Of course, every car has its faults. You’ll hear Internet chatter about the subpar interior quality and annoying check-engine lights of these BMWs, but the fragile cooling systems are perhaps their most troubling problem.
All these cars, from the four-cylinder base model to the halo M3, have radiators with plastic entry and exit openings. After 80,000 to 100,000 miles–figure seven to 10 years–these ports tend to fatigue and crack. To make matters worse, these cars also use a belt-driven fan made of–you guessed it–plastic.
Once these fan blades age and crack, they are known to snap off and puncture the radiator, creating an expensive problem. On top of that, the E36 cars are equipped with barely adequate water pumps, so an upgrade is a good idea before any sort of track use.
Not surprisingly, after 16 years and 155,000 miles, our M3’s cooling system developed a leak. We could have made a quick repair, but we decided to perform a full system overhaul. We intend to keep our E36 M3 for the long haul, so instead of using OEM parts for a factory fix, we decided to investigate more permanent solutions.
First we needed some expert advice, so we called up James Clay, owner of BimmerWorld. James has thrashed BMWs on track for years, so we figured he’d have a cooling system solution that would be durable–you know, something that could tackle our brutal Florida summers.
Finding the Best Radiator
The replacement radiator is so pretty, it's a shame it will be hidden from view.
Our first improvement was to ditch the stock BMW radiator and replace it with an all-aluminum unit from C&R Racing. This beautiful C&R Racing radiator features CNC-machined brackets that fit into the stock mounting points. It even accepts the stock overflow tank.
The BimmerWorld team uses these C&R radiators in their Grand-Am race cars, and James has already tried the alternatives. The stock ones, he notes, will eventually get brittle again.
“You can get a Chinese or Asian all-aluminum radiator for $200,” he notes. “These don’t have plastic end tanks, but also won’t likely last as long as the plastic due to poor build quality. We tried to provide a cheap route in the past and we canned the product.
“The major factor that separates the C&R from the rest–beyond being all-aluminum, fully welded, and made in the U.S.–is that it isn’t just a thicker OE core. It’s a true performance core, made to flow better with turbulators to increase cooling efficiency, and with a tube and fin design to maximize efficiency.”
Increasing the Flow
The difference in the Stewart pump's capacity is amazing!
Next on our list was to remove our belt-driven fan and replace with a Spal electric unit. Our low-profile fan moves 1300 cfm worth of air, which Spal says frees up approximately 7 horsepower. The blades on the Spal unit are also enclosed in a protective cage, eliminating the danger of damage caused by broken impeller blades.
The Spal fan kit includes a sensor that attaches to the radiator housing. When the sensor nears 190 degrees Fahrenheit, the fan switches on.
While we had our radiator and fan detached, we decided to change our thermostat and water pump. Instead of using the merely passable stock water pump, we ordered a Stewart Components pump on BimmerWorld’s recommendation. Stewart Components claims 15 percent more fluid movement, and the pump also features a long-lasting, stainless-steel impeller and a massing performance bearing. Its maker also stands behind the pump with a lifetime warranty.
Upon laying eyes on the Stewart Components pump, our first thought was that it was an incorrect part. The stock pump was so much shallower than the Stewart Unit that we couldn’t imagine it fitting in the same location.
Reassembly of the cooling system was simple–a beginner or novice enthusiast could handle it. Older BMWs are notorious for using fragile plastic clips to hold wiring looms and assorted brackets, so patience in dealing with these clips is extremely important. This is one case where slowing down does indeed make you faster.
We decided to keep the original auxiliary fan that mounts to the front side of the air-conditioner compressor. For extra efficiency, we also retained our stock radiator shroud. This required a bit of simply, straightforward trimming to ensure a proper fit.
Getting the Bubbles Out
Bleeding of the system is a must do to insure proper performance.
Then it was time to bleed the system, and all the air bubbles had to be removed. James shared his technique with us: “Install everything completely, loosen the bleed screw on the coolant tank, and keep the cap off. Then, jack the front of the car up a foot; keep the rear wheels on the ground.
“Disconnect the upper radiator hose from radiator and fill the cooling system by pouring coolant into the hose. Then, connect the hose and, only then, top off the system by pouring coolant into the expansion tank. This is the only way to prevent an air bubble that will later spit out all the fluid.
“When you have filled it correctly, tighten the bleeder on the tank and, with the cap off and the engine not overly hot and running, rev the motor. If it spits a stream of water across the coolant tank opening, it is successfully bled.”
When the installation was complete, all the components worked properly and fit as they should under hood. Our E36 came up to operating temperature and stayed put, even after long periods of idling in 90-degree heat.
Of course, quality components rarely come cheap, and a revised E36 cooling system is no exception. Fortunately, the cost wasn’t as steep as we feared. Plan on $1300 for an entire system revamp like ours. If this sounds high, keep in mind that replacing the factory equipment would run you about $1200 in parts at the dealer, and the system would need to be replaced again in a few years. We plan to keep this car–and enjoy it on track–for many years, so the added cost was more than justified.
