M56 Carbon Build Up

Post by **VStar650CL** » Tue Feb 23, 2021 7:44 pm

C6Joe1957 wrote: ↑
Tue Feb 23, 2021 7:25 pm
Would the cats be stressed in any way?

Not that I've ever seen, and we do it a lot at the dealership. I think I'd be careful about not overdoing it, you only need a teaspoon or two. But it's just mineral oil, the cat burns it up. You won't even get any smoke.

Post by **Shanehsmp** » Tue Feb 23, 2021 7:45 pm

C6Joe1957 wrote: ↑
Tue Feb 23, 2021 6:27 pm

I bought these awhile back when I was trouble shooting my P0087, P0300 and P0304 trouble codes. post6814737.html?sid=36cf7a6a0fe8993ee3 ... 4#p6814737

You can get them here: https://www.infinitipartsdeal.com/parts ... &filter=()

Or on Amazon: https://www.amazon.com/Infiniti-A4035-1 ... B00L2O0K0S

Ok, I saw that part number, but wasn't sure if it was individual or for all 8. Interested in selling yours? I'm in Canada and my dealer price would be waaay too high. If not, I'll try ordering from the Infiniti link.

Post by **Ilya** » Tue Feb 23, 2021 11:56 pm

VStar650CL wrote: ↑
Tue Feb 23, 2021 7:41 pm
While I'm in here, let me tell the war story about how I discovered glycol's flash point, it's funny. Some years back an Altima rolled into the dealership on a hook with the engine hood burnt to a crisp. The story was, it caught fire in a restaurant parking lot while the family was eating breakfast. After looking it over carefully, the location and spread of the fire seemed to indicate it started in the fat harness atop the engine, which on an Altie contains the alternator cable and a bunch of skinny ground wires. The heat shield was missing from the cat, and I figured they baked the insulation until something failed. It made sense, a short to one of those skinny grounds would flame up long before the 100A alternator link failed.

We had a DTS at the time who happened to be an engineer who tired of his desk and decided to hit the field. Japanese gentleman with a mind like a samurai bear-trap, he was just plain brilliant. Probably forgot more about automotive chemistry than some other engineers will ever know. I asked for his opinion when he visited. He pointed straight at the missing heat shield, and I thought, "Ahah, I got this right." But when I voiced it, he shook his head and patiently explained that the heat shield wasn't only to protect the car from the cat, it was also to protect the cat from the rest of the car. He educated me about glycol's flash point and opined that I would probably find a pinhole in the radiator.

Not quite ready to buy it, after he left I prepared to yank the radiator and run a pressure test. Turned out I didn't need to. When the radiator moved, I found a 6-penny brad nail stuck through the condenser fins and right into a radiator tube, no more than 3" sideways from the center of the converter. When the family parked at the restaurant, the cooking engine turned the glycol into fumes. It hit stoichiometry underneath the closed engine hood and went up like a candle from the converter's residual heat.

I guess there's a broader lesson in there about heat shields being in place for a reason, but damn... whoda thunk anti freeze could be that dangerous?

Wow! Crazy indeed!

Post by **Yoda's Master** » Wed Feb 24, 2021 7:45 pm

Which vacuum hose hose do you recommend using?

Post by **VStar650CL** » Wed Feb 24, 2021 7:54 pm

Yoda's Master wrote: ↑
Wed Feb 24, 2021 7:45 pm
Which vacuum hose hose do you recommend using?

Personally I use the brake booster unless the line is buried. Since it requires an assistant to race the engine anyway, it's easy enough to cap it with a thumb and then give it a squirt once the RPM's are up.

Post by **VStar650CL** » Wed Feb 24, 2021 8:00 pm

PS - It's also critical to make sure the engine is fully warm. The bigger the temperature differential between the ATF vapor and the carbon, the more easily it shatters.

Post by **Yoda's Master** » Thu Feb 25, 2021 12:47 pm

Thanks VStar

Post by **Ilya** » Thu Feb 25, 2021 1:31 pm

And just to confirm, this won't make my already bad cats worse?

