Front and Rear main seals on Sentra


Old 07-28-03, 10:42 AM
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Front and Rear main seals on Sentra

I am in the process of putting in a replacement engine in my daughter's 1994 Nissan Sentra, 1.6 liter 4 cylinder automatic.

I have an engine being delivered from a junkyard that has 112k on it and looks good. It is from a car that was totalled in the rear end. The front end was not hurt. The junkyard advised me to replace the front and rear main seals before installing.

I am wondering if it is worth the bother to do this. As long as it isn't leaking now, is there any other reason to do this? I am inclined to not mess with it.

Appreciate any help.

Thanks, Tim
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Old 07-28-03, 11:25 AM
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I would be replacing more than the front and rear seals on a junkyard engine. I HOPE you heard it run before you bought it and ran it extensively!

Junkyard engines are a big, big, big risk.

I'm sure the yard advised this for one of many reasons:

1) Common leaker on that engine,
2) They won't warranty a leaky motor---if you ran it out of oil per se.
3) The seals are bad and perhaps you just haven't seen the leak yet, so they are trying to be honest with you.

Usually half of the parts of a junkyard engine have to be thrown out---they are usually seized and useless. Especially the expendables.
Old 07-28-03, 12:06 PM
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I have not heard it run. It has a 6 month warranty, and the junkyard is a large dealer with an excellent reputation. I realize it is still a risk, but I feel like I am between a rock and a hard place. To pay someone to put in a motor with a warranty is cost prohibitive - it would cost nearly what the car is worth. I feel this is my only choice, short of selling the car for scrap.

Edit - The requirement for new seals is standard terminology on their sales receipt.
Old 07-28-03, 01:52 PM
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Thumbs down

If you didn't hear it run, regardless of reputation, you're asking for trouble.

The yard may not even know the cause of the engine's demise---and it may be more than just a hit to the rear that sent the car to the boneyard.

It could have been sitting there two years without running and may be a crop duster when it starts up (burns oil). Also, parts pickers may have taken parts for it or dropped things down the oil fill.

Who knows, what's inside that thing. When we used to junk cars, they used to get EVERY fluid you could fit in the crankcase . LOL No telling what's in there and how it got there.

Too many possibilities to gamble with. Hear this heap start up and run before you buy it.

Do a compression check on it, make sure it turns freely, and listen for any sounds to it, especially when warmed up. Drive it around the yard to see if it picks up smoothly.

These engines are bottom barrel off the showroom floor, I surely wouldn't trust a used one without hearing it run!
Old 07-28-03, 10:10 PM
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Junkyard engines are a gamble. I've bought engines sight unseen & had great results. I got burned on an engine that I heard run. It didn't smoke, leak, knock, etc. Seemed to be in good shape. It lasted 6 mos. & blew a head gasket.

As Joe said, now is the time to replace more than just 2 seals.

It would be wise to pull the oil pan & check the condition of the crank & bearings. Now would also be a great time to replace the head gasket. These engines have aluminum heads & the gaskets are more prone to failure than iron head/iron block engines. Replace the timing belt, water pump, camshaft seal, and both crankshaft seals.

Yes, you'll spend a couple hundred dollars in gaskets and parts, but you'll have a much better idea of the condition of the engine and you'll have a chance to reject the engine before you install it if you find debris in the crankcase, worn bearings or some other problem. This is much better than installing it & having it blow up sometime next month. Sure, it may be under warranty, but the warranty typically doesn't pay for your labor, so you'll be stuck doing the job again.

A couple hundred dollars and a few hours of your time spent now could save your big money and lots of time. Cheap insurance in my opinion.
Old 07-28-03, 10:46 PM
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i couldn't say it any better than knuckles did, with this basic "maintenance" you should easily get another 100,000 miles from this engine(with proper maintenance!!!)

or you could roll the dice and see what you get, if it's called a 'junk'yard, then you already know what they're selling. (before i let anything go the the junkyard, i usually have my fun with the engine and the rev-limiter and trans and tires)

i wonder what happened to the original engine from your car, is this one of the honda success stories of 400,000 miles with proper maintenance?

imagine if that junkyard engine still had it's original timing belt on it and it breaks in a month, you'll end up doing it the HARD way.
Old 07-29-03, 01:57 AM
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100,000 tired miles is alot for a 'Junker Motor''
those guys are right and YOU should be leary. I trust
junkyard motors as far as I can thrown one.
check you may find a nice
used japanese motor with 30,000 miles on it.

If you are bent on this motor, for the sake of
your daughter, get a gasket set ($99) and
change seals and gaskets yourself. But you
should have tools, torque wrench, Chiltons manual
and cherry picker and wooden blocks.

