Can you diagnose these symptoms?

F

Frontier719

New member
On my way home just now, I noticed a humming/buzzing noise. It's not extremely loud, but loud enough to be heard while in the car with the radio low.

When I got home I popped the hood and could smell a slight burning smell. Like something rubber maybe.

Any of this sound familiar? A quick check of the fluids showed everything full.
 
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Frontier719 said:
On my way home just now, I noticed a humming/buzzing noise. It's not extremely loud, but loud enough to be heard while in the car with the radio low.

When I got home I popped the hood and could smell a slight burning smell. Like something rubber maybe.

Any of this sound familiar? A quick check of the fluids showed everything full.
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Alternator?
 
Dragsterpilot said:
Yes.....
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Ha sorry man. I build motorcycles--they look different and some don't even have one.

Do 4Runners have an automatic tensioner? Or do you have to adjust it when you set in the new alternator? I've just been looking up how to change it out.
 
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Pretty sure its the alternator now that I've done some research. Does anyone have tips on how to adjust the tension of the belt after you slip the new alternator in? How much play should there be in the belt and is there a specific way to measure the amount of tension?

I saw someone posted that it should have 3/8" of tension, but where on the belt do you measure it from?

It looks like the belt has been replaced at some point and is still good but the alternator looks to be original.
 
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The moo box is the charcoal canister at the back corner of the driver's side. It's next to the master cylinder, bolted to the left (driver's) fender and about 5" or so in front of the firewall, and is a big black box. Early 3rd gen boxes make a 'mooing' or buzzing sound every several seconds after the truck's turned off. I have had mine make a steady angry bees sound while running while on a particularly very very steep downhill. Made a fuel smell at the same time though.

Have you an automotive stethoscope, long screw driver or some such thing you can aim at various places to listen through without getting tangled up (hair, fingers, clothes, any dangly bits) in fan or belts? At least the alt being on top makes it easy to carefully listen to without turning into fingerless hamburger face.
There are 4 belts alt, a/c, ps and timing, and a number of pulleys, alt, ps, a/c, idler, 3 timing, water pump. None are auto-tension except the hydraulic one for the timing belt under the black plastic cover on the front of the engine, to answer that question. Maybe try to narrow down where the noise is coming from? Was the same noise happening whether in neutral or drive? Was it happening when rolling or not? It sounds like you've already ascertained it changes pitch with engine rpm?
 
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You sure it's not the belts? That would explain the burning rubber smell. Do they show any signs of cracking or fraying? If you know they haven't been changed in a while, just have a shop put some new ones in (or do it yourself if you can) and rule that one out. Alternators aren't all that cheap, and aftermarket ones suck.
 
I took it on base (Air Force) to the auto hobby shop and had the mechanics look at it.

Naturally it wouldn't make the sound as loud when I brought it in so they couldn't for sure tell me what it was.

They told me that it sounded like the power steering pump was strained and that I needed to replace the rack and pinion bushings because there was too much movement in the rack and pinion.

I can hear the power steering pump making a faint whining noise but the humming I heard is something different.

Their advice was to wait until it gets worse so that way I can tell for sure what's wearing out. All of my belts look to be in good condition though. No cracks or frays
 
habanero said:
I usually get Wheeler's poly steering rack bushings. Steering Rack Bushing Kit for 95-00 Tacoma and 96-02 4Runner
Other companies sell them too.
How does the power steering fluid smell?

Quick write-up for the steering rack bushings (sorry, no pics) Post 2279
habanero's 1996 4Runner Build-Up Thread - Page 114 - YotaTech Forums

or there's prolly a real nice write-up around here somewhere
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Sorry. I'm pretty inexperienced. But what should I be looking for with the smell? I checked it the other day and the reservoir was full. A little bit dark so it could use a flush i'm sure.
 
Don't worry, the only way to get experienced is to learn and do things, right? I'm still figuring out stuff too, wouldn't have it any other way.

Remember checking the fluid level? Fluid is right there on the dipstick. Should not smell burnt. Flushing the system was easier than I thought it'd be. Messy, too. :D If you're going to replace the pump soon that'd be the time to flush, maybe add a filter too, imo.
 
Update

I've been driving around since the noise started so I figured I'd post an update now that I can better explain the symptoms.

Problem: Humming/whining noise from the engine compartment started immediately two days ago.

Occurs when the car is running. While in park the noise is fairly quiet. When the car is in gear (D or R), the humming/whining gets louder and deeper.

While driving, the noise is quiet, but when I come to a stop, it gets louder.

It does not change when the heater/ac is on or off.

There are no leaks, and fluids are all full. The burning smell must have been something else, or someone else's car as i do not notice any smells. Power steering fluid is old and slightly dark, but nothing abnormal.
 
Do you hear the noise while driving or when you are stopped?

If while driving, it could possibly be your wheel bearings.

Although the smell part is strange!
 
Sculsz said:
Do you hear the noise while driving or when you are stopped?

If while driving, it could possibly be your wheel bearings.

Although the smell part is strange!
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I hear it both while driving and while stopped. It is coming from the engine compartment so I dont think it is wheel bearings.
 
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