Coolant leak help!!!!

O.K. Guys, time to pick your brains.....

'98 Rodeo 3.2 4x4 with 80K miles. Suffering from coolant loss. Vehicle runs well, Temp shows to be within normal limits, and there is no visible sign of a coolant leak (Including during pressure testing). I am refilling the overflow tank about every 40 miles, as it will go from the max to the min levels in that time. Oil is clean, no sign of water intrusion, and no visible signs of antifreeze coming out the tailpipe. Even pressure testing could not show a leak, nor the typical increase in pressure or pressure surging that you typically see with a blown headgasket. My best guess is an intake manifold gasket, but my manual isn't clear on even if there is a water jacket running through it, other than the throttle body.

Can anyone give any recommendations on what to check, historical problems, etc. All advise and direction is welcome.


Thanks,
Matt

It sounds like you've got the dreaded 'bad run' of cylinder heads. Some 1998 3.2's had heads with a "K" designation stamped on the side. These are prone to coolant leakage into the combustion chamber. This sounds like what you have going on. Hate to say it, but you need new cylinder heads. Burning coolant will also ruin your catalytic converters and all 4 oxygen sensors.
G/luck
Joel

from what I have seen it is not always both heads first pull the coils and see if there is coolant in the tubes. If not pull the valve cover and look on the heads near the small core plugs between the tubes for a crack or any sign of coolant.