I've installed a used LS2 (2005 GTO) in my 57 2dr hardtop. I installed a new water pump and thermostat prior to installation and initial engine run in the vehicle.
Upon startup, I was hoping to top off the coolant and ensure no leaks, etc. However, the thermostat did not appear to open, the upper and lower hoses stayed cool. I was concerned when the engine temp started to get over 200 and climbing so I shut it down.
I pulled the thermostat and ran the standard thermostat test in a pan of heated water and a thermometer. The thermostat is an 86 C (187 F) model and opened around 190 F and was fully opened around 195 to 200 F.
An inspection of the thermostat and water pump fitup showed that the thermostat bypass flange actually made contact with the water pump bypass opening when I held it up to the water pump housing (I actually had to compress the bypass spring to get the thermostat to fit into position in the water pump), effectively shutting the coolant bypass off (at room temp). I would have expected there to be a clearance between the bypass flange and the bypass opening when coolant temps below thermostat activation temperatures.
I am guessing that this is why I'm not seeing proper thermostat operation. Not only is the bypass closed off on a "cool" engine but could the extra bypass flange spring pressure against the thermostat actuator keep the thermostat from opening at the proper temperature?
I double checked the thermostat part # and also checked the dimensions provided by Rock Auto with my thermostat and it appears to be correct for my engine. That would appear to leave the water pump as the culprit if my assumption, bypass should be open at room temp, is correct.
I'm wondering if I was sold the wrong water pump? Is anyone aware of differences in LS water pumps where the thermostat bypass depths are different for different engines?
I could change out the water pump or find the correct thermostat to go with this water pump if my assumptions are correct.
Hope this all makes sense and really hoping someone may have some information to help me resolve this issue.
Thanks in advance, Mike