C4 Throttle Body Coolant By-Pass

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is just another view of this procedure that was published 6/15/01. Horse
power can be increased by cooling the air that passes through the throttle
body, My ’93 routes hot coolant through the throttle body to prevent the
valve from freezing. The hot coolant also heats the air in the summer
months. So, if you don’t live in a freezing climate, here is a very
simple procedure that anyone can perform with a screw driver.
Lower the level of the coolant from the top of the engine by draining off
about 1 gallon of coolant from the radiator into a clean container (so the
coolant can be reused). This will prevent a coolant spill when you remove
the hoses from the throttle body. As an added precaution, pack a few rags
near the hose endings to catch any moisture that may remain in the hoses
(You want to prevent any moisture from entering the opti-spark unit which
is located just below the hose connections.
2. Remove the clamps
on each hose at the throttle body nipple. A 3/4″ ID hose enters the
throttle body from the right side of the engine compartment. A 1/2″ ID
hose exits the throttle body from the left side of the engine
3. Now you have two options:(a) connect the two hoses
together underneath the air-intake using a hose adaptor with a 3/4″ OD on
one end, and a 1/2″ OD on the other end.
Or, (b): simply plug the ends
of each hose using 3/4″ diam. and 1/2″ diam. stainless steel plugs (or
bolts) 1″ long. If you are using plugs or bolts, coat them with grease
prior to inserting them into the hoses. This will facilitate removal
later, if necessary.
4. Secure the adaptor, or plugs, using the
same clamps. Caps can be purchased to cover the throttle body nipples, if

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