94,gtp,v6,3.4L intake manifold gaskets replacement

Any shop manual for torque specs.

BIG tip, be VERY careful when removing the pushrods, to note their length. The intake and exhaust p-rods are different some years.

GW

push rods? to do intake manifold gaskets? this doesnt involve removing heads,I have never been inside one of these engines yet, but i cannot picture what part of this job would require me to remove the I,E push rod tubes please elaborate.... thx...A.j.

If yours is the DOHC version of the 3.4, you can ignore GWs comments about push rods since their aren't any.

Like Neil says, if it's the 3.4 DOHC engine, this info is irrelevant, but if you have the pushrod 3.4 (I don't think it was offered in that vehicle in that year, but could be wrong), then yes, you must remove the pushrods to do the intake gasket.

Ian

shiden_Kai said

Ian, I spent last night surfing google.groups and found your posts VERY helpful with todays project... a 3100 intake manifold.

If I might, I'd like to ask you a few questions.

1) In the Hanes manual, the heater hose that connects to the thermostat housing has a threader retainer, much like a fuel line into a old Quadrajunk. This heater hose connection on my MC is simply a interference-fit with a small rubber o-ring. This seems iffy? Are there multiple schemes for this connection?

2) There's a cover over what used to be the distributor. I've read on USENET this leaks oil sometimes. I never saw any leaks so I think I'll leave it alone. Comments?

3) Is the "lower intake gasket kit" likely come with all the gaskets I need? Should I get this from GM or is NAPA ok?

4) GM has written a bulletin 03.06.01.010. It details some new torque spec's and some threadlocker. Should I get these from GM or is NAPA ok?

5) My Hanes book recommends replacing the o-rings around the fuel injectors? Necessary?

6) Whilst I'm into this thing, is there anything else I should be doing? I plan to replace the plugs, t-stat, air filter, fuel filter, and PCV.

7) I planned on leaving the t-stat out and flushing the system via running a garden hose up the lower hose. It appears this might not be a good idea since replacing the t-stat will be a pain after this beast is all buttoned up. How does one flush this system to remove the satanic Dex-Cool. (I plan to use the green stuff)

9) Is it possible for GM to have designed this thing with a couple more machined gasket surfaces, different planes, and different materials? No wonder these things leak. Hope you can provide some feedback. It'd be GREATLY appreciated!

3.4 dohc, vin code x, to be exact, and i havent done the rpr/rpl yet ,will get back to you asap .thanx for all your help one and all ...ajm

What year, what vehicle?

Ah, you must have a later model. This connection is actually much better then the old style. Make sure that you replace "that" o-ring on "that" pipe. You will also note an o-ring on the coolant return pipe, (other black pipe that runs along the front valve cover and then bolts down behind the water pump). Replace that one too.

Depending on the year, you could get away with leaving it. But since I don't know the year, and I'm not certain exactly when GM changed from the old black o-ring to the new tan colored o-ring, I'd just replace it. You "do not" want to be trying to get at that oil pump drive later if it does start to leak.

Since it sounds like you have a later model 3100, you should get the updated latest greatest gasket from GM. Do you happen to know anyone who works for a dealer? If so, you might be able to get them to pick up the parts for less money. You will need: lower intake gasket (usually also comes with the upper plenum gaskets on the later models), two valve cover gaskets, o-ring seals for coolant return pipe, heater hose pipe into the rear of the intake, and the oil pump drive o-ring. You also need a new set of intake manifold bolts, 4 short, 4 long. And a good quality tube of RTV, I happen to be partial to the GM stuff, as I use it every day and rarely do I see any comebacks with it. Most times, a comeback occurs because of poor surface preparation. You "must" have the surfaces perfectly clean and more importantly, dry! I'm talking "brake cleen" dry.

There are new bolts available with the correct threadlocker and amount already installed on the new bolts. Little extra money, but maybe a little bit of extra insurance.

I've found that these o-rings are extremely tough and durable. I would inspect them, and clean them. You will often find on these engines, that a lot of dirt and crap collects right around the area where the injectors go into the manifold. Sometimes, when you pull the fuel rail and injectors out, some of the seals will stay in the holes. Be aware of this, and pick them out right after you remove the injector rail. Then clean the injector tips and o-rings and lubricate the o-rings with something similar to the silicone lube used for brake caliper sliders. I also try to smear a little bit of lube into the chamfered section of the injector holes in the intake. What can happen, if the o-rings don't slide easily into the manifold, is they can roll over and then you get a nasty vacuum leak that is can be difficult to diagnose. Guess how I know this?

Definitely replace the t/stat now. It's a five minute job while the manifold is off, as opposed to a 1-1.5 hrs job when the manifold is in place.

I'd leave the Dex-cool alone. I'm not a fan of it, but I think now that it's better to simply flush out the old stuff and put new dexcool back in. If you want, you can remove the block drains, but frankly, the rear one is snuggled up quite close to the transmission and is very difficult to get at. I'm always quite happy simply removing the return line of the heater hose (this would be the pipe/hose that eventually bolts in behind the back of the water pump) and flushing water "in that direction" thru the engine. You can pull the rad drain c*ck first, drain out as much as you can, then put your garden hose (or whatever you use) in that connection, back flush the heater core (and you will also push out a lot of coolant out of the block), and then run the hose the other way, then stick it into the over flow bottle. Just keep doing this until all you get is clear water running out. If you want to be really anal, put the connections back on, run the engine for a bit, then repeat the procedure.

Quiet, my good man! This particular job has helped pay for the bulk of my mortgage payments every month. GM is using you guys as the guinea pigs....we just get to fix the stuff.

Hopefully, this has been helpful.

Ian

shiden_Kai said

99 Monte, 3100, 58K miles

I'm simply amazed these two o-rings will seal. ;-)

Done.

I didn't realize the bolts needed replacing. But since they come with the loctite already applied, this sounds very convenient.

Money is not much of an object, considering I don't want to do this twice. (or, at least, for another 50K miles, groan...)

Thanks for the tip. I lube 'em with silicone.

I'm surprised to hear you say keep the DexCool. As I understand it, the only benefit of DexCool is longevity. I figure the chances of me getting a 100K of this coolant is nil, given the likelyhood of another manifold leak in 50K miles.

Do you think flushing the system like you describe is sufficient if I decide to switch antifreeze types? I think I might just fill it with water until I get everything set up. Then after I drive it an hour or two, I'll flush it out. This way I can flush it in my driveway rather than flooding my garage.

LOL, given the failure rate of these manifolds, you should have a guaranteed income for years to come. ;-D

Even more than I had hoped. There's nothing like discussing a procedure with someone who does it regularly. Again, thanks!

Thanks Ian. I keep forgetting that DOHC engine exists cuz I have yet to ever see one. Sure helps if people are specific. I was envisioning the 3.1/3.4 series naturally. GW

shiden_Kai wrote:

shiden_Kai said

Thanks again Ian. I finished my manifold a couple weeks back and all seem to be well. Your assistance was key to working this out.

Take care

Thank you for the feedback. It's always good to hear that things actually worked out.

Ian