Oil Cooler Failures

The following is derived from maintenance facility submissions to the FAA’s Service Difficulty Reports database.

Aviation Safety

Friday, August 23, 2024 at 05:45 AM ET

Verified

Edited By: Omar Filipovic

Key Takeaways:

Oil cooler failures are a recurring issue across various aircraft types, frequently leading to significant oil loss and potential engine problems.
These failures can occur even with recently installed or very low-time oil cooler parts, as evidenced by failures at 8, 18, and 51 hours of operation.
Common failure modes include leaks from cracks, faulty welds, internal component issues, or pleats, as well as operational problems like vapor lock.
In some cases, instrument warnings for oil cooler leaks may be absent, emphasizing the importance of thorough pre-flight inspections for oil residue.

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Cessna 177 Cardinal

New Oil Cooler Failure

Sometime after engine start, the eight-hour-old oil cooler developed a leak, resulting in engine stoppage approximately two minutes into the flight. The result was an emergency descent and off-airport landing. According to the technician, because the oil cooler is downstream of the oil pressure gauge, there were no warning indications on instruments.

Part total time: 8.0 hours

Cessna TR182 Turbo Skylane RG

Oil Cooler Vapor Lock

After installing a remanufactured engine, the turbo was found leaking from its center section during idle, but not when above 1000 rpm. Troubleshooting revealed oil cooler vapor lock caused the leak. Bleeding air from the cooler stopped the oil leak, but it returned after 50 hours of operation. Relocated cooler to horizontal position and oil leak was eliminated.

Part total time: Unknown

Cessna 421C Golden Eagle

Leaking Oil Cooler

During routine post-oil-change inspection, an oil leak was discovered on the outboard rear corner of the left engine. Investigation revealed a crack or void in the weld on the bottom of the oil cooler where the leak originated.

Part total time: 832.0 hours

Piper PA-28-181 Archer II/III

Cracked Oil Cooler

On preflight, no oil was visible on the dipstick. Examination revealed the firewall and cowling interior were bathed in fresh oil. The oil cooler had cracked. The sump was drained and 2.25 quarts of oil were found remaining. The aircraft had last flown the night before, departing with seven quarts of oil.

Part total time: 95.0 hours

Piper PA-28-181 Archer II/III

Leaking Pleats

Post-flight inspection revealed oil streamed the length of the fuselage and onto the wing. The airplane had lost five quarts of oil in 1.4 tach hours. Investigation revealed the oil cooler was leaking from inside the pleats and the engine had 3.5 qts. of oil left, a loss of five qts. in 1.4 Hours. The oil cooler had been installed new, three weeks prior.

Part total time: 51.0 hours

Piper PA-44-180 Seminole

Internal Failure

On preflight, the crew noted an oil streak emanating from under the inboard side of the right engine cowl. Investigation revealed fresh oil all over the inside of the engine cowling. The tech ran the engine with the top cowl removed and witnessed oil bubbling out from within the pleats of the right engine oil cooler. The oil cooler had been installed seven weeks earlier.

Part total time: 18.0 hours