I own a 91 ls400 when for a drive and it started spraying water from the radiator cap overflow the cap it self has a pressure release button I turned car off let it cool down and as it was I noticed it sucked the water tank dry but when I released the pressure to take the cap off it filled it self back up there are no leaks and its done this a couple of time over the last couple of weeks but the heat gage is sitting under half way so itss showing its not overheating would this have anything to do with the water pump or thermostat any help would be grateful

 

Sounds like a bad radiator cap to me. I think you only need a new cap.

 

yep, change the cap to a regular unit preferably OEM. the OEM units do not have a pressure release button on them.

 

Those ****ty "Locking radiator caps" are a weak link. That red lever leaks quickly, and they cost more. Just get a regular autozone one and move on. The little seals around the handle get all wacked from dicking with the lever and then they spray.