1991 civic mystery - no heat
 

Greetings everyone!

Can anyone help troubleshoot why a 1991 honda civic doesn’t have
any heat? just blows cold air; multiple mechanics stumped.

coolant system was professionally flushed. the mechanic bypassed
the manual control for the heater core -still no heat.

system appears clean.

replaced the thermostat with a brand new working unit (tested thermostat for function in warmed water).

personally ran water and coolant through all areas of heater core, both
directions, through the radiator, through the motor with the thermostat and pump removed.

bled system multiple times.

have taken apart dashboard and looked at heater system in detail.

at one point even rerouted system to bypass radiator.

tried milking pipes.

when the car is hot, operating temperature, water in the radiator is
boiling but the lowest pipe going back into the motor is cold, making me think there's no circulation of fluid.

replaced the pump three times; the third pump is brand new.

top of the radiator is hot; bottom of radiator is cold.

reservoir is full, gages work, coolant is full, everything else appears working.

many thanks for any suggestions!

very best,

r

Re: 1991 civic mystery - no heat
 

Is the water valve open? Will it actually pass water to the needed places?

Is the heater core completely bled out (burped)?

Can you hear airflow change when switching between HOT and COLD with the fan on full blast?



Are the heater hoses hot (at the firewall where they pass through)? Both, or just one? Neither?



Heaters are pretty simple.
These tend to trap air and are real tough to get burped out.

Re: 1991 civic mystery - no heat
 

thanks for very much for the suggestions. the heater hoses are cold. the water in the radiator itself is hot but the lowest pipe going back into the motor is cold...had the heater core proffesionally bled out twice, and after the second time the mechanics bypassed the thermostat completely just to try to get hot air - still no luck.

Re: 1991 civic mystery - no heat
 

Switch the heater core hoses, at the heater core. Go out and give it a good WOT 1st & 2nd. Should have heat. Then switch the hoses back. Essentially back flushing it using the pressure built from the engine.

If that doesnt work, you may have a clogged hose or a mythical beast

Re: 1991 civic mystery - no heat
 

You have a flow problem. Figure out why.

Doesn't sound professional to me.

Can be perfectly normal, if one understands what the job of the radiator is, and understands how the cooling system flows.

Done this many times. Sometimes it's the quickest way.
There are MANY less than qualified people that work in a "professional" job. You can find this in almost every profession.


IMHO, a pro would have solved the problem.



Many people work on cars.
Far fewer can fix problems.