10 bar oil pressure

[MaRu]

Hi guys,

from one day to the next the oil pressure of my 3.0 carrera engine is closed to 10 bar. Thatīs double than what the engine normally had at the highest. I installed another directly oil feed pressure gauge to double check it.
Any ideas what happend here?

Many thanks in advanced, Malte

[Flieger]

I assume that is cold oil pressure, in which case it sounds like the blow-off piston (pressure limiting spring loaded piston) has malfunctioned.

[MaRu]

Also when the oil is hot at high revs. I already checked the blow-off piston for any signs of wear or damage, but it looks fine, also the case. But I will order a new one and a new spring for testing. Are there any other possible things?

[Walt Fricke]

Remember, there are two pressure pistons. The most likely culprit is the one which sets the oil pressure - the vertical one. The horizontal one is the last ditch, safety feature, which is the one I'd be inclined to call the blow-off. But the normal pressure regulator ought to be adequate to control the oil pressure, hot or cold.

From my experience, you can remove this plug and the spring and piston without spilling a whole lot of oil, which is nice.

Malte - what have you done to your engine between the time when the oil pressures looked normal to you, and when you noticed somewhat high pressures? For instance, did you replace the oil pressure sender? I gather you have a European 1976-7 3.0 Carrera, and not a US SC? If the 5 bar sender from the later cars is used with the earlier 10 bar gauge you have, it will display twice the actual pressure.

[MaRu]

Walt, it was the same day. Everything was fine in the morning, I drove the entire day and at some time I saw the high pressue...

[Walt Fricke]

Malte - when you sit in the driver's seat and turn the key on to run, but don't start the car, what does the gauge do?

If it pegs, then you have a broken connection between the gauge and the sender. Most likely back at the sender.

But you say you used a mechanical pressure gauge to check, and had 10 bar on it too, so that can't be it.

Does the pressure vary at all with RPM?

[gncosta99]

Also when the oil is hot at high revs.

[MaRu]

I will check it this weekend, but when I remember right the max (10bar) is reached at 4000rpm hot and 2000 cold...

[silver_911]

Presumed you havn't changed any component (pressure sender), it can be a bad connection, e.g., via the 14 pin connector. No connection will indicate full pressure, bad connection (increased resistance) will give you a higher reading.
Hope this helps,
Jens