Hey guys, wanted some opinions please...

I'm topping up my water far too much. When I top up the header tank, do a few miles out takes it through to the reservoir, but not back, to the point of the reservoir filling up to the top nearly! The rad is full too. It's not over heating or has any steam or smoking! Might this need "burping" as could be air in the system?

Tried leaving both header and radiator caps off one night, all night with both full and car at an angle as advised by my mechanic, but no joy unfortunately

Any ideas???

Subaru STI, 2016, 68,000 not thrashed!

 

There's a very specific way to change coolant and avoid airlocks, but you don't state when or if that's been done. I'm guessing your mechanic doesn't specialise in Subarus? Coolant overflowing from the reservoir isn't a good sign, but not always fatal.
After a decent drive, and cool down, is the top reservoir low?

 

Hi yeh, sorry it hasn't had a recent coolant change and no my mechanic doesn't specialise in Subarus, but has worked in mine for last 10 yrs or so.

So yeh the top tank gets lower after a few longer drives (like 30 miles plus) and the reservoir fills, I've added 2 pictures to show what i mean

 

unfortunately that would generally indicate an over pressure issue, commonly head gasket problems!!

personally I would fully drain and check the Thermostat, etc and then correctly refill and see if it continues or its got an air leak / split hose / etc??

 

Get a new header tank cap first/too

 

Thanks for that, yeh replaced both rad and header caps (genuine subaru). Today I "burped" to try get any air out. I know people thinking head gasket but the most common things associated with that I'm not having, no over heating, no gunk in oil, no white smoke etc

 

you will rarely get any classic water / oil mixing symptoms due to the design of the Boxer engine which means if you do then the engine is catastrophically compromised!!

IMO "burping" isn't much use and you need to chek you don't have an air leak / lock and then fully drain down and refill correctly to rule out

 

i had the same issues with my old hatch. changed the caps and header tank etc. but eventually it did start overheating thus ended up being head gasket. after a drive id let it settle for 24hrs to see if any water has drained back into the header tank. if it hasnt, id have a test done to see if you have a gasket problem. to me it doesnt sound good