Air getting into coolant system - Mondial T

Hi all,

Well I seem to be getting one of those head scratchers. Car runs well, but I keep on getting air in the coolant and have to bleed it out from the outlet elbow (where the thermostat is). This is on a Mondial T. Trying to avoid thinking about the head gasket scenario, I am hoping it is just bit sucking in air - accepting that the system should be under pressure, but with water pump and differing flow speeds, perhaps an increase in flow speed somewhere is reducing pressure enough to suck in air. There are no coolant leaks and no coolant in the oil!

Anyway I looked at the hideous small pipe on the water manifold today, took the pipe off and found it completely blocked (it’s part 45 in attached file). It took a fair amount of swearing and prodding to finally unblock it. So this is the smaller tube that goes to the expansion tank, meaning the expansion tank was only connected by one hose to the engine. I believe I am right in saying that the manifold the small tube goes into is on the outlet side of the engine that then goes either back into engine with thermostat shut, or with thermostat open, then goes on to the radiator. I am not sure what effect having this ‘hot’ side blocked from the expansion tank would do?

Anyway I will stick it back together this week and test, but it is a nightmare getting the hose clip on with the inlet manifold in place.


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Not sure about your T, but my 3.2 requires some air in the system. If you try to fill it "full" it will expell the excess thru the discharge tube on the overflow tank. "Full" for my car is about 3" below the top of the overflow tank. The repair manual says this is normal.
Is your car overheating? If not, don't worry about it.
The 308/328 guys have come up with some crazy procedures to remove all the air from their systems, only to be told by our expert members to stop obsessing about the "air." It's supposed to be there.
Alden

 

Yes I have the 2” air gap in the tank, the problem is that air builds up in the elbow above the engine and stops water flowing to the radiator. Having said this I am mildly hopeful now as I cleaned the blocked pipe, stuck it all back together and it seems to be getting better as in she only started getting hot once and a quick bleed and that has not happened again. I think with only one tube from the coolant tank (other being blocked) it was trying to pull from the tank and was sucking in just a bit of air from somewhere. Now both tubes are unblocked, it seems to have fixed - I hope! It would be nice to screw the engine access panel back in and be able to drive without one eye on the temp gauge.

 

Right I am getting closer… for some reason when I found the blocked pipe in the manifold, I did not check the coolant tank. Anyway couple of days ago I took that off and found a lot of red junk in the bottom. That turned out to be something like dried up antifreeze. I cleaned it all out and the tank is in very good condition with silver metal visible. However the coolant return pipe bit in the tank that comes from the manifold pipe in the V, well that was blocked solid too.

Anyway cleaned it all up, tested the car and yet again after 8-10 miles, overheating (just above 90 and rising, I stop early rather than risk it). More air lock in the thermostat elbow. So today I drained everything again, flushed everything and took the thermostat out. There I found a small band of corrosion or muck that would have compromised the thermostat elbow seal. So I am hoping that the Venturi effect around the thermostat may have caused enough reduction in pressure to suck air in there. Now I would of course be rushing out to test this, but in my last run, the power steering hose split. This car likes to keep on throwing curve balls. That will be fun to change next week.

 

So to anyone in the future, I believe I can now say this with some certainty: The Mondial T and therefore 348 can suck in air into the coolant system through a leaky gasket seal on the thermostat elbow! It is good physics as even though the system is under pressure and this is after the water pump, the Venturi effect in the thermostat area is sufficiently strong to reduce coolant pressure in the elbow below atmospheric pressure.

After fixing my power steering pipes, using some permeated type sealant on the thermostat gasket and refilling the cooling system, bleeding it twice after a stationary start and warm up; I eventually built up the courage to turn hope into an answer (you see whilst she is sat with what I think to be the cure, I can be hopeful. Once I test, I find out the answer which may or may not be nice…). So today I took her out and whereas she would normally of got too hot after about 12 miles and with about 1.5 miles to go to my house; this time she got just a needle width above 90 (centigrade) and stayed there and I went another 4 miles with no issue. This test route has been somewhat consistent as I had to stop in the same place each time to bleed air and cool down. Upon my return to the house, I then bled the system and found some air in the elbow, but bearing in mind I had only bled air on the level on the drive and the trip had taken me up and down steep hills, it was expected that some air would appear in there, but crucially it had not been enough to stop flow through the radiator. I then took her out again and she was great and so nice to drive with the back seat access panel back in place - unfortunately I then went by the school and had to listen to all the screams of ‘it’s a Ferrari!’ I have now come to the conclusion that a red Ferrari convertible does draw a bit too much attention at times…