Re: thermostat nightmares
Don?t know if anyone has tried this for testing thermostats, but it worked for me.
For those like me who have the ?bubble back? cross-flow V4 (mine is a Johnny ?98 115 SPL) who suspect they may have faulty thermostats, the manual suggests removing the Tstats and putting them in a pan of heating water to test them?.but as we know, removing the Tstats from these engines just aint that simple and can be risky (they are located in the exhaust housing adapter under the exhaust housing on the aft side of the engine, below the lip of the lower engine cowling?hard to get to, bolts can break, etc?.). Here?s how I tested mine in place.
When closed, the Tstats stop water from exiting the cylinder head water jackets and flowing out of the engine. So you should disconnect the cooling hoses from each cylinder head cover but leave them attached to the Tstat cover (both sides), and rotate them so they are both pointing up. Of course if you pour tap water into the hoses, the thermostat housing and the hoses will fill up to the top and the water will stay there because the Tstats remain closed?..so instead, heat some water on the stove to the upper range of the thermostat?s opening temp using a cooking thermometer or a laser thermometer (my Tstats are supposed to be open by 136-144F) . Pour the heated water into the tops of one or both hoses until they are full?..if your thermostats are good, the water will drain through (because the Tstats open). If they are bad, they either won?t open (water won?t drain) or they?ll open at too high a temp (after repeated testing) and should be replaced.
Using this method allowed me to test the thermostats sufficiently so I could rule them out as a problem with my cooling system (my water pump was worn and was not cooling at slow engine speeds but was fine at higher speeds).
Hope this helps someone out there.
