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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > Walnut Blasting Uh-oh...



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      02-26-2021, 12:07 AM   #1
E93Dude
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Walnut Blasting Uh-oh...

So I pulled the trigger and finally got around to walnut blasting my 2007 E93. Nearly 14 years old and less that 100K on the odo - and never bothered to carbon clean it - never felt performance was suffering, and I guess I took a "if its not broke, dont fix it" attitude (in retrospect, not good for BMWs...)

I was shocked to see the amount of crap in the intakes and on the valves, and took a moment to remember all that hp and gas mileage I must have lost over the years. Anyway, I finished blasting the intakes and they looked great, only problem is that I belatedly realised that cylinder #4 valves were not quite closed when I blasted them. Unfortunatly, what appears from the borescope to be about 1/4 to 1/2 teaspoon of crushed walnut shells ended up in the cylinder head cavity. I fashioned a crude narrow spatula-thing to go though the spark plug bore, into the cylinder head and start to gently (and innefficently) scoop out the shells which are mixed with some CRC cleaner that had also seeped though prior to the walnut blasting. Not very efficient. I am looking for ideas (short of removing the head) to clean it out. My inital plan is to inject more CRC cleaner into the cavity to form a liquid/slush and then insert a narrow tube and try to suck it out. I assume I cannot just reassemble the engine, fire it up and hope the walnuts just burn up. Helpful suggestions welcome....

Last edited by E93Dude; 02-26-2021 at 04:22 PM..
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      02-26-2021, 12:51 AM   #2
Vivek.
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I'd think sticking a shop vac on either the intake port or the spark plug hole with the valves open would be able to suck it up.
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My wife would give me so much head if I did that.
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      02-26-2021, 12:52 AM   #3
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Let the CRC evaporate, then try something like a straw or narrow tube attached to a shop vac. Let it evaporate as it's likely a combustible product and you don't want that going through the shop vac. Also blowing compressed air through the intake(valves open) can help get the shells airborne while the suction from the vac will hopefully suck them out.

Also a small amount of walnut shells remaining shouldn't be a problem, that's one of the reasons walnut shells are used. They're abrasive enough to get the job done, while not hard enough to score piston walls and they do either burn up or make it through and out of the exhaust. But, do try and get the majority of them out. If there is too much in there, there's a possibility of contact between the piston and valves.
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      02-27-2021, 04:50 AM   #4
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Yeah, CRC cleaner could definitely ignite through the vacuum. I would think dry bits will suck up more easily since they will bounce around and not stick to anything.

Put compressed air in spark plug hole and vacuum on intake port, or vice versa.
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      02-27-2021, 05:37 AM   #5
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Like the other guy was saying use a shop vac connected to thin tube and go in from the spark plug. You can even keep inlet valve open and push compressed air in at the same time to stir thing up.

Another option is that narrow double sided tape you can push into the combustion camber via spark plug and the walnut shells should stick to the tap.

And there is the option to flood the chamber with solvent and then suck it out with a wet vac. And at the end use compressed air to clear anything around the rings.
I don't think walnut is abrasive enough to cause damage but better safe than sorry.
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      02-27-2021, 09:00 AM   #6
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Quote:
Originally Posted by Steve Sas View Post
Like the other guy was saying use a shop vac connected to thin tube and go in from the spark plug. You can even keep inlet valve open and push compressed air in at the same time to stir thing up.

Another option is that narrow double sided tape you can push into the combustion camber via spark plug and the walnut shells should stick to the tap.

And there is the option to flood the chamber with solvent and then suck it out with a wet vac. And at the end use compressed air to clear anything around the rings.
I don't think walnut is abrasive enough to cause damage but better safe than sorry.
Thanks for everyone's collective feedback. I'm going to have a go again this weekend with the compressed air/vacuum technique, but am only marginaly optimistic given that the walnut bits were clumped together with residual CRC valve cleaner. Were they completely dry, I would expect them to easily be vacuumed out when agitated by compressed air, but maybe they have dried out over past couple days.

