Walnut blasting a.k.a Dreaded Cylinder Head Blues

[fmorelli]

Barry and I started some house cleaning on the Z4 today. With 30k miles, after seeing this first-hand, I have to say I'm not at all surprised to what seems to be prevalent problems people have with #5, #6 cylinders. My car at 30k with high side BMS catch can since 23k looked pretty crappy. The low side stock PCV system (with RB PCV @ 23k) recirculates oil vapor down a sequential path, from the back of the head forward and into the intake runners. That means the intake runners get dirty most at #6, #5 and decreasing down to #1. The common reports of misfires and ring land cracks on those two cylinders seems clearly obvious to me ... and I guess I'll put a flame suit on as I suspect this is not a foregone conclusion. But even at a mere 30k miles, the turbulence caused by what I saw cannot be insignificant.

We were doing valve cover gasket, plugs, RB low-side PCV and head plug, and Tial black spring. (we used Harbor Freight stuff to blast, and this 3D printed adapter for the head, which was excellent)

Just a few photos. First is Dr. Barry Battle, "Just say ahhhhhhh".

Ok ... while the flame suit is on: IMHO there is little chance anyone is going to pay someone to do a walnut blast and have it done right, where everything is cleaned. While the blasting worked well, it consistently left lots of residue, mostly the soft stuff. The walnuts would work the film and brittle materials, but just didn't dent the rest. I used a combination of 2 cans of carb cleaner and several ounces of GM upper cylinder cleaner to scrub everything out, along with dentil picks, toothbrush, and about a half roll of blue shop paper towels sheets cut in quarters. We blasted intake runners between 3-4 times with chemical soak/scrub/cleanings in between. We spent approximately 3 hours just in the cleaning part, with both of us working. I'm not sure why anyone would choose to do the low-side external PCV setup and not tap and plug the low-side feeder holes in the head that cause this problem.

Here are thumbnails of the before/after. Both sets of photos are in order, Cylinders 1 through 6.

Filippo

BEFORE: [1] [2] [3] [4] [5] [6]


AFTER: [1] [2] [3] [4] [5] [6]

 

[derekgates]

Wow, I agree with everything you said here. I am waiting to do the walnut blast on my 'is but haven't picked up an air compressor (yet). Further, plugging the head is a fantastic idea... how are you going to tackle that? Any recommendations on tapping tools or the actual plugs? (I lost my bag from RB that had the plugs).

 

[silverstreak18]

FWIW the setup you guys are using is great for DIYs, but at the shop we have the pressurized tanks that shoot the walnut shells out at a higher velocity and normally get the ports cleaned after two passes. My normal routine is blast to get the majority of the gunk out, then use a couple different picks with different angles to get the stubborn stuff and then blast once more.

 

[fmorelli]

Wow, I agree with everything you said here. I am waiting to do the walnut blast on my 'is but haven't picked up an air compressor (yet). Further, plugging the head is a fantastic idea... how are you going to tackle that? Any recommendations on tapping tools or the actual plugs? (I lost my bag from RB that had the plugs).

Derek, plugging the head is simple. 10/32 tap (use lube - any grease will work), and install the plugs with loc-tite. You may need to back the tap out to clean it after going in about half way. Keep in mind the plug screw goes in at an angle so you want it deep enough that it does not sit proud of the head surface. Also remember, the tap's tip does not cut full threads (it's not a bottom tap); make sure you cut threads deep enough to set the screw plugs below surface. It's a good thing to capture the aluminum bits. We folded some shop towels and coated them with white lube to help catch them bits: one towel to catch dry bits during the tap procedure, then a second towel we pushed in the hole when we blew the hole out with brake cleaner. For the second towel that gets wet, it catches lots of bits.

Filippo

 

[fmorelli]

FWIW the setup you guys are using is great for DIYs, but at the shop we have the pressurized tanks that shoot the walnut shells out at a higher velocity and normally get the ports cleaned after two passes. My normal routine is blast to get the majority of the gunk out, then use a couple different picks with different angles to get the stubborn stuff and then blast once more.

In hindsight I had not considered a more powerful blasting system. That makes sense. Just curious, do yours come out more/same/less clean than the photos I show above? I'm sure in less the time and elbow grease, too!

Filippo

 

[Traf]

I always thought problems in cyl 5 and 6 were because they are the cylinders that run the hotest ?

