Put the thermostat in boiling water and see if it opens and how far it opens.

Edited November 28, 201510 yr by mikaleda

its opens all the way. i even ran the car without the tstat and it still boilsover.

if i do a pressure test on the engine by using a tool tat connects to the spark plug ports. should i be able to know if the gead gasket leaks? what is the safe amount of psi i can add to an engine? maybe the block has a small crack. im losing oil but very little.

if i have to much coolant and not enuf water would the car overheat? cause i just did a coolant test and it was of the charts it will freeze beyond -40 i dont have a 50/50 mix right now. it is mostly antifreeze would tat cause overheat?

Edited November 28, 201510 yr by legacysus

Sounds like your not getting all the air out the system. Start by pulling the upper block hose and filling the block first. There is also a vent on top of the radiator by the top radiator hose the needs to be removed when filling. You can mix your antifreeze up to a %70, mixture without any real issues. I suggest burping the system again and seeing what happens.

i blead the air out once again. i filled the block 1st. then i filled the radiator with the air plug removed. and i burbed it again. in the process of this a found the tip of the radiator adapter that connects to the upper hose stuck in the hose creating a blockage. there is still a small piece missing it must be stuck in my radiator hopefully its not stuck in my heater coil. going to check the flow of the radiator tommorow. car still overheats. can a pressure test be done to check my head gasket?

Edited November 30, 201510 yr by legacysus

I don't beleive there is any way to do that. As many issues as your having its sounding more and more likely its the headgasket. When its starting to overheat pop the cap on the resiviour and look for bubbles

Dont they make a diy hydrocarbon test for the head gasket leaks we get?

When a 99 Subaru Leggie with the 2.5 motor develops a bad head gasket, it starts out as a "some times" over heating problem. It was that way on my 99 OBW, which has the same engine as yours. Your best head gasket test is to immediately look for bubbles in the radiator over flow tank, when it begins to over heat. If you see bubbles, then it is certain that the head gasket is bad. Be aware, that you may not see bubbles when the motor is running, but not over heating. At that moment, your bad head gasket is not leaking, but only waiting to rear its ugly little head to cause you a problem in the near future.

 

As I have read, the problem is that Subaru designed the motor, so that the pistons actually raise up just slightly above the block at top dead center. So, to address this, Subaru made a super thick head gasket to seal the heads. However, over time, the thick head gasket becomes defective to allow exhaust gas to enter the engine cooling system.to cause over heating. Again, I read that Subaru has over time designed three different upgrade head gaskets to fix the problem. The latest and greatest head gasket design has held up for me for the last 3 years. Opinion on this forum, is that replacing the head gasket should solve the problem for 100K miles. Beyond that, it may be time again to replace the head gasket, if it starts acting up again..

 

I am not aware that a vac tool, or hydra carbon strips are much help in diagnosing bad head gaskets on a Subaru, maybe so on other makes of cars .Doubt that your radiator is bad. If so, you would have a constant over heating problem. You don't seem to have that.

 

After 1999, Subaru redesigned the 2.5 engine to fix the problem.

if i have a leak on my air intake manifold gasket would i get bubbles in my cooling system?

"What common symptoms indicate you may need to replace the Intake Manifold Gaskets?

Engine overheats.

Coolant leaks.

Red, green or yellow fluid underneath car.

Engine runs rough.

Check engine light is on."

If the intake manifold gaskets get leaky, coolant gets sucked into the intake. Or leaks out on top of the engine. There is no pressure to push air into the coolant system. You do end up with some air, since during cool down, the coolant system draws negative pressure. This would pull coolant from the overflow tank normally.

 

These typical headgasket failures when they are still in the realm of small / slow leaks do not show up with a compression test.

could the rad fans be intermittent? When it overheats, are you cruising down the road or does it always happen at a stoplight/railroadXing/idling? bad fans will allow overheating at a stop or very slow speeds - on the highway - air is moving thru just fine.

 

you might be able to 'map' the radiator with an infrared remote therm - maybe the radiator has cool areas because it's partly clogged.

 

how old is the timing belt? maybe the car has slipped a tooth and is not running at correct crank/cam timing - or the back-side of the belt is glazed and the WP is slipping?

Edited December 11, 201510 yr by 1 Lucky Texan

Not sure if you found your issue but I had a 2000 legacy with spuratic overheating. The headgaskets were good. Pulled the motor took the heads off and the block and heads, mostly on the 2 and 4 side appear to have a concrete type substance. The shop and I determined that it was most likely an overdose of stop leak. Since it wasn't me it must have been the previous owner.