I have a really weird problem with my b18 swapped civic. Just the other day I decided to swap alternators because I noticed that the voltage was low when driving. After doing so I noticed that the temp on the temp gauge would rise over half. This is abnormal for this car as It has never done this b4. I thought maybe headgasket but I have no symptoms so I replaced the Thermostat and verified that the cooling fan comes on. I still had the issue and upon further testing I noticed that my voltage was again low and the lower the voltage the higher the temp gauge would read. After cleaning the battery posts and verifying all grounds on the motor it seemed the problem had stopped. Today it happened again and I am baffled. I'm not boiling over coolent and the weird thing is when I run the car hard the temp says normal. Only when I slow down and stop does the temp rise. When I start moving again it will slowly come down.

I was thinking it could be either the temp sensor in the back of the block (not switching the fan on correctly) or the water pump. Anyone else have any suggestions? My voltage reads 13.7 to 13.8 when driving and when i stop or let off the clutch it can hit 13.4 to 13.5. I also have bad idle surge at times like the car cannot make enough voltage. Could this be related to the rising temp gauge?

My setup is a b18a in a civic with a brand new radiator (OEM from an automatic civic) the radiator has a aluminum core.

 

HELP PLS

 

Is the coolant bottle full?

 

Yea theres enough coolent.

 

bump #2