TOPIC: 2007 Buick Rendezvous 3.5litre V6

If there's any daylight left after supper, I'll shoot some pics while I check for vacuum leaks.
Turns out your insight to push some heater hose onto the hard plastic breather line from the back of the engine worked best, Tracy, and the PCV valve is in place, just capped, which is also for the best.

If I'm really lucky with daylight tonight, and my energy holds up, I may scoot over to the parts store and rent an engine tilt tool to swap out the spark plugs. Then another test drive...unless I have to chase vacuum leaks.

Good so far. good luck as you go!

Tracy G

Gotta love grandparents and how they hide treasures. I found this in the glove box around the time that granddad transferred the vehicle over to me when he decided to stop driving.

Gubmint fuel efficiency ratings, on the window sticker from the dealership.

{EDIT - see attached photos}

That's from my Gas Manager fuel consumption tracking app. Notice how on the right side of the graph, the few post-PCV re-route numbers are below where they had been historically. Not much, but more consistently.
Basically, the 10.7L/100km average thus far is pretty much right where GM designed it to be.

Now that I've re-routed the PCV, the numbers are starting to fall.

The tailpipe has started smelling cleaner - unburned gasoline smell has disappeared, to be replaced by the acrid smell of a full ashtray (as I suspect carbon was burning off), and now it's more like "overheating hairdryer" that's fading fast. I can't comment on the amount of water vapour in the exhaust, whether it has increased or remained the same, but it's warm and it doesn't seem to be collecting in the crankcase and creating the dreaded "milkshake goo" that is destructive.

And it starts fast and idles down seemingly faster and runs quietly. Eerily so. It was quiet to begin with, but now...it's unnerving at times.

Next up, the Groove itself.

Yo Greg, were you going to add something there? Nuttin' there.

Tracy G

Right, something about the file format is no good for the website

Re-route pics.
For the T and the right angle (90 degree) turn, I found 1/2" brass fittings used with PEX water lines at my local hardware store, about $5 for both.
I cut the hard plastic lines with aircraft snips, and the rubber hoses fit tightly over where they had to go, but the worm gear hose clamps are a bit of extra insurance against vacuum leaks. I used 3/8" ID fuel hose for the line that used to connect to the PCV, but I needed 15/32" ID to push onto the breather tube; both fit the brass fittings perfectly, and I believe I've maintained factory-spec for flows, if not improved on them a very small bit.



Overall, with capped PCV in place on the manifold.



Right angle off the PCV line nipple on the accessible valve cover.



T connection closeup with capped PCV. You may be able to see where the line comes from the back of the engine towards the firewall, and how tight it is there.

Breather into intake tube, before the TB.

Here's the fuel consumption chart from my tracking app. Note how consumption has dropped (or conversely, mileage/fuel economy has improved) the past few visits to the pumps since I did the re-route (4 or so dots on the right hand side of the graph, below the green average line, and towards the bottom of the range of the data-set).

EDIT - again no photo, but I've figured out out whay...stay tuned as I work with tech support to fix it...

nice work there, Greg. I learned, as you have, to use the various fittings and pieces to be found in the Irrigation section at Home Depot, and other hardware stores. Between various hardware stores, and auto parts stores, I can usually find what's needed. After playing with these parts awhile, you realize that there are many ways to do hose or tubing connections.

One thing that has always surprised me, is when I've been in someone's auto repair shop, they never seem to have much in the way of bulk hose, caps, or fittings. But then, most shops and mechanics spend their time just fixing/replacing existing parts, not doing custom stuff like we are here.

You have touched on the idea of improving/changing the flow potential in a hose system. This is actually advanced thinking, most would never even consider the concept! By varying the diameters, lengths, and even angles of hoses/tubing, you can alter flow dynamics. Like, say, in the crankcase vent system, if you want to remove liquids/vapors in the gas flow, you increase ID's and lengths of the hose. This slows the gas flow rate, and increases dwell time within the hose. This then promotes condensation of the vapors in the gas flow, helping the entrained vapors to drop out of gas suspension. Adding a catch can or oil separator to "tuned" hoses will remove much of the water/oil content in the crankcase vapors, and keep the engine cleaner inside.

Tracy G

Flows- I would think there should be a slight and variable vacuum present at the re-entry point prior to the TB in our re-route; the breather and former PCV lines would be passive except for blowby pressure. Those I'd guess you'd want to move fairly quickly into a can, with the gentle suction from it being mitigated to insure the bad condensate stays in it with only cleaner air re-entering the intake airstream...small tubes in to the can, a fatter path out of it, wouldn't you think? The can itself could possibly replace the T fitting, with two inputs and one output...

I'm a bit concerned about the cap on the PCV valve wearing out and failing still. The vinyl flexes at the tip when the engine is running. I may yet go to removing the valve and plugging the hole, or plugging the orifice of the valve inside the manifold somehow. That is, if it proves to be an issue. I'm just happy right now that it isn't leaking, and this mod works better than I expected so far, with no moisture problems. What's coming out of the tailpipe is warm, moist and smells SO much cleaner than it did before. Plus mileage is up nicely. At the speed limit in town, on straight flat and smooth roads, it seems to be trying very hard to sit at 5.5 litres/100 km, around 42mpg, or double the govt estimate from the window sticker. The highway number is better too, but not quite as dramatically better. If the groove improves both numbers again as I expect, and then if new ignition parts as part of tuneup take it that extra bit further...well, I'll be over the moon!

Well it's debatable whether to use different in/out hose diameters for a catch can or oil separator. But I have an idea that could clarify...use clear vinyl hose for the in/out connections. You will see any changes in residue or condensation. Vinyl hose could get stiff or deteriorate over time, so I'd just use a short piece, and replace as needed. OR just insert it to watch for a time.

And, of course all this is only needed if water/oil gunk shows up in the first place. Another choice for the PCV cap, is silicone caps, look online for those.

Monkey Man

Sounds like you are making good progress Greg.....

Waiting patiently to see further progress.........Hope you get the gains we all expect to see....

Since its been so quiet around here lately, but more because my job's workload is starting to taper off for the summer, I'm going to be grooving Wendy (the Buick) tomorrow.

Anybody with some last minute advice before I warm up the dremel??