My heater core was unplugged because of leaking. I am afraid to change it now (heard many stories about changing heater core on Imprezas). Can this be a reason that my car constantly getting overheated?

My heater core was unplugged because of leaking. I am afraid to change it now (heard many stories about changing heater core on Imprezas). Can this be a reason that my car constantly getting overheated?

When you say "unplugged", i hope you mean it was simply bypassed. If it was bypassed properly and there are no leaks then your car is not over-heating because of the heater core. If the place where the hoses were spliced is leaking then your engine will eventually seize since you'll run out of coolant.

If and when you bypassed the core did you "BURP" the cooling system very, very well?

I would take a look at why the heater core failed. Most of the time, they fail because of poor cooling system maintenance, which is also going to do a number on the radiator. I would guess that the rad has a bunch of junk in it, which is causing the overheating problems.

 

Does the car overheat during low speed driving or high speed driving? If it's high speed, I would bet money on the radiator needing to be either flushed or replaced.

My radiator (together with water pump and thermostat) were replaced and cooling system was flushed with chemicals. After that heater core started to leak.

 

I didn't "unplug" core myself - mechanic did. I saw him unplugging hose that goes to heater core.

 

I didn't notice any loss in coolant since that time.

 

 

Car overheating mainly on speeds less then 40 MPH, but sometimes it also happens on highway.

thermostat

If any coolant was lost period then you have to burp the system! Just do it and see what happens.

in my young and broke days... I would say usually when you bypass a heater the temp goes up a bit on the gauge but it does not boil.

If you were borderline before it is possible that this could put you over the edge but it means that something else is wrong. There is a bit of leeway built into the average car's cooling system to make up for being run in hot climates and the wear that happens over the years.