Dear Fellow Brickboarders,

May this find you well. I just replaced heater hoses and heater control valve. They were originals, so it was time. The hoses were in superb condition. The heater control valve also looked fine.

I append a few notes, which supplement what is to be found in the FAQs. These notes might save you some work. I am grateful to John Marshall, of New Zealand, for suggesting the use of a work platform over the engine bay. Rather than use sawhorses, I rested a wide and thick board directly on the fenders (with foam to protect the finish).

Yours faithfully,

spook

Heater Hoses/Control Valve 1993 940 N/A

Access. I used a 16" wide board (68" long and 1 1/4" thick) as a work platform. I put foam tape on the underside, at the ends (to protect the fenders) and laid the board over the engine bay. I made sure the leading edge (closest to the radiator) was not resting on the fan shroud. I made sure that the trailing edge (closest to the firewall) was not resting on the coil (Rex Regina coil sticks up). In this way, I was able to lay on top of the engine, and so to look down through the intake manifold branches, at the hose clamp, that secured the hose to the port on the side of the head, below the intake manifold.

Hose Removal.

Clamp removal. If the clamps are original (you will know this because the teeth are cut into - but do not go all the way through - the metal), use a 9/32" socket to loosen them. Loosen them completely.

If the clamps are not corroded, put a bit of lithium grease into the screw, and re-use them. Make sure no grease gets onto the inside surface of the metal: wipe this area with a solvent (e.g., brake cleaner). The grease in the screw area will make it easier to re-install the clamp.

To minimize the risk of cutting into the copper heater core hose ports (that takes water through the firewall and to the heater core), use a utility knife to cut through the heater hose 3" from the firewall. Then, using the utility knife, cut towards the hose port, spreading the cut hose with your fingers, behind the blade. You will see the edge of the hose port, before the blade touches it. Starting at the leading end of the hose port (that closest to the front of the car), gently make a cut along the length of the hose that is still on the hose port, towards the firewall. Do NOT try to cut all the way through the hose: you will almost certainly cut into the hose port wall: that will give rise to a leak. Once you have made the first cut, deepen it, while spreading the hose from behind the blade, so that you can see how deep you've gone. Gradually deepen the cut. At some point - before you've cut all the way through - the rubber will give way, when you spread the hose. You will be able to remove the hose stub from the heater port, without the blade ever having touched the heater port wall.

Generally, you can simply pull the hoses off the other two ports - that on the side of the head (under the intake manifold) and that on the pipe, which runs behind the exhaust manifold and around the back of the head. These ports are not especially fragile. There is no easy way to access them with a knife blade.

How you remove these hoses depends on your hand size. If you have a small hand, you will be able to grip the hose under the exhaust manifold. If you cannot do this, use a pliers to grip the hose, and pull it off of the port in the side of the head. You likely will need to wiggle the hose to "walk" it along the port.

Hose re-installation.

Clean the hose ports with solvent - I used methyl ethyl ketone (MEK, a chemical cousin of acetone, works well but is highly flammable and carcinogenic) - to remove any grit, rubber particles, etc. This will ensure a tight seal.

Do not forget to put clamps on the hoses, before you run the hoses to the port on the side of the head and to the pipe behind the head.

First, do the lower hose (the one that runs to the port on the side of the head, and into which the heater valve has been installed). It should pass between the wiring harness (with the ridged cover) and the oil dipstick tube, on the passenger side of the dipstick tube. Making sure that the clamp screw will point upwards, install the clamp on the hose at the end, which is to go on the port, on the side of the head. If you're right-handed, it will be easier to secure this clamp, if the clamp is positioned, such that the screw is positioned on the right side of the hose (i.e., towards the front of the engine).

Reach under the intake manifold, and push the hose to the point where the hose opening is just touching the edge of the port. Then, slowly work the hose along the port, until it is against the base of the port (as close to the wall of the head as it can go). Position the clamp 3/16" from the base of the port, and tighten the clamp, using the flexible shaft screwdriver, through the opening in the intake manifold branches.

The upper hose should pass behind the 1" thick wiring harness (with a ridged covering), on its way to the tube, which is behind the head, and which runs along the side of the head, behind the exhaust manifold, to the back of the water pump. Position the hose clamp on the end of the hose, making sure that the hex head points upwards. Push this hose onto the end of the pipe, until it reaches the stop. Position the clamp 3/16" from the stop and tighten it. This hose should fit into a black plastic clip - with a swivel - which attaches to the fuel return line.

When you slide the clamps over the hoses, before pushing the hoses onto the heater core ports, position the clamps so that the hex head of the clamp screws on the hose clamps, point to the passenger's door. Push the hoses all the way onto the port, until the hose contacts the foam gasket at the base of the port (closest to the firewall). Position the clamp about 3/16" from the end of the hose. Tighten the clamp until it is snug, using a flexible shaft screwdriver, or a flexible shaft extension, with a socket on the end.

Connect the vacuum hose to the bottom of the heater control valve. Make sure to reconnect the hose from the side of the flame trap to the intake manifold, and the vacuum line to the cruise control actuator (if either has been dislodged).

Refill the system will coolant/water (50:50) mix. Start engine, wait for it to warm up (temp indicator in the middle). Check for leaks where hoses attach to ports. If necessary, snug hose clamps.

Turn the climate control setting to max heat. If you feel a blast of heat, everything is fine. If the air is only warm, there likely is an air bubble in the heater core. Turn the car around, so that the nose is pointing down (if the car was angled up before, or vice versa). This should allow the air bubble to escape. If you then get a furnace-like blast of heat from the vents, you're good for another decade, or so.