TOPIC: 2007 Buick Rendezvous 3.5litre V6

Well, spring seems like it has finally arrived here in my part of Canada, so I've taken the opportunity to poke around a bit more under the hood and get to know where things are.
My first concern was to locate the PCV and breather lines. It appears that the valve is in the intake manifold, which seems backwards to me, coming from a Ford.
The breather appears to pass right above it, luckily, so if I'm right, this mod should be a simple one.
I'll post pics tomorrow for everyone's input before I go ahead, and just for a bit of verification; if I'm wrong, replacing the breather is a pain because the engine will have to get rolled forward to access, so I want to verify. Measure twice, cut once kind of thing.

For reference purposes, I've been tracking fuel consumption since I got this vehicle, and my app says I'm averaging a combined rating (city/highway driving) of 10.9 litres/100km, or 25.6 mpg. Not too shabby, but I'm fully expecting to better that by >30% once it's fully grooved, the plug gap has been widened, etc. Another thing that's on the agenda to remedy here is the wheel bearings, which are notorious for having short lifespans on this vehicle - GM under designed them is the general consensus - so if the wheels roll more smoothly, I'll get a fuel economy from replacing them.

Watch for pics/updates...!!!

So this pic is better than I thought showing what I described in the first post.
TracyG/Ron/Martin - what do you guys think of my assessment? Do I have the plumbing correct?
The PCV cap (I'm thinking of just capping the valve itself, and then T-connecting the line from the front valve cover into the one that I believe to be the breather clipped right above it) might be tricky to do. I may have one that will fit...

Hi Greg. You understand the theory of the PCV re-route. It's just sorting the pieces out and tee-ing the hoses right. OK I took another look at the pic, looks like the PCV is in that round boss just downstream of the TB, right on top. The Breather hose, it's in back? Can't tell, maybe more pics?

A tool that may help to get access to engine rear exists in several forms, GM has been using the "dog bone" front upper engine mounts since the 80's. The tool is installed in place of one of the dog bone mounts, and remaining mounts are unfastened as needed. The tool will have a nut or threaded sleeve that you tighten to rotate the engine forward. Works better than simply taking the dog bones out. Gives control, safety, and can move the engine farther. Check a parts store, as a rental tool.

PCV's can be direct on the intake man., or on the crankcase end, doesn;t matter long as you can access it. With the man. vac. source capped, crankcase gasses will vent out the other end of the hose, tee'ed into the Breather, or the main air intake duct, as you choose. If it's hard to get to the PCV, then pick a cap w/ care, most black rubber one's I've tried for years crack quickly. Heater hose caps are better, but again the regular black rubber deteriorates. Vinyl or silicone caps last longer. The Redneck option is a piece of hose, w/ a bolt shoved in, maybe RTV, and a hose clamp.

IF unsure of what is what back there, post more pics and we'll see! I know you will get great results, you're Doctor Dude, after all! Oh, and I'd Ohm those long plug wires, resistance might be high.

Tracy G

I was hoping to not have to tilt the engine...
I'll take a better pic tomorrow; maybe that will explain where my head is at with this.

Can I post videos directly here, bypassing YouTube??

So here are some (hopefully better) pics of the PCV and breather plumbing. In this first one, my hand is at the valve cover end of the one that seems to go to the PCV valve on the intake manifold.

...and now that I've seen the "insert photo" button, I'll use that instead!

This second one shows what I think is the breather, coming from the back of the engine. It connects to the plastic intake AFTER the MAF, and before the TB.



This next shot shows where they cross, and where I would put the T connection to mate them for Groove purposes. Could GM have made it any easier???

So I've found vinyl vacuum caps; multipack, in a variety of sizes in case I need to cut the PCV tube and cap the valve:



However, I would think that a plug in the intake hole would be the best solution. I'm thinking a freeze plug or one of these of the appropriate size with some loctite on the nut to prevent it from falling in and destroying the engine:

More Information for DORMAN 570005

Tracy, your opinion?

