Cooling System

As you start to get into your Subaru conversion, one of the key areas to pay attention too is the cooling system. A number of cooling system configurations have been used - there is the KEP configuration that works well but is quite a challenge to bleed. The current Small Car configuration works well but some people in our colder climates have had concern about the engine running hotter when the heaters are removing a lot of heat. To address the fact that the EJ22 engine does not have a dedicated thermostat housing and to address the cold climate concerns, I have designed a separate thermostat housing and am using this in my 86 8 passenger conversion that I am working on in early 2005.
Based on Warren's comment I have revised concept 3 to put the burp tank in the heater circuit and thus eliminate any heat loss in the thermostat circuit. This is our best effort so far: This configuration is implemented in our engine test stand and works very well with about 15 Deg F temperature drop in the heater coolant returning to the water pump - engine temperature stays steady.
Note: - the line to the dedicated thermostat housing should not be larger than 3/8 inch. This 3/8 inch line provides all the heating necessary to open the thermostat in cold weather. - The connections to the heater circuit should not be any larger than 5/8 in. In cold climates, if this connection is any larger, and the heaters are On full blast, the engine may never reach proper operating temperatures. - The valve in the SC type bleeder line can be very small 1/4 or 3/8 inch ball valve. This valve can be virtually closed after the air is bled out.
Here is another very successful cooling arrangement using the dedicate Thermostat housing: This is the configuration that Peter/Dieter used and they have reported excellent heat from their heater with No overheating of the engine in very cold weather. They are going to modify their Syncro skid plate to avoid the interference with the thermostat cap. Thanks goes to Dieter and Peter Miller for their testing and feedback.
Here is what my thermostat housing looks like:

This picture shows the thermostat housing loosely assembled to a water pump.
For details regarding the thermostat housing please click - Thermostat housing A small quantity, of the housing, are available for purchase.


By the way - do not be fooled into using after market thermostats. The small after market one was removed from an EJ25 vehicle I was servicing - with cooling problems. USE OEM THERMOSTATS only.