Heater core - the core exposed

Heater cores tend to fail on 9000's.  It has been said that the replacement parts are somewhat better, but I haven't been able to confirm that.  It's a fair assumption that most cars with 50k miles or more have had the core replaced.  The part is somewhere on the order of $100 to $150, and it is a real bear to install; installation labor might run $300, more or less (more likely more than less!).  Access is from the engine compartment, and the blower motor has to be removed to get at the heater core.  Some write-ups even say to discharge the A.C. system, which would make the job easier, but really expensive.  Many people say to replace the $100 to $150 blower motor also, while you're in there, because the blower motor has to be removed to get to the heater core.  It's your call.  All things considered, it's probably cost-effective in the long run, because the blower motor is good for not much more than 100K miles and the labor to replace it is about the same as for the heater core.  It's a lot of work to change either one.  Fairly detailed write-ups are available for do it yourself-ers.  Here's mine (no return to this page).

Saab originally used a quick-disconnect system on their heater cores, and I tend to suspect that a lot, if not most of the problems are associated with that "feature".  I don't know if they ever quit using it, but the better replacement cores do not have it; they use short lengths of rubber tubing and hose clamps to make the connections.  If you replace, I think you should replace with that type.

In any case, if you're in there to do one or the other or both, carefully check to make sure the insulation is securely glued down in the evaporator housing.  If some of the insulation comes loose, it will get into the fan, overload and unbalance it and probably blow out the fan controller circuitry.  The insulation is a pretty dense 1/4" foam.  I repeat: Make sure it's secure!  If you're having blower motor or heater core work done by a mechanic, tell him/her to look for this!  The evaporator housing is the chamber leading to the fan assembly, toward the driver's side (U.S. models).  Pull up any loose insulation, clean and dry all the surfaces, and use a good quality contact cement to glue it back down.

Preventive maintenance: Bob Davis, a long-time Saaber reports that he has never experienced a heater core failure in the ownership of two Saab 9000's, and I have matched his experience by doing what he does: He uses Bar's Leaks religiously (the liquid form in the silver bottle), following the manufacturer's recommendations.  Considering the notoriety of Saab cooling systems, I feel this is a great thing to do, as it is reputed to be beneficial to water pumps and any cooling system components that might leak (heater cores, water pump seals and head gaskets). I have used it for six years or so and have not had any cooling system failures - not one.  I don't just recommend it, I swear by it.   Bar's Leaks Web Site

As a matter of good maintenance, drain and backflush the cooling system every year or two using one of the kits that allows the connection of a garden hose into the system, and replace the thermostat at that time too - you need to remove the old one to get a good flush anyway, so replace it - they're pretty cheap, and you don't want one to fail (stuck thermostat = overheat = head gasket failure).  Many advise using Mercedes or some other extra-premium coolant that is PH balanced, and mixing it 50-50 with distilled water.  I don't think this is necessary if you do the maintenance and use Bar's Leaks (but I use Mercedes coolant anyway).  Careful maintenance should prolong the life of the heater core, the head gasket and the water pump.  If the car has records that indicate frequent cooling system maintenance, that's a good sign.  If records indicate that the core has been changed, that's probably a good sign also.