I took the car to Hi Tech Automotive in Silverlake. They have been great with the car generally and have good service, but they are a high turn-over shop.
So when the car was overheating, the did some tests and determined that the radiator had a pin-hole leak in it. They said it couldn't be repaired and recommended replacing the waterpump and radiator. Obviously OEM radiators aren't available so they suggested a aluminum aftermarket. I followed their recommendation, parts and labor was $800.
The car kept overheating. I didn't like this 'replace parts hoping that is the solution' mentality of high volume mechanics. I wanted someone that would take their time to diagnose a problem.
In the mean time I had been talking with Tom Colitt about some restoration work, so I took the car over to him. He meticulously worked through the problem (as well as some other restoration work). From pumps to pressure checks to everything. We were getting ready to pull the engine apart. It seems that the thermostat won't let coolant into the aluminum radiator.
When we swapped in a known-good OEM radiator, it worked as it should.
So the theory we've come up with is perhaps the aluminum core radiator is so good at cooling that the thermostat is never opening. Or at least that's what I understand. I fully trust Tom, he is dead-set an expert on E9's.
So in short, I don't care for an aftermarket radiator and want an original one. I'm PM you sfdon, thanks.
Drew.