Failing that, I will try gently inserting a stiff wire down the spark plug bore with double sided tape on the end (good idea Steve Sas). As a last resort, I was considering flodding the chamber with a solvent, and then using a manual fluid transfer pump or vacuum to suck it out. Any recommendations on what solvent would be best (and least harmful)? Brake Cleaner? Isopropol alcohol? Something where the residual easily evaporates, I would think. Am not sure CRC valve cleaner is the best choice, but I dunno.

This was one of the last DIY projects I was doing on the E93 as part of the 100K major service... OFHG, VCG, PCV valve, oil catch can, new plugs/coils, radiator hoses, new aluminum radiator hose flange, new vacuum lines, replace oil/differential/tranny fluids, new suspension bushings. I just want to get back on the road and drive....
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      02-27-2021, 12:06 PM   #7
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I'd be a little concerned using a stiff wire. Maybe not warranted, but there is potential to scratch cylinder walls using that approach. I would definitely not shove anything in there using double sided tape. If that falls off in the cylinder, you're pretty much screwed.

My first attempt would be compressed air though the spark plug hole with a shop vac connected to the head via the walnut blast adapter. Obviously, make sure the intake valves are open and that any residual chemicals are dry/evaporated.

2nd attempt would be the same, but stick something plastic down in there if the walnut shells have clumped up to break them up. Think of something like a long drinking straw with slits cut into the bottom 5-6 inches allowing it to flex flat in the cylinder while you rotate the top to try and break things up.
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      03-01-2021, 06:38 PM   #8
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So, I think I solved the problem of walnut debris in the cylinder.....

I initially tried using a long plastic probe with some double sided tape down the spark plug bore. It definitely worked on the first go, pulling up a good amount of walnut shell goo. However, I could tell the CRC was already starting to disolve the adhesive, so I decided not to continue this route.

What seemed to work was using a bit of plastic tube down the spark plug hole to introduce a few tablespoons of gasoline (duh...). I then used the tube to swirl around the mess in the cylinder. There was not enough liquid sludge to pump out easily, and I didn't want to use a shop vac on gas. So, in inserted the stainless steel tube attached to my compressor and blew. HOLY COW. Damn near everything in the cylinder blew back out the bore. Before, it was too much of a paste, but the gasoline liquified it enough to allow it to flow. Thankfully, I had a rag there to catch the mess, but some did sneak out over the engine. I think having the valves in closed position was the trick - the significant overpressure helped propel the crap out. In any case, the borescope confirms that enough of the walnut shells are out that I feel comfortable starting the engine and just blowing the minimal remainder out through the exhaust. I have pictues of all this - am looking for something transfer them from microUSB to my computer...

Next issue is re-installing the intake manifold. Am having REAL issues trying to insert it over the the stub bolts on the block. The air duct next to the firewall is damn near blocking it. Is there a trick to getthing the manifold back on? Thanks!
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      03-03-2021, 02:42 PM   #9
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Intake manifold successfully reinstalled after some head scratching, and everything else buttoned/cleaned up. Started the vehicle this morning, and it was initially quite rough. OBDII showed cylinder 4, 5 misfires, and I was worried that the walnut residue was causing problems. However, after a idling for 10 minutes, followed by a 15 minute Italian tune-up, the vehicle is running butter smooth and pulling very strong. In fact, noticeably moreso than a few weeks ago: in addition to the DIY walnut blast, I also installed DCIs, and the BurgerMotorSports air filter delete kit. Strange, but I've never heard the turbos whine before - the cabin air filter, engine cowl and the stock airbox really muffled them when they spin up. Engine temp seems to be about the same, though. I would have thought removing all that plastic would have allowed it to run cooler...

Attached are photos of the semi-successful zip-tie probe and tape contraption I used to remove walnut shells from cylinder 4. Also, photos of the successful results from inserting gasoline into the cylinder cavity, and injecting high pressure air to blow it out. Thanks everone for the helpful tips.
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