weird temp display

[Sonic Motor]

so i was going down hill on a cold night. and all of a sudden, my S13 temp reading was going lower. I thought the needle broke so i didnt care and went faster...then the needle just went to C...then below C

So i pulled over and let it idle for a minute, and the temp went back to norm.

the complain: temperature reading shows cooling down while going down hill on the mountains. it runs normal everywhere else i go. This only happens when i go DOWN hill for some reasons. Anyone have the same problem or know whats the cause and correction?

[nsn240]

might have something to do with the coolant flow... i dont really know, oem water temp sensors generally suck

[spoolin240sx]

you have air in your cooling system, get the air out and you'll be good to go

[Sonic Motor]

ah...i see...u guys are awesome.

btw, how do i get the air out?

my water pump is leaking, what that have been my problem??

just to clear things up, the low temp reading is a FALSE reading right???

[spoolin240sx]

yeah its a false reading, its reading the air thats stuck in there not the water. wait till it cools off and there is no pressure in the system then:
1) take the coolant burp bolt out and fill the radiator up till it starts coming out of the burp hole.
2) put the bolt back then mess with the hoses a little and get the bubbles out.
works for me but i believe the fsm might have a little different procedure

edit: yeah your water pump is why it got like that, replace that leaky water pump asap