Blown Head Gasket?

oregonjoe · 09-11-2009, 04:15 PM

I am in the middle of fixing a HG leak on a 90 Supra. It started off slow coolant use with no other noticeable symptoms then grew to pushing more coolant out the reservoir and running ruff on start up.

A few things to look for. Engine cold – start up with radiator cap off and coolant above the fins (not all the way to the cap) As the engine warms up the coolant will rise just a little if normal till the thermostat opens. After the thermostat opens you see water moving around but level should remain the same and no bubbles or foam. If you have a head leak it will bubble and foam and soon the coolant will start to push out the radiator opening.

You can also do this test after the engine run for awhile but let it sit and be very careful to open the cap slowly as very hot steam will come out and is painful. Again the coolant should be at normal levels and not gush out.

Another thing to look at is the plugs. They should all be nice and tan and dry. If one of them looks like a different color (usually the same as the coolant) then it is probably burning water. Start with number 6 cylinder as that is the most common.

Retorquing the Head bolts on a already leaking HG will not do anything as the coolant is already eating channels in the HG, block and head. Old coolant is a very nasty acid!

09-11-2009, 04:15 PM	#2
oregonjoe 3" Exhaust Join Date: Aug 2009 Location: Southern Oregon Coast Posts: 83	Hg? I am in the middle of fixing a HG leak on a 90 Supra. It started off slow coolant use with no other noticeable symptoms then grew to pushing more coolant out the reservoir and running ruff on start up. A few things to look for. Engine cold – start up with radiator cap off and coolant above the fins (not all the way to the cap) As the engine warms up the coolant will rise just a little if normal till the thermostat opens. After the thermostat opens you see water moving around but level should remain the same and no bubbles or foam. If you have a head leak it will bubble and foam and soon the coolant will start to push out the radiator opening. You can also do this test after the engine run for awhile but let it sit and be very careful to open the cap slowly as very hot steam will come out and is painful. Again the coolant should be at normal levels and not gush out. Another thing to look at is the plugs. They should all be nice and tan and dry. If one of them looks like a different color (usually the same as the coolant) then it is probably burning water. Start with number 6 cylinder as that is the most common. Retorquing the Head bolts on a already leaking HG will not do anything as the coolant is already eating channels in the HG, block and head. Old coolant is a very nasty acid!