Mondial T overheating - I'm at a loss of why...

So this all started quite some time ago when I replaced the original, rusted-out expansion tank and I've had nothing but problems since.

I went to change it out and all I did was pull the two hoses off the bottom - the main feed line which goes to the back of the water pump housing and the smaller ID air bleed line that comes from the cross-over piece that joins the two cylinder heads. There may have been 2 to 3 liters of coolant that spilled out which I thought was no big deal, I'll just top it off.

No matter what I've done, after a period of idling, or a short drive around my neighborhood, will eventually over heat. I have always confirmed operation of the gauge on the dash by taking laser gun readings at various points on the engine and any other component carrying coolant (lines, pipes, radiator, etc). I've seen temps as high as 230+*F.

I have tried all different ways of bleeding the system (jacking the car up at different angles, pressuring the system, drawing a vacuum, etc). I have flushed out multiple times, pulled the radiator and cleaned/flushed out.

I even went as far as doing a major-major service (which was a good thing because the timing and oil chain tensioner guides were completely worn out, plus it had the original needle bearing for the top timing chain sprocket), because I figured maybe the water pump was worn out (it wasn't).

I confirmed using my borescope that the block, heads, various coolant galleries are NOT blocked.

Somehow, air is getting trapped inside and it's preventing proper coolant flow.

I'm at the point of giving up.

Is there any other method of how to fill this system up and NOT trap any air in it?

I have NEVER had this issue with my 308. That car is rock-solid with temps and it's NEVER overheated. It's stupid-simple to fill and bleed. I don't know what I'm doing wrong with this Mondial...
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Yes the fans are turning on and I've spliced into the circuit a manual switch to turn the fans on permanently for an emergency, which I've had to do when the temps climbed up.

I have bled the system at the rad and the thermostat housing numerous times. I have added additional bleeder valves on the heater core line and also at the return neck of the water pump housing, just to help.

That fill level mark is the same with many of these cars from this era (6cm to be exact). It's the same with my 308.

 

I have pulled vacuum before I did all of this work. At most 25 to 30" of mercury which is pretty much the max. I've also pressurized the system too with no VISIBLE leaks.

I've tightened the clamps quite tightly. Norma clamps are superior to regular worm-gear types, but I'm always hesitant to go killer tight. Especially the smaller ID ones. Those formed threads are only so stout that they too can strip. Ball-park torque figure I need to shoot for?

I got docked concours points for having a 1.1 bar cap, so I switched out to the stock 0.9 bar. There isn't much difference between the two and I would expect that the 0.9 would be sufficient.

Like I said, this car was perfect before I replaced this tank. It appears my method of filling always introduces air. You mention: "suck in 3 gallons of coolant". Do you always pour coolant into your Ferraris with a vacuum system? I always POUR coolant into my GT4. No vacuum, no problems.

 

Yes, I got knocked concours points for having a 1.1 bar cap, so I switched out to the correct OEM 0.9 cap.

I already replaced the most difficult hose on this engine (the 20mm ID one behind the water pump housing). She's now tight and leak free.

 

No, that's the thing, when the fans come on, they do NOT cool the system down. At best, they may keep temperatures held, but will not bring it down.

I put my borescope into the block and the coolant galleries of the heads as deep as I could reach with it and I saw nothing in there. Same thing with the radiator. The long hoses down the middle of the car were wide open, but I did replace them because, like most items on this car, were original (you see that Alfagomma hose in my photo. Very reasonably priced and is the exact size and spec vs. the pricey original hose T352AA157X12.6 Alfagomma by Kuriyama | Radiator Hose | Black | 1-9/16" — HoseWarehouse ).

 

I’m on my 3rd TStat and the one in the car is the last OEM Behr 82*C that I could find. I tested every one in a pot of boiling water on my stove and checked opening and closing points. I also made sure it extended the correct length to block off the lower port in the housing.

 

I followed my pictures and the parts catalog. The pipes can’t really be put in wrong because of the specific tight bends and the tight areas they fit into.