Kings of Cool

| April 07, 2005

Erickson recommends checking isolators out, especially on an older or used truck. Isolators suspend radiators on a bed of soft rubber so chassis vibration will never reach them. If they get hard, vibration will pass right through. If they “get loose in the sockets,” says Erickson, the radiator may even bounce around. This can cause deterioration of internal seals and relatively delicate brazed joints in the unit, resulting in leaks and the need for repairs. Also, check the bolts mounting the brackets to the engine – vibration can occasionally cause them to fail, leaving the radiator vulnerable.

Radius rods, often used to anchor the radiator at the top, also deserve a close look. If loose or misadjusted, they may allow wind pressure to push the core back into the fan as the correct clearance may be less than an inch. Make sure all mounting bolts are tight and any bushings are in good condition. Make sure the radiator is vertical or at the correct angle to ensure adequate clearance between the core and fan. Erickson says this is a critical maintenance area as fan blades can fail catastrophically when rubbing occurs.

Falendysz points out that modern trucks have “cooling modules” that often consist of a metal frame that surrounds and supports not only the radiator, but also the charge air cooler and air conditioner condenser. Maintaining the mounts for the radiator will also often help prevent expensive repairs of these other devices.

“Most radiators have lightweight aluminum cores with plastic tanks,” Falendysz says. “A rubber seal between the core and plastic tank prevents coolant leaks. Minor damage of the core can be repaired by brazing, welding or with epoxy, but most of the time it makes more sense to simply replace the radiator with a new one.”

Erickson says different rules apply with the “tougher, all metal” units, like those used in the Peterbilt 379. Each tube is welded into a corresponding hole in a flat “header plate” located at top and bottom of the radiator core. The header plate holes serve as rigid mounting points for the tubes. The upper and lower tanks, made of stainless steel, are bolted onto the header plates and sealed with rubber gaskets. Radiators in other brands of trucks of traditional design may be similar.

If you develop a leak between the upper tank and header plate, you can easily drain the system, unbolt the tank and replace the gasket. But Erickson warns against attempting to remove the radiator on your own to replace the lower gasket, or for the other repairs a radiator shop might perform on a damaged unit. The unit is so heavy – about 200 pounds – that a large A-frame must be used to support it during removal and replacement. Without such equipment, it’s easy to “mash fins,” says Erickson.

Clogged radiators

You’ll know a radiator is clogged, Erickson says, by cautiously feeling the temperature of the core just after shutting down the engine. Areas of the radiator where tubes are stopped up will be much cooler to the touch. If the radiator isn’t too badly clogged, it may be possible to clean it right on the truck.

Allow the engine to cool and then remove the radiator cap and peer down into the tank to check for clogging. You may see corrosion around the ends of the tubes. This often takes the form of “solder bloom,” where the solder used to seal the tubes into the tank expands when it corrodes, fully or partially blocking off the end of the tube. On systems with a pressurized overflow tank and no cap on the radiator, you may be able to get a look inside the tank by partially draining the system and then disconnecting the upper hose.

If only partly clogged, it may be possible to clean the system by using an “on-line” cleaner that works while you drive. You simply drain some coolant, add the cleaner, which consists of one gallon of liquid, and then drive 25,000 miles. The cleaner includes corrosion resistors to protect the system during the process. After the mileage has elapsed, you drain, flush and refill the system with fresh antifreeze.

More aggressive chemical cleaner can be used while the engine is running but the truck is sitting. One example is Penray’s 2025 Twin Pack. One pack consists of the very acidic cleaner and the other of a neutralizer needed to flush the system after cleaning so the acid won’t damage system metals.

If these do-it-yourself efforts fail, you may still be able to save the clogged radiator core, which Erickson says can cost more than $1,000 to replace. Radiator specialty shops can do the most aggressive and effective cleaning with the unit off the truck, Falendysz says.
Of course, the key to preventing such drastic repairs and cleaning is careful maintenance of the supplemental coolant additives or oxalic acid system that combats system corrosion. “Preventive maintenance by regular interval system flush and refill is the best way to prevent internal clogging from becoming a problem,” Falendysz says.

Doing all these things will help guarantee that you’ll be able to climb long hills with confidence even on the hottest days of the summer.

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