 

[The Convert]

I always thought problems in cyl 5 and 6 were because they are the cylinders that run the hotest ?

Not saying you’re wrong, but why would 5 and 6 run the hottest?

 

[Traf]

Not saying you’re wrong, but why would 5 and 6 run the hottest?

Confined close to the firewall and exhaust ? At least thats what i heard.

 

[Rob@RBTurbo]

Cylinder 5 is literally right below the PCV Valve thus it is first inline when using the internal vacuum reference scheme as was designed by BMW. Cylinders 4 and 6 are next up in line (equally) followed by 3, 2, and lastly 1. This is why the back bank tends to gunk up much quicker than the front bank, as PCV valves can and do pass oil/muck through them as they function.

Agree with Filippo in that plugging the head ports is highly recommended, and is so very simple there is no point in not doing it as soon as you can (once you go to the RB External PCV). It is also reversible if ever wanted to go back to the OE/Valve cover based vacuum reference, so really it is win win aside for the little time it takes to do it.

Rob

 

[mikeseli]

Cylinder 5 is literally right below the PCV Valve thus it is first inline when using the internal vacuum reference scheme as was designed by BMW. Cylinders 4 and 6 are next up in line (equally) followed by 3, 2, and lastly 1. This is why the back bank tends to gunk up much quicker than the front bank, as PCV valves can and do pass oil/muck through them as they function.

Agree with Filippo in that plugging the head ports is highly recommended, and is so very simple there is no point in not doing it as soon as you can (once you go to the RB External PCV). It is also reversible if ever wanted to go back to the OE/Valve cover based vacuum reference, so really it is win win aside for the little time it takes to do it.

Rob

The reason why I did not plug those head ports is because these ports provide the necessary vacuum inside the valve cover during idle (low side) to get the turbo to drain oil quicker into the oil pan and avoid smoking conditions.

 

[Rob@RBTurbo]

The reason why I did not plug those head ports is because these ports provide the necessary vacuum inside the valve cover during idle (low side) to get the turbo to drain oil quicker into the oil pan and avoid smoking conditions.

Well then you obviously do not have the RB External PCV if that is the case, so yes of course absolutely do not plug the head ports with the OE style Internal PCV system intact.

Rob

 

[fmorelli]

Couple other things, since this was the RB low-side setup.

The reason why I did not plug those head ports is because these ports provide the necessary vacuum inside the valve cover during idle (low side) to get the turbo to drain oil quicker into the oil pan and avoid smoking conditions.

I'm curious how you determined this (I have no freaking idea, which is why I ask)?

Filippo

 

[Rob@RBTurbo]

I'm curious how you determined this (I have no freaking idea, which is why I ask)?

Filippo

To some large degree he is correct, in that if he does not have his PCV externalized he shouldn't be plugging those ports. This does not apply to those who have their vacuum reference externalized via RB External PCV.

But he also is one of those FrankenTurbo guys too, who literally all (one by one) seem to be biting the dust with smokers. From what we hear all of those units are DOA or turn into smokers within a couple thousand miles, even with the latest generations. So who knows what all is being discussed on that front, in attempts to mask the chronic issues they are still seemingly going through. Anyway that is just another debacle of a topic altogether.

Rob

 

[dyezak]

I don't know what thread produces more fireworks:

PCV discussions
Oil discussions
Hybrid turbo discussions
Single turbo discussions
Or Stormy Daniels discussions

Glad this fine thread digressed into one of those holes however.

 

[mikeseli]

Couple other things, since this was the RB low-side setup.

I'm curious how you determined this (I have no freaking idea, which is why I ask)?

Filippo

When I had the stock TD03 turbo I had smoking turbo after installing the RB inlets. I could not understand how the inlets created this condition. I replaced drains, it helped a bit but smoking was still there. I played with many tests and finally someone suggested to introduce some vacuum into the valve cover by tapping a fitting on oil cap and this worked.

BTW, I also tried the external RB pvc setup but it did not resolve it.

 

[mikeseli]

To some large degree he is correct, in that if he does not have his PCV externalized he shouldn't be plugging those ports. This does not apply to those who have their vacuum reference externalized via RB External PCV.

But he also is one of those FrankenTurbo guys too, who literally all (one by one) seem to be biting the dust with smokers. From what we hear all of those units are DOA or turn into smokers within a couple thousand miles, even with the latest generations. So who knows what all is being discussed on that front, in attempts to mask the chronic issues they are still seemingly going through. Anyway that is just another debacle of a topic altogether.

