1995 Buick Regal Custom 3800 series 1, 227K miles. Last winter leaked coolant, mechanic friend could not find leak so I put in powdered aluminum and leak stopped. The summer after, I had to replace the thermostat gasket. Then 2 months ago, leaking began again. I replaced the thermostat gasket and the leaking stopped. Just yesterday I started it, and looking under the hood I saw bubbling coming out from under the throttle body, just behind the thermostat housing. What can I do to control this leaking? Never had problems before, but when its cold in MI during winter I seem to have the worst problems. I don't want to get rid of the car, so what should I do?

pull off throttle body and replace block-off plate gasket on the end off the intake about 5 dollars for gasket

Is this leak coming from between the upper and lower intake manifolds? If so you will need to remove the UIM and replace the gasket. As well as the UIM. They crack and leak coolant. When this happens it can fill the lower manifold and then run in to the cylinders causing a hydrolock.

Will I be able to see all cracks in UIM by just looking, or will there be non-discernable cracks or warping that will make the old UIM useless? Can I get away with just putting the old one back on, because it was done at around 140K. Or do I need to get a new one, so that the leaking won't occur again?

The crack, if it has one would be inside. You can cap over the two coolant ports on the LIM and it will no longer leak.

Dan.. Series 1

The UIM won't crack and cause a hyrdo lock on the Series 1 motor. The EGR is located in a different place. On the Series 2 NA motors, this is a common enough issue.

Yours should be a simple gasket issue.

Ack, I missed that one.

You know, I've done it hundreds of times, that'* why I've gotten so good at catching myself on the S1 stuff.

Going to replace UIM gasket, from what the guy at ORiellys told me it could be one of the coolant ports under the throttle body side of the intake? that is only spot where it is leaking from. The leaking did stop for a day, but then it began leaking again the next day. Very confusing. Will let you know how it goes.

replaced UIM gasket and block of plate gasket on end of intake. throttle body had some coolant crusted on side of it. two coolant port gaskets were smashed all the way flat. coolant was in the air slide on the side of intake opposite the throttle body side. so far no leaking two days after changing gaskets. UIM did not look damaged, hopefully it still holds.
thanks a lot guys. very good forum.