97 pathfinder upper and lower intake removal

[A1218]

So I’m going to remove the upper plenum on the 97 pathfinder vg33e engine to change the fuel injectors, fuel pressure regulator, IACV, seals under the fuel rail, gaskets of course, and some coolant hoses.

I figure I might as well remove the lower intake one time to change out its gasket and the knock sensor. Is this worth the trouble to remove the lower intake as well? I’m afraid of stripping any threads on it from a stuck bolt. There’s 4 bolts and 4 nuts holding it down.

Has anyone removed the lower intake? Any issues with the bolts and screws?

[VStar650CL]

The lower plenum fasteners rarely cause problems, but on a 25 year old vehicle you never know. Caution is warranted, I wouldn't just hit them with an impact wrench. However, if it's a 25 year old knock sensor, there's a pretty good chance it's off-frequency and not doing its job. You won't get any code for that because the ECM has no way to tell it has a problem, it can only detect if the circuit is open. It's a judgment call, but if you're removing the top hardware anyway, if it was my vehicle I'd change it out.

[A1218]

The lower plenum fasteners rarely cause problems, but on a 25 year old vehicle you never know. Caution is warranted, I wouldn't just hit them with an impact wrench. However, if it's a 25 year old knock sensor, there's a pretty good chance it's off-frequency and not doing its job. You won't get any code for that because the ECM has no way to tell it has a problem, it can only detect if the circuit is open. It's a judgment call, but if you're removing the top hardware anyway, if it was my vehicle I'd change it out.

How would you go about removing them? Soak with some liquid wrench for a couple minutes? Not going to use impact gun for this.

Socket set and extensions might be better.

[VStar650CL]

How would you go about removing them? Soak with some liquid wrench for a couple minutes? Not going to use impact gun for this.

Socket set and extensions might be better.

Yah, a good soak with Liquid Wrench or PB Blaster is probably in order.

[A1218]

How would you go about removing them? Soak with some liquid wrench for a couple minutes? Not going to use impact gun for this.

Socket set and extensions might be better.

Yah, a good soak with Liquid Wrench or PB Blaster is probably in order.

The engine block has to be drained before removing the lower intake? How is that done?

And when assembling, I’m using OEM Nissan gaskets. There is no sealant required on the gaskets when installing for upper and lower intake right?

[VStar650CL]

The engine block has to be drained before removing the lower intake? How is that done?

And when assembling, I’m using OEM Nissan gaskets. There is no sealant required on the gaskets when installing for upper and lower intake right?

Don't recall on a '97, some of the other guys will know better than I do. If the cooling jacket does extend into the upper plenum, you just need to drain enough coolant to empty out the heads, not the whole system. I recall the gaskets should be dry, yes.

[mdmellott]

The engine block has to be drained before removing the lower intake? How is that done?
And when assembling, I’m using OEM Nissan gaskets. There is no sealant required on the gaskets when installing for upper and lower intake right?

It's time for a decent repair manual so you can use it for critical reference points you must follow to do this job right. https://www.amazon.com/Nissan-Frontier- ... 563926105/
You do need to drain the cooling system at least low enough to drain the coolant from the coolant pipes attached to the lower intake manifold. The pipes need to be unbolted as well. Additionally, the fuel rail and injectors have to be removed from the lower intake manifold before the manifold can be removed.

The upper and lower manifold bolt removal and tightening sequence is critical. Removal and tightening must be done in the prescribed sequence and in the multiple step process of only partially loosen or tighten the bolts in sequence until fully loose or torqued completely.

Details of all this is in the Haynes manual I linked to above. The actual black and white photos in this manual are excellent guides to help with the tasks and the detailed step by step instructions give you the whole picture of the work that has to be done. The greasy and torn pages of my manual remind me of how many times over the cost of it has been paid back to me in the years I have used it to save so much time and effort. It will pay for itself many times over.

[VStar650CL]

It's time for a decent repair manual so you can use it for critical reference points you must follow to do this job right. https://www.amazon.com/Nissan-Frontier- ... 563926105/
You do need to drain the cooling system at least low enough to drain the coolant from the coolant pipes attached to the lower intake manifold. The pipes need to be unbolted as well. Additionally, the fuel rail and injectors have to be removed from the lower intake manifold before the manifold can be removed.

See, I told you one of these R50 oldtimers would have better info. Thanks Md!

[MisterH]

So I’m going to remove the upper plenum on the 97 pathfinder vg33e engine to change the fuel injectors, fuel pressure regulator, IACV, seals under the fuel rail, gaskets of course, and some coolant hoses.

I figure I might as well remove the lower intake one time to change out its gasket and the knock sensor. Is this worth the trouble to remove the lower intake as well? I’m afraid of stripping any threads on it from a stuck bolt. There’s 4 bolts and 4 nuts holding it down.

Has anyone removed the lower intake? Any issues with the bolts and screws?

FWIW, since you're going to remove the upper I would definitely remove the lower intake as well to refresh some key components. Given the number of steps involved in removing the upper, the removal of the lower should only take about 25% in additional time spent. There are tons of videos on YouTube showing all the steps in doing upper and lower for a VG33.

[A1218]

So I’m going to remove the upper plenum on the 97 pathfinder vg33e engine to change the fuel injectors, fuel pressure regulator, IACV, seals under the fuel rail, gaskets of course, and some coolant hoses.

