation (the thread was some time ago and I didn't try to find it so I may have confused that last part of the discussion with some other issue!).

If your engine has been modified with larger internal clearances and you have also modified the various restricting orifices that Honda uses to control oil flow rates, then this may not be a relevant issue.

 

[Mac Attack]

To be clear, is your question that you are now having problems with VTEC while it has worked fine the past five years? Same oil viscosity, same oil temperature, same track... basically same conditions?

Why are you running 60W oil? Did you increase bearing clearances when you did your engine rebuild?

Did you ever check to see if your oil pump bypass plunger slid freely in the bore like Larry suggested?

A couple of more thoughts:

How clean is your oil pickup screen? Is your oil pan dented near the pickup?

Did you use a new o-ring on the oil pickup that goes into the pump suction?

Were there any major scratches on the oil pump housing?

I would also be concerned with the head oil restrictors like you mentioned. When I rebuilt my engine, I thoroughly cleaned the restrictors to make sure nothing was caught in the orifices. They were clean, but the rest of my engine was very clean too with almost zero gunk buildup.

Dave

 

[menfou]

Hello,

1 Oil pressure :
I always had 85-95psi after the oil pump (swith oil pressure) , but only 30-45PSI on the Head oil pressure location.

I rebuild my engine, change all O-Rings, but still have the same pressure in the Head.

For 3-4 years, I never had Vtec issue with Oil>250°F , but since 1 year my VTEC doesn't work if my oil temp is > 250°F.

I replace my SOS Sandwich plate by a Ebay, and my oil pressure was increased by 10psi.
I put a small washer in the oil pump spring, and I won 8psi.

I will try on Track in few weeks.


2 Best place for your Oil cooler
Actually, I have my oil cooler in the rear fender.
I bought a anemometer to find the best place for my oil cooler, I have not finished to find the best place, but I have some values (40mph speed) :
-Air Inlet in the Rear fender : 5.5m/s
-Air Inlet in the Rear fender with a aluminium protoype scoop: 7m/s
-In the front bumper 15m/s
-Out my arm outside 17m/s

So I don't think the best place is in the Rear fender, I will try close to the oil pan this weekend.

 

[Mac Attack]

That is low head oil pressure. Between 6k and redline, my oil pressure as measured at the OEM sender location on the front head location is ~90 psi depending on oil viscosity and temperature. That also assumes OEM main and rod bearing clearances, and OEM oil pump.

My camshaft caps were a lot cleaner than yours and didn't have any "mud" when I rebuilt my engine at 125k miles.

Did you make sure the head orifices (one on each engine bank) were not clogged when you reassembled the engine? That seems to be the most likely restriction of oil flow for your scenario since your pump discharge pressure is "OK."

A good discussion of oil pressure with thicker oils is here:
http://www.nsxprime.com/forum/showthread.php/124613-oil-pressure-with-15w50/page2?

Dave

 

[nsxspdfreak]

I don't know if anyone is following this thread anymore, but just in case someone is. I am having a problem with the front bank vtec kicking out due to low oil pressure and then getting a CEL 22 code (Front Vtec Oil Press Switch). I've already eliminated the pressure switch as being the problem. During a high rpm test run to today while trying to figure out what was going I was able to feel and hear the vtec come on, but as it did and as I continued to accelerate I watched oil pressure on the dash drop from a 4.5 to under 1. Simultaneously the CEL light came on again (later determined to be a code 22). When this happened I immediately backed off of the throttle, and watched the oil pressure come back up to above 4. I then repeated the run and watched the same thing happen again. The oil pressure runs anywhere from 1-2 at an idle and 4-4.5 at 3000-4500 rpms, which is normal. I just replaced the front cylinder head so I was thinking that the oring seal on the vtec oil passage way fell out of position during reassembly and the oil for the vtec is just dumping without any restiction into top of the head, hence the low oil pressure after the valve is opened. To eliminate this possibility I first disconnected both Vtec solenoids and then did another high rpm run. This time pressure actually climbed to above 6 as rpm climbed, which was to be expected with no vtec operating to bleed down the pressure. Next I reconnected only the rear bank solenoid and repeated the run. This time oil pressure remained stable at about 4-4.5 throughout the rpm range including into vtec. I then disconnected the rear solenoid and reconnected the front, and repeated the run again. Again oil pressure remained stable as it did with the rear bank with oil pressure remaining at approximately 4. There was no severe oil pressure drop like I had with both vtecs engaged simultaneously.

It would appear that the oil pump can't keep up with the demand of both front and rear vtecs running simultaneously, and when the valves open pressure drops dramatically causing the ECM to sense low vtec oil pressure. What doesn't make sense is why am I getting only a code 22 for the front bank and not a 52 for the rear bank. I would think that if one cuts out due to low oil pressure the other should.