Is there such a thing as too high oil pressure?

[james280779]

As above, started the 3.2 aircooled this morning, oil pressure is over 5.

Its been sitting a while (few weeks), its colder than normal (24 degrees) and I put in slightly thicker oil than normal before I laid it up (10w/40).

Even when running mobile 0w/40 she had over 4 bars so I am guessing its ok as she always has high oil pressure??

or is it something about to go bang?

[Rockster]

james280779 said:

As above, started the 3.2 aircooled this morning, oil pressure is over 5.

Its been sitting a while (few weeks), its colder than normal (24 degrees) and I put in slightly thicker oil than normal before I laid it up (10w/40).

Even when running mobile 0w/40 she had over 4 bars so I am guessing its ok as she always has high oil pressure??

or is it something about to go bang?

Yes, there is such a thing as too high an oil pressure but your engine ain't manifesting too high an oil pressure.

And no something is not about to go bang.

[james280779]

Rockster said:

Yes, there is such a thing as too high an oil pressure but your engine ain't manifesting too high an oil pressure.

And no something is not about to go bang.

thanks, I didnt think it was anything to worry about but just wanted to be sure. She has been running rather fabulously lately so all good news!

[alexisn]

Almost certainly the oil pressure sender, had the problem myself in a 996 and 997, a very common fault.

[computamedic]

Surely the combination of a 10W oil and the colder than normal temperature would exactly explain the higher oil pressure. A 10W oil is thicker than a 0W at colder temperatures so the more viscous oil would equate to a higher pressure. Once the engine is warm the 10W/40 would have the same qualities as the 0W/40 so oil pressure would return to it's more "normal" state.

I see no reason why you would assume any fault with the pressure sender.

Regards

Dave

[porkey]

Sounds ok to me.
My 964T has about 5bar on tickover when cold. It will crank 2.5 bar when cold.
Hot idle is about 2-3 bar.

[alexisn]

Silly me, assumed that James would warm the car up to establish if the pressure was high or low....

[fergus]

Your oil pressure relief valve can get stuck, in which case you risk blowing crank seals....

If you have high oil pressure at idle when the oil is up to normal operating temp, I'd get this investigated, otherwise, you could consider swapping to a thinner oil?

[supersport]

I suspect no two cars are the same, especially at 20+ years old. I remember Peter Morgan saying that it should be between 1 and 2 at tick over, when warm and roughly K revs + 1.

Mine has never run at 5 though and is about 4 at motorway speeds and generally seems to follow the above.

[kitesurfer2]

Your oil pressure sounds perfectly normal.

[james280779]

I didnt have time to run it properly as I only work a few minutes from home and I didnt want to risk anything without being sure.

I will give it a decent run tonight and hopefully it will sort itself out, the engine was rebuilt a few years back and always had high pressure since- uses hardly any oil too which makes a nice change. (maybe a capful every 1000 miles)

thanks

[Rockster]

james280779 said:

I didnt have time to run it properly as I only work a few minutes from home and I didnt want to risk anything without being sure.

I will give it a decent run tonight and hopefully it will sort itself out, the engine was rebuilt a few years back and always had high pressure since- uses hardly any oil too which makes a nice change. (maybe a capful every 1000 miles)

thanks

I was taught to when rebuilding a street engine to build it "tight", to for instance try to arrange the main/rod bearing fits to be close to the minimum along with crankshaft end play and the piston/cylinder clearances.

This makes for a quieter running engine -- important for a street engine -- and one that requires less oil and often runs a higher oil pressure, too.

[james280779]

Rockster said:

I was taught to when rebuilding a street engine to build it "tight", to for instance try to arrange the main/rod bearing fits to be close to the minimum along with crankshaft end play and the piston/cylinder clearances.

This makes for a quieter running engine -- important for a street engine -- and one that requires less oil and often runs a higher oil pressure, too.

well all sounds good then, maybe the rebuilder knew what he was doing- unfortunately the folder containing all the rebuild was lost so I dont know who it was.

As for the high oil pressure, after a number of decent runs its has not budged from 5 so I am guessing it might be a little more than I first thought.