roppa440

Quick question.
Which hose is the RADIATOR outlet on the LS1?

Top or bottom?

Thanks in advance.

tentuna

Bottom, all radiators flow top to bottom. thermostat open heated coolant flows into the radiator and returns to block through bottom hose.

roppa440

But the thermostat is in the bottom hose on the LS1. Which is why I am asking.

Also I am sure I read somewhere that on the LS1 the heads get the cool water first. So I am a bit confused.

C6_Racer_X

On the LS1, the thermostat is in the return hose to the water pump. The working part of the thermostat is in the bypass return passage into the pump and senses engine temperature there. When it opens, it allows cool water from the radiator into the water pump inlet (suction side).

roppa440

So the thermostat is in the return hose to the water pump, which is the bottom hose, which makes that the radiator outlet. Have I got what you are saying right?

roppa440

You see to my mind the thermostat holds water in the block until it is warm enough. Then opens and let's water OUT the block to the radiator. So with the thermostat being connected to the bottom hose that to me suggests that the bottom hose is connected to the pump outlet. Therefore the radiator inlet.

Am I completely wrong here?

C6_Racer_X

You're not completely wrong. You're only wrong for some engines.

The Germans (VW/Audi and Mercedes Benz for sure) have had the thermostat at the water pump, in the return (lower) hose from the radiator. They place it with the operating parts (the pellet/spring) in the bypass coolant path so it gets flowing coolant from the engine while the engine is running and warming up.

I'm fairly certain The LS1 family (including the iron block truck engines, as well as the later LS2 family) uses this type of thermostat arrangement. The LSx engines also pump water into the top of the heads and draw hot water out of the lower part of the block into the bypass passages and the radiator. So everything is "backwards" on the LSx engines.

roppa440

OK thanks for that.