very odd cooling problem

[saxman47]

hey guys, I have searched up and down but haven't found anything that really describes my symptoms. Recently I was sitting in my car letting it idle (engine was already at full operating temp) and after 10 minutes or so I noticed my temp gauge was almost to the 3/4 mark, and my car never usually goes above half way. I shut her down and checked the coolant only to see coolant pouring out of the overflow resevoir. I let it cool down and drove it home (about a 20 minute drive) and everything seemed fine again. I'm not sure if it makes a difference but I did have the heat on when it overheated and I had bypassed the heater VSV a while back because mine is busted.

Anyway, today I decided to burp my cooling system to see if that fixed anything, so I put her up on ramps, popped the rad cap and let it run for a while. The coolant in the overflow was just above the full line but in the radiator itself it seemed a bit low.....as in I could see the tops of the fins. Well after about 5 minutes coolant just starts gushing out of the radiator neck....like not slowly overflowing but almost erupting a good couple inches above the neck. I let her cool down, tried it again, this time with the heat on full blast and a couple mintues after the engine reached operating temperature the radiator erupted again.

Anyone ever seen these symptoms? I would think a BHG would be more consistent overflowing......the coolant level was fine and then all of a sudden the radiator just starts gushing coolant. My car never lost a drop of coolant before either, and up until this incident my overflow resevoir has never puked all over the place. I should mention that before this incident, when the car was cold, I would get a slight bubbling noise behind the dash when I give it some gas....which is why I attempted to burp the system in the first place.

Thermostat? Blocked coolant passage somewhere? BHG?

any help would really be appreciated....thanks guys

edit: btw I did change my oil today and didn't notice any milkshake symtoms, so I have my fingers crossed

 

[TurboWarrior]

it could be a bhg. but if not it could be that the rad is clogged, and you need to take it out and clean the dirt between the fins and flush it with water. You should get a compression test to rule out the bhg. If it definetley is not change a bhg change the thermostat, clean out the rad, change the coolant if its old.

 

[GrimJack]

Sounds very much like classic BHG symptoms. Get a block test done on the coolant, if it fails, you need to replace the head gasket. The test should only cost a few bucks at a shop.

As TW mentioned, could be a clogged rad - but change the thermostat first. Then pull the rad, check that water flows through it properly and that it's not clogged for airflow. Then pull the water pump and make sure it still works.