My fan clutch messed up today

[ToyTech99]

So my 2004 4Runner has been 100% perfect without a single issue....until today. After sitting in a rain/snow mix for about 10 hours on a crappy day here in New York, I hopped in my 4Runner and started the engine. As it started, I thought I heard a faint "chirp" almost like a quick belt squeak. A second or two later, I noticed something was wrong, but I couldn't quite figure it out. Then another 5 seconds passed before I heard the "roar" of the fan as it started spinning.

So that's what was wrong....I didn't hear the fan roar from the moment I started the engine. I'm sure all you guys know exactly what I'm talking about.....that loud roar from under the hood when you first start up your engine. It's amazing how quiet the engine is when that fan isn't spinning right after start-up.

So here's the question--- Do I replace my fan clutch based upon this once incident? Or do I wait to see if it happens again? I really don't like the idea of waiting because an overheated engine is not a good thing...lots of damage can happen if my fan clutch malfunctions and I'm not paying attention to the temp gauge.

So has anyone else had any fan clutch issues on the 4th gen?

 

[CJ3Flyr]

The fan-clutch can be big trouble and is worth paying attention to...

1) How many miles do you have?

2) Does the fan feel tight on the shaft. I don't mean rotationally I mean the bearing the fan rides on.

3) How does your fan-clutch look? Does it look as though oil has oozed out of it and caused the center of it to look like a big, greasy mess? I don't mean a minor bit of dampness, I mean a mess.

FYI- Mine occasionally starts quiet too. It happens if I just move the move the vehicle in the driveway, shut it off and then start again. In other words I start it, the fan 'stops' and I shut it off before the engine warms. When I start it again it's quiet.

The other time it has done it is when I park it nose to the wind on a cool day when I wasn't running the A/C. (Low underhood temps after shutdown.)


I'm not saying you don't have an issue 'in the making' but you may have just stumbled onto one of those rare set of circumstances that makes it seem as though something is wrong. My T4R, my Trooper, my Titan and my Chevy truck all started "quiet" 4 times a year when the stars were aligned just right and the moon.... :lmao:

 

[ToyTech99]

The fan-clutch can be big trouble and is worth paying attention to...

1) How many miles do you have?

2) Does the fan feel tight on the shaft. I don't mean rotationally I mean the bearing the fan rides on.

3) How does your fan-clutch look? Does it look as though oil has oozed out of it and caused the center of it to look like a big, greasy mess? I don't mean a minor bit of dampness, I mean a mess.

FYI- Mine occasionally starts quiet too. It happens if I just move the move the vehicle in the driveway, shut it off and then start again. In other words I start it, the fan 'stops' and I shut it off before the engine warms. When I start it again it's quiet.

The other time it has done it is when I park it nose to the wind on a cool day when I wasn't running the A/C. (Low underhood temps after shutdown.)


I'm not saying you don't have an issue 'in the making' but you may have just stumbled onto one of those rare set of circumstances that makes it seem as though something is wrong. My T4R, my Trooper, my Titan and my Chevy truck all started "quiet" 4 times a year when the stars were aligned just right and the moon.... :lmao:

No, believe me when I say I took a good look at the fan & clutch after I got home. There is no leakage anywhere to be seen. No bearing issues. The fan spins with just the right amount of drag on it (checked it after the engine had cooled) and my 4Runner only has 32K miles on it. The other thing that bothered me is that I heard a "chirp", which makes me wonder if the belt chirped on the pulleys because of the "extra" load present because the fan wouldn't turn as the engine first started. Does that make sense? I wouldn't think the fan could create that much of a load to make the belt chirp, but I'm at a loss to figure out what else could have caused the chirp sound??

Since this happened after a cold start, I'm thinking it's a sign of bad things to come if I don't swap it out soon. I can see your scenario happening after restarting a warm engine.

 

[CJ3Flyr]

Hmmmm... I notice the chirp of my idler pulley when I get a 'quiet' start. I assumed it chirped all the time (for the first few seconds) but I don't hear it under the roar of the fan.

I am not sure what you have going on. I think I read a thread on TTORA or ToyotaNation on rebuilding the clutches including options for fluid...

 

[ToyTech99]

Hmmmm... I notice the chirp of my idler pulley when I get a 'quiet' start. I assumed it chirped all the time (for the first few seconds) but I don't hear it under the roar of the fan.

