2000 Lexus Es300 Thermostat Trouble

[carpetman112]

I'm trying to change my thermostat on my es300. I was first told to follow the upper hose to the housing so I took everything apart there to find out that's not where it is. I now know that it's on the lower hose. It doesn't look very easy to get to. Any tips to help me through with this? Never changed a thermostat and don't want to screw this up. The car won't shift into overdrive and a local mechanic told me this could be my problem. Any ideas? Thanks in advance.