I have read that what ever you go with, make sure the gauge and the sender match. That makes sense. Further reading, I see that there is a long type that appears to work with the unique factory taco plate. The short model must work with the "home made" taco plate. I have already found that the unique plate can cost as much as $70 and I can make the home made one. Couple of home made versions: 1 welds a nut inside the plate and this one apparently just uses a nut inside the plate.
And the factory one also includes an extra cover plate to keep the cool breezes from the hot oil sender.

What are some thoughts about which is best, most reliable, doesn't leak, etc....?

Click to view attachment

Click to view attachment

Since my 75 1.8 just has a standard plate, how was the oil temp measured or was it?

I have first hand experience in this. I had a customer who didn't want to find and pay for a true oil temp sender plate, so I made him one like the paper above except I welded the nut onto the plate. The problem he reported was that the oil temps were reading really low. So he glued a think piece of styrofoam onto the plate to protect the sender from airflow, and then he started getting accurate readings.

The cover in the factory arrangement (black piece in your picture) acts as a protector to keep air from cooling the sensor and giving false readings.

So, if you're going to use the 'cheapie' setup, make sure to sufficiently protect your sensor from airflow cooling in order to get accurate readings, otherwise don't bother.

Or just pony up for the OE version.

I was leaning that way. Anyone know where I could get the whole rig? Plate, sensor, air sheild, wire and guage?

Thanks,
Clark

Most of that stuff, especially the plate and cover, has been NLA new for some time, but post a WTB in the classifieds -- they show up periodically.

You can also buy a more modern, although not original, sender and gauge (for example from HERE). For the wire, any 18-22 gauge stranded copper wire with a spade crimped on the end will do the job.

Hmmm. I have never seen a cover as pictured above. I have a factory plate, but never had a cover for it. Could you post a better pic?

Also, does that gasket go between the cover and the plate? I only have an O ring inside my plate (no gasket). What is correct?

yep -- the gasket goes between the cover and plate

There's also 2 small screws, M6 maybe, that hold the plate and cover to the case. There are 2 copper crush washers that go under these screws to seal that area. Pelican carries them.

Tightening torque is very small, maybe 5 ft-lbs, for those 2 screws. Really, just enough to compress the crush washers against the mating surface.

For best sealing, the "seam" of the crush washer should face the bolt head.

In my limited experience: if you make sure the parts are super clean AND put things together in this order AND none of the parts are warped, this area won't leak.

YES

Here is another location....
Click to view attachment

http://www.vw-resource.com/overheating.html#know

Threaded into the oil pressure relief (OPR) hole and replaces the slotted plug. Link goes on to say that they tested the temp differential using a candy thermometer. And the OPR unit gave the truest reading. Link does not say where to buy this unit. I guess if you can determine the threads, the eguages site had lots to choose from. seems to me the height would also be critical for the OPR to work correctly.

BAAAAAAAAAAAAAD! There is no oil flow there.

How about the lower of the 2 galleys, NW to the oil pump?
Any obstruction there?

I would never install a sensor in the flow path. Use the sump.

There will be some oil flow past the pressure relief valve and draining out of the spring chamber. Is it enough flow? I don't know but Audi seemed to think it was good enough on their 5 cylinder engines. They put their oil temperature sensor there for years. It is probably an Audi sensor pictured above.

Jim

Click to view attachment

Hmm, how about that. I suppose as long as the spring chamber is full of oil you'll get enough thermal transfer to get an accurate reading.

Seems like a lot of work. I just threw in the drain plug style one in and was done with it.

No one ever asked, but tell me more about the "drain plug" style. You got a picture? How about a supplier, or website?

Thanks

VDO 323-055 M14x1.5 - $9.95

Click to view attachment