I just replaced the stock d15b7 for a jdm d15b and it runs just fine but it starts overheating right away, and the cooling fan does not come on. the temperature readout is not accurate and the car does not idle high when its cold it idles at 800 then 600. coolant levels are fine, a little black smoke came out but that might be left over from the old oil burning engine. Both coolant lines become hot so thermostat is functioning on a basic level. The car also has NO POWER. i punch it and it takes forever to accelerate. no white smoke coming from the engine and the black smoke has cleared up. the new motor has up to 45k on it. Any thoughts?

 

also it idles normally and doesnt die or sputter just takes a while to make power

 

thirdly the Check engine light is not coming on.

 

How do you know that the temp readout is not accurate? Is your timing off? Retarded timing will cause an engine to overheat...

 

retarded timing would explain loss of power

 

the timing was adjusted because the car would only start on full throttle and would not rev past 2k. so the timing might still be a problem

 

if it overheats right away its either going to be a bad head gasket or water pump, im thinking its a bad water pump

 

If the fan does not come on, have you tested the thermo switch to see if it is working? For the water pump, pop the radiator cap (when cool) and give it some gas (will need a friend to help), after the thermo opens up, you should see water being pulled down into the radiator. If the bottom hose is as hot as the top you need a new thermostat, same goes if the top is hot and the bottom is cold.

 

it appears the water pump is doing its job. not sure on the thermo switch...but like i mentioned both coolant hoses get really hot after a few minutes

 

Its probably not your cooling system, though I would probably replace the thermostat, if it has been a while. I would also look into why the fan is not kicking on. I would look into timing retardation as your main issue. How many degrees before or after TDC are you currently running it at?