I have a new rad and t stat on the sc300.
Car comes to temperature on the needle. Heat inside works, but I don’t have any pressure in the lower hose.
Thoughts?
Could be a radiator cap if it doesnt have pressure. Did you bleed air out? Maybe put the nose up on ramps if there is air
Air is still the system or maybe water pump is garbage? Maybe put the original hood back on the car? 
Waterpump and T Stat are brand new and the radiator is used but low miles.
The lower radiator hose is at the point of lowest pressure in the entire system.
Did you properly bleed the coolant system with a coolant bleeding funnel?
Yes
still guessing there is air in the system.
Yeah, I am going to try and jack the front end sky high and see what happens
try the bleeder valves yet?
i am having same issue in my car now. usually i just pour coolant in a funnel until it is full let it run until warm put that cap back on and then bleed it with the valves. this time it is not working though and my fans won’t turn on lol
so jacking the car up in the front while doing this will work?
I dont have bleeders on my radiator…just a drain. I still have not tried to remedy it…too cold to mess around with it
I dont know how your car is but I have one on the firewall and another on the intake manifold
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In trying to figure it out, I think I have to disconnect a heater hose behind the engine along the firewall…but I might just say screw it…blow the HG if it happens and put an LSX in it haha
i just finished mine today and it took like 2 hours yesterday and 3 hours today lol.
here is the method i used. this is s2000 specific so some things you may be like “wtf is this shit”
Fill the radiator with the front bleeder open
open bleeder valve on firewall fill with coolant until overflows. fill bleeder valve on intake manifold until over flows. fill over flow tank a bit. fill radiator with funnel and let run until warmed @ 3bars . turn off , cool for 1 minute. put cap back on.
let run for few minutes. heat full blast. if lower radiator hose is not hot use bleeder valves.
Close bleeder. Turn heat on high. Start car, idle to operating temp
TURN CAR OFF. Open bleeder slowly, air will come out. Squeeze upper radiator hose, addition air will come out. Close bleeder WHILE HOSE IS SQUEEZED. Release hose.
Open rad, fill to top. replace cap.
Run car another 2 minutes, shut off, repeat bleed above.
Repeat until all air is out, and heat blows hot air.
The key here is never open the bleeder with the car running. If you read carefully you will see at no point do you do so. All that will do is waste coolant, and stop you from getting the air out.
after doing all of this i found that it was still not blowing hot enough air lol. i let it cool a bit, took the radiator cap off and squeezed the lower radiator hose many times until the fluid in the radiator went down a bit. i then topped it off, and put more coolant back into the overflow tank as it had went into the rad from cycling thru.
did this twice and now it works.
you may be able to still do it without the bleeder valves it will just require more pumping of the hoses