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Intake valve cleaning with pics

26K views 109 replies 28 participants last post by  UnlimitedMatt 
#1 · (Edited)
Last week I finally decided to see for myself how bad the valve coking issue is on my truck, and decide whether I needed do a manual valve cleaning. I took my 2015 Colorado 3.6L CCSB over to my buddy's house (who owns a 2015 Canyon 3.6 CCLB, and a bigger work space), we cracked a few beers and got to work. For the record, my truck had about 39,100 miles at the time of this valve cleaning.

As has been noted before, the engine cover is a little tricky to get off, starting in front of the engine there are two T30 bolts, front and left, and two 8mm hex bolts in the back. I think its easiest to unscrew the flat head screws holding the air box on, loosen the hose clamp attached to the cover and remove the whole air box assembly. With the air box out of the way you can work a long flat head screw driver under the left side of the engine cover and loosen the hose clamp that connects the air hose that's integral to the engine cover to the intake. Remove the airline attached to the cover and an electrical connector and the cover can be pulled off.







There is a pad on the top of the intake manifold secured with two plastic fasteners. Underneath, there are six 13mm hex bolts directly through the top of the intake manifold that must be removed, and two 10mm hex way at the back holding a bracket on that also must be removed (the ratchet is sitting on one in the second picture underneath). There are a few airlines and plugs on the left side that need to be removed, also several plastic one time use fasteners (one not really visible at the back of the intake) securing various wire runs and air lines to the intake manifold... be prepared to break most of the fasteners, they really don't want to come out.





At this point I would highly recommend using compressed air to blow every bit of sand and dust you can away from the intake area, when you lift the intake off, all of that crap can fall into your intake valve ports. Removing the intake manifold will take some finagling with the three 13mm manifold bolts in the rear because they are too long to come all the way out of the top. I had to hold them up a bit while my buddy and I lifted the manifold straight up and off of the nice, reusable manifold gasket, and then shimmied it out. Remove the gasket and set aside. The intake ports should now be visible.





These are the before pictures of my intake valves, starting on the front left (as viewed standing in front of the truck) and zig-zaging to the back.













The valves of four of my cylinders were closed, I taped the other two ports and used compressed air to blow any dust or loose debris out of the uncovered ports. I then sprayed plenty of CRC GDI IVD Intake valve cleaner to the uncovered ports and let them soak for about 20 minutes. Once the coking was loosened up, I used a long flat head screw driver to scrape the worst of the gunk off of the valves. I then used a 12 ga. copper shotgun brush screwed onto one section of a Hoppes gun cleaning rod chocked into a drill to further clean the valves (Note: shotgun brush threads are 5/16x27, and standard gun cleaning rods are 8x32, you either have to use a shotgun specific cleaning rod section, or buy an adapter like I did... $2 at Sportsman's Warehouse).





After cleaning, I stuck a shop vac nozzle into the intake ports, turned it on, and used a thin compressed air nozzle snaked past the shop vac nozzle to blow the remaining liquid and chunks of coking off the valves. All of the left over liquid and coking chunks were sucked up into the shop vac. After all of the closed valves were clean, we taped up those ports, and took the tape off the remaining two ports. We then used a 19mm socket to turn the engine until the two remaining ports were closed and repeated the whole process.

These are the valves in the same order after cleaning.














Everything went back together fine, and the truck cranked right up and ran smoothly.

The valves obviously had some build up, but not nearly as much as I was expecting from reading about issues on the internet. The buddy that helped me clean my valves decided not to bother with his until he swaps spark plugs at the scheduled 100k miles. Had I known their condition, I probably wouldn't have bothered with cleaning my intake valves until 80k - 100k miles either. I can't really say whether the truck feels like it gained any power, if it did, the difference is almost imperceptible.

I have no idea why some of these pictures are showing up rotated... they were correctly oriented on my phone and computer.
 
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#6 · (Edited)
39,100 miles
I used all of my free dealership oil changes, and have been using Pennzoil Platinum since, except for this past oil change when I tried Supertech full synthetic. I usually fill up with top tier mid-grade gas (Exxon).
Have you noticed any spark knock using 87 octane verse using mid-grade octane gas? Does your truck use any oil between oil changes?

Thanks for taking the time to do and excellent write up.
 
#11 ·
Seafoam is much easier than tearing of your intake manifold.
 
#18 ·
Actually it's an easy question to answer about elevation and octane,,
As the higher up on elevation which effects the atmosphere pressure on engine that causes a decrease in compression ,, basically it makes your engine seem like it loses compression ,,plus it will run richer to a point due to the thinner , higher up, air .. That's why aircraft engines run alot more compression.
Also that's why racers run faster and make more HP at sea level or lower , more atmospheric pressure,like in increase in compression and runs a bit leaner too.. Kinda like a little natural superchargering principle.
Basic fueling 101.
 
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#19 ·
Right, the engine's peak compression pressure and compression induced charge heating is less at higher elevation (lower ambient pressure ~12 psi vs 14.7 psi at sea level), requiring less octane to prevent pre-detonation. It's also why my truck probably makes on the order of 60 hp less than it would at sea level :frown2: . Many places over about 5,000 ft in elevation offer 85 as "regular".

The whole process took about 2.5 hours, going relatively slowly and taking plenty breaks for refreshment, shooting the breeze and picture taking. I would say 1.5 hours would be doable if you were trying to finish up quickly.
 
