A4 Cooling
Pretty Good Rich. Here's how it works:
The bypass loop transfers coolant from the pump via the sideplate Tee to the top of the thermostat housing. If the thermostat is closed (cold, prevents coolant from leaving the head/block) the coolant passes through the top of the T stat housing from the bypass directly to the exhaust manifold through the short hose. Nothing or very little flows through the block or head. When the stock Holley T stat opens it closes off the bypass to the manifold forcing coolant into the sideplate, circulating coolant through the block and head to the bottom of the thermostat recess, through the open thermostat and to the manifold. Said another way, the head gets it coolant from the block. The thermostat housing is a coolant exit from the head, not an entrance.
As already stated: Moyer Marine has everything needed to keep the A4 running sweet. Yeah, $250.00 is too much.
http://www.moyermarine.com
Mike... Have you tried soaking that T-stat in vinegar overnight? Try that and then set it in a pot of water and heat it up. If it's functional you should see it open.
One other item for you to consider is the housing itself. If it's severly corroded in the inside it might prevent your T-stat from operating properly.