Water leak turns out be an oil leak

[rj scotty]

Went for a spirited drive over to my parents house last night and just as I pulled up outside low coolant warning light came on, flipped the bonnet and sure enough water was low, quick look around the engine and I spotted liquid on the side of the block under the water rail. Had a look this morning and decided it must be leeking from the hose that connects the thermostat housing to metal pipe that run around the back of the engine.
This a 100% completed and utter barsteward to get at with the rad in place, I had to destroy the old hose to get it off, only way it was coming.
Anyway managed to get the new hose on, bleed the system and went for a run got back and the leek had returned

Turns out it was not water but oil and it looks like it's coming from the oil pressure switch.
I can only assume the water was low due to having recently changed the matrix and this was the last of th air coming out



Car is to hot to work on now so this is the job for the morning.

Questions:
Is this a common leek ?
Is the method of sealing these senders just a copper washer ?

Advice:
If there is a leek confirm what the substance is first

[Rusty]

A lot of the time it's oil that's missed the filler hole and flowed down the side of the block

Easy enough to clean it up and then go for a drive and re-inspect for oil.

[BrianSmith_S2]

If its the sender i would replace as soon as because its not too expensive (£10ish), and if it does fail at high speed your gonna dump a lot of oil very quickly. I cant remember if mines came with a new copper washer but the new sender will need one.

By the way renewing the copper washer on the old sender is a wasted economy cos when mines failed the oil came through the middle of the sender so washer didnt help.

Brian

[rj scotty]

If its the sender i would replace as soon as because its not too expensive (£10ish), and if it does fail at high speed your gonna dump a lot of oil very quickly. I cant remember if mines came with a new copper washer but the new sender will need one.

By the way renewing the copper washer on the old sender is a wasted economy cos when mines failed the oil came through the middle of the sender so washer didnt help.

Brian

That could be good advice there as I noted when I had a quick look there dose appear to be oil under the boot on the pressure switch

[johne]

The oil pressure switch is notorious for failing by leaking out through the centre of the switch but it's common to many Audis and available from the likes of GSF.

The oil pressure sender which is above in your picture can fail, but it doesn't leak but is expensive - around £60.

John

[rj scotty]

Looks like we have a working theory then

Cheers John

[Greg_S]

I had this problem a couple of years back, and was due to the sensor and its little washer going. Was a PITA to change but sorted the leak. I now need to do the little water hose I think which is a PITA too.

[rj scotty]

Those 2 hoses, the one I changed today and the smaller one which connects to the turbo water feed are the are the worst jobs I have ever done on the s2 the clutch, dash out climate job and January's snow crash repair all resulted in less cuts and skinned knuckles than these 2 hoses

[rj scotty]

Found a neat way to access these sensors.

You split the fan cowling from the rad and use cable ties to keep them apart !

[rj scotty]

Problem !

Fitted new sensor from GSF and leak has stopped. Went for a drive and the oil light keeps coming on

Turns out that the new sensor is faulty as when it closes there is a 400 ohm resistance to earth, the old leaky sensor is near 0 ohm's.

Ill order a genuine one from Ben.

Confirm part number 056 919 081 E

Just noticed GSF sensor is listed as equivalent to 056 919 081 C, might just be wrong as apposed to faulty.

Earthed out the sensor wire for now just need to keep an eye on the pressure gauge

[Greg_S]

Good luck getting sorted, thats a much easier way to do it!

[s2_wot]

Mine is leaking like a sieve, nice one, I know what I'm after now

[s2driveruk]

if you have gone to the hassle of getting in there for one its probably worth doing them both given its a biatch of a job. I have a weeping pipe on the turbo return line under there somewhere...cane barely wait to get started in this weather

[UrS4boy]

3B and ABY Oil and Water Temp and Pressure Senders

056919081E is the correct PN for the oil pressure idiot light switch. Also same as AAN and ADU. Item 5 is the after-run pump switch. Item 7 is the Multifunction Temperature Switch. Item 9 is the G62 coolant temp switch/sender used by the ECU to determine if the engine has warmed up enough to back-off on fuel enrichment.

[s2_wot]

Item 3 in that FA shot

That's what looks to be leaking on the AAN, hopefully I'll be able to get one pretty easy and pop it in there.