Mustang Overheating With Underdrive Pulleys

by charlie
(goshen ny)


I have installed aftermarket underdrive pulleys on my 1988 Ford Mustang GT. It seems to run a little hotter than it did before they were installed. Is this normal for the car to have the Mustang overheating with this set up?


Hi Charlie

In answer to your question about how underdrive pulleys can affect your cooling system, I'd have to say yes, this can be a factor.

There are both pro's and cons to using underdrive systems.

While the advantage of changing the pulleys in these systems can be an increase in engine and absolute performance, as a result of reducing parasitic horsepower losses from components such as your alternator or a mechanical cooling fan, another issue can result from the change.

For instance, in the situation of your 1988 Mustang's cooling fan, if you are driving it more slowly, then you are also sending a lower volume of cooling air through your radiator, making the job of keeping the engine temperature at its peak performance level more of a challenge.

Similarly the alternator can have performance issues as well.

For instance, since so many owners of pony cars, from the classic mustangs, to newer more hi tech cars like yours have additions never considered in the original manufacture of the car like high powered sound systems, with big amps and huge subs, combined with the standard new car features like power windows, air conditioning and other power robbing devices, it's easy to put strain on the oem stock components.

When you under drive the system, it increases the strain on these systems and can result in early failure.

Possible Solutions ?

OK. This first one may seem like an oxymoron, but you could add an additional electric cooling fan. That may take a bit more power and add some stress to the charging system, but will help restore air flow to your radiator and reduce the chance of overheating.

Or, you could consider adding a bigger radiator. If you now, have a single core rad, you could move up to a two core radiator, which increases surface area, helping to cool your engine.

And I'm not recommending removal of your under drive setup because it's just too good of a deal in getting some "free horsepower".

Good idea to get that figured out before the days of summer.



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