Rob

Rob, why are you like that!!! Relax, this is not a competition.
I do have Frankenturbo almost 8 months now with 8800 miles on them with no smoke. Why do you keep attacking your competitors, for a day or two can you keep your negativity to yourself, things will be better for all of us.

 

[Rob@RBTurbo]

Rob, why are you like that!!! Relax, this is not a competition.
I do have Frankenturbo almost 8 months now with 8800 miles on them with no smoke. Why do you keep attacking your competitors, for a day or two can you keep your negativity to yourself, things will be better for all of us.

If you feel as if that was an attack then boy I'd hate to post the actual email chains we get about this stuff weekly. Now that would be some entertainment.

As for the WHY's? Perhaps that is just it that if it weren't for our competitors customers complaints about these things we'd have a very clean slate when it comes to tech diagnosis questions every week. It's like mum's the word and like clockwork the same stuff over and over again. Glad your setup is working out after all and my apologies for insinuating you too had fallen victim.

Rob

 

[fmorelli]

@Rob@RBTurbo question for you, since we are gnawing on this thread. When I went to install the external PCV, I removed the plastic cap/o-ring, and pulled my internal RB PCV valve (I had installed at 23k). I'm exceptionally careful whenever threading anything together, but even more paranoid when dissimilar materials are involved. On the new PCV assembly, I lightly coated the o-rings only with white lube, as well as the outer o-ring land. Installing the PCV assembly by hand it started to tighten a bit. I thought it was the o-ring but stopped, pulled back out. Upon close inspection I could see about a 20-30 deg sweep of a thread being cross cut. I cleaned it up and tried again, applying even pressure to the back of the PCV, so the o-ring would not cause an issue. Same thing. Once can see the PCV and o-ring not being completely parallel to the intake boss face. We pulled out the PCV, cleaned the thread (since it was just a bit ... we were being very careful), pulled the o-ring and ran the PCV straight in with no issue.

We then concluded that the outer o-ring should not be needed, given the 10/32 plugs sealed that area, and the inner PCV o-ring served the other sealing function. Is no outer o-ring with plugged head a safe assessment? Thoughts?

Thanks,

Filippo

 

[Rob@RBTurbo]

@Rob@RBTurbo question for you, since we are gnawing on this thread. When I went to install the external PCV, I removed the plastic cap/o-ring, and pulled my internal RB PCV valve (I had installed at 23k). I'm exceptionally careful whenever threading anything together, but even more paranoid when dissimilar materials are involved. On the new PCV assembly, I lightly coated the o-rings only with white lube, as well as the outer o-ring land. Installing the PCV assembly by hand it started to tighten a bit. I thought it was the o-ring but stopped, pulled back out. Upon close inspection I could see about a 20-30 deg sweep of a thread being cross cut. I cleaned it up and tried again, applying even pressure to the back of the PCV, so the o-ring would not cause an issue. Same thing. Once can see the PCV and o-ring not being completely parallel to the intake boss face. We pulled out the PCV, cleaned the thread (since it was just a bit ... we were being very careful), pulled the o-ring and ran the PCV straight in with no issue.

We then concluded that the outer o-ring should not be needed, given the 10/32 plugs sealed that area, and the inner PCV o-ring served the other sealing function. Is no outer o-ring with plugged head a safe assessment? Thoughts?

Thanks,

Filippo

Filippo,

It can be somewhat of a pain to thread in- but personally the units I've installed went in with relative ease even with the outer O-Ring in place thus I would typically suggest to leave it. However you are correct in that it is not going to be needed BUT ONLY AS you have plugged the head ports (just don't want anyone else to read this and get confused as is so typical). So if you are getting a better threading without it that would be fine in your case.

Rob

 

[WOT808]

In hindsight I had not considered a more powerful blasting system. That makes sense. Just curious, do yours come out more/same/less clean than the photos I show above? I'm sure in less the time and elbow grease, too!

Filippo

I've used the Harbor Freight portable blaster and pressurized blaster. The pressurized blaster required less passes to get the valves clean.

Tip, let the ports with closed valves soak in a little gas for a few minutes then hit em with a gun brush and blow out into a rag before blasting. It's a little messy but cuts cuts down on blasting time.