Hi scotty, i have Seat Leon 2003 , 1.8L, 170000km, automatic. opened up the hood and discovered coolant reservior is full to the top. i emptied the reservior to half way, started the engine and the coolant is rising slowly to the top and i do not see any flow from the return hose to the reserviour even at high RPM. worried about overheating issues that it can cause. Thanks very much.
You gotta clog somewhere. Start buy flushing the radiator. There's a radiator flush fluid that you can buy and you just mix it with distilled water(BE SURE TO USE ONLY DISTILLED WATER if you do this) You put that in and run the engine for about 10 min or so and drain it all out and then before you fill it up with coolant just fill it up with distilled water and see if you get the same problem. If it keeps happening you have a SERIOUS clog somewhere squeeze the coolant lines and see if theres anything stuck in there(I doubt it but you never know) and if all fails your going to need to take it somewhere and it professionally flushed and inspected. GL with the flushing hope it helps!
I would recommend doing the flush/air purge procedure for your vehicle first and then report back.
By the way the radiator and waterpump replaced 4000km ago. thermostat hasen't been replaced. haven't done flush or purge yet but discovered something new. while driving the engine does not overheat. the coolant still keeps rising in the reservior and still no flow in the return line. after i shut the engine off and slowly open the reservior cap a little bit ( which i know is dangerous and never dared to do), i see coolant finally flows in the return line which i thought was clogged and after sometime the level drops down to halfway of the reservior. is there an explanation for this ? thanks.