If you look at the picture on the upper side of the T-stat seal plate on the right upper side. It is hidden but you can se a piece of medal sticking up. That is a piece of medal is sticking througha hole that seals the hole when pressure is applied (water pump pressurizes). But when there is no pressure the small medal plug falls down and allows any air that might be trapped between the manifold and the T-stat neck to be released.

Some people drill a small hole in the seal plate to allow air out. I don't recommend this. You can just buy it with the bleeder.

As for the head issue; Yes there is a problem with the 52L/5.9L heads cracking. This is due to the old castings that Dodge continued to use on these motors. Problem is these head casts were made way back when and they used 180 degree T-stats. Well the same molds were in use for todays. Problem is they run 195 degree T-stats for emissions. They just don't hold up running that kind of temps that they were not meant for. Thiswas oneof the reasons for the Hemi.

Anyway test a T-stat before installation. Use a pot of water and a thermometer and make sure it opens when they are supposed too. Do not over heat them because the spring can relax causing issues.


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Hydra, I'm going to add a little to this if you don't mind. If you replace that thermostat, do not buy one from autozone. We did and the medal piece hydra is referring to is not on their stats. However, they do have the correct stats for a couple of bucks more at O'reilly's.

Ang

 

Ya, you need to look at em.

I really prefer these over the others. The 5.2L/5.9L do not have a bleeder on the side of the housing so it helps out great bleeding the system.