Anyone who has tackled heater core replacement will tell you they’d rather have an all-night root canal than have to perform this dreaded task. Heater core leakage begins with the subtle aroma of antifreeze and evolves into a small wet spot on the driveway. By the time you have coolant on the pavement there is no way around it. You’re going to have to replace the heater core or load up on Stop Leak.
Back in the day, on older Ford F-Series trucks, heater core placement involved going up under the dashboard and removing the heating and air-conditioning unit. In the ’70s, Ford began installing HVAC systems before dashboards were bolted into the vehicle. Dashboards, which were preassembled on rotisseries, were installed in the vehicle via an installation fixture and a couple of assembly workers. This approach made vehicle assembly easier and quicker. However, it also meant extensive labor for the technician faced with heater core and/or air-conditioning evaporator replacement.
We’re working with a ’98 Ford F-150 with nearly 267,000 miles on the odometer after 18 years of service. That’s pretty good, considering most F-Series trucks have experienced chronic heater core failure earlier in their service lives. Heater cores have always been a weak spot in Ford vehicles for various reasons, including excessive cooling system pressure and volume, which has been improved in production via the use of heater hose restrictors between the engine and heater core.
Heater core replacement in the F-Series, Expedition, and Lincoln Navigator involves removal of the dashboard to where it can be disconnected and swung away from the HVAC unit bolted to the firewall. Some technicians have managed to unbolt the dashboard and swing it out far enough to gain access to the HVAC unit. Others disconnect the steering column and remove the entire dashboard for easier access.
It is suggested you use genuine Motorcraft parts where possible, which are available from Rock Auto, in your heater core replacement, including cooling system hoses, which have the factory-style quick connections at the firewall. Motorcraft heater hoses also have the flow-restrictor in the “in” hose designed to prevent heater core failure from pressure and excessive flow. Not all aftermarket replacement heater hoses have this restrictor. Heater hose quick-connects are anything but “quick” disconnect. You’re going to need the quick-disconnect tool available at any auto parts store or Summit Racing Equipment. If you’re replacing the heater hoses, you can cut the quick-connect tabs and pull the connectors.
Although we’re working with a ’97-to-’03-generation F-Series truck, basic principles of replacement are the same from for ’97-to-’17 models. Let’s get started.
| Ford F150 Heater Core Seat Belt
| In the interest of safety, the first order of business is to disconnect the battery before performing any disassembly. Drain the cooling system and properly dispose of any coolant. Seat and jack bracket removal is suggested for improved access to the dashboard and HVAC assembly. A Torx wrench is required to remove seats and seatbelts. It is a good idea to have the cooling system flushed before heater core replacement.
| Rocker sill molding removal is easy. It pops in and out with no tools required. Kick panel removal, which pops in and out, is next to gain access to wiring and modules, which have to be disconnected from the dashboard.
| We removed the A-pillar panel and handhold for improved access and photographic purposes, but you won’t have to do this.
| This flexible dash cap on top has to be removed carefully. If you get aggressive with this piece, it will crack—especially when you consider how old these trucks are today. Plastic parts become very brittle and can crack over time. Retaining tabs were originally coated with white grease for easy installation and removal.
| Ford F150 Heater Core Airbag Removal
| Airbag removal is performed with the removal of three bolts (two bottom and one top), using a 10mm socket. We have removed the glove compartment door for photo purposes, but you won’t have to. Tabs at the top of the glovebox door can be carefully bent to each side, which enables you to lower the door far enough to access airbag bolts and dash screws.
| With the three bolts removed top and bottom, the airbag assembly comes right out. A two-pin plug connects the airbag. We caution you must be very careful with airbags during service. Store them facedown in a protected location. Even static electricity can cause an airbag to fire.
| Airbag bolt locations on ’97-to-’03 F-150s are in three places (arrows).
| Passenger-side airbag looks like this from behind. There’s a two-pin connector tied to the canister inside the module. Exercise extreme caution with airbags: store them on their faces, away from people, to minimize the risk of accidental deployment.
| We’re dropping the steering column for ease of access. The steering column cover pops out without tools.
| The bezel above the instrument cluster is attached with three screws using a 7mm socket. Once these screws are removed, the bezel pops right out.
| You will find the dashboard is tied to the body via seemingly dozens of these sheetmetal screws (dozens!), which are removed with a 7mm socket. Follow these screws around the perimeter of the dashboard. They secure the dashboard to the body. The F-150 dashboard consists of the shell you see, backed by a plastic inner frame/ductwork assembly tied to a steel framework at the cowl. Gold cad-plated dash screws are coarse thread for threading into plastic. Black or natural cad-plated fine-thread screws are located at copper-plated (metal) inserts.
| The instrument cluster is removed for improved access. Some technicians remove the entire dashboard to make it easier to get to the HVAC assembly, but you don’t have to do that. The objective is to remove enough of the perimeter screws so you can swing the dashboard out of the way. Be very careful with the main wiring loom and its connectors.
| The steering column is secured with four flange nuts. This removable framework is part of the dash structure and is removed as shown to drop the steering column.
| There are four steering column support studs. This is an integral part of the collapsible steering column.
| The dash pad “bubble” is removed next. Although this looks like a padded dash, it is little more than a removable shell. Use a 7mm socket to remove these black cad screws.
| Disconnect the dashboard from this cluster of harnesses and modules behind the right-hand kick panel.
| Once the dashboard has been moved out of the way, heater core access becomes easy. A series of screws secure the top of the HVAC plenum, which is removed for heater core and air-conditioning evaporator access. You will need a 10mm socket for this purpose.
| Ford F150 Heater Core Solid Parts
| While you’re performing heater core replacement, it is a good idea to check blower motor and variable resistor status. Both are easy to access with the dashboard installed, which means you don’t have to replace them at this time. We’ve opted for a Motorcraft heater core. However, the factory heat blend door has a weak spot at its pivot and should be replaced. The pivot point at the blend door actuator tends to crack and break, which is why we’re suggesting the Dorman heat blend door kit (#902220 or #902207) for your F-150 heater core service. The aluminum pivot on the Dorman replacement is solid and will not fail. It is also suggested you replace the blend door actuator.
| The variable resistor package is what affects fan speed, not the fan switch. Fan power is routed through this resistor package to control fan speed.
| We’ve chosen the Motorcraft heater core mostly for reasons of guaranteed fitment. The aftermarket also offers replacement heater cores for F-150s.
| The original factory heater blend door assembly, which pops out without tools, is removed and replaced with the improved Dorman blend door assembly.
| The installed Motorcraft heater core is fitted with new foam around its perimeter. The arrow indicates where the heater blend door splines into the electric actuator below. It is impossible to install the blend door any way but the right way. The HVAC cap is reinstalled using a 10mm socket.
| The new Dorman heater blend door is installed as shown. Reinstall the HVAC cap and dashboard/steering column.