Good pics there Greg. Since the PCV valve is the vacuum source as well, I think I would cut the plastic tubing an inch or two away from the PCV valve, and just cap the tube. I would ideally put a spring clamp on the cap to help retain it, I'd look for one of those spring steel clamps so prevalent on late model cars (junkyard?). I'd cut the breather tube, and either move it so I could add a piece of hose w/ the tee in it, or cut the breather plastic tube back a bit to allow adding the tee and short piece of rubber hose. By using rubber hose (fuel hose) it's far easier to work with than attempting to stuff a tee up into that stiff black plastic tubing. I would join the ends of the cut breather hose w/ the rubber hose, then cut the rubber hose to add the tee.

When thinking about the PCV re-route, I sometimes reduce it mentally to the basic idea: Remove hose/tubing from the manifold vacuum source. Seal off the vacuum source. Tee the open end of the PCV valve hose into the crankcase breather hose. Sometimes It's easier to tee the PCV hose into the main air intake duct instead, after the air filter, before the TB. This is how it's done, regardless of which end the PCV valve is on: valve cover, Intake manifold, or engine block.

Cutting the plastic tubing and using quality rubber hose, also enables reversing the mod, should that ever become necessary.

I would skip the rubber expansion plug, Greg. Simpler to just leave the PCV valve where it is. As long as it maintains a good vacuum seal it's fine (carb.cleaner or brakeclean spray test at idle).

Only view missing here is where the breather tube goes into the crankcase--is that in the rear valve cover somewhere?. Really doesn't matter, long as it's in good shape.

See what I mean about mentally checking off the steps needed? Some cars/engines are visually confusing in their layout. Once I can I.D. the PCV valve, the vacuum source location, and crankcase breather setup, it's easier to figure out.

Tracy G

Ok, that's exactly what I was looking to hear!

When I was taking those pics, I pulled the elbow of the pcv line off the valve cover nipple - there wasn't much resistance, nor was there much pulling it off the tube, so I'm sure they leak vacuum when the valve is open. The plan was to replace the tube entirely with rubber hose from the nipple on the valve cover to the T in the breather line - matching the inner diameter (it seems smaller now) to that of the breather line.

I really want to pull the valve itself and plug the hole up, solid-like and permanent. But you're probably right that the easiest would be to cap the valve itself if it doesn't leak. I'm going to get one of those plugs to try - if it's not as solid as I hope, I can always go back to this.

Back to the breather - yes, it's back where I can't see where it comes from. Probably the same valve cover as the front one, with a nice nipple, but I can't see it, and doubt I can without rolling the engine. When I do the planned tune up, I'll be sure to check into it.

Thank you kind sir! And stay tuned! It'll be a busy lunch hour for me tomorrow, unless work throws me a curveball!

There ya go Greg! Just once it's done, check connections and PCV port w/ carb. spray at idle for vac. leaks.

Right-0, carry on!

Tracy G

PCV re-route complete. Pics to follow.

People, after I completed the work, I didn't do the ECU re-learn procedure. I just took it for a 60ish mile drive that included city, country and highway driving on my lunch break.

I wasn't concerned with mileage numbers, I just wanted to verify drivability. It seems to me that the engine doesn't work as hard. It's just quieter...and it was quiet to begin with! Another thing I noticed was when cruising, the instantaneous mileage readout in the instrument cluster was much more stable. I had it as low as 4.4 litres/100km in the city, but it averaged 5.5-6 at 50-60km/hr, 6.5-7 at 70-80 km/hr and 8.3-8.8 at 100-110 km/hr. (That's 39-42 mpg at 30-40mph, 33-36 mpg at 40-50 mpg and 27-28 mpg at 60-70mph). Pre-groove, pre- tune up and needing an oil change!

I have a 100mile highway jaunt coming up by the weekend, so I'll have a better idea of where it's settling then, but it's looking like just the re-route and the computer relearning as I drive has given me a gain of 3-5 mpg, rough estimate, or 12-15% rough guesstimate. On mid grade fuel with none of our MPG Remedy juice.

If the groove improves efficiency by that much again, I'll be a VERY happy Gadgetman with a truck/SUV that is reaching for 40mpg.

Doing well, Dr. Dude, we shall see just how far you can take the Buick patient!

Tracy G