Alfa Romeo 1991 164L Heater Core Replacement

Apparently, heater core failures occur often somewhere between 70-100K miles. Mine was giving an odor of anti-freeze. If they fail entirely and blow, they may short the wiper motor and an ECU. Please read through all instructions, check other sources and manuals, and proceed at your own risk. This is what I did, your car and experience and tools may be different. Statements similar to "do this" "do that" are simple ways of saying "I did this".

The first thing I did was to get the R134a refrigerant removed--take it to a good A/C shop and let them evacuate and cap off the system for you. Disconnect the battery negative lead. Loosen the power steering reservoir and move it back a bit toward the windshield. Disconnect all the electrical leads under the plastic bay cover (you cannot reconnect them wrong), including the grounds on the driver side of the firewall. It will be easier to pull out the big vertical relay (with its bracket) there to give yourself room to work those cables out. Loosen the A/C system hoses on the evaporator box and filter/drier can, just be sure you use two wrenches and hold onto the stationary hex with one while breaking the hose fitting with the other. Avoid any strain on the evaporator and other connections! Disconnect the anti-frost switch, the trinary switch, and the re-circulation air damper motor way back under the corner, passenger side. Remove the 2 or 3 screws that retain the big rubber grommet where the cables penetrate the false firewall. Then pull the cables through as possible, making sure everything's properly disconnected. You'll have to disconnect the hot leads at the 40 amp fuse links on both sides of the false firewall. Label or make a drawing of how those leads are arranged on the posts, because it's tough to reassemble them if done incorrectly, and you might wind up also without fuse protection if you do it wrong. There are small spacers too, so best thing to do is to remove them one post at a time, and zip-tie together temporarily, so it all stays in order. Remove the vapor separator can from the back side of the intake plenum, also the idle control valve next to it. I also pulled out the bolt there from the engine dog bone strut, so I could rock the engine forward a bit to give me more clearance for the evaporator box in/out.

Now you can pull out the false firewall. It sits in 3 or 4 clips at the bottom and is retained on the ends by screws. At this point, you should be ready to pull out the heater core box, which seemed relatively easy to do with two screws holding it in place. Rotate and tilt it as you carefully bring it out of the cubby hole. Separate it carefully from the fan housing where the rubber flex seal fits around the assembly. Then, release two clips way down there on each side of the fan housing, and that comes out, revealing the heater core.

There are 3 heater hose sections, one with a molded tee for the coolant reservoir. Replace all three- this is the only time you'll want to do this job and have access to all this stuff! Use good quality hose clamps, and tighten them securely, but only enough to start squeezing the rubber on each side, if the hose starts to extrude through the slots in the clamp it's too tight.

The inlet/outlet tubes on the new core should not be stressed- support them with your other hand when you attach the new hoses and clamp them. This also may be a good time to check/replace the insulated fuel lines running in back of the motor and below the false firewall. I also took the opportunity to clean that components bay out thoroughly, clean the two big drains at the bottom, and vacuum out the crud from both corners at the base of the windshield posts. Don't forget your sunroof drain tubes. Use light oil to lube the bushings in the HVAC fan, also (not too much or it will short out the windings). While access is good, take the time to go over all the details you normally would struggle to get to. Some important details: On the molded hose with the tee in it, there's a plastic hose barb molded in that's not overly tough, so when you push the new coolant reservoir into this hose, place the spring clamp on first, then wet the nipple on the bottom of the reservoir, and support the tee from below with your hand while you push the reservoir straight into the short vertical hose section. Then slide up the spring clamp and release. That way you avoid strain on the molded tee section. Another tip: the plastic cover for this entire area has openings and a drain valley that lets leaves, tree seeds and pine needles down into the bay, clogging the drain tubes and causing electrical problems. Consider making a plastic gutter screen held by rivets. Take sections of gutter screen and rivet them onto the openings and across the discharge end of the drain valley. Use larger pieces on the right side- cut to fit where the power steering reservoir sits. One could cut an opening in the screen for the security system switch, then pop a rubber grommet over it to retain the screen in place. It's easy and effective for keeping this area free of debris.

As I recall, the parts I used are as follows:

1- heater hose, core inlet, 1- heater hose, core outlet, 1- heater hose, engine-to-coolant reservoir, 1-new coolant reservoir, 1- new cabin air filter (original pleated style), two new 40-amp fuse links, 3- new radiator hoses (2 lower/1 upper), 2- gallons premium anti freeze, 1- gallon distilled water, 1- heater core, 1-flushing tee kit (install into heater hose accessible in front, above transmission case), NAPA/Echlin "CE-1" contact enhancer (aka Stabilant 22), 1-A/C filter/drier, 1/4" x 3/8"w stick-on foam weatherstrip (for core), 1-roll plastic gutter screen, 1-lot pop rivets w/ washers.

Parts sources at the time: Paul Spruell 770-458-8458, Centerline Alfa 303-447-0239, Alfa Parts Inc 800-890-2532, IAP 800-726-0555, West Suburban Auto Group 708-450-4430 (George ext 223), Alfa Ricambi 800-225-2532, Mastro Motors 813-884-7513 (AlfaBill).

The local shop refilled the AC refrigerant. They had the o-rings, the R134a, the tools, the gauges, the tech data, everything they need right there, and if there's a problem with AC afterward one can just return for a check over.