Anyone know where its located on a gs400 trying to search for this having issues plus at work but any help would be great got to try to burp the system make sure it isnt a headgasket issue

 

Do you mean bleed the system? If so this is how to do it to a GS430, don't know if it is the same for a 400. Remove air cleaner inlet. Start the engine and open the heater water valve. Maintain the engine speed at 2,000 - 2,500 rpm and warm up the engine. Stop the engine and wait until the engine coolant cools down. Refill the radiator reservoir with coolant until it reaches the full line. Install air cleaner inlet.

 

On a GS400, if you take off the engine cover. You will find a fill plug on top of the throttle body. If I remember right, you will need a ten millimeter allen to remove it. Stick a short wide mouthed funnel into this fill hole and fill it up. (Wrapping electrical tape to the funel will help "seal" the funel into the fill hole.) Don't forget to remove the radiator cap to let the air escape. This is the best place to fill the cooling system because the funnel will sit higher than the heater hoses. This is where air bubbles get stuck. If you have air bubbles stuck in this location. You can feel it when you push down on the heater hoses while revving the engine. You can also hear a girgling noise in the heater core/dash when you are sitting in the drivers seat and accellerating. DO NO START THE ENGINE WITH THE FILL PLUG REMOVED. Reinstall it when you are done filling.
I hope this helps,
-Will