I recently replaced my radiator and thermostat (195). All is well when parked in the garage, the temperature reaches 210-220 and I hear the fan turn on with no issues. Today when I drove the car around I noticed the temperature gauge would slowly drop from 210 to 160 and consistently stay at 160, i also wouldn't hear the fan turn on either. Before I swapped both the radiator and thermostat it would take a bit for the car to reach operating temp but once it did, it never dipped. What could be causing this? I will note that when I was burping the system, the cone tilted and fell so I had to slowly add coolant with a normal cone until the radiator was full. Could it be air in the system?

 

Sounds like you got air in the system. It shouldn't fluctuate that drastically

 

I just took a look at my receipt and I got the 180F thermostat instead of the 195F. But regardless, it shouldn't be fluctuating this wild, I'll burp the system tomorrow afternoon. Should I replace the thermostat again?

 

Nah I'd just leave the thermostat alone. But use a coolant funnel to burp the system. My LS was an absolute nightmare to get all the air out

 

Burped the system for a good 40 minutes and quiet a bit of air came out. I then test drove it and it stated at 205F up until I hit the avenue, it then went to 190 briefly until finally settling to its beloved 155-160 like last night. I'm starting to think I got sold a 160F thermostat and not a 180F one. I will double check my physical receipt since my digital one says 180F. It's just odd how it goes to 205 when idling pretty consistently but when moving it eventually drops to 160/155F constant. This car loves being a headache

 

Do you have a real, marked gauge or are you going off the factory one in the cluster?

 

Factory one. Hadn't had this issue prior to installing the radiator

 

So I can tell you that about two needle width over the first line is about 190f. With a 180f thermostat and fan cal'd to turn on at around 190f on a stock L98 it should float around that area when moving and creep up to almost the 220 Mark when not. Which is about 210f per the computer.

 

Sorry forgot to add that I have a 305 TBI. Would it apply for it too?

 

I got a 427 with a Holley sniper in one car and a stock L98 in the other both cars seem to read the same cluster vs computer.