OK, So in keeping with the cooling/heating problems I was having with my 200Tdi, I bought a VDO coolant temp gauge and sender kit from egauges.com.
This topic has been covered endlessly on these boards, but I just wanted to add something that I did that maybe someone can search for.
I pulled my OEM coolant temp sensor out of the thermostat housing and it had some different type of threads then the adapters that came in my little kit from VDO. So I was thinking of re-tapping the housing to fit one of the adapters that came in the kit. I wasn't a big fan of re-tapping 20 year old cast aluminum.
I wish I had done a little bit better DIY, but this is what I've got.
-Took the original 200Tdi Coolant temp sensor and cut the brass sensor well off the end of it
-Drilled backwards through the sensor body towards the electrical connector using a 21/64 drill bit
-Smashed the chunk of electrical bit out of the top of the body with a punch
-Ground down the raised bevel on the outside of the body to make it a little more compact
-Then I tapped the 21/64 hole with a 1/8 NPT tap to fit the VDO sender
-Put it all back together and everything was MINT.