lyleswk

Beyond what John535 and assuming you bought a quality green sensor, the only other thing to consider is the "Black" 2 pin plug at the base of the radiator. I used to have a description of how the 2 sensors are used by the ECU and couldn't find it.

jflow45

It's likely your system is pulling in air from somewhere. Check your reservoir tank for cracks and swap caps on your coolant system. I ran the Porsche cap for a while and it would cause my coolant temp to rise just over half way. Switched back to stock cap, no problems. I'll experiment again if/when I purchase a new OEM coolant tank.

ShakesterB6

Tried it all. Replaced the CTS sensors. Flushed the cooling system and replaced with fresh Pentosin Pentofrost SF. Bled it as well. No leaks but realized the coolant just wasn't moving. Going to replace the thermostat again and a new j-plug as well. Keep ya updated.

ShakesterB6

So I've replaced both sensors and the thermostat with a new ECS billet j plug. While replacing the thermostat, I inspected the water pump and things are in tact. But after all that, it still overheats. The heater does blow out hot air when revving but at idle it's not as hot.

lyleswk

Well, only two other things come to mind: 1) radiator is clogged, 2) you have a serious clog somewhere else (very unlikely), or worse (see below). The heater core is not a direct indication because all it indicates is a clogged heater core (fairly common) and the system is designed to completely bypass the heater and still cool adequately. What is the coolant system history? Periodic flushes with G12? Unknown?

Last thing I will suggest is blown head. Depending on where it goes, you can get lots of heat into the coolant. Had this issue on a Merkur years ago and drove it for 6 months until the head went completely. Any signs of a head issue?

ShakesterB6

An update.

I found out my brother, who drove the car for the last few years, used regular coolant for quite some time. I didn't a complete flush. Ran a hose at full blast through the system and a bunch of black flakes starting pouring out. I'm assuming its build up for a worn hose that probably partially clogged an area to disrupt the coolant flow. I ran it for about 15 minutes until the water was clean of debris and coolant. Filled it up with distilled water and drove around for about 15 minutes. Flushed it again and everything looked okay. Filled it back up with Pentosin Pentafrost ++ (G12+ equivalent). Its been over two months and it hasn't gone over the midway point since. Been stuck in heavy traffic, in 85 degrees weather, taken it on 100 mile trips and its still perfect.

lyleswk

Good to hear. Maintenance is crucial...