Radiator Cap

[Christopher G. Moog]

> >> I'll probably get scalded for this one, but I think that removing the t-stat
> >> actually can allow the water pump to cavitate, and possibly cause a pressure
> >> difference between hot engine and cool (relatively) radiator which prevents
> >> coolant from circulating.  While it may seem like I'm grasping for straws, I've
> >> seen something like this in my work many times.

The dreaded "water flowing too fast to give up heat" crap again.  The removal of the
thermostat can (not will) cause overheating.  This is caused by:

1. Cavitation in the pump,
2. Cavitation in the block, or
3. Cavitation in the head.

Cavitation is in fact boiling due to localized low pressure, usually caused by high
flows.  Localized areas with high flow will boil (or cavitate) due to low pressures.
The boiling will isolate (and insulate) the area from the water causing greater
temperatures and overheating.  As an example, several years ago Cummins diesel went to
a high flow (through the block) higher temperature cooling system (bypass type).  This
caused erosion of their blocks from the inside.  What was happening was that as the
hot coolant flowed around the cylinders low pressure was created on the back side of
each cylinder.  Localized boiling was occurring there.  Over the course of 200,000 -
500,000 miles this local boiling was eroding the block and causing leakage on the rear
of the cylinders.

As to the too fast to reject heat water theory.  The flow is in fact too fast.  This
fast flow rather than causing low heat rejection (if the coolant is hot so is the
radiator, increasing heat rejection not decreasing it) is causing localized areas of
low pressure.  These low pressure areas are boiling (at relatively low temperatures)
blocking coolant flow to some areas of the head or block.  These areas now deprived of
coolant will overheat.  Placing a blanking plate in the housing will help reduce the
coolant flow rate and prevent cavitation (or boiling).