[mitch32]

My car is a 1991 r32 GTR with 109,000km. Compression is 165psi across the board, except cyl-6 is 170psi. Upgrades are exhaust, and intake.

So my problem is that I have good idle oil pressure and good oil pressure up until 3000rpm. After 3000rpm the pressure never increases. Its as if the gauge just gets stuck. I checked with mechanical gauges, changed my stock sending unit, used a defi gauge, everything gave the same result. I have maximum 2.8bar no more. I read alot and I'm pretty sure its the relief valve, but also I read it could be bearings. If its bearings though wouldn't my idle pressure be wrong? Also I never get more then 2.8bar on a cold start.

I'm not sure what to do. I'm kinda of just leaning towards changing the oil pump to an N1, its a big job but I can do it at a buddies garage on a lift (hopefully within a weekend, or a day) and hoping my oil pressure is good after the swap. Then waiting until it blows completely and do a rebuild then. I'll probably also do the timing belt (and water pump) with the oil pump eventhough my timing belt is fairly new. I want to avoid a rebuild right now if I can, I barely driven the car since I bought it, also I have alot of parts waiting to be put in. I just don't want to put the parts in until I get rid of this issue.

Tell me what you think! Can it be the bearings also, what would you do?

Thanks in advance,
Mitch

 

[kismetcapitan]

the oil relief valve is in the pump, so changing the pump will solve a valve relief problem if one exists.

What oil are you running? Thicker oils show more pressure when cold. Stock oil pumps don't flow much oil. Don't waste your money on an N1 pump; they break, and they don't flow any better than stock. Yes, a good pump will run you $1000, but it will SAVE you money over the long run. Trust me on this, I am on my 4th oil pump, and exchanging oil pumps along with the problems they create like spun bearings, having to replace the crankshaft, etc, you will wish you just bought the good pump at the beginning.

Note however that high flow pumps require an extended sump. The Nismo pump is the only one that doesn't. I have a Tomei pump which has no reports of ever breaking, but needs a lot of extra bits to support the huge oil flow it produces. With my Tomei, I have 7 bars at startup, 3.5 bars idle when the oil is very hot, 6 bars as soon as I get on the gas, and although the relief valve opens at 7 bars, the pump will overcome it and reach up to 8.5 bars at redline.

 

[mitch32]

I'm pretty sure my crank is the old type with the short oil pump drive. So if I'm going to put a good pump I would have to do the crankshaft as well, and then I should also do the main bearing also. So if I'm doing that should I just do a rebuild, since I'm already there?

On top of all this what if the new pump doesn't fix the oil pressure issue? What else could it be?

 

[marka1230]

I would try an oil pressure sender first, I had similar symptoms and changed the sender and all was well. A lot less hassle than changing a pump and worth a try first. They do go quite often.

 

[mitch32]

The oil pressure sending unit has been changed, I also have aftermarket gauges and mechanical gauges I have tried all with the same result.

 

[Cornhoolio]

Unfortunately old son, it sounds like you have the same issue as I had.....................Standard Nissan oil pump failure (quite a few posts if you search) one or more of the Phillips head screws that retain the pressure plate of the pump backs off over time and you loose pressure between the rotor and plate. I changed to an N1, could have repaired the old one as there looked to be no damage or wear whatsoever.............seemed weird.........but opted for a new pump. All good now
If this is the case, engine out I am afraid............by the way, my crank journal was fine hardly a mark ('89 R32 GT-R)

:nervous: