rebuilt 420a overheat problem

[sandiballs287]

Alright.. i recently had my motor rebuilt by Precision Machine shop. only the block and head and they put it together and timed and all. All i had to do was put all the accessories on then slap in the car. new thermostat upper and lower hoses the water pump is new and was installed with the long block. the radiator still stock. its been over heating after 10-15 min after i take off BUT only if i stop at a light for a min. if im driving down the highway its at normal temp then creeps up alittle then goes back down. a week ago i took off the thermostat to see if it would run better and it did only for alittle bit. as of now its still off. i changed the coolant temp sensor last night and its still creeping up. ive checked the flow of coolant by opening the radiator cap and has and keeps fluid flows good. but every time it creeps up alittle i turn on something electrical like the a/c fan and it goes up more. turn on the headlights goes up more and press the brake lights on and its all the way up there. fml. so its all the way up there but i noticed also that when i turn off the car then turn the key one click with out turning on the car the temp guage reads normal.

please someone help me i dont know if its an electrical problem or a heating problem.fml

 

[VelocitàPaola]

Is this question about your GSX, or do you have a 420A as well?

 

[sandiballs287]

i do have both. i think its pretty obvious

so i drove my 99 GS home today and it was overheating again but not as much. while i was driving i turned on my a/c and again the gauge goes up but then drops alittle bit. but when i got home i noticed it creep up and my fan didnt kick on. anybody know which fan is supposed to kick on to cool the engine down and how it does. when the a/c is turned on both fans turn on. i cant seem to figure it out

 

[EglTalon_ESi]

i believe the fan for cooling is the right fan. is the rad fins clogged or full of dirt? you say the gauge moves up when when you turn on the a/c, headlights etc... can it be a possibility there is a short somewhere from sensor output to gauge?

 

[sandiballs287]

the rad fins looks clean and no major damage. it does seems there is a short somewhere or something. it does go up and down slowly when i turn something on. how can i test for that.


last night i put the thermostat back on and tested the connection of the smallest thermo sensor and the guage read high. i pretty much grounded it out. then i put the sensor while connected in a pot of boililng water and even went up 1/3. i also checked the t stat the same way to check if it open and it was good. so i put everything back together and started the car. the block was cold before i started it. both fans come on on start. not even a min goes by and it hits normal operating temp. then its starts creeping up with fans on. as its running and creeping up i open the rad cap and no pressure is there and thermostat hasnt opened yet. about 3 min went by then saw the t-stat open and the coolant flowing. so it seems the coolant system is fuctioning correctly but with the wrong indication. could it be the gauge cluster?


i drove it today and the gauge was all the way up there at the red so i kept both fans on with the a/c. did not come down lower than 7/8. IF the engine was actually overheating there would be smoke from the rings frying up out the exhaust. am i correct?

somebody told me about a thermo switch. where is that? what is its function?

also does the sensor to the gauge go through the ECU?

 

[VelocitàPaola]

i do have both. i think its pretty obvious

If it were obvious, I wouldn't have asked.

Perhaps a copy of the electrical portion of the FSM would be helpful to you:

Download Useful Files - SymTech Laboratories

 

[EglTalon_ESi]

well you have a electrical/sensor problem going on there then if the gauge is reading normal temp from a cold start.

 

[sandiballs287]

thanks VelocitàPaola. that schematic helped me figure out that the temp sensor was linked somehow to my speed sensor which was bad. $87 later i semi fixed it. the gauge would still go up alittle then as i was feeling around on different connectors i notice the ground bonding wire, from the intake mani to the body, was hot. i wasnt connected properly so i added another thick gauge wire and connected them both properly and BOOM problem fixed. the gauge works perfectly.

but as i was driving it today ithe gauge crepped up to 3/4 but no fluctuation when i turn anything on. so now im planning to do a radiator flush.

 

[sandiballs287]

alright.. so after i changed the VSS and reset the computer. the check engine light came on again. it was due to the AIT( air intake temperature). so i changed it. after a drive to work the temp gauge went up and threw the same code. since i have a aem short intake pipe it sits right in front behind the radiator. the temp gauge only goes up if i sit for a minute or on continuous stop lights. it goes back to reg temp when it get some air through the radiator.

when i was at home coming from work i let it sit running and my fan dont turn until the gauge goes up above the half. when it goes up more the second fan kicks on.

can any help to see what it is.
is it the radiator or what.

 

[sandiballs287]

just to put it out there. the overheat problem was caused by the coolant temperature sensor being the wrong part. i purchased one from advanced auto parts and the temp was goin up. i replaced it again but with a stock one from a junk car and it works perfectly now.

so beware, if you have the same problem make sure you have the right temp sensor or just go to your local junk yard, they are the same on all 420a motors. have fun

 

[starfish]

glad to see somebody making progress