mithrilG60

My oil temp gauge is acting (what I think to be) a bit weird in that it will sometimes stay at 60C and other times it cycles up to 150C (the last white bar before the red) only to drop dramatically and noticeably back to the 60 - 80C range. Coolant temp is a steady 90C always, never budges once the car is up to temp, and there are no DTC codes of any kind stored in the car. As a result I'm assuming it's a wonky oil temp sensor but I can't find any reference in either my Bentely or ETKA to where the oil temp sender is for the cluster in the 4.2L.

Is this normal? Perhaps a thermostat that's operating in the oil cooling system? What is the the typical operating temperature for a C5 4.2?

Thanks for any feedback or info!

socalclimber

My 4.2 oil temp is usually on the third line from left on a U.S. gauge, or just slightly right of it, around 200 F or 93-94 C. I have the stock 87 C thermostat in it.

Here's a pic when I had an 82 C thermostat, oil temp was just left of third line. This is a bit on the cool side.

When my thermostat stuck closed, coolant temp climbed as well as oil temps climbing to 4th line (225 F or 108-110 C) or almost 5th line (250 F or 121 C) when it was time to shut it down.

Note that my coolant temp is right in the middle, where it should be, or a hair right of middle (now that I have an 87 C thermostat).

I don't know where the 4.2 oil temp sender is located, but that seems like a logical starting point.

SloopJohnB@mac.com

Sender is right below the exhaust manifold on the oil cooler housing on the passenger side.
Itza beatch to get to...from the bottom with the alternator and the lower engine mount and engine mount bracket removed.
Some people claim the alt can be removed w/o moving to service position, YMMV.

There is an argument for taking the time to replace the plastic coolant pipe between the block and the oil cooler housing if you have to get in there and take out the alternator and etc. There's a guy on the BB who sells a billet aluminum pipe with twin viton O-rings vice the crappy OEM plastic piece.

mithrilG60

Thanks! ETKA lists the sender on the oil cooler housing as oil pressure, does that sender do double duty as the sensor for both oil pressure and the oil temp gauge?

Do you know if it's possible to reach the wiring for that sensor without having to remove the alternator and brackets? All the oil cooler seals and the coolant pipe were replaced back in January this year by the PO so I'm hoping it's just that the sensor wiring is loose from that service and therefore is sending intermittent signals to the cluster.

mithrilG60

That's exactly where mine "resets" to if I turn the car off and either restart it or move the key to accessory. Can't understand why the shop chose not to replace a $2 sensor when they had the oil cooler out of the car for the gaskets and coolant pipe earlier this year, you'd think it'd be common sense to replace all normal and small cost items on a job like that which involves significant hassle to re & re

SloopJohnB@mac.com

My bad...it's that squareish sensor on the bottom of the oil pan. I should have remembered that...had to replace it on the 2K4.2A6 when the oil temp went dead cold.

SloopJohnB@mac.com

That oil pressure sensor on the housing is like $32, have seen them for $15.

The oil temp sender on the bottom of the oil pan was over $100 but I've seen them for 40-80, Hella is more expensive but has the same part number as on the OEM.


http://www.sjmauto.com/searchitem.ep...for=1J0907660B

mithrilG60

Ah, that one's a heckuva lot easier to access!!

Just Me

first, oil temp changes very, very slowly.

The steady-state temperature varies from abotu 170F - 225F depending on load and ambient temp. Mine typically runs around 180 (S6, who's quibbling?).

Note that the WATER temp gauge is damped. If its within some reasonable normal range, it sits dead center. Until it's WAY off, it wont move. So your water temp can be higher but not show.

G

Airbag

yeah absolutely it is in the oil pan . i am staring at one right now as i am waiting to put it in during my next oil change. lots of reports of none hella ones not working on some model years. got my hella unit at europa parts or something like that for around 50.00.
will be nice to see my oil temp guage actually move.

http://www.audizine.com/forum/showth...-Read-Oil-Temp