I figure I might as well remove the lower intake one time to change out its gasket and the knock sensor. Is this worth the trouble to remove the lower intake as well? I’m afraid of stripping any threads on it from a stuck bolt. There’s 4 bolts and 4 nuts holding it down.

Has anyone removed the lower intake? Any issues with the bolts and screws?

FWIW, since you're going to remove the upper I would definitely remove the lower intake as well to refresh some key components. Given the number of steps involved in removing the upper, the removal of the lower should only take about 25% in additional time spent. There are tons of videos on YouTube showing all the steps in doing upper and lower for a VG33.

Yeah I saw the many videos on removing the upper and lower intakes. A few didn’t mention draining the block but the manual did so I just was checking back on that.

I know it’s only a matter of a few more steps after the upper intake and fuel rail is off. But what I am nervous about is stripping any threads when trying to remove those bolts. I’ve read through some forums for removal and a couple mentioned that.

I have all the coolant hoses, except the straight one behind the plenum, it’s discontinued. I got the knock sensor and lower intake gasket also if I decide to remove it after replacing the IACV, injectors, FPR, seals for fuel rail, and coolant hoses.

[A1218]

So I have all the parts and I’m going to start the job this weekend and hopefully finish it with no problems. I’ve watched countless videos and read through the manuals for this job. Felt like I was studying for a test

One thing I’m having a thought about from talking to others who have done a job like this. Do any of you think it would be necessary or a good idea to add sealant to the surfaces of the engine block and lower intake before installing with the Nissan gasket? Or would this cause any leaking issues with coolant or air leak.

I’ve heard that there could be some pitting or imperfections on the surfaces of the manifold/head? Or should I be fine with just the new gasket?

I’d hate to know I have a leak in the end from adding the sealant (ultra black silicone) or not adding it.

[VStar650CL]

Severe pitting on the active area of a mating surface would be unusual, and generally means the gasket failed a long time ago. Obviously the first choice would be to replace the part. If that isn't practical, for intake parts, regular silicone is fine for surfaces not exposed to the oil or water galleries. If it's one of those, regular RTV is asking for a failure. Use Gray Death instead (Permatex Ultra Gray). Just be aware that if the part ever needs to come off again, you'll be using dynamite and shovels instead of a scraper. I personally know a guy who successfully sealed a crack in a Ford small block between the crank and cooling jacket, the repair lasted a good 3~4 years before it gave up. I know another who fixed a Hyundai transmission with a hole punched in it by road debris, that repair outlived the car.

[A1218]

I think I might just see how it goes with the new steel Nissan gaskets. And will clean the surfaces really good as well.

Don’t think I’d want to put that on there after that description.

[mdmellott]

One thing I’m having a thought about from talking to others who have done a job like this. Do any of you think it would be necessary or a good idea to add sealant to the surfaces of the engine block and lower intake before installing with the Nissan gasket? Or would this cause any leaking issues with coolant or air leak.

I’ve heard that there could be some pitting or imperfections on the surfaces of the manifold/head? Or should I be fine with just the new gasket?

I’d hate to know I have a leak in the end from adding the sealant (ultra black silicone) or not adding it.

Sealant is not necessary on the upper or lower gaskets. The port openings have a crush gasket ring that assures a proper seal if you have properly prepped the surfaces first by removing every bit of old gasket and residue. I like to use a razor blade for this to be sure I get very bit of rice paper thin, baked on residue removed before installing the new gaskets. Take your time and do not scratch the aluminum. Sealant will cause potential leaks. These gaskets are not designed to accept sealant.

[VStar650CL]

Chances are it won't be an issue. Like I said, pitted mating surfaces usually mean the gasket went to crap a long time ago, and on an intake, that would mean a noticeable leak. You're worrying too much.

[A1218]

Yeah I’m definitely worrying too much about this project. And yea I don’t see any noticeable leaking. I’ll clean everything up good and install the gaskets. Along with the new parts I’m changing.

Thanks to everyone for their help and advice.

I’ll update this weekend once I’m compete. And possibly if I run into any issues during the job and would need some help if anyone wouldn’t mind just taking a look at this thread this weekend incase.

[A1218]

Finished the job this evening, took a total of 2.5 days. My dad an I worked on it. Pulled the upper and lower intakes and changed the IACV, injectors, coolant hoses, fuel rail seals, manifold gaskets, knock sensor, cleaned out the intakes, new coolant and bled the system.

I did run into a little problem when putting the lower intake on. I’m not sure if my torque ratchet was working properly but I ended up stripping the far back right bolt hole threads in the block. And I had it set to 4ft-lbs for the initial tightening. It wasn’t much threads that got stripped though. So I got a little longer hex bolt and it worked perfectly fine. There was a lot of good threads below that. Ditched the torque ratchet and tightened by feel.

No air leaks, idle problems, or coolant leaks anywhere. Took it for some city driving after and a 30 minute highway drive. Hopefully that warm restart stumble is gone.

[A1218]

I’m seeing my fuel trims higher than before.

SHRTFT1: 20.3%
SHRTFT2: 14.8%

The long terms are still 0.

I’m not sure if it’s reading high because everything is reset and all the spray from cleaning could be burning off?

I took a drive on the highway and some city.

The vehicle is running smooth and idling normally in park and in drive. Smoother than before the job was done. It used to idle rough but not anymore.

The intakes are tightened down properly. I’ll check back the egr valve. I think I’m hearing some air noise from there. I disconnected it from the intake, but installed back with new Nissan gasket.

But the check light came on just now for a bank 2 sensor 2 oxygen sensor. PO156