Engine Oil leak worsened, oil pressure sender leak?

[quattro004]

12v 2.8 w/ 237,xxx miles has had a very minor oil leak for most of the 6 years I've owned it. This past week it has gotten worse. Just went through a quart in about 5 days. I've suspected the upper pan gasket for awhile but while looking today I noticed it was a lot of oil right on and around the pressure sender just behind the oil cooler. Also when I start the car and watch where the leak originates first, it comes from behind the cooler and runs down and around the lower pan. Does anyone think this could be whats causing the leak? Looking with the mirror the upper pan gasket really does not seem to be leaking after cleaning and observing again.

Here is the leak location which then runs down all over the underside of the lower oil pan:


The best pictures I can get of the sender...



This is the part linked from a DIY thread on AZ.

http://www.ecstuning.com/Audi-B5_A4-...m_campaign=DIY

[walky_talky20]

Leaking from an oil pressure switch is not uncommon at all. There is a failure mode of those switches such that they leak slowly. At that point it is generally advisable to change it ASAP because it can completely fail and turn into a huge leak at any moment. I would suggest you change that switch, and definitely change the oil cooler o-ring (the seal behind the oil cooler) at the same time.

I would say it is not very likely that the upper pan gasket would be leaking that much. There isn't really any pressure on that gasket, just splashing really. The switch, however, sees high oil pressure all the time.

It seems to me that you might be able to get this done without disconnecting the coolant lines. Just move the cooler out of the way enough to get at the switch. But I haven't done it before so you may have to disconnect them. That would just make it easier if you don't have to deal with draining and filling the coolant. Good Luck.

[quattro004]

Leaking from an oil pressure switch is not uncommon at all. There is a failure mode of those switches such that they leak slowly. At that point it is generally advisable to change it ASAP because it can completely fail and turn into a huge leak at any moment. I would suggest you change that switch, and definitely change the oil cooler o-ring (the seal behind the oil cooler) at the same time.

I would say it is not very likely that the upper pan gasket would be leaking that much. There isn't really any pressure on that gasket, just splashing really. The switch, however, sees high oil pressure all the time.

It seems to me that you might be able to get this done without disconnecting the coolant lines. Just move the cooler out of the way enough to get at the switch. But I haven't done it before so you may have to disconnect them. That would just make it easier if you don't have to deal with draining and filling the coolant. Good Luck.

Thanks for the input. I really hope it is because it shouldn't be to bad of a job to replace. It would be nice if there is enough slack in the coolant lines that I could disconnect the cooler to put the new O-ring on without having to drain the coolant but certainly something I've done before so it isn't a big deal if they need to be pulled.

Hopefully I can give this a shot tomorrow sometime.

[KinkySlayer]

this is relevant to my interests

[quattro004]

I would suggest you change that switch, and definitely change the oil cooler o-ring (the seal behind the oil cooler) at the same time.

Any chance you have a link or picture to that part. Looked on o'reilly's, napa and ecs and cannot seem to find what size o-ring it takes. I'm sure its just a general sealing o-ring but not sure on the diameter.

[walky_talky20]

It is an o-ring, but it has "locating tabs". They aren't much money:

http://www.ecstuning.com/Audi-B5_A4-..._Block/ES2776/

[quattro004]

Went and got a new o-ring for the oil cooler, got that installed. Have to take off the short lower coolant hose from the oil cooler to make room for the 24mm socket and 1/2 ratchet to remove the old pressure sensor. Installed new one, new oil, refilled coolant and purged air from the system and so far so good after a short drive tonight it seems to be leak free. I'm going to keep an eye on it for the next week or so to make sure its good to go.

Thanks again for the help.

[walky_talky20]

Good work. Thanks for the update.