Where is vacuum hose from heater 1998 Ford Taurus?

Answer 1

Depends on which engine.

For the Duratec, there are 3 vacuum hoses on the backside of the upper intake manifold - UIM.

One large diameter hose goes to the right, and connects to a 'reservoir' on the firewall, just to the left of the master cylinder. One of the hoses that connects to this reservoir supplies the master cylinder/brake booster.

A second line from the UIM feeds the EGR valve and the fuel pressure regulator - goes to the far left first to a black box mounted to the left end of the UIM. The hoses then come all the way back to the EGR/regulator, and are routed underneath the throttle-body. Look for green and red, small diameter hoses.

The third line off the back of the UIM goes to a vacuum reservoir box on the firewall, way over to the left. This is the one that supplies the heater controls that provide directional control, e.g., defrosters, vent, floor.

I found this out when my car was having very random starting problems (the line going to the fuel pressure regulator). Some of these vacuum lines are small diameter hard plastic hoses - mine were so brittle they were snapping left and right.

I suspect hairline cracks were the cause of the intermittent starting problem.

The vacuum diagrams came from Autozone.com's free repair guide.

Also note, the vacuum diagrams are very different across the various engines and model years!!