About a month ago I took my 07 Lexus ES 350 to an auto shop to have the water pump replaced because there was signs of water leaking and because it was getting hot. While we were doing the paperwork I mentioned to the worker that if he seen anything else that needed to be replaced to just bill me for it. In which he agreed. I get a call 4 hours later from the shop telling me it was done and charged me $800 and change. No problem paid him and left. A few days ago I noticed that the car started getting hot. So I give the mechanic a call and asked him if he replaced the thermostat. After checking his computer he noticed that the thermostat was not replaced and he did not bill me for it. His response was he did not have to take off the thermostat or the housing to replace the water pump. Can somebody tell me if this is true? Because the videos that I have watched looks like the water pump housing has got to come off in order to replace the water pump. Can somebody please help me with this I'll be waiting patiently thank you so much

 

You may have heard him wrong. The housing has to come off but it is a two part housing with the thermostat sitting inside. The housing does not need to be separated to replace the water pump.
Did they fix the overheating? Did they not adequately bleed the system?

 

They probably failed to properly bleed the cooling system. Take it back.
It is unlikely your thermostat decided to fail so soon after the water pump was replaced. However they should have replaced it while they had easy access.

 

A similar situation happened to me where I paid for a coolant flush and the engine started overheating afterwards. The radiator started leaking and I got it replaced. A few days later, the radiator hoses blew out. I took it back and they replaced both hoses which still didn’t fix the issue. Eventually they changed the thermostat and it was back to normal. I can’t say for sure if the original work pushed these parts to fail or if it was improper work like failing to bleed it correctly.

You would think a seasoned mechanic would advise replacing easy access items alongside a repair, but that is not the case. You have to be informed enough to tell them to. Be careful who you trust to do work involving the cooling system. In my case, a simple coolant flush almost resulted in a blown engine.