So i've been observing an occurance of coolant push to the overflow as i've increased the power level. I have yet to determine a cause and solution. I thought i had a bad radiator which was not drawing the coolant back in.
Here are some details that may be related. Water pump housing was smoothed and ported internally to remove casting flash and soften the edge/corner at the top, #4 cooling mod flows to heater core valve. 180 tstat. Was Nissens type brass/copper 2 row radiator, now Spectra Premium aluminum 1 row.
When i first noticed this i looked over the overflow system because once the engine cooled, the radiator level was low. I added hose clamps to the overflow hose because the spring clips seemed loose and i thought they might have allowed air in instead of vacuuming the coolant back in. I tried a different overflow reservoir. I tried a new radiator cap. Stant 10331 (lever vent) vented cap.
Recently i tried a stant 10330, lever vent unvented cap.
As an aside, I researched what the actual difference is with these caps and the return valve.
The vented caps have the valve hanging, and the seat upward when there is a quick rise in pressure, but normally they dangle and allow vapor to escape to the overflow. However i thought it was also allowing coolant to push out.
The unvented caps have the spring on the return valve. These will build system pressure and maintain it.
The lever venting feature on both isn't supposed to affect normal function, but provide safety release of pressure to remove cap.
I found the bottom tank on the Nissens radiator leaking slightly, and figured it was drawing in air when the system cooled so i changed the radiator. Still the level would not come back from the overflow.
Some recent and older threads talked about the possibility of coolant boiling in the turbo and being a cause. I am using a 50/50 mix of coolant right now.
I ordered a pressurized expansion tank, and i'd like to try installing it to see if that would help.
If there is some boiling occuring, that vapor needs to get out of the block but not occupy space in the radiator, and then when cooled that fluid needs to get back to the radiator. Having an expansion tank, with pressure cap, and maintaing a fluid level higher than the radiator cap should help. I would use the vented cap, or remove the valve from a cap for the radiator, the current low pressure overflow hose will be replaced and will attach to the bottom of the coolant reservoir, the reservoir has a pressure cap and an overflow line that will return to the overflow tank. The coolant will be removed entirely from the overflow tank. The pressurized reservoir will have about 30% level of coolant and 70% vapor space.
This is the reservoir i ordered:
Dorman 603-029 Coolant Reservoir https://www.amazon.com/dp/B00FY80P6M..._ciDmwbXP5RH7J
It looks like it comes with a 16psi cap. I looked at those coolant VW jetta ball shaped ones, but they appeared to be around 20-22psi.
I am trying to nip this in the bud so i can try increasing the power a bit. But right now i'm not sure if this situation is giving me some hot spots of vapor entrainment in the head as this coolant level gets lowered.
If anyone has further suggestions or ideas, i'd like to hear. To me it doesn't make sense why i would have to reinvent the wheel here. Something is going on, but i just can't find it. This should be a worthwhile improvement anyway.