Plugged return line from overflow tank?

 

The way I was always taught to diag. overheating problems was (if you have to replace something) to start with the cheapest and work your way up simply because obviously the worst case scenario is HG's..First....Are your cooling fans cycling properly? If they do cycle do they blow hot air? How many miles are on the car? Any recent cooling system work done on the vehicle? If so are you sure all the air is out of the system? do you have any coolant leaks? modifications to the vehicle? I dont mean to throw red flags but the symptoms your describing are typical of a blown HG...Ive seen it hundreds of times...however The Turbo models never really developed HG problems....as said we cant really tell you much until the few questions above are answered...you could always do a cooling system pressure test that might be of some help...

 

Hmm, though if was a blown HG, don't you think the coolant ending up in my overflow tank would be dirty? The coolant in there is just as green as when it went in . The car has just over 120k on it. No major coolent work that I know of has been done to the car, (just got the car running). The fans are cycleing fine last time I checked (just to make sure, I'll run out and check them again). It has a few mods, but really none that would affect the cooling system. No coolant leaks, just what spills out the top of the overflow tank.

Also, when the car is at good running tempature, and I turn it off, I hear this bubbleing sound from one of my turbo coolent lines, I grab the hose (ow, it was hot :tongue I swear the coolant was practically boiling, I could feel it. But my temperature gauge was reading normal. I noticed this before I noticed the overflow tank problem, I don't know if this is unrelated or not.

 

Not necessarily Ive seen subarus before that have coolant looking new with blown HG's..As i said i have doubts it being a HG problem...from the info youve given I will say three things water pump failing, clogged radiator, thermostat stuck...do you have a CEL on? I would def. check that the fans cycle first though....Obviously your going to hear the coolant bubbling becuase its overheated...Man your getting really hot the boiling point for 50/50 is 265 F....Im assuming you shut her down when the temp rises? until you get the problem resolved...

 

Either the thermostat is bad or there is air in the system.Generally you only get air in the system when you do a coolant change or you fill up a drained radiator.Blown headgaskets eat coolant,not over pressurize it.The tale-tell sign is also discolored oil.Pull the dipstick and if it looks like yoohoo you have blow a head gasket.FYI-overheating conditions cause aluminium heads to warp = blown head gasket.So if you don't have a blown head gasket yet,you will if you keep driving the car in the state it's in.

 

I wouldn't think that it would be a bad HG because my plugs are clean, the oil is clean and I don't ever see any smoke comin from my exhaust (even though I am burning a little oil).

Even though the coolent is boiling from the turbo, my gauge is reading normal and cool. It has only overheated fully once, I pulled over and saw my radiator and turbo were both empty and I had coolent comin out of the overflow tank... filled it up with water at a gas station and drove it home fine where it has been sitting ever since....

Could the reason be that the coolant (well now water I guess which has a lower boiling point) be boiling and the gauge staying normal, is because it is reading the air in the system rather the coolant?

I have no CEL on. Though I dunno if it would be an air bubble in the system, because I flushed it myself at my old job (we had a pressurized flush machine) but the machine was a POS, so maybe I will try flushing it again. My friend is coming over tonight and were gonna run a pressure test on it, so I am preying it is not the HG... I just put a new transmission in this thing.

Also, would the water pump be an option?

 

After your pressure test..depending on the results...If I was in your situation...I would jack the car up...flush the coolant out of the block and radiator reinstall core plug and pet****...add the proper mix 50/50 coolant (distilled water) and warm to operating temp (make sure the fans cycle on and off)...Straight water does have a lower boiling point than 50/50...Personally I wouldnt even start diagnosing this problem until the system is full of the proper mixture...

 

Yeah that is a good idea, I'll do that tomorrow. Though I have a hinting feeling that it is the thermostat. Why I say that is because today I opened the radiator cap and turned the car on while it was cold, after the car warmed up I gently revved the engine and coolent started spraying out the top of the radiator.

So my thinking is, that it is not the waterpump, because it is pushing the coolent out of the top, the thermostat is seized up not letting it flow through, so I was also gonna take the thermostat out tomorrow and see if that solves it.

 

you could also tell if your thermostat was stuck if your cooling fans would come on at the proper temp and never shut off...just make sure you get a Subaru OEM thermostat...

 

Yeah I ran the car today for a good solid 20 min out front my house and the fans didn't come on once. I checked the relay and it appered to be fine. Although I have a piggyback ECUtek on there and I don't know if that could be the reason. I have only had this car since early october and I just got it up and running a couple of weeks ago.

 

well look at it this way..each fan on your car has seperate relays so what are the chances 2 or 4 (sometimes) relays would go bad at once?...I would jump the fans to make sure they both work..otherwise i am going to say coolant temp sensor...was your lower hose hot and pressurized after you let it run for 20 min.?

 

Hello!
I seem to have same problem on my Impreza STI 2006 2,5 206kw. Can you please tell me how did you fix this and what was the exact problem that caused this?
My car coolant temperature is allso normal but coolant boiles in the turbo coolent line and I can allso see it in the overflow tank.

Sry about my english!
Kermo
from Estonia!