My 2003 H6 3.0L engine is experiencing a coolant system issue.  At idle the heater blows cold air and if left to idle will start to overheat in a few minutes.  The coolant overflow tank was at the correct level hot.

The engine ran at normal temp and provided normal heat on the 50 mile hour ride to work this AM 

 

The engine has 200500.0 miles on it, 130,000.00 miles were put on in the last 3 years and are mostly highway miles.  Three weeks ago the steel crossover pipe leaked and the engine overheated.  I brought it to a local shop where they bypassed the pipe using hose.  The car ran fine and everything seemed normal except I smelled burned coolant for 2 weeks, that I wrote off to the bath the motor took when the pipe leaked.

 

My sense is the water pump is shot, but I hold out one last long shot hope which brings us to my question.

 

Do H6 engines need "burping" after a coolant change and would the lack of burping cause this problem 3 weeks later?

 

In my experience, overheating and the heater blowing cold has always been either low coolant (air block) or a failing water pump. Low coolant 95 times out of 100. 

Check the coolant level in the radiator when the engine is cold. It's probably still too low.

That's the root of my burping question.  Could the system be air blocked? Do the 3.0L engines need to be purged of air manually or does it do it on its own?  My 97 2.5 had a small plug at the top the radiator for that purpose.  I don't see one on this radiator.

 

UPDATE:  The coolant level in the overflow tank is unchanged even after the engine is cold.  Tells me systems is not sealed

This also explains why I smelled coolant for two weeks, it has a small leak.  It also explains the one bubble every 3 seconds in the overflow tank with the engine running.  It's to few  bubbles for a head gasket leak or cracked head; but a loose clamp on that bypass job will do it.

 

So gentlemen I believe you are correct low coolant.  I have a gallon of mix I'm going to add at next break.  Thanks for the replies.

Edited January 22, 201610 yr by screwbaru2

Needing burping could also make it not put af into the overflow or suck it back.

 

I have just always filled my 3.0 after draining with the front end up in the air on jack stands, always worked fine.

Could also be a gummed up radiator cap. The small metal cap in the center can get gunk on the back of it and prevent it from opening when coolant needs to be drawn back into the system.

If the outer seal gasket on the cap is damaged that can cause the same issue.

it's not the water pump.  modern Subaru water pump failure is nearly unheard of...at most they leak but you'd find the leak first and then identify the pump.  99% of the time they're replaced it's preventative or mis-diagnosed. 

 

get all the air out -  the H6's are nothing special with burping.  like any other subaru - take care and get all the air out. 

 

look for leaks and make sure the fans are coming on.

 

replace radiator cap with a subaru one, blow out overflow coolant hose, make sure it's tight to the radiator, make sure the end is free and not obstructed in the overflow tank. make sure the radiator cap sealing surface in the radiator neck is smooth and sealable.

 

bubbles in the overflow are indicative of an H6 headgasket issue but of course we have very limited info and you haven't confirmed any leaks yet.

H6's often exhibit random bubbles, random overheats, and can even go months between any syptoms at all and can take years to get bad enough that people finallly figure out it's the headgasket.