mc1 200tqa oil pressure problem?

[Huw Powell]

> Just finished putting a motor in my 89 200tqa and i am getting a low oil
> pressure warning at over 3000 rpm.  While over 3k rpm, I have about 3bar on
> the dash gauge, i dont remember what it should be at higher rpms though.  I
> have switched the sensor out with another one I had, and same problem.

> I know common reasons for low oil pressure are bad oil pump and worn main
> bearings, but these problems are almost unheard of in an I5 from what I
> know.

Well, obviously there are two possibilities - one is that actually have 
low oil pressure, the other is that the warning system is not 
functioning properly.

The first option is the one to be careful of, because it would be bad 
for the engine.  3 bar on the dash gauge over 3k rpm sounds a bit low, 
lower than I have ever seen, so I'd be worried if I were you, and at 
least see if you can get a higher precision device somehow to measure 
the oil pressure.

Barring sad internal issues like you mention causing the low oil 
pressure, here are some random ideas as to what might cause it that I 
can think of:

- the regulating spring/valve in the oil pump is stuck or installed 
wrong or bad.

- one or more oil squirters (in the block, next to the crankshaft, sort 
of, aimed up at the piston backs) may be broken/missing/messed up.

- ditto that for any other oil spray type outlets, I think there are one 
or two in the camshaft area on top of the head.

I think the system failure option is unlikely in your case, since you've 
already verified it with a gauge and a sender swap.  I can never 
remember which switch is combined with the gauge sender, though - the 
low pressure (under 3k rpm) one, or the high pressure (over 3k) one. 
The odds of the control unit being bad are similarly low, due to your 
actual gauge reading that says there is, indeed, a problem.

I suppose it is possible also that the three oil pressure wires are 
mixed up, but I can;t think of which "wrong" combination would result in 
what you are observing...

Good luck finding a cheap rather than expensive flaw!

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/