My coolant reservoir keeps overfilling I recently change the knock sensors last month and changed the coolant but every now and then my reservoir goes past the full line even though I don’t add any coolant to it. My car is currently at 200,619 miles and when it over fills my car does this weird thing we’re it shifts to gear and then just stops and then releases. Not sure what it is I was wondering if you guys might now

 

Coolant îs incompressable and expands in volume due to temperature, but it should not expanding this much. Please make sure that you have purged air out of the coolant.

Re-examine the hose connections. There is coolant line to the throttle body. Another potential cross over is the gasket sets. I assume they are fine as the engine runs else you would loose compression.

Salim

 

yeah I haven’t gotten any misfire or anything it’s just my reservoir keeps going past the full line. So you said I should check that coolant line that goes under the throttle body and how do I purge the air out?

 

There are many posts on purging air .. please check the DIY thread on radiator drain fill.

Essentially you let the engine cool down and open the radiator cap. Start and let the vehicle warm up. Observe steady flow in the radiator and while the engine in running slowly add coolant. Squeeze the hoses to rid of trapped air. top of the overflow tank. Also move the cabin temp up [heat]. After about 15 minutes make sure the level is full in the radiator cap the radiator.

Also make sure the high-pressure overflow tube by the radiator cap is clear.

Salim

 

When my ES300 did that, it was a bad head gasket. There was a tiny leak that would leak exhaust into the cooling system, and it would increase the level in the overflow tank. You can buy a kit that lets you test for that, to be sure.

 

Very possible after knock sensor change specially if new gaskets were not used. There is a possibility that the leak is mixing oil an coolant.

The test mentioned above, pressurizes the coolant and if it leaks and does not drip on the outside it is leaking inside. Chamber leak down down test is another method but then you have to figure is the valves or the piston is leaking.

Salim

 

That is not the test I use. This test involves a dye chamber and you start the engine and let it run and the exhaust fumes come into the bottle and let you know that it is leaking. Also, you do not deal with the head gaskets when you are changing knock sensors. Only the intake gaskets.
https://youtu.be/wcDe2QYN8As?si=FJLwUCd1rY16RR3X