Originally Posted by Paul1981
Is it possible that the new UIM gasket is faulty. Can it just leak externally on it'* own? Or does the LIM gasket have to be blown for the upper to leak?
It is possible for the new UIM gasket to be faulty, but not likely. And, no, the LIM gasket does not have to be blown for the upper to leak. The upper has its own coolant passages to provide coolant to the throttle body, and thus its own source for leaks. These passages are just behind the thermostat housing and between the throttle body and the UIM. As jr's3800 indicated, you may have a bad (warped) UIM that is causing the leak. If the old UIM got nice and hot and warped, the old gasket probably warped with it to compensate. Now that you replaced the old UIM gasket with a nice flat, new one, it leaks. Or maybe the problem is a bolt or two that he forgot to tighten...or overtightened....or stripped.