It's all there on page 16 of the manual. Unfortunately, the text is in German: Wenn der motor seine betriebstemperatur hat max 80 wasserthemperatur... The manual is for a 1981 Porsche 924 GTR, made in limited numbers (no more than a couple of dozen) for FIA Group 4 and IMSA GT racing. In typical Porsche fashion, several prototypes were built and tested before being made available for customer teams. Three entered the 1980 24 Heures du Mans, one for a German team, one for the Brits and one for the US, driven by Al Holbert and Derek Bell.
The road-going 924 Turbo (type 931) had just been introduced and Porsche, as ever, saw the wisdom of having a version participate in the world's most famous sports car race. The 924 GT prototypes had the usual Weissach touches: titanium everything, axles, wiper shafts, a dash panel that weighed a couple of pounds, center-lock wheels, brakes from the 935, etc.
The 1980 race was one of wettest in recent history and the balanced handling of the 924 chassis was of great benefit as the underpowered GT drove around much faster cars. The slower pace helped get all three cars to the finish, posting overall results of 6th, 12th and 13th.
The 003 chassis went to Holbert, who drove it in the 1982 season. Then the car did a stint with Bruce Leven in the Trans-Am in Bayside colors. I found it years later in Portland, used as a club racer and painted purple. Not having the funds to purchase the car, it went to David Morse (no relation) to join his stable. Part of the deal was that I would get to drive 003 upon restoration.
At Laguna Seca, during the Monterey Historics in 1998, Porsche's 50th anniversary was celebrated in a manner befitting a company that had come to dominate sports car racing. Anything of importance the factory had raced was present. The main event included 911 RSRs, 934s, 935s, two 936s and a 924 GT. That lone wasserpumper was me, aboard 924-003. Fortunately, I had some test time in the car at the pre-Historics, so I felt pretty comfortable. Of all the Porsche racers I had driven, the 924 was by far the easiest. And remains so.
One tends to forget that modern racecars are, for the most part, fairly reliable. This doesn't translate to older machinery. For all the positives of the 924, the motor wasn't one of them. It suffered overheating problems and constant head gasket failure. Get it hot once, you may get away with it, but failure is certain on the next outing.
Back to the factory drivers manual: ACHTUNG: FUR DEN WASSERKUHLER IST KEIN GEBLASE EINGEBAUT (translation: there is no fan for the radiator). If you ain't movin', you're cookin'. I got in five solid laps before I heard the gurgle, like farting in the bathtub, and noticed the temp gauge heading towards sauna territory. Weekend over, the big race went on without me. I stood on the pit wall, watching.
Fade to present-day August 2007, the 34th Monterey Historics at Laguna Seca. By this time, 924-003 had been repaired and moved back east, where it lived among a collection of Porsche auspuffers. Showing little restraint or manners, I called the owner, Matt Drendel, and asked if I could have another chance. I felt I had unfinished business with the car. For some insane reason, he agreed, with the warning that if I break it, I fix it.
The car arrived on the West Coast and went straight to Ron Gruener of JWE for preparation. Gruener did much of its original restoration. It needed no work, having won its class at the recent Amelia Island Concours, the motor was in good shape, and all systems functioned properly at a recent test at Sears Point. What could go wrong? A repeat of history, that's what.