92 deville I've replaced heater core heater control valve water pump thermostat raditor and recovery tank and cap . had a pressure check to se if a headgasket. Have no coolant or oil mixing no white smoke motor runs smooth . Still having bubbling in recovery tank after driving it

Maybe the heater core is plugged or you haven't bled it properly?
If the heater hose returning from the core to the water pump is NOT hot, while the hose going to the heater core from the thermostat area IS hot, then the heater core is plugged probably.
You need to remove the heater hose while cool,from the thermostat area and remove the hose from the water pump area (that's the outlet of the flow thru heater core) AND THEN take a garden hose with p-is-tol grip type sprayer,and blow water back thru the outlet hose out the inlet hose. This will blow any bad plugging material out the way it got in.
Don't apply too much pressure if it is plugged bad. The heater core isn't made to stand 50lbs. water pressure. don-ohio (:^)

If the heater valve operate properly then the line to the heater core is plug.
Check & replace or flush.

Good luck

Mai

the cooling systems consists of a radiator, radiator cap, water pump, thermostat, hoses, heater core and sometime a heater control valve that open water lines to heater core. You may need a cooling system flush if water pump, radiator have been replaced. flush the system.change the thermostat and have the heater core checked too if you can get to it.
does the cooling fan kick on to cool the radiator..check that too.replace radiator cap and check cooling fan yourself...let me know if need anything else.
Thanks for using fixya and please vote.

heater core could be stopped on low heat hot but on high not hot enough fan cooling it down check heater core

i didn't see you last posting about your water pump but theres is a tiny radiator called a heater core. it has the same hot water running through it as your big radiator and engine have.so when you turn your thermostat to hot and kick on the fan the fan blows through the heater core and wallaa you have heat you probably need a thermostat.if you have no heat and it is overheating hear and there that's probably what you need.make sure you see if you filled the radiator up all the way when you changed the water pump.

could be a head gasket (coolant going into exhaust or into oil) pull oil dipstick does it look light brown like the color of a chcolale milkshake if yes u have bad head gasket does exhaust blow white smoke? if yes bad headgasket ? pull radiitor cap off let van run for while does water come out of raditor at a fast rate if yes (possiable ) bad head gasket
also could have leak your not seing look closely around where intake meets heads notice any water trails or see any water leaking ? if yes bad intake gaskets look closely around water pump any trails of water there ? if so bad water pump also check closely around seams of raditor for water trails
after all this u dont see any thing might need to take it to a shop and have it pressure tested (some leaks will only show up under pressure) most shops won' t charge much if anything for this service

did you replace the thermostst? have you got an airlock in the heater/header tank.

Check for water in gas.

Reverse flush the cooling system and put in fresh antifreeze to -20. (20 below zero). If that doesn't help, replace the thermostat.

Check your coolant level first. Next check your heater control valve. With engine at operating temp and heater on high, do this:

1. Heater hose from water pump should be hot (if not, water pump may be dead or thermostat is stuck closed)
2. Heater hose from thermostat housing should be hot (if not, thermostat may be stuck closed or water pump is dead)
3. Heater hose going to heater core should be hot ( if not, heater control valve is not getting vacuum from heater control unit, or valve is broken)
4. Heater hose returning from heater core should be hot (if not, heater core is blocked, undo both hoses to core and flush with water hose until clear)

Test thermostat: with cold engine cranked, watch water temp gauge. As it gets hotter and hotter, when the thermostat opens, the temp should drop suddenly and then go back up.

Test water pump: with engine at operating temp. Squeeze top radiator hose tight, when you release it, you should feel/hear a surge of water. It is much like when you pinch a water hose closed and release it.

Test vacuum from heater control unit to heater control valve: undue vacuum line from control valve. It should have a vacuum when pressed against you skin in addition to releasing the actuating arm on the control valve.

If there is no vacuum, a quick fix will be to disconnect the plastic actuator from the silver arm on the heater valve. This will let the hot water to always flow to your heater core.