#20 ·
In my mind, the octane question comes down to how altitude changes the manufacturer recommendation. If 87 is the recommendation, is it safe to assume that is at sea level and would change to 85 at 5000'+ following the gasoline retailer "standards"?
 
#21 ·
interesting question. The bottom line is it doesn't seem to change their recommendation because they really have none at different altitudes. Right? I bet there is some info out there somewhere that will tell you what octane you need at different altitudes using the recommended as a starting point.
 
#30 ·
I just pulled my intake and took some pictures, disappointed with what I found. I have 10k miles and have used Mobil1 Extended Performance since I drained the factory oil at 1500 miles. I currently have about 45% left on my current oil and I just had to add a quart. I followed GTscotty's direction to pull the intake manifold off, not a bad job to do, thanks for the directions.

What's disappointing is how much buildup I have after only 10k miles. The center cylinders seem to have the most, the front's the cleanest. I drive mainly back roads with a few trips between Connecticut and Maine. I did take one trip down to Georgia and back.

I will be adding a catch can, I just didn't realize how much I needed it. I've been using full synthetic thinking it would slow down the problem. Apparently not.

Anyway, I've attached some pictures, the names indicate location. I took them with a a little borescope camera but the quality wasn't that good. I took another with my regular camera of one of the center right (passenger side) valves. The buildup is not an even coating but more like little beads of accumulation. That can't be good for airflow.

Anyway, here's what I found. Now I have to find a good way to clean them up.
 

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#34 · (Edited)
Thanks for posting - very interesting.

It would be great if someone with a catch can in place since new checked their valves and reported in. Wondering if one could snake a $25 LED borescope down in there to get at least a view of one pair of valves without pulling the manifold.

Another thought - the rate of carbon buildup may not be "linear." By that I mean as gunk starts to accumulate, it's roughness may attract more gunk. It very well may be 60K miles may not be twice as much accumulation as 30K miles, I suspect it will be a lot more.
 
#38 ·
I'm going to check my valves again after I build up some more miles to compare after the can install. (checked them at 5k already).

You very well could be right about the gunk building up more quickly but lets hope not!
 
#39 ·
Not sure how many miles on this change, but I've changed the oil twice so far.

There's another weird thing I've noticed. When I start the truck up first thing in the morning, there's a little blue puff. Not much, but just enough that you can see it. I wouldn't have noticed it if I hadn't used the remote start and been right behind the truck. And it has that rich smell, like it's getting a little too much fuel. If it's a little too rich on start it could be wearing the rings too fast, burning more oil than it should.

I made sure to keep it on back roads for the first 500 miles. Up and down on the throttle, no long steady highway drives. I changed the factory break in oil after 1500 miles and went right to full synthetic.

If I'm burning oil it's not for lack of trying. Anyone know the factory spec for oil usage?
 
#46 ·
I was under the impression that synthetic oil would handle engine heat better and produce less oil mist being vented through the PCV system and less buildup on the valves. No hard facts. Just going by what I've heard.

Another question, does anyone know how to differentiate the buildup from valve seals versus buildup from the PCV system?
 
#47 ·
Another question, does anyone know how to differentiate the buildup from valve seals versus buildup from the PCV system?
I wouldn't expect buildup from valve seals to be evenly coated over the entire valve. More like just a clump at the bottom of the stem. I could be wrong.
 
#50 ·
an interesting read for sure! i have nothing with DI but my girlfriend does + she is a very conservative driver with many short trips said to be worse. italian tunes are said to help, either way DI has its dark side! a little note on oils, almost all "synthetics" are more refined CRUDE oil, technically group III + prolly a bit better but Ester oils are totally superior as they are naturally cleaner running + withstand the most heat of any type of engine oil!
 
#52 ·
Evaporation of oil is a reality. the measurement is the NOACK value which was first used by Amsoil as a volatility measurement in North America and is now a standard measurement for all oils. Synthetics, yes even Group III have a lower NOACK value than regular oil or semi-synthetics like those that come standard in our trucks an is used by the dealers for the free oil changes.

If you want an oil friendly to your PCV operation and intake valves, look for a lower NOACK number.

The standard is ASTM D-5800.

These are both Amsoil test result, but very revealing.

Technilube.com - Base Oil Categories and Definitions

AMSOIL Synthetic Motor Oil - BestSynthetic.com - Volatility and the NOACK Test
 
#57 · (Edited)
I read a post today on an Impala forum from a guy who had 175K miles on his 2012 Cadillac with a 3.6 motor and he said it was still running great. NO catch can. Yes, imagine that. :surprise:

Way too much hysteria here over some deposits on the back of valves. I was almost sucked into the catch can vortex too, but I pulled myself out at the last second. lol Yes, Audi, VW and others had some serious issues when DI motors first came out, but it appears that a lot has been learned since then and I highly doubt GM was stupid enough to warranty a lot of DI vehicles with 60K and 100K mile warranties if it was still an issue. 33K miles on my Colorado and no reduction in mileage or power yet and I expect it will stay that way for a long time.
 
#58 ·
I read a post today on an Impala forum from a guy who had 175K miles on his 2012 Cadillac with a 3.6 motor and he said it was still running great. NO catch can. Yes, imagine that. :surprise:
Well if you read it on the internet, then it must be true.
 
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