January 2012
Paul Saurenman, owner of Pacific Oil Cooler Service (POCS) and Aero-Classics Heat Transfer Products Inc., stood in front of Jen and Kent Dellenbusch, publishers of Piper Flyer, and me, freelance aviation writer who after 45 years in the av bizz views all things aeronautical with a shade of skepticism, and told us that the average light plane’s oil cooler acts as an oil filter and becomes more choked up with carbon as engine hours pile up. During the POCS oil cooler cleaning process, Saurenman explained, “about a full ChapStick tube of carbon and metal particles” are cleaned out of the average cooler.
Saurenman went on informing us about oil coolers when he said, “The passages in a new oil cooler are smaller than the diameter of a piece of 0.032 safety wire.”
He ought to know; he’s been in the heat exchanger—oil coolers are the most common General Aviation heat exchanger—refurbishment business for over 25 years. Saurenman recently expanded his business to include Aero-Classics, a state-of-the-art heat exchanger manufacturing company.
We had stopped in to visit the new home of POCS and Aero-Classics in mid-November of 2011. After 26 years at a small (4,000 square feet) facility in South El Monte, Calif., Saurenman recently moved both companies to a 44,000-square-foot facility in La Verne, minutes away from the Brackett Field Airport (KPOC). We were given a tour by Saurenman and a member of his sales staff, Wayne Thomas.
We first weaved our way through the cleaning, repairing and overhauling end of the building and then walked across the line that separates POCS from Aero-Classics Inc.
Aero-Classics fabricates heat exchangers for aero systems that range from the liquid engine coolant required to keep the Rolls-Royce Merlin V-1650 on a P-51 Mustang from melting, to the small, nine-row, drawn cup oil cooler that sticks out like a bristly mustache below the prop on the 105 hp Lycoming O-235 on a Piper Cub Special.
“We hold more FAA-PMAs than the rest of the industry combined,” said Saurenman. PMA, the acronym for Parts Manufacturer Approval, is defined on the FAA’s website as: “Parts Manufacturer Approval (PMA) is both a design approval and a production approval. It is issued for the production of modification or replacement parts, which includes materials, parts, processes, and appliances.”
The Aero-Classics PMAs apply to new heat exchangers that are approved to replace heat exchangers produced by other manufacturers. If you need to replace your Stewart Warner oil cooler (most of which are not FAA-PMA), Aero Classics has a PMA one that is 30 percent less costly, according to Saurenman.
Company History
Saurenman readily admits that he can’t work for anyone else. His entrepreneurial work history zipped here, then there, before he purchased POCS. Saurenman owned the Pasadena Off Road Center—a store he describes as the largest four-wheel drive supply store in Pasadena—in the late 1970s and early 80s, when four-wheeling was big.
After that fad cooled, he owned a Baskin-Robbins ice cream franchise in Lake Havasu City, Ariz. but was frustrated and finally sold his franchise due to what he describes as poor management in that iconic ice cream business.
In the mid-1980s, Saurenman found himself looking for the next opportunity. He purchased Pacific Oil Cooler Service from the widow of the company’s founder in 1985. He didn’t know anything about aircraft oil coolers, but eased into it by hiring the one existing employee and moving the company to South El Monte. Slowly, POCS grew.
Today there are 46 employees working at the two companies, and business is good. According to Saurenman, the company is currently overhauling about 600 heat exchangers each month and business in 2011 was 20 percent ahead of 2010 by the end of October.
Overhauling Oil Coolers and Heat Exchangers
Generally speaking, oil coolers for Lycoming engines are remote-mounted on the firewall or engine baffle; the oil flows to and from these externally-mounted coolers through hoses. Oil coolers for Teledyne Continental Motors (TCM) aircraft engines are bolted onto the engine case.
Let’s say your trusty Lycoming engine is signaling that it’s getting tired. The oil turns black within a few hours after a change; it’s using oil at a ridiculous rate; it’s not the powerhouse it once was; and it’s been decades since a field overhaul. You’re sending the engine to the excellent engine overhaul shop located at your home airport.
The shop recommends sending the cooler in for an overhaul while they’re building your new engine. You wonder why. There hasn’t been any evidence of a leak; the oil temperatures have been in the green. Why spend the money?
Because it’s cheap insurance. Oil coolers are part of the engine oil system. Every bit of carbon and sliver of metal circulating in the engine oil system may lodge in the oil cooler, especially if your engine isn’t equipped with an oil filter.
Even oil filters don’t capture everything. Some carbon gets through even the best filter. When it does, there’s a good chance it will end up deposited on the walls of the tiny passages in the cooler, and much as cholesterol clogs human arteries, these deposits will restrict the amount of oil flowing through the cooler.
Some mechanics don’t understand the POCS cleaning process, so they will say something like, “I’ll just run solvent through it for an hour; that’s good enough.” Don’t listen; solvent at 3 or 4 psi—the pressure output of most solvent wash tanks—won’t even begin to scrub clean the inside of a cooler. It doesn’t make any sense to connect a freshly-rebuilt engine to a cooler that isn’t guaranteed to be clean.
The Process
What happens to an oil cooler during a POCS overhaul? Every cooler undergoes an extensive 25-step overhaul process that begins with a pressure test to check for leaks. Buildups of carbon and contaminants plug small leaks. POCS salesman Wayne Thomas said that 40 percent of the coolers sent in for overhaul end up leaking at some point in the cleaning process. If leaks are found, the cooler is sent back to the repair bench.
After leaks are fixed, the next step is submersion in a chemical fluid for the ultrasonic step in the cleaning process. According to Saurenman, POCS is the only company in the industry that includes a step using ultrasonic vibrations in its FAA-approved cleaning process.
