[Public-List] A4 overheating

[Daniel Sternglass]

Hello Gord,

Two things have helped with short-term A4 overheating problems in my 
experience:

(1) Back flush by removing the crossover-tube on the front of the engine 
and connecting a "garden hose" to blow out accumulated crud.

(2) Partially or entirely closing off the cooling water bypass hose (see 
below) which forces all the cooling water through the engine. In a 
pinch, rather than installing a ball valve (very common on A-4s), is to 
clamp with some wood blocks and vice grips in an emergency, or even just 
kink the hose. NOTE: According to Don Moyer, that hose has to be 
significantly open when starting the engine to ensure it cools 
initially.. I think you need the thermostat in place in order for this 
to work.

*Description from http://yankee30.org/thermostat_housing_fix.htm*
....Water entering the pump is pumped through a hose running along the 
starboard side of the engine to a T on a water manifold plate where it 
may enter the engine or go straight to an inlet on the thermostat 
housing. When the engine is cold the thermostat is closed. Water stays 
in the block and head. This facilitates a quicker warm up of the engine. 
While the engine warms up, water is being pumped through the bypass hose 
to the thermostat housing, then to the water chamber in the exhaust 
manifold, and finally to an injection point on the exhaust line where it 
is mixed with exhaust gases.

On a raw water cooled engine the thermostat opens at about 145 degrees. 
When it opens, water from the block and head is forced into the 
thermostat housing by the pressure of the water being pumped in through 
the water manifold. This cools and regulates the temperature of the 
engine. At the same time as the thermostat is opening it is closing 
against the boss or nipple which allows the bypass water to flow into 
the thermostat housing.  When the bypass is closed off, all of the water 
is being pumped through the engine and head, etc....

Good luck,

--Dan S.
#201 Watcher of the Skies, 1966, Cayuga Lake, Ithaca, NY

dans at stmktg.com
mobile: +1607-592-8012

Strategic Marketing Associates
403 Highgate Road
Ithaca, NY 14850


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