Extreme low oil pressure after engine rebuild

[nsxinkl]

Problem: extremely low oil pressure after engine rebuild. Half to one bar (5 to 15 psi) at idle and maximum of 3 bars (45psi) at WOT.

Engine rebuild details Block sleeved by Dan Benson of Benson Racing. Cyclinders, con rod and crankshaft (Brian Crower) supplied by FXMD. Built by local mechanic. Cometic MLS headgasket and new OEM oil pump with Dali billet oil pump gear. Conrod and main bearings are gapped within service manual specifications (I.e. Around 0.005mm).

What could be the cause of such low oil pressure? Could it be caused by the design of the crankshaft? At recommended oil level, the oil is aerated (noticeable bubble in oil observed on the dipstick). The aeration disappears when we add oil above recommended level. So far we have tried 5/50 and 15/50 oil. We have also ruled out malfunctioning oilmpressure senders. We have manually measured the oil pressure with an external gauge.

Could the problem be caused by a faulty oil pickup?

We have opened up the engine to check and reinstalled it 3 times. So your advice will be much appreciated.

 

[E-Nough Logic]

Haven't built a C30/32 myself but on my B series I left an oil plug out from underneath my the intake came and never had enough oil pressure to engage vtec. I didn't have an oil pressure sensor though so couldn't comment on the actual pressure though. Could be something as simple as that. Have you tried an oem oil pump? A problem like this is nearly impossible to diagnose over the internet especially if you have pulled it apart a couple times and haven't found anything. Good luck.

 

[nsxinkl]

Haven't built a C30/32 myself but on my B series I left an oil plug out from underneath my the intake came and never had enough oil pressure to engage vtec. I didn't have an oil pressure sensor though so couldn't comment on the actual pressure though. Could be something as simple as that. Have you tried an oem oil pump? A problem like this is nearly impossible to diagnose over the internet especially if you have pulled it apart a couple times and haven't found anything. Good luck.

Have you tried an oem oil pump?

Thanks for chipping in. I had new OEM oil pump installed.

Cody of Lovefab suggested that i check the following which I will check tomorrow morning: oil pickup. Restrictors between cylinder head and block, O-rings under the cam caps and main girdle and that the relief valve is not stuck open.

Dan Benson is of the opinion that the Brian Crower crankshaft may have holes in it which needs to be plugged. I have asked my vendor (Ken of FXMD) if this is the case but he has yet to revert to me. Is there anyone out there who has Brian Crower crankshaft or knows the answer?

Any other advice will be much appreciated.

 

[Briank]

How are you checking the oil pressure? The stock gauge sensor is not the best and frequently highly inaccurate.

 

[Mac Attack]

"The aeration disappears after we add oil above normal level."

Does your oil pressure read normal then too when overfilled, or do you just notice the aeration disappears?


Aeration is caused by a couple of things. Combined with low oil pressure (since you said you checked the sensors), it sounds like a oil pickup not sealing as mentioned, or a leak in the oil pump housing that is letting air get to the suction side of the oil pump that then gets compressed and sent to the rest of the engine.

Air getting entrained in the suction of the oil pump will cause what you see, and also account for the low oil pressure at all RPMs since air is compressible.

If the engine was assembled improperly with a missing o-ring or orifice, then you could have low oil pressure or not have enough pressure in the heads to engage VTEC with the oil pressure sensors reading up there, but that typically wouldn't make the oil get mixed with a lot of air. Also, the bypass stuck open may cause low oil pressure at idle, but won't explain the air entrainment.

My money is on the pickup or oil pump/housing itself. Remember, it could be a combination of things too. The SM lists the correct clearances for the oil pump and housing. If those clearances are too large, then oil pressure will be low. How come you changed the housing? Unless you went with the larger capacity Dali oil pump, you should have been able to reuse your old housing. For my rebuild, I bought the Dali replacement pump, but OEM capacity. I'm keeping my OEM housing unless the clearances are off.

Sorry to hear about that. I wouldn't run the engine personally until you figure it out. Also, not with the higher weight oil (since you maintained tight clearances) or filled much above nominal level.

Dave

 

[nsxinkl]

How are you checking the oil pressure? The stock gauge sensor is not the best and frequently highly inaccurate.

Both my DEFI and OEM gauge gave the same low readings. I have also measured oil pressure using an external gauge at the engine directly.

Thanks for chipping in. Much appreciated.

 

[nsxinkl]

"The aeration disappears after we add oil above normal level."

