My 1996 Bonneville's Heater recently stopped blowing out hot air. the temperature guage is remianing steady, so I am thinking it is a heater core problem. Has anyone replaced a heater core in this year car?

Replaced the heater core on my '96 in December after I stopped getting heat. Still no heat. My mechanic is baffled, seems some sort of debris is clogging the core, but we can't figure out where it's coming from. Have flushed the coolant twice, with no luck. heat is intermittant at best.
Anyone else have this problem?

Replaced the heater core on my '96 in December after I stopped getting heat. Still no heat. My mechanic is baffled, seems some sort of debris is clogging the core, but we can't figure out where it's coming from. Have flushed the coolant twice, with no luck. heat is no intermittant at best.
Anyone else have this problem?



Are you sure the problem is with the circulation of coolant through the heater core ? Is there cold air coming out of the vents ? I had no heat in my '92 Bonneville and I discovered that the airflow diverter flap in the ducting under the dash was stuck. There is a servo/actuator that controls the position of the flap via a small metal link. The link sits on a plastic pin that had broken off so the diverter flap would not move to the proper position to allow heat to flow. I was able to fix it by substituting a screw for the broken plastic piece and it worked fine for years thereafter.
This may not be your problem but I just thought I would mention it.
If it's definitely something to do with the flow of coolant, have you checked your thermostat ? Maybe it's stuck shut.

Cheers, Hugh.

Thanks for the response, Hugh. My mechanic spent hours trying to locate the problem, with no luck.
The reason we think it's a flow problem, is if I rev the engine in neutral for several seconds, the heat comes on briefly, then cools down again. Thermostat is fine.

It was not my heater core after all. My lack of heat was attributed to an intake manifold leak. This caused a coolant loss anf therfore lack of heat.
Basically, GM has changes to a plastic intake manifold on all 3.8, 3.4 and 3.1 engines. Over time the area near the EGR valve cracks and loses coolant into the engine, resulting in a $700-$800 repair. GM has acknowledged the design issue but is not willing to offer a recall for 1995-1999 SeriesII engines. Only the 2000-2003 models years have been recalled.