Hi All

I have a 96 that has a vacumn leak behind the front heater control panel. You can hear it hiss while the engine is runing and it stops about 30 seconds after the engine stops and the vac resevor is depleted.

Everything still works but the leak is getting larger, is this a common problem? What should I expect when I pull the control panel, what parts should I have on hand. With the size of the leak it's only a matter of time before something stops working or it sets a lean code

Thanks

Hi Kevin
I have a '96 and have done some vacuum work. I have not had the same exact problem - my system leaked in the engine compartment and none of my A/c doors would change position, hence the default - defrost- was all that was available. If you can change your airflow to direct it out of the various ducts as advertised you don't have much of a leak.

I have not pulled the panel control block, but I can tell you it simply directs vacuum to the appropriate place to give you the airflow you want. You should have a black line coming into the control which is engine vacuum. The yellow and blue lines go to the floor/defrost vacuum motor. The red and green go to the panel/floor motor. The orange line goes over to the recirc/outside air vacuum motor under the glovebox. The two motors with two lines have a partial and full throw position to provide you with your "blends" i.e. panel and floor or just floor. As I recall, the colored lines are somewhat pliable whereas the black engine vacuum line is fairly rigid. My line in the engine compartment was of the rigid variety and had a hole worn in it. I was able to lay a small length of 1/4" clear tubing, cut along the outside edge, over the vacuum line and duct tape it in place to seal the hole. The colored pliable line might be a little harder to repair since I don't think you could easily wrap tape around it as it would, I think, colapse it. Perhaps if you do find a small leak, a lightweight clear tape could be laid over it to shore up the wall of the tubing. I do remember reading in one post that someone had also traced the leak to the control panel itself, and replaced it with good results.

You will find a vacuum hose block above the accelerator. It is about 2X1.5 and is a clear rubber connector. The colored lines from the panel control meet there with the lines out to the vacuum motors. I have used a hand held vacuum pump with a needle nose fitting at that point to pull vacuum on individual lines for troubleshooting. Perhaps you could do the same and narrow your search. I believe if your panel switches are in the off position, those lines should hold vacuum between the block and the panel. Pulling vacuum on the other half of the block should move the vacuum motors, and should hold vacuum once the valve is in the new position.

As to your concern for the lean condition due to a leak - I can only say that my system was sucking air totally - zero vacuum at the connector block - and ran fine. Your desire to track it down sooner rather than later however makes good sense.

Hope that helps. Let us know what you find.