Question about available ports for coolant temperature sending units.

Luke.T5R · Post by **Luke.T5R** » 28 Aug 2021, 07:31

Hi, I have recently rebuilt the engine in my 850 and i'm currently ironing out all the small issues. Right now im having an issue with the fans not kicking on and the car overheating in traffic (obviously). I have tried another relay because I have two cars and it was easy to swap, no change. the coolant temp sender is new and it reads correct when the engine starts heating up. The fan will kick on if i wire it direct, so the fan is not the issue. Im not sure what is going on with the stock cooling fan system and I'm not too jazzed about trying to trouble shoot it. I found a kit from champion cooling systems to replace the whole system, sending unit and all. My question is could i replace the stock sending unit with the new one? there isnt exactly a bunch of ports on this block for me to use. Secondly could I drill and tap another hole on the thermostat neck, space permitting of course. My third option i can see is the part pictured in my post. the pipe going into the block that appears to have some sort of air fitting on the end of it, and its some sort of NPT so I could utilize that port, assuming that fitting isn't vital. Just looking for thoughts on which of these 3 options would be the best. ideally I would like the run the new sender for the fan control system and then get an aftermarket temp gauge to keep a better eye on the actual temperature. I am okay with the temperature gauge in the dash not working. Im open to any input and if you have done something similar I would love to see it. Thanks!

Post by **erikv11** » 28 Aug 2021, 11:55

The wiring to the relay is a common failure spot that can give that system.

Thet's the coolant drain port on the rear of the engine block.

Luke.T5R · Post by **Luke.T5R** » 28 Aug 2021, 14:03

Thanks for your reply! I will check the relay, seems like I found a video showing how to test it. Where is this coolant drain port at?

Luke.T5R · Post by **Luke.T5R** » 28 Aug 2021, 14:03

Luke.T5R wrote: ↑28 Aug 2021, 14:03 Thanks for your reply! I will check the relay, seems like I found a video showing how to test it. Where is this coolant drain port at?

NVM re red your reply I see what you mean so that will work perfect for my needs! Thank you

Post by **abscate** » 31 Aug 2021, 07:18

The coolant temperature isn’t uniform around the engine. Reading at that pipe may or may not give you useful information. The ECT is immersed in flow whereas that pipe might be a dead end, I don’t know

Luke.T5R · Post by **Luke.T5R** » 01 Sep 2021, 17:11

abscate wrote: ↑31 Aug 2021, 07:18 The coolant temperature isn’t uniform around the engine. Reading at that pipe may or may not give you useful information. The ECT is immersed in flow whereas that pipe might be a dead end, I don’t know

I was thinking the same thing, but with the proximity to the water pump, I believed it would be okay. Thank you for your input.