i got a 97 bonneville with a 3.8 non supercharged and i can home the one day from work the car ran like crap. pulled the plugs out and a couple cylinders on different heads were full of coolant. so i disconnect the igniton system and turned the car over to empty the cylinders. me and my dad pulled the air plenum off and found the gasket was leaking. i picked up a new gasket and put it all back together and checked everything over and turned it over. well it stopped dead and there is still more fluid in the heads. i also noticed that it used a whole jug of rad coolant and when i squished the lower rad hose to get the air out, i could hear the coolant slushing around in the air plenum. and even when i reinstalled the air plenum, the gasket goes around each port. is coolant suppose to be around the ports under the air plenum and does anyone hav any idea wat i could of over looked or is it possible that the air plenum could be cracked? any help would be great thanx.

Yes, we have a very good idea what happened and how to fix it. Unfortunately you have experienced a common failure mode for the UIM (Upper Intake Manifold) or plenum. The UIM itself has failed.

You need to repair this ASAP. Read this whole TECHINFO article...first...then ask any more questions:

95-03 Upper Intake Failure Information

CHANGE YOUR OIL ASAP

thanx guys for ur help. the worst part is that i just did an oil change to synthetic 100kms ago.

DRAIN IT NOW! It will rust out your rod bearings very quickly if you don't. SAVE THE MOTOR!

To elaborate, when the water got in your cylinders. Some pushes past into the oil pan. You have pumped a little water through all the lubricated parts of your engine. You want to remove the oil in the pan changed, get the upper intake fixed, run it for say 30 minutes allow all the oil to drain to the pan and change it again.

Two oil changes may save or cost you the price of a motor. it'* well worth every bit of oil if it saves your motor.

Here'* some pictures of what you're going to be doing.

http://www.bonnevilleclub.com/forum/...47882&start=20


LeifW

Exactly....you need to make sure that you get ALL the coolant out of the oil

I know this is mentioned in the article that you were linked too, but as long as youre that far into things, you might as well change the lower-intake manfiold gaskets as well, they are prone to failure as well, and they arent horribly expensive. The only common thing you have to worry about when changing those is that the plastic coolant elbow that flows into the LIM will usually break, so you might want to pick up a new one of those if youre going to do the job.

funny thing. when i first got the car the plastic elbow was leaking. so my dad and me put in a new one. i just got a new air plenum for it this morning. $250 with tax. i got looking at the old one and sure enough there was a little hole by the egr inlet. the car should be running by tonight. i probobly should replace the lower intake gasket but i'll leave it for now. its been off the road for a week and i gotta get it running again. my parents let me use the truck to run back and forth to college and wat a difference in gas millege. thanx for ur help.