A while back, after seeing quite a bit of speculation tossed back and forth about when the upper intake design was changed for VIN K engines, I somewhat humourously posted that maybe I should just ask the quality manager down in Flint...
After a little thought, I realized that wasn't too bad an idea. So I wrote an email to the quality manager, who I've done a little work for in the past. That person (who'* name won't be posted, unless someone can give me a really good reason too) had on of their underlings write back to answer some of my questions...
Originally, of course, I simply asked when the upper intake manifold was changed, and when it was changed, if there was a new casting number on the manifold that would allow me to differentiate the new from the old. The inital response simply had a GM TSB, which documented the procedure for looking at a car with coolant loss. Of note, it tells the dealer that if the upper intake has failed, they are to replace the lower intake manifold at the same time as the upper...
I wrote back and asked again about the change in the upper manifold, again, so we could get an actual time line in place for when the change was made. in response:
"the original lower intake had an EGR stove pipe that under some conditions would allow over time the heat from the EGR to distort the upper intake. The change was to the material of the lower intake stovepipe as odd as it sounds."
Through some more writing back and forth, I was able to find out a little more. This particular worker was not at the plant during this time period, but from what he'* heard:
the egr stovepipe material was changed - although he doesn't know the specifics of it. he went on to mention that the amount of distortion of the upper intake around the egr stovepipe varied - some were worse than others. also mentioned was that there are aftermarket kits available that replace only the lower egr stovepipe, but no-one seems to be completely sure (and i don't believe gm has studied it) if this comprimises the egr characteristics and flow.
There was a little more throughout the emails, but I think this is the important information, and i do after all like my job
. to sum it up:
1) the upper intake (as i've been trying to say
) is the symptom - not the problem. The problem, and the correction, are focused on the lower intake'* egr stovepipe.
2) gm dealers SHOULD (according to the TSB) replace the lower intake manifold if they find any distortion of the upper intake manifold.
3) aftermarket solutions that 'beef up' the egr portion of the upper intake or replace the egr stovepipe are not tested (officially by gm), and as of now, there is no way to verify what all it does to the egr system
4) if you replace your upper intake and not the lower, it'* kinda throwing the dice as to if you're going to be doing it again...
you can now resume your regular posting