Tapping for oil temperature sender and others

[Fanie]

I am in the process of reassembling a 1600cc Type 1.
Previously I have been using the sump drain plug and oil pressure relief valve to read the oil temperatures. As none of the above are exposed to direct oil flow, I am seriously considering this setup.



It is situated in an area exposed to direct oil flow - post the oil pump - as I understand it.

Question 1: Which metric thread size should I use?
The ID is 21 mm - a 22mm 1.8 would thus not work.
I believe 23mm 1.8 metric tap is hard to come by - I am thus left with a 24mm 1.8 as the smallest size. Would I have enough "flesh" for that size not to jeopardise the strength of the block at that plug.

Question 2: If am to use a blueprinted 26mm oil pump with the setup in the picture below as my oil return, do I need to only tap the existing plug hole or is there additional engineering / machining required?



Question 3: Is it normal for the sump temperature to read substantially lower than the oil pressure relieve valve. I would think it normal but then a few people have been reporting the contrary?

Thanks for your values advice...

NOTE: All images used with compliments of http://www.huelsmann.us/bugman/

[david58]

Drilling, Tapping, & Full-Flow Filter Tech
http://www.huelsmann.us/bugman/FilterTech.html

[Gavin]

I had the temperature sensor on the sump and then changed to the location you show - I found a big difference in temperatures - with the sump much lower. (stock 1600 dp). The sump plug temperature is useless IMO.

I've forgotten what the size of the tap I used was - got an old case and practised. I used the boss and sump temperature sender that VDO supply.
Ended out cutting down the boss to expose a greater amount of the sensor. The alternative was to use a sensor with a longer "nose" but I didn't like this because it might obstruct the gallery.

[bugninva]

The sump plug temperature is useless IMO.

.

a sender in the sump plug hole is right at the pickup...it senses the temperature of the oil that the oil pump is pulling into the pickup...far from useless...

[Gavin]

I say useless because it read cooler than the temperature measured next to the pump (shown in the picture above) and cooler than the Berg dipstick sensor. And when I say cooler I mean 20 C cooler.

[bugninva]

I say useless because it read cooler than the temperature measured next to the pump (shown in the picture above) and cooler than the Berg dipstick sensor. And when I say cooler I mean 20 C cooler.

its been several years, but the last time i checked temperature through the dipstick hole it was right there with the sump sensor... a sensor in the sump plate is a good indicator of oil temp in the sump...if you want to know your operating oil temperature(what the bearings see) it needs to be taken after the cooler...not before the pump...

[WildBill]

I mounted mine on the inlet side of my remote oil filter. Used a homemade adapter.