Hello HT. Recently, I noticed that my temperature gauge in my Si cluster hasn't been working. I ordered a new Temp Coolant Temperature Sensor thinking that was the issue, but no luck. I noticed that there was some dark liquid (probably oil?) inside the temp gauge unit as well as the wire that connects to it. I don't think it's a fuse because my entire cluster wouldn't be working if a fuse was bad, right? Are there any other suggestions or thinks to look for? I'm going to use a good cluster later on today to see if the cluster is bad

 

Continuity test the sending unit wire between the sending unit and temp gauge. If it's fine, the gauge is bad.

 

Check upper and lower radiator hoses for warmth.. Could be a stuck thermostat.

 

I looked up one of those diagrams for the temp gauge and I used a jumper wire for the sending unit wire and grounded it to the block, the temp gauge rose all the way to "H" so the temp gauge is good.

 

Is the sending unit supposed to flush with the engine? I tried tightening it and it's pretty stiff already. The last thing I want to do is break it off from over-tightening.

 

If it's stiff then leave it. Clean those connectors tho.. They look pretty oily from here which could be interrupting readings.

 

Nice job. This tells you that both the wire and the gauge are good.

If, after replacing the sending unit and bleeding the cooling system, the temp gauge stays on cold, then chillerice's idea about a stuck open thermostat may be correct.

 

Will do. I noticed that it takes about 5 to 10 minutes of driving for my temp gauge to "almost" go halfway. Maybe the sending unit is going bad. I'll find out if the thermostat is stuck open.

 

I found a quick test for a stuck open /partially open Thermostat.
Set the temperature to cold, and keep the heater fan off, and recirculate door closed (no outside air flow through).Drive for a few miles, and see if the temperature rises sooner than before. Change the heat lever to hot, and see if you get some heat.