Any suggestions/answers would be greatly appreciated -

I have a 1996 Bonneville SE with 148,000 miles - suddenly I quit getting heat on the driver'* side - but lots of heat on the passenger side. We have changed the water pump, hoses, tstat, flushed the system, etc.. If we block off the vent on the dash on the passenger side I get heat on the drivers side - system keeps getting airbound and we can't find any problem anywhere.

We have checked with our local dealerships and nobody has ever heard of this happening, especially in the 3800 - This wouldn't be a problem except that winter is here for us (over 16 inches of snow yesterday!).

Have you tried purging the air out of the cooling system?

You can do this by starting the car, let it warm up, and then slightly open the bleeder valve on top of the thermostat housing elbow (I think it'* an 8 mm screw). Let all the air out through that bleeder and once coolant starts oozing out tighten up the screw. See if that helps.

Yes - we have done this several times and have now added a "bleeder hose" so that I can do it myself before I leave work - some how air keeps building up in the system and like I said in the original posting - we have no idea where or why or what'* going on. And as I said before - any help is greatly appreciated!

Have you ever replaced your upper intake manifold or lower intake manifold gaskets?

Are there signs of coolant in the oil?

Does the coolant level ever decrease when you notice the lack of heat? And also, what does the temp. guage show when you have no heat?

intake mainfold gasket ever been changed??

The coolant levels are right on - nothing in the oil - spark plugs are dry - temp. gauge is right on the money at all times - never "runs" hot or cold.

Haven't touched the intake manifolds (yet) - as the garage doesn't think that'* it because there'* no other "symptoms" of it being the intake.

I agree...doesn't have any of the failed intake symptoms! Wait around for a gearhead to help you out. I'm spent... LOL...

Glad to hear that there'* somebody else out there that is scratching their head over this - thank'* for all your input though!

Any other ideas will gladly be tried

I got a similary problem. My drivers side does not heat up as fast as the passneger side, whether it be vents, floor, or defroster. All levels of fluid are fine. Eventually it gets to be luke warm, while the passenger is burning up.

Does your car have climate control?