Post by **VStar650CL** » Thu Feb 25, 2021 1:53 pm

Ilya wrote: ↑
Thu Feb 25, 2021 1:31 pm
And just to confirm, this won't make my already bad cats worse?

Nope.

Post by **Ilya** » Thu Feb 25, 2021 11:24 pm

VStar650CL wrote: ↑
Thu Feb 25, 2021 1:53 pm

Ilya wrote: ↑
Thu Feb 25, 2021 1:31 pm
And just to confirm, this won't make my already bad cats worse?
Nope.

Final question. How often do you do this? lol. My wife's '16 QX60 has 47kmi on the dot and my M56x has like 128 and change. I usually do Seafoam through the brake booster like every 30k but might switch to doing ATF every 30k...good?

Post by **VStar650CL** » Fri Feb 26, 2021 5:32 am

Ilya wrote: ↑
Thu Feb 25, 2021 11:24 pm
Final question. How often do you do this? lol. My wife's '16 QX60 has 47kmi on the dot and my M56x has like 128 and change. I usually do Seafoam through the brake booster like every 30k but might switch to doing ATF every 30k...good?

Depends on the injection type and how you drive. With normal EFI you may never need a de-carboning unless you drive like grandma. Pouncing on the pedal periodically will usually suffice to keep them clean. Paradoxically, DIG engines often build up more carbon on the intake side the harder you drive them. That can be true with turbos as well. But generically, yes, I'd say 30K is probably a good interval.

Post by **Ilya** » Fri Feb 26, 2021 9:15 am

Thanks! I'll need to add this to the list for the next maintenance round.

Post by **Shanehsmp** » Sat Feb 27, 2021 9:21 am

So I'm likely Walnut Blasting today - at the very least I'm removing my intake manifold to check the condition of the valves....

Question is, do you HAVE TO drain the coolant or can you just remove the throttle bodies and place them to the side then proceed with the rest of the removal?

Manual says I must, but also had some other notes that are a little unclear (The note under Part 9)

Post by **VStar650CL** » Sat Feb 27, 2021 9:30 am

Might be something different on M's, some of these guys would know better than I do, but in general if you're simply lifting the plenum for a look-see, you can set the TB aside without draining. You might want to consider just hanging the plenum on bungees and taking loose as little as possible, some of the other plumbing can be a PITA.

Post by **Shanehsmp** » Sat Feb 27, 2021 9:56 am

VStar650CL wrote: ↑
Sat Feb 27, 2021 9:30 am
Might be something different on M's, some of these guys would know better than I do, but in general if you're simply lifting the plenum for a look-see, you can set the TB aside without draining. You might want to consider just hanging the plenum on bungees and taking loose as little as possible, some of the other plumbing can be a PITA.

I think this is what I'll be doing, having to change the coolant would make this even much more of a hassle. I just have to figure out the path of the coolant, I think it actually loops around to the other throttle body now that I think about it....I'll have to get creative.

BTW VSTAR, do you recommend anything for fuel injectors? Now that I've kind of pinpointed my issues to excessive carbon build up, I'm less inclined to pull my injectors and actually lest each one. I bought some Lucas fuel additive, but if there's anything better you'd recommend I'll try that....

Post by **VStar650CL** » Sat Feb 27, 2021 11:05 am

Shanehsmp wrote: ↑
Sat Feb 27, 2021 9:56 am
BTW VSTAR, do you recommend anything for fuel injectors? Now that I've kind of pinpointed my issues to excessive carbon build up, I'm less inclined to pull my injectors and actually lest each one. I bought some Lucas fuel additive, but if there's anything better you'd recommend I'll try that....

Like I said, DIG's tend to build up more the harder you drive them. Using a fuel with carbon-retardant properties like Techron can mitigate it, but preventing it is just about impossible. The best thing is just a routine de-carboning with every 30K service. Thin layers of carbon don't usually cause issues, it's when they thicken enough to create hot spots and occlusions in the flow that problems happen.

M56 Carbon Build Up

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