sc80877520

hi guys, i have a A8 d3 3.0L petrol engine(BBJ), just went through a big fix with the engine(oil consumption very high) put new piston rings, all brand new seal for the whole engine.
it runs better.
but yesterday i took it on the highway , almost everytime it reached 80KM/Hour the red low oil presure light will come on and beep. but i took the car to above 120KM/h, it went off a again. i tried many times , it seems to me that the light will only come on between the speed of 80km/h-110km/h.
im confused. plug the car to the VAG , no error code was stored. tested for the engine pressure when idleing, it says its below 2Bar which is not enough, when i rev the engine over 2000RPM, the test showed the pressure was OK.
any thought??? my mechanic ask me to change the oil pressure sensor first to see how it goes. if not, change the oil pump. by the way i just put a brand new EGR valve and tubes as well, will this be the problem?? any leak?
thanks for the input

JohnnyJ A6Q

SC80877520,

Do not even run the engine !!!

Tow the vehicle back to the shop that rebuilt your engine ASAP and document your mileage, every time your let the oil pressure drop you are doing damage to your engine, and the more you do it and then tell your mechanic, the blame will fall on you for driving with low oil pressure, it very well could be the sensor, BUT I think not, And why take the chance.....

Odds are that during reassembly something was not done correctly.

Johnny J J

mishar

+1

Panelhead

Do not know the 3.0 engine. But usually bearings cause low oil pressure.
Could be a rod or main. If they did not pull the crank it is likely a spun rod bearing.

Jack88

Debris or gunk in the oil filter or oil pump pickup screen can cause low pressure, as well. Any other symptoms or odd behavior?

sc80877520

thanks guys, i tried the easies and cheapest way first, changed the oil pressure sensor beside the oil filter for an OEM part(which is the same as an A6C5) cost me 5bucks.
wala problem solved

sc80877520

false alarm it has been oked for 3days , now its back again.

sc80877520

it only has the light on when u cruise between the speed zone 80KM/H-120KM/h
when its below 80 it will not come on.
or when u drive past 120KM/h even with the light on ,light will go out.
i have tried to take it back to my mechanic, he sets the car and rev the engine. the light will not come on, and there is no DTCS in VAG.
the oil pump filter and oil pump has been just cleaned during the engine fix.
to me
i dont understand what the pressure has to do with speed ,it only linked to the engine speed i think.
it seems fine when u rev the engine and perform the pressure test.so it means the oil pump is OK, no clog or anything.
i am out of option here. just to replace the pressure sensor again. it looks fine to me now. but i dont know how long it will last.
BTW, it drives fine when the light was on.

Jack88

The mechanic didn't try driving it at the speed you told him the problem occurred to try to replicate it? Not every engine problem can be replicated in a parking lot, the mechanic should know better, I wonder if he just doesn't want to get into it and have to fix for free something he didn't do right the first time. If that's not the case, I'd say he's either lazy or incompetent.

If the light is still coming on, something is still not right, and it's very likely related to the job just done. Give this mechanic one more shot at it, if you like, but then take it elsewhere and explain everything. If it was something the first mechanic did wrong, he ought to be on the hook for the bill. It can be difficult to get them to pay, though.

That's my two cents, anyway. In terms of what's actually wrong, I have no further ideas than what's already been suggested.

Added note: Park it until this is sorted. More than a few engines have been destroyed from insufficient lubrication. If you decide to keep driving it until more symptoms appear, you will find repairs much more expensive.

mishar

If you drive it 120 km/h after you have been told not to drive it at all there is no point to ask anything here.