Virginia Auto Service

Walnut Blasting – BMW Carbon Build Up

Matt Allen, Owner of Virginia Auto Service, cohost of Bumper to Bumper Radio
Matt Allen, Owner of Virginia Auto Service, cohost of Bumper to Bumper  Radio

Ask the Car Guy:  Walnut Blasting and BMW Carbon Build up

“I went to my BMW dealer because my car was acting sluggish.  It had lost its get up and go and it only had about 60,000 miles on it!  The dealer said that my intake manifolds had carbon build up (a common problem with direct injection engines)  and  recommended walnut blasting.”   I thought he was playing an April Fools’ Day joke on me but then I heard it’s a real thing. What is walnut blasting?”  Steve F, Phoenix.

What is Walnut Blasting?

Walnut blasting is a process that some dealers use to treat carbon build up.  According to Consumer Reports, it’s one of the cons of owning a vehicles with gasoline direct injection engines including Audi, BMW, Cadillac, Mercedes-Benz, Mini Cooper,  Volkswagen and more.

Direct injection is becoming more common because it allows manufacturers to increase fuel mileage, power and efficiency.

Just like us, cars require good old fashioned oxygen to go. Every time you put your foot on the accelerator you are telling the car to release gasoline into the combustion chamber of the vehicle. The spark plugs then ignite the gasoline in the combustion chamber causing the car to run.  Carbon is released into the engine as a byproduct of this process.  (Just like when we breathe!)

Carbon build up on an intake manifold of a direct injection engine.
Carbon build up on an intake manifold of a direct injection engine.

The carbon interferes with the vehicle’s normal combustion, altering the compression ratio, operating temperature and sensor readings on your vehicle.  It addition, it builds up and coats the inside of your engine including the air intake valves, combustion chamber and exhaust which restricts your car’s ability to breathe! Thus, it also affects your car’s efficiency and power.  Basically it’s like your car has asthma! The carbon build up is suffocating your car!

When the carbon builds up, one of the common ways to clean it out of your engine is through walnut blasting.

How Does Walnut Blasting Work?

Walnut blasting is when crushed up walnuts are blown into the car’s engine with an air compressor. It works like a sand blaster, except that if sand gets inside of your car’s engine, it will wreck the engine. That’s why they use crushed up walnut shells.

Basically it’s done by removing the intake manifold and blasting it with crushed walnut shells and compressed air, and blasting away all of the carbon build up so your car performs like it was supposed to.

The walnut blasting is a good way to do it, however, what we’ve found is that it often misses those hard to reach places in the engine including the valves and the rings.

The Best Way to Remove Carbon Build Up – It’s Not Walnut Blasting 

We’ve found that you need to get the whole system clean for your car to drive efficiently; including the rings, the valves, the intake manifold. It’s going to require an oil change at the same time as well as the spark plugs.

Walnut blasting isn’t able to reach all of the hard-to-reach areas of the engine where the carbon is caked on. So we use a chemical carbon build up removal process that just melts all that carbon goo away.  And because we’re putting that chemical into the engine and the combustion chamber and we’re getting the compression rates back up.

Intake valve after carbon build up removal.
Intake valve after carbon build up removal.

How Much Does Walnut Blasting or Carbon Removal Cost?  Prices range from  700-$1200.  It depends on the make and model of your vehicle and the size of the engine, i.e. V6, V8, etc.

How Often Does Does Carbon Need to Be Removed from your engine?  It depends on a variety of factors; Your driving habits, the quality of gas you use, how well you take care of your car…etc.   Some dealers would say however, that it should first be done between 22,000 and 40,000 miles.

What are the results of carbon build up? 

Loss of power which can be unnoticed because it’s a gradual loss over time, engine misfire, not specific to a cylinder, random engine misfires, check engine light codes, P0300, P301, P302.

Other symptoms of carbon build up include: Check engine light,  sluggishness, extended starting times, extended cranking, cold weather startup affected.

Is your BMW experiencing sluggishness or any of the other symptoms of carbon build up? Or did the dealer recommend walnut blasting for your BMW?

Bring it in to Virginia Auto Service for a free second opinion or contact us to get a free estimate for carbon build up removal or call us at 602-266-0200.

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