Defrost Manifold - 83 Quattro Rally Build Update

Posted on Feb 28, 2019

Now we had the heater in we thought it a good idea to install some of the ducting to spread that heat where it might be needed. The foot wells heat comes right out of the side of the heater box so we don’t have to deal with that, and the center and side vents are fed from flexible pipes so we can figure those out later. But the windshield defrost blows through the firewall bulkhead and into a distribution manifold that used to be part of the molded dash pad. Fortunately we hadn’t managed to throw the dash pad away.

This is the plastic distribution manifold on the underside of the dash pad.

From what we gleaned looking at hundreds of restoration pictures is that you cut the dash pad to leave just this front area containing the manifold and vents then remove all the molded on dash pad foam from the top and bolt it back into place. Of course our manifold was cracked so we had to disassemble the thing.

This is how the manifold interfaces with the bulkhead/dash tube once it’s all put back together. You can see the central feed from the heater box below the dash tube. 

Next we removed the excess dash pad material with a cutoff wheel and set about cleaning it up.

We covered up some excess holes that were previously blocked and painted it and the vents satin black.

Then we set about fixing the plastic manifold.

While the glue was setting up we riveted the vents back into place.

Then we applied some sealant before riveting the two parts back together.

And then popped it into place.

For some reason this was one of the most satisfying projects we have tackled so far. Next time we’ll restore and install the washer bottle and coolant reservoir. Maybe not so satisfying.