Beware Direct-Injection Engine Cleaning if You Have Nut Allergies
The other day I dropped my car off at a European specialist shop, and while I was there, a technician was working in the engine bay of a Mk7 Golf R, cleaning out carbon deposits off the intake valves. A fairly routine—say every 30,000 miles or so—service for modern direct-injection cars. Since no fuel is injected into the intake manifold, there's nothing to clean the carbon, leading to nasty buildups on the valves. The mechanic was hitting the engine with what appeared compressed air, generating clouds that resembled sawdust.
I didn't think much about it until I got on the subway and thought I was having an asthma attack for no apparent reason. I took my inhaler a few times, and told my colleagues about this peculiar experience when I got to the office. That's when I learned about walnut blasting. I had an allergic reaction.
A 2020 Consumer Reports article explains walnut blasting well: "The process of walnut blasting, which entails cleaning the intake manifold and valves of a car’s engine with a high pressure air blast of finely crushed walnut shells (a biodegradable abrasive), is meant to help clear out carbon buildup on older gasoline direct injection (GDI) engines, thus helping the car run better."
Walnut blasting a good—if expensive, as the intake manifold has to come off—way to maintain engine performance for the life of a direct-injection car. Consumer Reports even notes that it's BMW's recommended method for cleaning its direct-injection engines made between 2006 and 2016. It's also a potentially huge hazard for people with tree-nut-allergies like myself.
My symptoms were minor, relatively speaking: a numb feeling on my lips and shortness of breath. Basically the same things I feel when I exercise vigorously, though the symptoms lingered for far longer. A Benadryl later in the day helped, as did taking my inhaler a few more times. But, my allergies come mainly from actually eating nuts—I'd never had an issue with airborne nut particles before. It could've been so much worse. In 2017, an Edmonton, Canada man, Justin Mathews, died after going into anaphylactic shock after inhaling walnut particles used to strip lead paint from a firehouse. Mathews was reportedly in the building for 20 minutes before walking outside and collapsing. He was taken off life support at the hospital after doctors told the man's family that he would never recover from the brain damage experienced as a result of the anaphylaxis.
Believe me, I'm thanking my lucky stars.
Allergic Living, a publication for allergy sufferers, reported in 2017 that the particles used for walnut blasting wouldn't trigger allergies if they're washed, but that's typically not the case.
Direct-injection has huge benefits for boosting the performance and efficiency of internal-combustion engines. Consumer Reports says that some automakers now use an injector in the intake manifold to help keep the valves clean, and of course, there's also dual fuel engines that rely on port and direct injection. As for the walnuts themselves, using them for cleaning also makes a lot of sense, too. They are obviously biodegradable, and thus, more environmentally friendly than man-made cleaning products. It's just that their use—for cleaning direct-injection engines and otherwise—can be potentially deadly.
Dr. Joyce Elaine Yu, an allergy specialist at the Columbia University Irving Medical Center recommended I wear a mask to pick up my car. "The better the mask, the more particles you keep out," she said. "The walnut particles are generally much bigger than a viral particle like COVID, so whatever will keep out COVID will certainly keep out walnut dust."
For allergy sufferers who have to perform a walnut blasting, Dr. Yu said one should wear goggles, gloves, and a clean-room suit. Special care should also be taken to clean up any residual walnut dust after the intake is cleaned, as contact with the skin of an allergy sufferer can cause a rash.
I called the shop and explained my situation. I don't blame them, of course, they're just doing their job, and apparently I was the first customer that raised the issue with them. They kept my car away from any walnut blasting, and give it a thorough clean when they were done.
Shops would be wise to put up signs warning people about the effects of walnut blasting, as the consequences of inhaling this dust can be deadly. Even at best, as was my case, it can be extremely uncomfortable.
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