Water Pump '79 S2000

[BillFz1]

Greeting Fiat Fans,
This is a general question. I have a 1979 S2000. I have been having the classic burping overheating problem. I have tried several of the bleeding methods with no joy. i had been having a long period of really good performance, but then had a heater core leak. Replaced the heater core, control valve and tubes. I had no trouble bleeding the air last time. I have the tee with the plug between the hoses. My thermostat has the little hole. Radiator is new aluminum one. I have the tee in the heater hose. I bleed with the heater control valve full open. But I can't seem to get the air out this time.
I have one big question for all you experts out there. HAVE YOU EVER HAD A WATER PUMP GO BAD WITH NO EXTERNAL SIGNS? My pump doesn't seem to be rattling and I have NO coolant on the floor even when put away hot. Typically when I see water pumps fail the first thing is the seal closely followed by the bearing/s. The other question is how many different water pumps are there? I have a friend that has a spare and I thought i would use his and be all up to date. passages are different and it leaks on my car. perhaps it was for a 1.8 of earlier motor? Any help would be appreciated, thanks.
Bill

[AriK]

According to autoricambi's parts list the early motors had a different pump but it seems like the 1.8 and 2 l share the same unit.
Are you sure that maybe you have a bad head gasket. If you have compression leaking into a coolant passage it may be bubbling into your coolant tank. Perhaps the heater core failure originated by higher than normal pressure into the cooling system?

[BillFz1]

Thanks Ari, I did a leak down test and didn't have any bubbles into the coolant. engine is RUNNING great, just heating up.
Thanks Bill

[So Cal Mark]

continually getting air in the cooling system is a pretty good indicator of a leaking head gasket

[BillFz1]

Thanks Mark,
I would have expected bubbles when doing the leak down test. What do you expect for a percentage when you do a leak down test?
Bill

[fiatfactory]

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