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Discussion Starter · #1 · (Edited)
So! My beloved Altima (QR25DE) seems to have a blown head gasket. Oil, gas, coolant, temperatures, spark plugs, ignition coils, wire harness, battery, and fuel pumps are fine, but the car fails to start after cranking and cranking only to fail and throw misfires repeatedly (P0301 through P0304 codes), and the spark plug tips (threaded/electrode side) are steeped in black liquid.

I have a gasket set in my trunk. Brand new and sealed. I could take it to a shop, which would charge me $1,000+ in labor, or I could do it myself.

Getting to the head is a long and arduous task, but I'm determined to do it. I live on campus at my university and I don't actually need the car until I have to go home for spring break. As such, I plan on doing this job little by little over the next couple weeks.

I figured I'd do a public log, as most of the existing DIY threads on NC and here, more often than not, contain broken images and broken links.

Before doing all of this, I made a trip to AutoZone for the following, as listed by akashmer on NC.

"½” Torque wrench to 160ftlbs.
3/8” Torque wrench down to 2.5ftlbs (not necessary) Can you feel it?
¼” ratchet
3/8” ratchet with adapters as needed
5mm Allen wrench or 3/8” socket
10mm Allen 3/8 socket or w/1/2” adapter for breaker bar
10mm Deep well / Standard/ and Quarter inch socket
12mm Deep well / Standard/ and Quarter inch socket
14mm Deep well / Standard/ and Quarter inch socket
19mm socket
17mm socket
Large Adjustable wrench or 24mm box end wrench
O2 sensor Socket
Impact wrench w/ 14mm socket or long breaker bar.
14mm,10mm,12mm box end wrench (BE wrench)
2 colors of paint pens (Lacquer Pen)
Paper clip (VERY IMPORTANT)
Tooth brush
Emory cloth
Parts cleaner and Lacquer thinner
Long screw driver
5 way scraper and double edged Razor blade
Long flathead screwdriver
Protractor or 3/8” socket degree meter
1” ratchet strap
Plastic baggies and sharpie for bolts
Long zip-ties or string."


I had about half of these things already. It was $100 for the half that I purchased. It sounds steep, but better $100 in tools than $1,000 in a shop's cost.

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I already took off my plastic engine cover, which takes an allen wrench to remove.

Here is the engine. Assembled and all.


Using a 10mm I removed the 4 nuts that keep the ignition coils in place. I then used a 5/8" specialty deep socket for removing the spark plugs, and a 4 inch extension for my 3/8" socket wrench. It all comes out pretty easily. I separated the ignition coils from the jacks they plug into using a simply needle-nosed wrench.

I then labeled each plug "1" through "4" just to keep track.



I then drained the coolant and the oil from the car. The oil pan is on the bottom of the engine near the passenger side, and has a 14mm hex drain plug. The coolant drains from the radiator, and there is a plug on the bottom passenger side at the very front of the car. It has a standard "+" phillips screw head. I used two plastic pans/buckets for this. Unfortunately I didn't get any photos.
 

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Just a heads up to make your life a whole lot easier. You DO NOT have to remove the front cover to remove the head. Every manual says you do for the timing chain. If you paint mark the chain and sprockets before removing the cams, you will know how they need to be reinstalled. Dont worry with the bottom end. The front cover is designed to prevent the timing chain from slipping. Just zip tie the chain to your a/c line and your good to go. Sounds sketchy but trust me. Ive done it and seen it done at least 20 times with no issues. Just dont forget to mark the chain and sprockets. This trick will easily cut the time needed in half.
 

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Discussion Starter · #3 · (Edited)
I then removed the drive belt. The easiest way to get this off is to remove the small plastic tensioner located in between the bigger pulleys.

In this picture you can barely see it just under the cylinder with the rust-pink pin at its center. I had already removed the 14mm bolt that holds the tensioner in place by this time.


For easier access, remove the front passenger-side wheel. Once the bolt is loose you can put your finger up there and manually pull it out, along with the plate that holds the nut to the tensioner.


Reach and tug on the newly-freed tensioner. It will pop right off.


The drive belt is now loose. Just wiggle it out. Be careful not to damage it.
 

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Discussion Starter · #4 · (Edited)
Unplug the two cables from the alternator. It's in the way. Then, remove the small bolt, and the two pins behind it. One is about an inch and half long, and one is about 3 inches long. They keep the alternator on.

To remove the big pin, you'll have to (temporarily) remove the black fuse box. Undo the 10mm nut that's keeping the black box onto the car. There is a small clip that is also keeping the box on to the right, on the alternator side. Use a flathead to remove this.



Once you pull the alternator out, you'll have access to the bolts that keep the header on. There's 5 of them.

Good job! Now remove the 10 bolts that keep the valve cover on. They're all 10mm.



Examine the mechanical beauty inside:



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More to come soon.
 

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Discussion Starter · #6 ·
Loosen the bolt that the keeps the intake piping connected to the throttle body. Pull it out gently. Unclip the air box from the plate it sits on. There should now be a nice big gap allowing you more room to work.



 

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Discussion Starter · #7 ·
One of the hardest parts is removing the intake manifold. We're gonna need to remove at least some of it, because it's rather unwieldy and will make it hard to remove the head.

I removed the upper intake manifold. It was really annoying to do because there are 7 or 8 nuts and bolts to remove from the back, and they are very difficult to get to. You'll need a flash light and extensions of various lengths, and a 12mm deep socket. They are in between and around the massive steel piping.

Once it's removed, you'll be able to see the butterfly valves. If all the screws are there, take a breather, because it's a known issue with the QR25 for these to come off and fly in, which results in scoring of the cylinder walls and general deterioration and possible failure.




At this point, I would recommend (if it hasn't been done before) for you to buy some Loctite Red screw sealant, and undo the screws and put a drop or two in and seal them. You don't want these to come out, ever.

The goal for all of this has been to isolate the head (the massive rectangular block which sits atop the cylinders and contains the camshafts and whatnot), such that once we adjust the cams a little later and remove them, we'll be able to easily pull it off and finally change the head gasket and clean up the cylinder walls.

We are very close to that now.

To be able to remove the camshafts though, we'll need to expose the timing chain and the sprocket (the gear on which the chain sits), which is located in the covered area on the engine's left side. There is a large steel plate covering it up, held on by 10 or so 10mm bolts. Most of them are very easy to get off, but one of them may be hard to get off because it is at an awkward position below the A/C line (the massive hosey thing that's getting in the way). I would recommend unclipping the windshield wiper fluid and radiator overflow fluid tanks. (the two white bottle-like things)

Take your time and use a flash light. Once it's out, you'll be able to see the timing chain. Do not mess with it yet. We will get to this in a little bit.

 

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Discussion Starter · #8 · (Edited)
Take a really long, pencil-thin dowel rod or something similar and put it in Cylinder 1. Take a 17mm deep socket and turn the exhaust camshaft sprocket (the right gear thing in the photo above) clockwise, gently. You should see the cams rotating and the stick should be going down or up. Your goal is to make the dowel gets to the highest point. If you see it going down from its tallest point, stop and very gently turn the other way, just to get to the top.



This is known as "Top dead center," or TDC. You see little indentations on the two camshaft sprockets? Take a photo of this. This is where you need everything to be when you put it all back together. Take a paint pen or silver sharpie or anything that'll stay and mark the chain and sprockets such that the markings match up when you put it back together. This is how you'll know it's at TDC.

 
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