Does your oil pressure read normal then too when overfilled, or do you just notice the aeration disappears
Dave

The oil pressure still remains at the same low pressure when overfilled but the aeration disappears.

My money is on the pickup or oil pump/housing itself. Remember, it could be a combination of things too. The SM lists the correct clearances for the oil pump and housing. If those clearances are too large, then oil pressure will be low. How come you changed the housing? Unless you went with the larger capacity Dali oil pump, you should have been able to reuse your old housing. For my rebuild, I bought the Dali replacement pump, but OEM capacity. I'm keeping my OEM housing unless the clearances are off.
Dave

I have Dali billet oil pump gear and new oem oil pump.

 

[nsxinkl]

We have double checked and ruled out the following: Restrictors between cylinder head and block have been properly installed with the right new O-rings, O-rings under the cam caps and main girdle and that the relief valve is not stuck open.

The only thing left to verify from the advice above is the oil pickup and whether there is any holes in the crankshaft design which must be plugged (FXMD who sold me the crankshaft has yet to revert to me on the question).

Thanks for helping. My nsx has been on the service lift for months now. Any other advice will be much appreciated.

 

[Mac Attack]

I would also check the oil pump gears and housing too if the pickup is bolted in correctly with it's o-ring intact.

Maybe you didn't see my question above, but why did you replace the oil pump housing? Was it worn excessively or out of tolerance?

 

[nsxinkl]

I would also check the oil pump gears and housing too if the pickup is bolted in correctly with it's o-ring intact.

Maybe you didn't see my question above, but why did you replace the oil pump housing? Was it worn excessively or out of tolerance?

The oil pressure was low so I got a new oil pump because the old oil pump was a little worn but the new oil pump didn't solve the low oil pressure problem.

The billet oil pump gear is within service manual specification.

If a have a new oil pump gear that would rule out any housing problem?

I will check the pickup and it's o-ring tomorrow.

Thanks for your time and effort.

Any more advice would be much appreciated.

 

[Ponyboy]

What exactly are the oil pressure numbers you're reading during idle?

 

[Mac Attack]

The replacement Dali gear is separate from the housing.

There is no need to change housings unless your OEM one was really worn and out of tolerance, OR you purchased the Dali high volume gear (Dali has two designs). The larger high volume gear requires a special-machined housing to accomodate it.

But, if you had problems with oil pressure before you did the gear and housing replacement, then that's probably not the cause....

Probably the pickup then. It's hard to miss putting the o-ring in the ase where the pickup bolts on. Also, if you say overfilling helps with the aeration, then maybe the pickup is bolted in correctly, but it is cracked and letting air enter after the mesh screen.

 

[nsxinkl]

What exactly are the oil pressure numbers you're reading during idle?

On the factory gauge it is close to zero. On the DEFI gauge it is half to one bar (7 to 15 psi). At 4000rpm, the OEM gauge does not even reach halfway (4) and DEFI gauge is around 3 bar (45psi).

 

[nsxinkl]

The replacement Dali gear is separate from the housing.

There is no need to change housings unless your OEM one was really worn and out of tolerance, OR you purchased the Dali high volume gear (Dali has two designs). The larger high volume gear requires a special-machined housing to accomodate it.

But, if you had problems with oil pressure before you did the gear and housing replacement, then that's probably not the cause....

I initially had the normal Dali billet oil pump gear in OEM oil pump housing. When the oil pressure is low, I changed back to OEM oil pump gear but the oil pressure still remains low. Then I noticed that there is a slight free play between the OEM oil pump gear and the housing. This is why I bought a new OEM oil pump. Unfortunately, it did not solve the low oil pressure problem. Now I have the standard Dali billet oil pump gear in the new OEM oil pump housing.

 

[nsxinkl]

Probably the pickup then. It's hard to miss putting the o-ring in the ase where the pickup bolts on. Also, if you say overfilling helps with the aeration, then maybe the pickup is bolted in correctly, but it is cracked and letting air enter after the mesh screen.

Overfilling the engine with oil only solved the aeration problem and didn't solve the low oil pressure issue. Does this rule out the pickup as the cause of low oil pressure?

 

[Ponyboy]

It will help, marginally, if the overfill totally engulfed the oil pickup. Has FXMD got back to you on the crankshaft yet?

I'm afraid you may have to disassemble the engine and build it back up again.

