Subaru Head Gasket or Waterpump?
Question:
Kevin
My Subaru builds up presure and blows the top pipe even with the radiator cap is of and it sounds like the water is boiling in the block i pulled the thermastat out tested it its ok then put it back in then i changed the radiator because i thought it mite be blocked but it still does it im pretty sure it ant the head gasket or cracked head that is the problem there is no water in the oil or oil in the water but i think as a resalt of it getting so hot. i think or hope it mite be the water pump what do u think
Answer:
With the engine warm, when you rev the engine, does the water level in the radiator go down? This would be an indication that the water pump is working if the level drops when you rev the engine. (don’t take the cap off when the coolant is hot to avoid getting burned, take it off before you start the car). This won’t tell you if the water pump is leaking though, and won’t tell you if it’s working at higher RPM’s. Sometimes the vanes on the pump will separate from the shaft and will keep the pump from pumping coolant at higher RPM’s.
It could be the head gasket or a cracked head even if there is no oil in the water or water in the oil. The head gasket can leak between the combustion chamber and the coolant passage and create excessive pressure in the cooling system. Also if the head is cracked in the combustion chamber area, as the intake charge is compressed, it will leak into the coolant passages and pressurize the cooling system. The only way to tell is to pressurize each combustion chamber one at a time and look for bubbles in the radiator. This should tell you which cylinder the leak is at. Most compression testers can be hooked to an air compressor to perform this test.
Good Luck,
Kevin
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