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Old 06-14-2022, 07:47 PM   #1
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Default 1996 KA24E Engine Replacement- A Few Questions

Hello all.

I have been a member since 2014, but I seldom post. I lurk here a lot soaking up the wisdom you provide, and I appreciate those who give time and effort to provide this resource.

I have a 1996 KC SE (KA24E, 2WD, manual transmission) that I bought with 180,000ish miles in 2014. Upon buying it, I immediately had my mechanic install a timing chain set, oil pump and water pump, since it had the dreaded rattle and I knew about the timing chain from this site. Over the years, I have diligently fixed what needed to be fixed on my truck. The transmission, radiator, thermostat, sunroof, headliner, radio, tail lights, turn signals, various suspension parts and various air conditioner parts have all been replaced, and I also had it painted. Mostly, I have driven it and enjoyed it because it is such a great vehicle. It doesn’t look perfect or run perfectly, but it makes me happy to drive it. I want it to last to at least 300,000 miles.

It now has 235,000ish miles, and I recently took it to my mechanic because of an oil leak on my driveway. There was some leaking from the oil pan, and in checking that out, the mechanic found parts of the timing chain guides in my oil pan. I discussed doing another timing chain (same guy did it last time), and he is a little reluctant because he saw play of the crankshaft. He feels that this may cause an even faster timing chain guide destruction. He’s not a Nissan expert, but he is a competent mechanic and an honest guy, so I took him at his word.

Since this news, I’ve been driving the truck only a few miles on Saturdays to keep it running while I figured out what to do. The chain rattles a few seconds after starting, and then everything is good. I could probably drive it longer, but I don’t wish to completely destroy the engine, I will probably rebuild it.

I checked compression on the engine last weekend, and it doesn’t look so good either. All 4 cylinders are below 142psi and the lowest (cylinder 1) is around 100psi. Adding oil into the cylinders brought the pressure up, and I have read that this may mean that the rings are in need of replacement.

I ordered a replacement 1996 engine from a salvage yard specializing in trucks. This replacement is now sitting in my driveway. The salvage yard apparently knows a bit about KA24 engines, because they had already replaced the timing chain set. They also did the head gasket, front/rear seals and oil pan gasket. Having all of that already done was attractive to me, so I bought it. I do not know how many miles it had before they re-did it, nor do I know if there were any issues with it running. I also do not know if they used OEM timing chain parts or not.

The replacement engine has both the intake and exhaust manifolds attached. The intake has all the injectors and the throttle body. Most (if not all) of the intake-mounted electrical gizmos are still attached (although a lot of the wires, vacuum tubes, rubber fuel lines, etc. have been cut). The O2 sensor is still on the exhaust manifold, but they cut the wire so short, I don’t know if they left me enough wire to solder it.

Currently, I am in the process of carefully removing the wires and vacuum hoses from the existing engine, taking care to mark each one with respect to where it plugs in.

My questions are as follows:
1. 1. Should I leave the intake / exhaust manifolds on the replacement engine and install them in the truck or should I remove them and use the ones from my old engine?
2. 2. Do you have any suggestions about the O2 sensor? I have read on this site that they can be a bear to remove. I have begun spraying the sensor with PB blaster as outlined on this site.
3. 3. Are there additional items that I should replace while the engine is out? I already plan to replace all the vacuum tubes, rubber fuel lines, distributor cap, plug wires, etc., but what else should be done while I have access? Clutch?, PCV?, EGR?, etc.?

T This is a long post. Sorry I am so verbose. I tried to anticipate questions that might be asked. Thanks in advance for any advice you can offer.

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Old 06-14-2022, 08:07 PM   #2
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it can be easier to install the block with the manifolds off. It doesn't really matter since its a 4 cyl. though.

As for the O2 sensor, yes soaking it helps a ton, a proper socket helps as well (they have a slot on the side for the wires to feed through.

I would replace the clutch since you will have to swap it out anyway. Don't forget the pilot bearing too. Other parts are totally up to you.
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Old 06-14-2022, 09:21 PM   #3
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Good advice from Dave…

I will ad the following:

- Test all of the parts you intend on keeping on that replacement motor. It’s MUCH easier when the engine is out of the engine bay.
- Test the actuator “bulb” controller with a vacuum pump and see if the tab near the EGR valve is. The Actuator should move in relation to the intake “butterflies” inside of the intake tunnels. If it doesn’t move. The actuator is done(unlikely) or the intake butterflies are broken, sticking from carbon on its swivel points or just done

- You will destroy the O2 sensor in your attempt to remove it from the threads being heat seized and essentially welded together. PB Blaster helps. But I use a large vise grip pliers and rock the component back and forth, being sure to be continually spraying PB Blaster or similar, onto the threads to give a complete soak into the threads of the O2 sensor and the exhaust manifold sensor adaptor. But be warned that the heat seizing will make it “a bear” as described. Not at all impossible. But…

- PCV is only $10. So cheap insurance when replaced.

- Get the service manual and do a basic preventative maintenance check and replace all rubber hoses and consumable parts under the Maintenance Schedule, since the mileage on the engine is unknown.

- Check the exhaust manifold for any cracks. If any, replace the manifold altogether and then the O2 sensor removal will be a moot point. As it will be tossed along with the cracked manifold

- Clutch replacement is a great idea at this point too while the motor will be out(I did my clutch when I pulled my motor).

Others will have more to add to help…
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Old 06-18-2022, 06:32 PM   #4
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OK, so here's an update and two questions:

I downloaded the FSM and I have several sections currently open in my pdf reader

Fuel pressure released, oil drained from pan, water drained from radiator and block

All electrical connections on upper part of the engine have been disconnected and marked.
Accelerator cable disconnected. All tubes on the upper part of engine (vacuum, fuel, coolant, AC, power steering) have been disconnected and marked.

PS pump, water pump, alternator, AC compressor, shroud, fan, radiator all disconnected and removed.
Removed the AC high pressure tube that runs from the firewall to the condenser. (I had to replace this tube two years ago year and could not find one. It was hard to find even at nearby junkyards, so I don't want to break it while I extract the engine.)

Covered up all AC ports to prevent debris from entering.

Stored the AC compressor with its right side up and ports covered.

O2 sensor came out surprisingly easily.
Two of the three studs in the bottom of the manifold (bolting the exhaust pipe to the manifold) broke when removing the nuts in spite of copious amounts of PB blaster.
I broke the high pressure power steering hose. I did not understand how to disconnect this hose.

Next up:

Electrical connections to starter and transmission, remove starter, remove shifter, disconnect driveshaft from transmission, remove crossmember, and disconnect mounts.


1. Do I need to drain the transmission (it's a manual) fluid? I've read that it will leak out some when I remove the drive shaft, but I couldn't find a definitive answer to whether to drain it or not in the FSM or in this forum. (I plan to remove the tranny with the engine).

2. Since the O2 sensor came out easily, should I re-use it or buy a new one? I've not looked at the cost. If they're cheap, I will probably just get a new one.

3. The exhaust pipe is not readily separating from the end of the manifold. I am going to unbolt the nearest hanger and tug on it to see if this helps. Is there another trick that I have missed?
As always, thank you!
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Old 06-18-2022, 06:33 PM   #5
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Oops, sorry that was three questions!
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Old 06-18-2022, 06:44 PM   #6
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If the transmission is staying in the truck and the driveshaft is not being removed, no need to drain it.

Oxygen sensors aren’t particularly expensive, I would just replace it.

You may have to unbolt the exhaust a little farther back to get enough play to get it loose.
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