I rebuilt
a junker $100 Nissan P/u motor myself on my spare time
in high school and it took a week and a half.
However, I took the
head to my Napa Auto Parts and they did a valve job

It was a fun experience. Except for my
father who yelled at me for taking over the garage.
Make sure the block
ain't cracked though, then you'd be screwed!
Also, if the head is cracked(its aluminum ya know)
that will be a bummer. Like Joe n' them said---I'd run the damn motor
at the junkyard and check for cracks, smoke, n sounds, and check
compression(use a handheld compression tester)

Its still summer and I think you can do this.
Its not cheap, nothing that you want done
right ever will be. I thought I was going to get
away cheap on my Nissan, but little things like:

---oh shoot! better buy the Chilton book for specs($22)
---darn! I'd better borrow some tools(knock knock)
---damn! I'd better change all belts and hoses, too.($40)
---Or--damn! Since I have it off, why not boil the carb?($75.)
----Or change fuel injector nozzles ( $100)
---Or---damn! Since the motors' out, better put on new mounts($60)
---Or---damn! lookit them CV boots--theys ripped up!($50)
---Or---damn! since its out, y-not a new water pump!($65)
---Or damn! since its out, better change that timing belt($39)
---my hands are dirty----stalube cans (99c each)
----better buy all fluids ($20)
----better rent that cherry picker ($25 ea time)
----shoot! I need a shop light ($12)
----better call my buddy to help me pull out the motor(beer)
----better call my buddy to help me align the motor in(beer)

My favorite time is when a motor is sitting on blocks in your garage,
(I've also rebuilt a chevy 327, 350, Isuzu truck and 2 Nissan Z motors)
You have a beer in your hand, ratchet wrench in the other and you
start taking the parts off, little by little, labeling them and placing them into boxes, until you get to the bare head(s) intake manifold and block.
"I lovingly say to her---you are mine now, baby! And strip her
down, ruthlessly watching her fluids(whats left) drip out as I
eagerly unbolt her down until I see her bare block. Her crank is
showing underneath, since I stripped off her oil pan, and her
pistons heads are out in full public for me to view! You nasty
girl, I always seem to say, you're cheating on me!!!!!!Lookit
number 2---you've been burning too rich, you are soiled! I hate you!
I'll teach you! And I send the heads to my Napa's machine
shop for them to give her a valve job with new valve seals.
I am an animal and if I pull out her cam, who knows what I might do.
So I let the guys at Napa do it.
Get the head(s) back and mate her to the block, which I changed
piston rings, crank bearings and torqued everything to Chilton specs.
(if the crank was OK and the piston walls were OK to just use
a drill and a wall grinder)
Put everything back on the motor, DTC, making sure timing belt
and head were in sync.

Good luck, man!

Last edited by fatcatdj; 07-29-03 at 02:41 AM.
Old 07-29-03, 03:40 AM
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Lol. FatCat has me laughing in my chair. LOL. Good ones!

I agree with all as stated. We did a Supra Turbo some years ago for someone. The vehicle was hit by a TRAIN. LOL. But we heard the engine run before buying it, and it had clean oil in it when it arrived. NOT an engine to do twice!

I'd price out what it would be to have the machine shop work done with you doing the R&R on the original engine. What is wrong with the original? Again, it may be better than the one you are getting .

As Mike said, you wouldn't want some of the junkyard engines we've come across. LOL. Junked cars are very convenient places to put all the fluids you don't need. Did you know a Nissan oil pan really holds 8 quarts? J/k.

Honestly, no telling what you're going to get. Also, no telling why it was REALLY junked. Sure, there are some cars that get junked which could have simply repairs done to make them MINT again.

For every ONE there is like that, there's 500 that belong in the junkyard!
Old 07-29-03, 03:53 AM
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I've heard that used Japanese engines that come from Japan are fairly cheap, run tested, checked for compression, etc. I believe there are a number of firms in this country selling these engines. As I've heard to register a car in Japan is a mind blowing experience, no rust, no dents etc. In Japan one can't go very far as the island is rather small so used engines with low mileage are available. And I think that the Japanese have money to burn so everyone want new. You should check out this option as it may cost no more than the junkyard engine.
Old 07-29-03, 04:01 AM
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Taxes and fuel costs (along with parking) are killers in Japan. My 79 T/A would take Mr. Honda's salary to keep going in Japan. LOL

(Believe it or not, the 79-80 Trans Ams have a special Japanese ONLY country export option! VE4 or something like that)

I agree with EW, but make sure the engine is US EPA certified. If you buy an engine for the Japanese home market, it may not be US compatible and emission legal. That can net you a bigger headache.

My .02.

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