Al,

I'm looking at the picture of you're coolant bottles.

OK, the pressure bottle has a feed at the bottom, and an overflow at the

top.

The overflow of the pressure bottle goes to the bottom of the overflow

bottle.

 

What are the two al pipes going to the pressure bottle about half way up?

 

What is the sensor in the overflow bottle? Low coolant? Can I get this from

NAPA?

John

 

The two small tubes (3/16 Al) are air bleed lines from my two radiators.  Both my rads are horizontal flow – tanks on the ends.  Air can be trapped in the upper corners when filling; but also, since the flow velocity in the tanks is very low, it is the likely place that any entrained air will eventually separate.  Because that bottle is at the lowest pressure point in the system (the bottom of that bottle connects to the line near the pump entrance) any air will be driven to that bottle where it is eventually bled from the system through the overflow bottle.

 

That is a low-level switch - magnetic reed float type, right angle.  You can get it from Mcmaster-Carr.  It is the nylon one which is good to about 300F – Part #47465K83.

 

Both bottles would be filled on initial fillup.  As the coolant expands it would be ejected overboard via the overflow bottle until the max temp point was reached.  Air is drawn back into the overflow bottle upon cooling.  Subsequently the air is compressed and expanded in the overflow bottle as the coolant temp level changes.  If the level gets below the float switch it would indicate loss of coolant while the actual cooling system was still full.

 

The pressure sender at the pump outlet side will see fairly high pressure at full power (temp) as it is reading cap pressure plus pump pressure head, minus the drop through the engine block.  You can play mind games with how the pressure will fluctuate as power level varies, but there will always be positive pressure (above ambient external) at the pump inlet, and somewhat higher pressure in the block, giving max protection against boiling or pump cavitation.

 

At least that’s the theory; and probably more info than you ever wantedJ.  Oh, yeah; I haven’t flown this yet, so actual operating data will be interesting.

 

Best,

Al