Well, I think my 2nd heater core is toast. Pulled it from a 78 z in the junkyard, very clean, good condition as far as I could tell. That was 6 months ago. It leaks inside the housing and the water drips down the sides soaking the carpet. It leaks mostly when the engine is off, when pressure is maintained in the system, as I removed the heater control valve due to that leaking several years ago.

My question is, is the heater core meant to be subjected to constant pressure all the time like when the heater is on it's hottest setting? Perhaps it's a slow destructive process.

Well, here'e a possible solution: Local parts shop said they'd sell me a new one for $100 with a lifetime warranty as long as I kept the reciept. You think that's a decent deal?

Buy a new heater control valve and a new heater core...This heater system sounds like a Euro job ie BMW and of course Merkur XR4Ti.They only work as a system and with out the control valve you have pressure all the time..And used heater cores are like used radiators you take your chances...The new valves might need brazing on the joints but that's it no worries...(To prevent leaks) BTW I do not have alot of wrench time on a Z but looking at this system it's pretty much the same..As the other cars with this setup.

Well, here'e a possible solution: Local parts shop said they'd sell me a new one for $100 with a lifetime warranty as long as I kept the reciept. You think that's a decent deal?

Joey,

That's about what I paid to replace the heater core in my old 280 and also the current 240Z. I can't think of a job I dislike more on these cars.

On both cars, I replaced the heater core, the heater valve and all the hoses because I didn't want to fool with it ever again!

If your leak is coming from inside the metal housing I would also suspect the core, just make sure it's not the valve or any of the hoses/connections.

Good luck with your efforts.

Bruce

....which is why in my turbo build up I am completely removing the heater core and blower motor.....

I have the very same problem with my 280, not looking forward to the operation. Will probably follow the path Bruce took in replacing everything so as to eliminate potential problems.

Well, I have to say, the design of the 280z heater assembly makes it fairly simple to remove. You don't even have to remove the control face. After removing the hoses down there, theres a plastic panel screwed to the side of the center hvac bulkhead. Once that's removed, the heater core just slides out the side. I think on 240z's there's some major teardown required.

I think the point is, I'm not afraid to replace it again, but it's a bit of a pain to do so. I even think a new heater control halve would be more difficult to re-install than a new heater core.