The following is a question we received from a customer. It was interesting enough to warrant a short article on the topic. Read on!
Quick question: I have the Dakota Digital cylinder head temp gauge installed on my van (it’s a 1982 Vanagon, 2.0L, fuel-injected and air-cooled). I have the cylinder head temp sensor ring installed on the #3 spark plug, sitting between the head and the crush washer of the spark plug.
I am seeing what I believe are very high temp ranges and wonder if I am getting accurate readings. Any thoughts on this? For example, at 55mph @3100 rpm, I’m reading about 400 degrees (this on a level road). This morning I went over a relatively small mountain pass 4,000 feet) and I had to drop down to 20-25 mph to keep the temp below 450 degrees. Even then, it was reading between 442 and 444.
Am I being too overly cautious/concerned here?
Our response: There is a reason the typical VDO cylinder head temperature gauge goes up to 600F (316C), and the middle of the gauge is around 350F (177C), the “normal” range.
The engine in an air-cooled Vanagon was originally designed for 1968-74 VW Type 4 sedan and wagon, and also used in the Porsche 914 from 1969-76, and in the 912 for one year 1976. It was originally a 1700cc/~60HP engine, and the vehicles weighed around 1500-3000#. In 1972 they started using it in the VW Bus, and by 1976 it was up to 2000cc/~70HP with the same cooling system with the Bus Westy topping out over 5000# fully loaded.
The engine was then used in the 1980-83 Vanagon that could top out over 6000# in fully loaded Westy form. The cooling system had met its match, and as a result it is almost impossible to drive a fully loaded, Vanagon Westy “normally” and keep the cylinder head temperature below 450F, as you can see. This is precisely why VW switched to liquid-cooled engines starting in 1983.
With a properly functioning liquid cooling system it is literally impossible to overheat the engine. The key words of course, are “properly functioning” which means continuous cooling system monitoring and maintenance.
Whereas the air-cooled engine has a “maintenance-free” cooling system. But the word “cooling” deserves quotation marks!
The good news is that occasional 500-degree temps for a short period won’t kill it immediately, but the more you do it the shorter the life of the engine. If you run over 500 degrees for more than a few continuous minutes—you can pretty much destroy the engine in short order.
Adding an oil cooler can help, but oil is not a very good coolant, and very little oil gets up into the heads - just whatever gets pumped up there through the push rod tubes to lubricate the rocker arms.
To keep an air-cooled Vanagon engine alive you just have to baby it like you have been, or risk severe engine damage—no way around it.