Should I proactively replace my stock alternator at 200K miles?

CBR.worm

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'06 Infiniti G35 w/ 200K miles. I am resealing the timing cover and replacing the water pump and associated parts for the first time, due to a small oil leak at the bottom edge - it's not dripping yet, but it is getting the front of the motor grimy and I'm sure it will get worse. While I have the alternator off, should I replace it with a new OEM one?

While the alternator is off the car, it would be very easy to replace. This car isn't worth much, but it is fun and in good shape. I plan to drive it until something catastrophic happens, or until it becomes unreliable. I'm replacing the idler pulleys, the radiator, and other pieces that I had to remove to get the timing cover off, also the primary timing chain, chain guides, crank sprocket, tensioner, and gallery gaskets. I read so many horror stories on the internet about the VQ35 tensioner and guide issues and gallery gaskets, but I have no visible wear on anything other than the crank sprocket. No signs of impending doom. I've got the new OEM parts, so I'm going to put them on.

I expect to do a couple of cross-country trips this summer, and while I don't want the car to ever leave me stranded, it would be worse if I was thousands of miles from home. I don't expect the OEM alternator to fail in the next 10 or 20K miles, but it might and I would prefer to not have to touch the serp. belt-driven components again for a long time.

I don't know what the lifespan on these is. It is a Mitsubishi branded alternator. I would think that I have probably used up most of its life, but I really don't know. The mechanical parts on this car seem to last forever.
 

D60

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Colo
I carry a spare OEM (used, JY) in my SuperDuty, but roadside replacement is totally possible.

The Fords need OEM as there's been a really big problem the past few years with aftermarkets charging fine but for some reason the battery light stays on. Seems to happen with both the 6.2 and 6.7 diesel and even in some engines before that (pre-2011)
 
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Tracy, CA
The Legend is on its fourth alternator. It has an early warning alternator failure mode; the battery light will start to flicker at idle.

The original one lasted 305,767 mi (14 years).
The second one (rebuilt) lasted 104,649 mi (10 years).
The third one (rebuilt) lasted 17,162 mi (2 years).
The current one (rebuilt) is at 38,152 18,162mi (9 years).

The second one came from my father's parts supplier. I can't recall where the third third one came from but obviously it was crap. The current one - 🤷‍♂️
 
Joined
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Illinois
I'd be most concerned that any replacement alternator probably won't last as long as the one from the factory.

Not an alternator, but similar: My Impala has gone through a couple aftermarket rebuilt starters since I replaced the factory unit a few years ago. This most recent time, I sprung for an new AC Delco starter. If it dies prematurely, I'll get one from the junkyard. Chances are, the car in the junkyard isn't there because of a bad starter!
 
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Alderaan
yes, bad starter, you can always hit it with a hammer. If alternator brushes go, you have no options. And if happens away from home, you'll need a tow.

you can check the old alternator's brushes by removing it. but by that point, you might as well put in a new/reman. alternator.
 
Joined
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It's one thing to replace an alternator before it dies, but if you already have it out of the car, it's a no brainer to just replace it while it's out. It's mechanical and it won't last forever, it wears out from use.
 
Joined
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you can check the old alternator's brushes by removing it. but by that point, you might as well put in a new/reman. alternator.

It depends. On some engines, like the Ford 4.6L, removing the alternator is a 5 minute job, and it has to be removed to do other work like changing the water pump. I wouldn't even consider replacing an alternator on an engine like that before it's time.
 
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ecotourist got me onto something. Before I drove my Dad's Mercury needed an alternator. Sis and BiL had an '89 Probe which ate 3.
I've had 2 go in used cars; a '72 Corolla @160K and an '07 Volvo @ about the same. My new '95 Subaru also @135K. It had an open warranty.

A rare occurrence when you look at it.
 
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Ames, IA
Based on some of the comments on batteries in this forum, I think a newer battery is a driver of alternator health than the replacement of the alternator. How old is the battery? Maybe a new battery is a better option? Neither are cheap anymore.

I don’t know if the alternator on my 232k mile Camry is original or not, but I’ve yet to think of needing to replace it. I’ve thought more about the fuel pump than the alternator.
 
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A rare occurrence when you look at it.

I've had three alternator failures:

One happened on my first car at about 90K. Alternator totally dead.. was able to make it home on battery. 1986 Dodge Omni.

One happened on another car at about 150K. Alternator was putting out less voltage, and was warm to the touch the next morning. Shorted diode? 1988 Ford Mustang GT.

One happened on another car at about 130K. Alternator totally dead. Battery with a shorted cell probably killed it. 1996 Ford Contour 2.5L
 
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I am guessing even the brand new alternator purchased from Nissan dealer ($$$) will NOT be the same quality as the one which came with the vehicle build decades ago.

Do you know if this vehicle will instantly be dead when the alternator dies or it can at least let you drive on the battery alone? I have had vehicle where dead alternator erroneously kills the flow to the carburetor (Ya, yes, I am old!) This was the only two times I was stranded in that car which I drove for decades at 250K miles.
 
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You live in an area where the car doesn't need much from the alternator, not likely you use the heated seats, the rear defogger. Additionally, you don't sap the battery much from cold starts in Winter. So I would use your time to find a good rebuilder in your area and keep the info for when you really need it.
 
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I would replaced it, Ive had 4 alternators fail on our cars over the years, twice left me stranded. Last one failed in the van but i was able to limp home and replace it there. Reading some other answers here how some people never had to replace them makes me think that hot weather has something to do with it.
 
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It's totally up to you but unless it's a real pain to change I'd leave in the original. Alternators seem to last a lot better over the past 30-35 years than they used to back in the 60's and 70's. The original alternator on an '88 Escort I used to drive lasted until the car had 518K miles, all I did was replace the brushes in it one time. I've owned vehicles now for about the last 45 years and as I recall I've replaced 2 alternators in that time.
 
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I would replaced it, Ive had 4 alternators fail on our cars over the years, twice left me stranded. Last one failed in the van but i was able to limp home and replace it there. Reading some other answers here how some people never had to replace them makes me think that hot weather has something to do with it.
Well I'm in a cold state and I never had an alternator last 200k. Mostly around 100k. I figure it's probably more like how many hours you have on it. City and traffic puts a lot more hours on it than easy highway driving.
 
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With the belt off, spin the pulley and listen for bearing noise. Then grab the pulley and see if there is any play, back and forth and up and down. If not noisy and no play…..carry on.
 
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