Saurenman also said that “ultrasound does in an hour what used to take 14 hours” using previous methods.
Following that, each cooler is connected to a series of solvent wash machines. These automatically flush another chemical fluid back and forth through each cooler for between 30 to 40 hours at a pressure of 80 to 100 psi. Fluid flow direction is reversed every 60 seconds.
Coolers are deemed to be clean when contaminants larger than 10 microns are no longer caught in filters during two successive checks separated by two-hour intervals.
After the cooler is clean, it is again hydrostatic and static pressure tested. If the oil cooler is leak-free, it undergoes a final inspection. This is where minor problems such as bent fins and mounting flanges are straightened.
TCM case-mounted oil coolers mounting surfaces are ground back to flat by hand-lapping. This extra step helps ensure a leak-free installation.
POCS urges engine shops and owners to send in the oil cooler adapter plate along with the cooler so it can also be lapped back to as-new condition at no additional charge.
POCS also tests cooler thermostatic control valves (Vernatherm) for operation and repairs and recalibrates as necessary—again at no additional charge to the customer if supplied with the cooler for overhaul.
Finally, every cooler is prepped for surface corrosion protection treatments—either Iridite conversion coating, Mil-Spec primer, or paint as specified by the manufacturer.
Every POCS overhauled cooler is returned with an Airworthiness Approval Tag (FAA Form 8130-3).
Customers have three options. They can send their cooler in for overhaul; normal turnaround time is five days. (This is the least expensive option.) They can exchange their cooler for an already overhauled unit if the airplane is in AOG status or time is short; or, they can trade their existing cooler in for credit on a factory new, zero-time cooler.
Newer Processes Reduce Chemical Usage and Reduce Costs
The POCS and Aero-Classics facility is located east of Los Angeles in one of the most pollution- and work safety-conscious regions in the country. Saurenman, like every other business owner, is always seeking ways to cut the costs of doing business without compromising quality of same. This environmentally-minded approach has also improved the working conditions in the POCS/Aero-Classics plant, and lessened the costs of disposal and special handling of materials the state of California has judged to be harmful.
For example, the fluid required during the ultrasonic cleaning stage has been reduced from 200 gallons to 80 gallons. To provide corrosion protection and provide a good paint adhesion surface on the new aluminum parts out of Aero-Classics, the older Alodine conversion coating process that used to be the standard on aluminum has been replaced with a trivalent coating that is much more benign.
Saurenman told us that 75 percent of the business is overhaul work and 25 percent is new.
Aero-Classics Heat Transfer Products—For New Coolers
Aero-Classics, the new heat exchanger manufacturing company co-located in the POCS building—and managed by Skid Saurenman (he’s Paul’s son; no one would tell me how he got the nickname)—is a modern manufacturing facility.
During our tour of Aero-Classics, we watched Sandra Arreguin stack the components that go into one of the stacked-plate coolers the company produces.
Stacked-plate coolers are manufactured by hand-stacking components such as turbulator plates, air fins and mounting brackets. Stack height and component sizes are varied for different coolers.
All components must first undergo a rigorous cleaning to prevent problems during the vacuum brazing process. After the components are stacked and straightened, each stack is clamped tightly together in a fixture and then slid into a vacuum braze oven that’s as big as a VW Bus.
The oven is heated to 1,130 to 1,135 degrees F., and a vacuum pump is turned on to reduce the pressure and pull the oxygen out of the large oven. The stacked layers are bonded together in a process called vacuum brazing. After two hours, the heat is lowered and a fresh batch of new coolers are ready for final testing and labeling, and then put into inventory.
Aero-Classics has recently developed a line of high efficiency (HE) oil coolers under the FAA’s PMA process. This line of new coolers is approved for installation in place of almost all Stewart Warner cooler part numbers, and FAA approval is pending for rest of the HE line.
The Aero-Classics FAA-PMA also provides new replacement coolers for popular units built by Harrison, Lori and Niagara. Saurenman said that every new part undergoes testing to 400 psi, and that all new Aero-Classics coolers and POCS overhauled and exchange heat exchange products have an excellent warranty.
In addition to the new manufacture of popular light airplane coolers, Aero-Classics’ processes facilitate the manufacture of new coolers to replace the old technology coolers on hardworking utility aircraft such as the deHavilland DHC-2 Beaver, and rare warbirds such as the Lockheed P-38 Lightning.
Aero Classics utilizes modern techniques such as computer-aided manufacturing (CAM) and five-axis milling machines to turn out replacement aluminum heat exchangers.
These FAA-PMA coolers not only replace existing coolers which in some cases were manufactured 30 and 40 years ago, the Aero-Classics aluminum coolers weigh a lot less. Replacing the original brass shell, copper tube heat exchanger on the P-38 with a new aluminum unit saves 50 pounds.
In addition to saving weight, new aluminum coolers by Aero-Classics are unsurpassed in thermal heat transfer: if your airplane’s oil or engine liquid coolant temperatures can’t be maintained within the manufacturer’s temperature parameters with an Aero-Classics heat exchanger, you have a problem that no heat exchanger will solve.
POCS and Aero-Classics are leaders in the heat exchanger business. It doesn’t matter whether you are flying the most popular light airplane ever built, or a one-of-a-kind warbird or antique, it’s close to a certainty that these companies can satisfy your heat exchanger needs.
Steve Ells has been an A&P/IA for 38 years and is a commercial pilot with Instrument and Multi-Engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as Associate Editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (www.EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Paso Robles, Calif. with his wife Audrey. Send questions and comments to editor@www.piperflyer.com.
