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MG TD TF 1500 - TF pressurised cooling system

According to my research, a 50/50 antifreeze solution raises the coolant boiling point to 265F whereas a pressurised system raises the boiling point only 3.6 degrees F per psi. Thinking of leaking gaskets, waterpumps,frost plugs, etc, it seems that running unpressurized with antifreeze (like a TD) makes sense. My old Ford 8N tractor worked fine without a pressure cap and my TF appears to run steadily at 85C ( although its newly back on the road and hasn't gone very far).
Any comments on deleting the pressure cap spring?
T W Moore

Mine is pressurized at 7 lbs. My rad is newly redone with new core and nothing else leaks under pressure in the system, so I'm leaving mine the way it is as long as no problems arise. PJ
Paul S Jennings

So...7 X 3.6 = 25.2. With 50/50 coolant boiling at 265...Paul has an additional 26.6 degrees with 7-lbs. 290.2 degrees. That's Cook'n!
M Brand

Might want to recheck the sources. It seems that the boiling point of 50/50 ethylene glycol is, indeed, 265°F, but that's with a 15 psi cap. This comes from a source called 'Today's Technician: Automotive' thanks to Google. Bud

Bud Krueger

Yes, and you could increase antifreeze to 70% and get a base boiling point of 276F, according to Prestone.
I think that's why heaters are best separated from the car's occupants.
But has anyone first hand experience with a TF 1250 or 1500 using an unpressurized cooling system?
T W Moore

Yes Bud, I failed to read the fine print on the bottom of the
Prestone container. My mother was always warning us about that.
That would drop the unpressurised boiling point to about 230F with a 50/50 mixture (assuming a 35F increase in BP from the 15psi cap @2.3F per psi) . A standard 4psi cap would then raise the BP by about 9F to about 240F for a TF.
T W Moore

The unpressurized TF1250 should be very much like a TD. With my newly rebuilt (by Butch Taras) water pump and my closed cooling system (http://www.ttalk.info/Tech/Overflow_tank.htm) I can operate my TD with the pressure cap open or closed. This year's July 4th parade was fine for basic TD operation. Bud
Bud Krueger

The pressurized system helps keep the coolant @ the exhaust valve area a liquid, instead of a vapor, or steam pocket. This helps prevent a blown head gasket.
My TD runs @ 85 C I have pressurized the system with a pressure cap & neck attached to the overflow pipe.
Len Fanelli

No car that can cool to 212 or below actually NEEDS a pressure system. A large enough radiator and coolant flow will handle a nuclear reactor.

The whole point is to allow engines to run hotter and more efficiently without boiling over, not cooler.

The XPAG wasn't designed to need higher temps, so what's the point of raising the pressure when we're having no problems running at 85 to 90C anyway - unless you WANT to run at 100C+.

....
MAndrus

If the TF 1500 was designed with a thermostatically controlled pressurized system, why would anyone want to change it? If it leaks under pressure, fix it. If it runs too hot, fix it. Simple solutions to not too complicated problems. JMHO PJ
Paul Jennings

The coolant temperature at the exhaust valve is the concern, it is much hotter than the rest of the coolant in the system. From the mid 50's until perhaps the 90's most thermostats were 180 or so degrees, all were pressurized with about 12# caps.
Len Fanelli

Appreciate the (somewhat diverse)inputs. Food for thought. Thanks all.
T W Moore

This thread was discussed between 22/07/2015 and 24/07/2015

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