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Experience of K-Seal suggests it is pretty safe on these engines, but I wouldn't use the old school raddiator sealers.
Air gets trapped in the metal coolant pipe that runs from the bottom hose over the top of the bellhousing back to the thermostat housing on the water pump. Located below the throttlebody trunking there is a coolant bleed screw (8mm hex) bleed from here with engine off and expansion cap removed. If no coolant comes out with the screw slackened or even removed try applying a couple of pounds of air pressure to the coolant tank.
The layout of this pipe can lead to airlocks forming if coolant is lost or drained and is one of the minor issues that causes overheating on these engines. Using a thermostat without a bleed hole can also lead to problems. If doing cooling system work on these if the thermostat was still located in the original position on the thermostat housing we used to drill a couple of additional 3mm holes in the thermostat to allow a bleed through the thermostat to prevent air locks.
If we had the inlet manifold off we also used to remove the check valve which is built into the air bleed outlet on the righthand corner of the inlet manifold.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
ok I will look into k-seal. I just dont know what other thing it could be.
no external leaks no dye shows up. leakdown test is good. there is no exhaust pressure in system. pressure tester holds pressure in both cold/hot. if it was going into exhaust it should show pressure in the system. its not a one-way path. maybe the heater core is the issue who knows without tearing down the dashboard to inspect it.
