cadiz

Hi there,

I have spent over 1 hour searching your forums on these two issues, but unfortunately, I did not find topics on the subject that equal my situation.

I have a 1996 Audi A6 quattro, it has 173,000 miles and for the most part it has been running great. Recently I have been geting the P0401 code and it's related to the EGR valve, which I have read all about it and will take action on that.

Now the main problem that I have, is that the Engine Oil temperature gauge remains at little less than the 60 degrees mark, at the same time the warning oil icon flashes, indicating that the oil pressure is too low.

When I turn the car off and start it again, the warning light does not come on, it only comes on when I start driving and get to 10 miles per hour, the oil temperature gauge does not move at all, and the coolant temp gauge remains normal.

I did notice that hot air would come out of the vents, even when the AC/heater was off, I guess this was happening because the radiator fans were kicking in at that time, in addition, the switch that controls the mirrors, does not respond at all.

In doing some research, it seems that I need to replace both, the oil pressure switch and oil temperature sensor.

By the way, I did change the oil and filter today, hoping that this would take care of the problem, but didn't. Can I keepdriving the car until I replace these two items?

Any help that you can provide is greatly appreciated.

Thanks

austinado16

First, I would spend some time looking at the wiring that comes from both the oil temp sender, and the oil pressure sender. The temp sender is in the driver's side of the oil pump housing at about the 1 o'clock position if you are facing the front of the engine. The oil pump is that front plate, right behind the big crankshaft pulley. So around the 1 o'clock position on that pulley, look for the temp sensor and it's wire. The oil pressure sensor is in the block, just to the right (facing the engine) of the oil temp sender, but it's sort of back in a bit...so look at about the 8 o'clock position on the a/c compressor and you'll find the wire and then the black boot that's on the pressure sender, screwed into the block.

Because the wires for these 2 senders run up the front of the block, behind the plastic timing belt covers, and then across the valley area of the block, it's possible that yours have rubbed through and are touching the engine block.

The oil pressure switches love to fail, so if you see oil on the black boot, or below the switch, just buy a new one. Get the switch from Audi or VW. Don't buy one in the aftermarket. They are pressure rated and there are various versions of this same switch depending on what car/engine they were used on.

If you want to do an actual oil pressure test, you can build your own oil pressure test gauge for cheap. Go to an auto parts store and buy a 24" whip hose for a grease gun. It comes with male 1/8th inch pipe threads at each end. Then buy an inexpensive pressure gauge from from a hardware store, industrial supply, etc. and use a 1/8th inch pipe female connector to connect the gauge to the whip hose. Unthread the oil pressure sender and thread the end of the whip hose into the engine with just finger tight pressure. DO NOT USE A WRENCH!! Make sure the whip hose is clear of the serpentine belt and fire up the engine. You should have a minimum of 20psi at hot idle and something like 50+psi, hot at 3,000rpm.

An a/c-heater system that's putting out heat when it shouldn't, is not due to the radiator fans running. It's because you have a vacuum leak to the heater box. So instead of the vacuum operated functions of the heater box working properly, they only work at idle or during deceleration when there is high manifold vacuum sucking on the leaking vacuum lines. At cruise speed, or during acceleration, or when climbing a hill, manifold vacuum goes away, and the heater stops being controlled.....so you get heat out of the center vents and you'll even feel the air moving through them.

You should find my info on checking/fixing these vacuum leaks if you search the forum archives.

cadiz

Thanks for the quick reply.

You were right on in the explanation of the location of the switches, as stated in the url below. (Am I allowed to post external links?)

I did check the oil pressure switch,it had a plastic cover and the switch itself has a white round cap on it. I did not see the wire rubbing against the block, nor did I see oil. I did not pull out the switch, because it was kind of difficult, but I will go ahead and buy this switch, do you think that I should also change the oil temperature sensor?

I will check the vacuum leak info, finally, is it safe to drive the car until I get these two switches?

Thanks<ul><li><a href="http://www.12v.org/engine/index.php?section=cl&amp;view=front">http://www.12v.org/engine/index.php?section=cl&amp;view=front</a</li></ul>

austinado16

I would resist the temptation to "throw parts at it" until you've done more diagnostics.

If it were mine, the first thing I'd do would be to pull the wire off the oil pressure switch and do an ohm test of the switch's function. Both with the engine off and with the engine running.

Next, I'd do an actual oil pressure test using the test gauge I described.

If I hadn't found the problem in these 2 tests, I'd grab test the oil pressure sender wire and do an ohm test of it from it's end at the switch, to the furthest point on the wire that I could get my probe to.

rmccomiskie

That's a non-issue. As Todd suggests, better confirm that you've got proper oil pressure before driving.

Update: I'm wrong. It's typically around one mark above 60. Never even close to 130 though.

kday

Mine was on the rear side of the oil filter mount area (electrical plug facing the firewall) until I moved it.

I think I already commented on this long ago, but I wouldn't screw a NPT pipe into a metric hole tapped into aluminum. The proper metric fittings are available.

Just Me

The senders do fail. There are tow that must agree or it sends the warning ( fail safe). It is odd that both the temp and pressure senders went at the same time. That's the only thing that makes me wonder.

If you open the crankcase oil filler with the motor running, is there oil splashing around, indicating that the pump is pumping normally? So long as oil is flowing, it will get hot if the motor is hot.

G

austinado16

You're not putting a bunch of force on the whip hose. Literally, just snug with your fingers. I've even driven cars around with the test gauge in place so that I could monitor hot pressure out on the road. It doesn't leak either.

austinado16

60C is only 140F. Seems low for what normal oil operating should be in order for the oil to get hot enough to lubricate properly and be able to burn off the moisture and some of the impurities of combustion.

I would think that with the oil passing through the heat exchanger, it would at least be the tempurature of the coolant......87C=188.6F

Just wondering. Mine has always run just below the "1" of the 130C mark......so I'm guessing it's at about 90-100C. But that's out on the road after everything has gotten good and hot.

rmccomiskie

Don't know why but I've got/had 3 C4s that read low oil temp on the gauge.