Overflow tank issues

[Doug]

Looking for some ideas. I've just increased the capacity of my radiator by 33%, and also replaced the 3.9 with a 4.6 modified engine. I've got things worked around so the temp is steady at 190 degrees. But she still pisses a bit of coolant now and then, even with no pressure in the system (can squeeze the radiator and heater hoses while running at full temp and you can feel there's little or no pressure build up anywhere). Everything else is good. (Analog temp gauge, in addition to the stock temp gauge, directly reading the radiator temperature at 190.)

So what I'm thinking is that the 3.9 93 110 overflow tank is just to damn small for the bigger block and vastly increased radiator size....

Thoughts? Suggestions?

DW

[Mike Hippert]

Or your over flow tank has a crack in it. Your Cooling system should be under 15 to 16 lbs of pressure. When coolant is pressurized the boiling point increases, so your cooling system can have water in it and not boil over at 212*F. But if your expansion tank has a crack then the system will not pressurize and the water will start to boil out at a lower then overheating temp (240*F). I would have the tank pressure tested, and if it is leaking you can have it soldered up. This is just an idea, you said you are not building pressure, is that just based on squeezing the hose or when you pop the cap off the expansion tank it does not hiss, or relieve pressure. You can also get a pressure tester at an auto parts store yourself and check the system (works good to find leaks also).

Like I said just an idea.

[Doug]

Mike, wouldn't I then get a leak at the crack? There's no coolant appearing anywhere but from the overflow tube...

[BarryO]

Or the cap on the tank isn't holding pressure.

The tank on my wife's Disco developed a leak on the tank right at the seam. Would only leak when the fluid level got up to the seam itself, but the system wouldn' hold pressure.

[Mike Hippert]

True it would leak from the crack; I wasn't to sure where yours was leaking from. And good point on the cap Barry, you can get a new cap at the auto parts store, I have one with a handle you pull to unlock and let the pressure out. The overflow tank hold I think between 1/2 and 3/4s of a gallon, I would think that would be enough. When it spits out, if you let it cool off over night does the amount of coolant in the overflow tank decrease?

[Doug]

BTW it was the cap. Had an aftermarket cap on it -- replaced with genuine and no problem.

News: re-doing the rad again. The oversized rad still won't cool the TVR on hill climbs, so in looking for a solution I just discovered that the new Morgan remakes, which are powered with the same TVR 5.0 as mine, all run hot. The Morgan dealer out here has solved the issue using wide-tube race-tech Farrari radiator cores. Works 100% of the time, brings the Morgan temp gauges down from pinned to lower 1/4 of the dial. On and on, but I'm feeling pretty confident on this one....

PS Please don't ask about the money. I'm taking that data to the grave with me. ;)


DW