need my heat its cold please help 90 mark vii

[cinz4064]

if i put the climate controll on manual high 90 degrees it blows semi warm at an idle the car temp sits normal while idleing however when i rev the engine in park anywhere over 4k rpms the heater blows hot air until i let off the pedal i would be greatiful for any input you might have

 

[cinz4064]

i think it may be the heater controll valve but would still like a second opinion thanks again

 

[fuzzmancometh]

check your coolant level. its probably low

 

[cinz4064]

just replaced the water pump and the thermostat pressure tested the system at 20 psi coolant levels are where they are suposed to be and staying i was having a run cool issue before i replaced th tstat ans found some debris keeping the old tstat open i flushed the system without the tstat in and put it all back together dont think its a low coolant issue

 

[cinz4064]

still having the same issue does the heater blend door work off vacum

 

[Ricks90billblass]

More than likely a vacuum leak, or the diaphragm inside the door motor has ruptured and leaking.

 

[OldSchool1]

A rise and fall in discharge temperature with a set point of heater override at 90 degrees signifies an issue with flow, be it low coolant or (gasp) an incorrect water pump installation.

1984 water pumps turn in the direction of our crank shafts.
1985 - 1992 water pumps turn opposite of our crank shafts.

If you tested the integrity of the system then fill the overflow bottle to HOT, run the car until it reaches operating temperature, shut it off. If your system is full and sealed, it should overflow.

Test it and let us know what you find.