 

[Mac Attack]

Overfilling the engine with oil only solved the aeration problem and didn't solve the low oil pressure issue. Does this rule out the pickup as the cause of low oil pressure?

No, because a really restrictive pickup, or one that is leaking therefore allowing air to enter in the suction side, will still cause low discharge pressure.

If the pickup is blocked or restrictive, then the pump will not discharge at the required pressure and also have cavitation.

If the pickup isn't sealed correctly or is cracked somewhere above the oil level, then air can get entrained or "sucked in" along with the oil pulled from the pump. This can also cause cavitation, and can also degrade pump discharge pressure since air is compressible.


Of course, it can be a combination of pickup and crank holes that should be blocked. Hopefully it's just the pickup since that's much easier to fix.




Thanks for clarifying the oil pump woes. Man, that really sucks all that you're going through.

 

[FXMDKen]

Sorry to hear about all these issues you are experiencing, putting together the NSX motor is typically not recommended as a DIY as it takes experience to cover all the intricate details. All of the advice given thus far are all plausible scenarios that may be causing your problem. In addition, I just responded to your email in regards to the oil galley plugs for the crankshaft. I hope these words of advice solve your problem. I would like to add to double check that all of the orifices are clear of debris. In addition, double check that no parts were damaged while running the car with low pressure or removing them many times over. This is a proven motor package for many years and we have never had any issues with the assembly, but it does help that our builder has about 10 years of experience with this specific motor as well. If you have any more questions shoot me an email as usual and I will do my best to help.

 

[nsxinkl]

In addition, I just responded to your email in regards to the oil galley plugs for the crankshaft. I hope these words of advice solve your problem. I would like to add to double check that all of the orifices are clear of debris.

I am so glad to hear from you. I didn't get the plugs nor the instructions. I have checked the package many times when I received the package and recently. Could you please email the instructions to me and send me the plugs ASAP?

Thanks for your help.

 

[FXMDKen]

Not a problem, it's hard for me to respond within twelve hours on the weekends as family events like weddings and such tend to take up time. Hopefully dan has them as they can easily be removed from the box and forgotten about. If not I have extras at the shop.

 

[angus]

So the mystery is solved? I suppose the oil escaping through the missing oil gallery plugs caused the aeration and when overfilled the holes were below the surface of the oil, preventing aeration...

 

[nsxinkl]

So the mystery is solved? I suppose the oil escaping through the missing oil gallery plugs caused the aeration and when overfilled the holes were below the surface of the oil, preventing aeration...

Hi Will, great to hear from you! I hope you are right. I am waiting for FXMD to send me the plugs. Can't wait to get my nsx up and running.

 

[E-Nough Logic]

So you checked the crank and the plugs were not installed in it already?

 

[nsxinkl]

So you checked the crank and the plugs were not installed in it already?

Yes the plugs were not installed because it was not included in the packaged that was shipped to me. This little omission caused me considerable time, cost, anxiety and frustration. The problem is compounded by the fact that this is my first complete engine rebuild and my builder is not familiar with Brian Crower crankshaft design which requires the holes to be plugged. There is not such plugs in the OEM crankshaft. That is all water under the bridge now. I am really looking forward to solving the problem and completing my engine rebuild and finally driving and enjoying my nsx!

I will keep you guys posted on the outcome. Thanks so much for your advice, help and sympathetic ears.

NSXPRIME is such a great forum!

 

[E-Nough Logic]

Yes the plugs were not installed because it was not included in the packaged that was shipped to me. This little omission caused me considerable time, cost, anxiety and frustration. The problem is compounded by the fact that this is my first complete engine rebuild and my builder is not familiar with Brian Crower crankshaft design which requires the holes to be plugged. There is not such plugs in the OEM crankshaft. That is all water under the bridge now. I am really looking forward to solving the problem and completing my engine rebuild and finally driving and enjoying my nsx!

I will keep you guys posted on the outcome. Thanks so much for your advice, help and sympathetic ears.

NSXPRIME is such a great forum!

I would expect them to be installed already out of the box, but I have never used an aftermarket crank, given stock Honda crankshafts are some of the best forged cranks ever made. It is not unusual for a crankshaft to have these galleys. Below is the picture of the oem ball plugging the oil galley. Whenever I have a crankshaft cleaned up my machinist pulls these plugs cleans the galleys and then re-plugs them with allen plugs. I know this is your first build but an experienced engine builder should have noticed these missing regardless of the crankshaft being used. Especially pulling it apart 3x.