Sounds like there could be an air pocket or even a failing head gasket.
We need to start with checking for a head gasket issue but the fact that the temp is coming up and down shows the system is able to cool the engine but once it cools down, it just heats again because it is running hot. Basically these types of issues only get worse so it best to try and find it now before it gets worse.
Here are some guides that will get us up to speed. Does it still have white smoke?
https://www.2carpros.com/articles/white-smoke-or-steam-coming-from-the-exhaust-pipe
https://www.2carpros.com/articles/head-gasket-blown-test
https://www.2carpros.com/articles/symptoms-of-an-overheating-engine
https://youtu.be/071_-NGrk5s
If the temp is going up and down then the fan is responding to engine temperature which is most likely what is cooling it back down when it kicks on.
If the head gasket passes then we need to pressure test the system and make sure there are no leaks and that it holds pressure.
If it does then I would suggest just changing the coolant and bleeding the system so that we ensure there are no leaks.
https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars
Please run through all this info and let us know what you find.
Thanks
SPONSORED LINKS
Sunday, August 8th, 2021 AT 9:09 AM