Bad heater core - 1993 Saturn SL1

Sounds like a bad heater core. You will get steam/vapor out of vents from this. If you are referring to the over flow tube being the evaporator drain tube at the firewall its because the heater core shares the same case with the A/C and its filling up with anti-freeze.

If the hose is leaking at heater hose,maybe heater core is bad,here's a repair guide to the heater core and hose.

Bad heater core you will need to replace it. About a 2 hour job, very easy to do:


Remove the HVAC module assembly. Refer to HVAC Module Assembly Replacement.
Remove the HVAC filter cover.
Remove the heater core/evaporator tube seals from the module.
Remove the heater core cover screws (1).
Remove the heater core retaining screws (1).
Remove the heater core retaining straps.
Remove the heater core.
Remove the rubber seals from the inlet/outlet pipes of the heater core.

Installation Procedure

Install rubber seals to the outlet/inlet pipes of the heater core.
Install the heater core to the module.
Install the heater core retaining straps.



Install the heater core retaining screws (1).
Install the heater core cover.



Install the heater core cover screws (1).



Install the heater core/evaporator tube seal from the module.
Install the HVAC filter cover.
Install the HVAC module assembly. Refer to HVAC Module Assembly Replacement.

First check and make sure that your coolant(antifreeze) level is full, the hot coolant runs through the heater core and than air is blown over the heater core heating the air for the heater. if the coolant is full you than need to check the thermostat and make sure it is functioning properly. finally if both of those are not the problem it is possible that your heater core is bad, however if the heater core is bad you will notice coolant leaking onto the passenger side floor. so if the floor is dry I would say the heater core is not the problem

If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired.
Heater Housing

• The heater housing is usually under the dash and must be removed to gain access to the heater core.
• Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.

The heater housing is disassembled to get to the heater core. Heater Core

• Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
• Remove the heater coolant hoses.
• Remove the cable and/or vacuum control lines (if equipped).
• Remove the heater core securing brackets and/or clamps.
• Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
• To reinstall the heater core, reverse the removal steps.

When the heater core leaks and must be repaired or replaced, it is a very difficult and time-consuming job primarily because of the core's location deep within the firewall of the car. For this reason always leak test a replacement heater core before installation.

If the tubes going to the rear heater core are the problem , drain the system and replace the bad tube/tubes. If the actual heater core is leaking and you do not want to go to the expense of replacing it, unhook both tubes at the back of the motor , cut out a good section of hose and use it to loop/connect the outlet line and inlet line on the motor side (not the rear heater core side). This will bypass the rear heater core , the front heater core should be adequate to heat the whole car. If you have a pin hole in a section of solid (copper) tubing, you can cut out the bad section and reconnect it with some heater tube and two hose clamps.

Most likely the heater core what color is the colant

Bad heater core. Replace it.

Clogged or disconnected drain hose from the heater core box. Or bad/leaking heater core. Does the liquid smell like coolant. If so bad heater core. If not and the water only when you use the AC then it is a drain hose issue. If neither of those pan out you could have a leaky windshield. However 99% of the time a wet passenger floor is caused by a bad heater core or drain hose.

Textbook bad heater core symptom. Might be a blown/leaking heater hose....but I doubt it. My monies are on a bad heater core.