2003 Deville - cooling system problems

Re: Overheating please help!!

The surge tank should not be "nice and full". Proper coolant level, checked cold only, is just about at the tank midseam.

There is a COLD FULL legend molded into the top of the surge tank. Next to it is a flat arrow that runs across the tank top and down the side - it points to just about the seam line.

As advised, check the purge line and water crossover bolt/nipple for blockage. Your symptoms are classic for that.

............. and, if you see fairly constant bubbles in the surge tank with the engine running, there is a good chance of one or both head gaskets failing due to pulled head bolts.

Replace that tensioner pulley - yesterday !!!!

The cover is held by two 10mm nuts on long hex headed studs and a bolt into the water crossover pad. The entire tensioner assembly itself is held by those 2 long studs. You can replace the pulley only by removing the center bolt. Use a small crescent wrencdh on the formed lug on the tensioner arm to lever it toward the firewall to remove tension. Have fun replacing the belt. NAPA.

If that tool has a slot and slides onto the groove in the steel pulley hub, then turning the bolt to the right will pull the pulley off the cam extension. ............ and it will be TIGHT. Wait 'till you go to press it back on with the other tool.

Why are you removing the drive pulley ? If that plastic pulley and its belt grooves are not messed up you don't need to remove it. The tensioner is what seizes, THEN destroys that big plastic drive pulley.

My picture is of the tensioner assembly, not the drive pulley.