Pontiac Repair: 98 pontiac transport heating issues, cylinder head gasket, intake manifold gasket

Question
Ok, so I have had numerous overheating issues with my van.  The thermostat has been changed several times, the radiator is new, the water pump has been checked, and the lines were bled.  Finally, the lines going to the rear heater core were capped off.  This solved my overheating problem, but now my van barely heats up past 110.  The air that blows out of my vents does not get warm.  Do you have any idea why the engine wouldn't be warming up enough for me to get any heat?

Answer
Hi Amanda:
I think you have 2 issues here #1 the major one is the overheat issue. These engiens were noted for lower intake manifold gasket failures and the engine would run low on coolant and then damage a cylinder head gasket or cylinder head.  That could be the root cuase here. Another issue could be the wrong temp. thermostat was installed in the van. as for the no heat now that van was designed to have front and rear and the way the water flows to the rear helps the front sounds dumb but what might have happend is an air pocket formed in the front heater core and dueto the fact the rear is not hooked up anymore it can't purge the air out of the heater core.. Just a guess without seeing it I can't say for sure. But I would still look inot why it was overheating. Capping off the rear unit shouldn't have made a difference here.. Possably someone took out the thermostat is hopes to stop it from overheating????
Good luck :)