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1987 454 How to Bleed Air from Thermostat Change

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CrusaderDave

New member
I am the proud new owner of a 1987 Tollycraft with 454 Crusaders (Model #350 SNs 64172 & 64175). I am changing the thermostats in an effort to isolate a problem where the starboard engine overheats at cruising speed. The manual does not articulate how to "bleed the air" from the fresh water system. I am able to locate the "vent screw" on top of the thermostat housing.

Is the proper way to bleed the air to open the vent screw (post thermostat change and reassemble) and with the engine running let the air vent until coolant comes out - indicating all the air is out? Then retighten the vent screw.

If not, any other input is welcome.


View attachment Thermo Housing w Vent Screw.pdf
 
The thermostat itself should have a tiny air bleed hole in the flange, which should allow any air to be purged up to and beyond that point.
I suppose that the housing bleed screw could be opened up as an extra measure.
No harm/no foul.


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The 'bleed screw' is best used for purging the air in the manifolds...as far as the residual air inside the cooling system, the best way is to run it at fast idle until warm, then let it cool and check the coolant level....it make take as many as three cycles to get all the air out.
 
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