Pontiac Repair: Radiator Steam, copper radiators, pontiac sunbird

Question
QUESTION: My son has a 1990 Pontiac Sunbird 2.0 liter. We've replaced the motor, water pump, thermostat, radiator cap, and hoses. Intermittently, he will notice steam from under the cap, no raise in temperature on the guage and no apparent leaks. We're stumped. Any thoughts?

ANSWER: Hey Robin:

well it's either the cap sealing surface on the radaitor is bad allowing a small amount of coolant to seep by or the radaitor it's self is starting to leak and it's just showing up by the radaitor cap. It's one or the other. these older cars had copper radiators and the core would tend to leak at the side tanks.you can get a product called coolant tracer dye "any good parts store will have it. like NAPA or Carquest" add it to the coolant it is a florecent green color let the car run a few days and if you have a black light shine it on the radaitor and the leak will show up bright green where the leak is. good luck :}


---------- FOLLOW-UP ----------

QUESTION: Hi Todd, thank you for getting back to me.  When you say the cap sealing surface on the radiator - could that mean that the neck itself needs to be replaced?  We're not seeing any antifreeze on the ground at all, but I'm assuming by your answer, that doesn't mean the radiator isn't leaking minimally?

Answer
exactly. the sealing surface on the neck could have some pitting or corosion and the seal on the cap may not be able to seal it off or like I said the core is leaking along the side where the tank is. usually towards the bottom It's hard to see it on this car and if it has A/C it makes it harder to see.