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1989 and earlier 911 engine cooling

1989 and earlier 911 engine cooling

911's through 1989 have had a variety of auxilliary coolers, in addition to the engine-mounted cooler. The first auxilliary cooler was on the 1969 911S, and there were basically 3 variants after 1974: the loop cooler, the brass-tube cooler, and the radiator-type cooler. In most cases, for street driving these coolers work just fine. However, the demands placed on the engine while on the track can overtax the stock oil cooling capabilities.

First, you need to know if you engine is running too hot. For temperature gauges with numeric temperatures, instead of "zones", if your temps go up above 250 degrees, you need to augment your 911's cooling capacity. For those with "zones" on their oil temp gauge, if you look from the right side onto the far left edge of the gauge, you'll see the degree centigrade temperatures that the zones correspond to. An easy upgrade, which takes less than an hour and around $70 in parts, is to swap out the "zone" oil temp gauge for a numeric gauge, which includes changing the oil temp sensor on the engine. Here's how do do it:  First, getting the gauge out of the dash is simplicity itself: open the front hood, move the carpet aside behind the master cylinder, and push the housing with the oil temp/oil pressure gauges out of the dash. 4 small screws hold the oil temp portion in the larger housing. Old out, new in, change wires to new, push housing back into the dash.  The second part requires replacing the existing temperature sender on the engine with the new, pre-1977, sender. The sender is on the right side of the engine where the cam oil line comes out at the base of the fan. You'll see a yellow/black wire attached to the end of it. Detach the wire, undo the existing sender, put the new sender in (don't forget the washer), attach the wire, and you're done.

So, let's assume you've just completed a driver education event, and your oil temps got into unfriendly territory.  First, before installing or replacing your external cooler, be sure that your engine is in a good state of tune (not running lean, for example), that the airways to the pistons and engine-mounted oil cooler are clear,  that one (if you only have one), else both thermostats are opening around 185 degrees, and that there are no kinks in the brass oil lines running to the external cooler. If these all check out OK, your next action depends on what you already have, and whether you want to upgrade in steps, or jump right to the valance-mounted cooler.  The steps are: No cooler, add one.  Loop cooler and brass-tube cooler, upgrade to radiator-style. The 84+ Porsche Carrera cooler is one option, as are coolers from Earl's, Mocal, B&B, and others.  Already have a radiator-style cooler? Ensure that it's getting good airflow and/or add a fan. Sources of air come from the valance (84+ valances are shaped to flow more air to the cooler), or you can remove your turn signal on the track, or Paragon Products and Pelican Parts sell a scoop which replaces the right side marker lamp, or you can drill holes/cut out some metal behind the right headlight (removing the headlight at the track). Porsche and SPAL are two fan sources.  Already have a working fan? Add a front valance that allows a valance-mounted cooler. There's a gaggle of front valances (I like the RUF polyurethane valance, as it has some flex, which can be important on a lowered daily driver), and B&B, RUF, and others make valance-mounted oil coolers. Some also adapt Honda or Mazda oil coolers. If you're customizing your cooling solution using Earl's, Aeroquip, or similar stainless-covered rubber lines, make sure you don't size them too small, as that can damage the engine. -12an is the minimum, and -16an is better.    To hook up -an connectors to the Porsche metal oil lines, you can buy the appropriate metric-to-an adaptors from Pegasus Racing.

If your oil temperatures are too high, in addition to upgrading your cooling, you might also consider changing your oil to the appropriate grade of synthetic oil.  Synthetics, like Mobil 1, can withstand higher operating temperatures than most dino-based oils. 

Written by Bill Gregory for the "Challenge", monthly publication of the Connecticut Valley Region, Porsche Club of America.

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