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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

Eng Refresh, Health Check, etc 14

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As mentioned so many times, please drive your NSX regularly.

Just 15min of cruising is enough, ideally every week but if not, once a month.

No need waiting for the engine to fully warmed up unless you are living in the freezing cold sub-zero environment.
Instead, start driving gently as soon as the CCU starts blowing the air with temperature set at your preference and fan speed in auto mode.

For example, in UK, if the car was kept inside the garage,
you should be able to start moving the car in just over 5min after starting the engine even in the cold winter.

As reported earlier, I found several extra markings on the centre rocker arms at the rear bank intake side on this engine.
It's probably caused by the sticky LMA being used for ages/miles.

The front bank was covered in sticky blowby gunk that I couldn't check anything in detail until I started the 1st stage cleaning.

This is what I found.

I spoke with the owner to see whether he is happy for me to use these photos to warn other owners and he was very kind allowing me to do so.

For the clarification, these markings (already smoothed out by years of running the engine) happened years/miles ago.
Most likely during the time of previous owner(s).

When you switch off the engine, some of the valves are kept open.

Or, if you just keep running the engine at idle rpm without driving or repeat the multiple short distance journeys,
you are circulating the moisture/fuel rich blowby gas inside the engine.

Once the engine cools down and temperature drops, it will create condensation inside the engine.
Not a problem if you drive regularly.
However, if you park the car for months, it may allow the build-up of rust at certain places.

Next time when you crank the engine, the rust may cause scratch markings.
It won’t cause immediate issue but if this process was repeated many times over the years,
it shall cause bite markings.

It's different from oil film issue caused by oil pressure drop.
With oil film issue, you will see lots and lots of scratch line markings at entire width of the area if it's metal-on-metal contact.

And if the temperature got too high, you will see changes in colour or even the melted materials.

With the rust issue, the markings are more like the material being chewed off and spot like shape instead of full width.

Fortunately, over the years/miles after this happened, the edge of the chewed off section was smoothed out with no wear to the cam lobe surface.

Considering the cam rotation direction, the width of cam lobe and no further contact between the dimple and the cam lobe,
the rocker arms can be re-used.

This can happen at the crankshaft journal/main/rod metal area and the damages would be even more serious than the rocker arm section.
I already know at least 3 engine failures caused by this.

So, once again, please try driving your NSX regularly.

And don't rely too much on the air conditioned storage.

It can't remove some of the moisture inside the engine.