This GMC cargo van was brought in because it ran poorly and had no heat. I was able to verify both concerns easily and brought it into my bay to see what was happening.

The running poorly concern was pretty straight forward. The underside of the distributor cap was heavily corroded. A tune up, (distributor cap & rotor, spark plugs, and plug wires), solved this problem.

The first thing I did for the no heat concern was to check the coolant level in the radiator and was greeted by the mess seen in the photos above and below.

The radiator cap was heavily corroded which is a good indication of what the rest of the cooling system looked like.

This seems to be what happens with GM's Dex Cool coolant over time.

Generally, if the radiator cap looks that bad, the inside of the cooling system is worse.

And yes, it's worse on the inside.

This cooling system looks like it's not only never been flushed, but never maintained.

More than likely, the entire cooling system in the van looks like this.

Thinking I was dealing with a flow problem, I decided to replace the radiator and thermostat. I also disconnect the heater hoses and flushed the system as best as I could with the garden hose. Luckily, the heater core wasn't plugged.

The thermostat was equally as clogged with rust as the radiator.

I replaced everything and was able to get the heat working. Flushing the system got rid of a lot of the rust and corrosion. But there is no way to remove all of it. That means this cooling system is going to have to be maintained often to prevent this from getting bad again.