Oil temp slowly rising when driving down freeway

[1990R32GTRmcphee]

R32 GTR

So recently my oil temp has started being funny slowly rising when on the freewsy sitting on about 3000rpm but if im cruising along doing 2000rpm or sitting at idle the temp slowly comes back down.

Engine had a full rebuild only just over 5000km ago.

I've changed oil filter and oil, thermostat, flushed radiator and have bled the cooling system but hasnt changed anything.

Ive let my car idle in my garage for 45minutes and all it did was get to the normal temps then stay there.

I wouldn't think my HG would be the problem as its all still new without having any thrashing. Nitto oil pump and a genuine nissan water pump were put on when built.

It was 2 years ago the engine was built and i cant exactly remember but i think they told me i would need to come back in at 5000km to have the head re tentioned down. Does this sound right with arp head studs? If so this could be my problem?.

Cheers for any input.

[GTSBoy]

If your hot oil is from hot coolant is from exhaust gases in the coolant is from not retensioning your studs......then you'll be wanting to give yourself a slap.

Get the coolant tested for CO2 contamination to confirm/eliminate and get the head studs tweaked.  Then see if it keeps getting hot.  Keep in mind that the coolant temperature gauge will stay in the middle across a wide range of temperature so will mask if it is getting hot too.

[1990R32GTRmcphee]

If your hot oil is from hot coolant is from exhaust gases in the coolant is from not retensioning your studs......then you'll be wanting to give yourself a slap.
Get the coolant tested for CO2 contamination to confirm/eliminate and get the head studs tweaked.  Then see if it keeps getting hot.  Keep in mind that the coolant temperature gauge will stay in the middle across a wide range of temperature so will mask if it is getting hot too.

Thanks thats what i was thinking but looking at water temp on my pfc hand control it's staying at about 80 whilst my oil temp rises past that.
But is that an actual thing for the studs to need to be re tentioned after some time? Because I've heard that once they are torqued down that should be it..

[GTSBoy]

Depends on the gasket more than the studs.

[1990R32GTRmcphee]

Multi layer steel gasket

[ss6745089]

3-things i can image... either piston, radiator, and overhead cam holder. Anyway, better to consult an auto mechanic expert from nearest store in your location.

[Ben C34]

If by overhead cam holder you mean the   cylinder  head then maybe. Radiator is pretty obvious, piston is completey not possible.

[Birds]

If it's happening at 3000RPM but not 2000 then a few things spring to mind based on higher pressures exerted at higher RPM:

- Oil pump not circulating enough or circulation blocked somehow

- Engine leaning out / running hot at mid-high RPM; fuel system; tune etc.

- Cooling system not efficient enough (test that water temp sensor too, in case it incorrectly reads 80 all the time)

- Head lifting under pressure; a compression test may not show anything but still worth doing given how easy it is

- How much oil is in the sump? Enough to cool at low RPM, not at high?

- Oil temp sensor not functioning properly?

- Head gasket leak/blow issues into the cooling channels tend to show themselves first at idle with no airflow and, as they progress, eventually appear during highway driving when even heaps of airflow isn't enough to cool the engine. Yours doesn't happen at idle which says to me head could be lifting under the extra pressure.

- Possible too that some sort of weird piston blowby only rears its head at higher RPM?

[ossy]

Have you checked the PCV valve?

I had this issue on a MR2 and a Celica and the cause was a blocked PCV valve. My exhaust was also smoking slightly whitish blue sometimes when I planted it because of this. I couldn't see it myself but I had a few friends following say so.