Here is some background info on the eventual failure of late model plastic coolant pipes on 1986-91 2WD & 4WD Vanagons—and our low cost, semi-permanent solution. The Coolant Pipe Repair Kit.
THE SITUATION:
The engine in all water-cooled Vanagons is in the rear and the radiator is up front. Running the length of the vehicle and underneath are two tubes through which the engine coolant is transferred to and from the radiator. At each end of these pipes are attached rubber hoses with hose clamps. These tubes are commonly referred to as “radiator coolant pipes.” On early water-cooled Vanagons (82-85) the pipes were made of 1-1/2 inch OD steel and painted black. On later model 1985-1/2 models, VW switched to 1-3/4 inch OD white plastic tubing with steel inserts at each end. In 1986 the entire cooling system changed, and the pipes were shortened in the rear, one by about 18 inches, the other by about 24 inches on 2WD models, and both about 24” shorter on 4WD models. They remained white plastic with steel inserts at each end. The system was unchanged through the end of the Vanagon production in 1991.
THE PROBLEM:
The problem with the steel pipes is that they would rust and fall apart. The plastic parts, of course, don't rust—which is great. But the problem with the plastic pipes is that over time the plastic barbs at each end would fail, and the metal inserts (also at each end) would work their way out into the hose (see photo above). This happens because the coefficient of friction between the plastic and the steel insert is very low compared to the friction between the plastic and the rubber hose. Heat, coolant flow, and vibration cause the metal insert to wiggle out of the plastic over time. Eventually, the metal insert wiggles out from under the spring clamp, allowing the plastic tubing to collapse. When this happens, the clamp can no longer exert any force between the hose and the plastic. So, the force generated by the coolant pressure exerted over the cross-section of the hose (pressure x area) is no longer counteracted by the frictional force between the plastic and the rubber hose (clamping force x µ). In engineering terms, this is called a "free body diagram that is no longer in balance." In layman's terms it is called, "Holy crap, what is all that coolant doing on the ground!" Result: The hose blows off, which leads to all of the coolant rushing out, which in turn causes the engine to melt down and ruin an otherwise perfect road trip.
The trick is keeping the metal inserts in place. Some people, including us, first thought that the way to go was simply to push the metal inserts back in, drill a little hole in the side, and use a fastener to keep the metal insert in place. In fact, that is how we fixed a set on one of our personal Vanagons back in 1996. What happened over time was this: the hole we drilled caused the pipe to crack, and then we were completely screwed—and eventually had to replace the pipes with a set of new stainless steel ones. That is the ultimate solution: switch to stainless steel pipes. They can't rust or fall apart. HOWEVER, this is a somewhat costly fix, and it might not be necessary.
THE BUDGET SOLUTION:
If your plastic pipes are still otherwise serviceable (not cracked or otherwise damaged), the GoWesty kit can breathe relatively inexpensive new life into them. The kit consists of a set of custom-made brass fittings of the appropriate size and shape. These fittings are placed inside the hose and clamped down securely. Then, the hose is installed on the plastic pipe and secured by a separate clamp (see cross-section photos below). Now the frictional force between the plastic pipe and the rubber hose acts to hold the whole thing together because the steel insert can't wiggle out of place. How do we know this works? We installed this kit in our shop for years. Many of these vehicles came back for service work, and we could see with our own eyes that the hoses are in place and nothing has moved. Plus, we have sold hundreds of these kits online. If this solution did not work, we probably would have heard about it by now!
THE BEST SOLUTION:
If you've got the clams to fix the problem forever, forget about the repair kit, and replace those long plastic pipes entirely. We stock super-quality stainless pipes that will most certainly outlast the rest of the van. Do it once, do it right!
Stainless Coolant Pipe Set - Early Vanagon, Late Vanagon and Syncro 
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