I am not sure what you have going on. I think I read a thread on TTORA or ToyotaNation on rebuilding the clutches including options for fluid...

So I've been thinking about this a bit more...

First, if we have a thermostatic fan clutch, why is the fan spinning at all upon a cold start-up? I never really thought about it before, but the fan clutch is designed to engage the fan when the engine is HOT and allow the fan to disengage when the engine is cold. If the fan is engaging upon cold start-up, the question in my mind is this: Does the fan ever really disengage at all? And if so, under which circumstances?

 

[CJ3Flyr]

So I've been thinking about this a bit more...

First, if we have a thermostatic fan clutch, why is the fan spinning at all upon a cold start-up? I never really thought about it before, but the fan clutch is designed to engage the fan when the engine is HOT and allow the fan to disengage when the engine is cold. If the fan is engaging upon cold start-up, the question in my mind is this: Does the fan ever really disengage at all? And if so, under which circumstances?

I always assumed (and we know the danger with that) that the engaged fan at start up was a result of heat soaking the underhood area at shutdown. At shutdown the airflow under the hood and across the thermostat (on the fan) ceases. The engine block, heads, exhaust etc are still at normal temp and the whole compartment warms up.


Stupid human tricks, don't try this at home... When I was younger I did many things in an attempt to win the Darwin award. One of them freaking my friends out by grabbing the fan while a vehicle was running. If the engine is cool and the fan has released from initial start-up you can absolutely stop it, easily, with your fingers. (The fact I am typing this proves I still have most of my fingers.) The fan never "stops" completely, there's always some drag of the clutch and some spinning due to air being forced through the grille. The only time it would completely stop is when some moron grabs it And please, nobody reply with :worthless
:lmao:

That's my take...
:cheers:

 

[ToyTech99]

Well, it makes sense that there would always be some drag on the clutch, causing the fan to spin.

But would that be true even on an ice-cold engine that had been sitting for a few days during the winter? There wouldn't be any heat soak to cause the fan clutch to partially engage, right?

And what about a cold engine that is idling (before it gets a chance to warm up)? If the vehicle is stationary, then the fan wouldn't be spinning due to air flowing in through the grille area.

It's funny, but I've never really thought about this before. I'll have to see what kind of info I can dig up...

 

[PredBlue]

It seems like you've checked for leaks in the fan assembly and if it doesn't seem to be acting up during driving, I don't think there is a problem. I know several of us have had weird or strange things happen in the damp/wet and cool/cold weather you were describing upon a cold engine start up. I don't recall anyone of those people actually having any problems and even when those conditions and "weird things" were reproduced at a garage, the techs all said they couldn't find anything wrong---at least that's what I recall.

Also, didn't a couple of people on here say something to the effect that you aren't supposed to put the vehicle in drive until the fan "roar" stops, which is supposed to be within ten seconds of start up? That according to what Toyota techs told them that the fan clutch could prematurely wear out if a load is put on the engine immediately when the fan clutch is roaring. I can't remember for sure, but it seems like I read that here (or somewhere). I can't remember the explanation for why exactly it would damage the fan clutch either. I basically can't remember very much today.

 

[CJ3Flyr]

Here ya go... http://neuralfibre.com/paul/4wd/tuning-and-understanding-your-toyota-viscous-fan-clutch

 

[ToyTech99]

Thanks for the link. Looks like some good info in there.

So I guess the fan clutch never really freewheels 100%, which explains why the fan is spinning right after a cold start-up.

 

[4-Legged-Runner]

I live in the woods in SC Pennsylvania. On damp and cold mornings after a good nights cool-down, I occasionally get a quick squeek on start-up. I dismissed it as damp belts. This has probably been happening for the last 20,000 mi (now at 50,XXX). Yet it only happens occasionally.

 

[4-Legged-Runner]

I had another thought: what if the chirp sound you heard had something to do with the shutdown procedure? Forgive me, because I may not understand the system properly, but perhaps the clutch was DIS-engaging in the morning at start-up and the sounds we hear are the belts slipping????

 

[ToyTech99]

I had another thought: what if the chirp sound you heard had something to do with the shutdown procedure? Forgive me, because I may not understand the system properly, but perhaps the clutch was DIS-engaging in the morning at start-up and the sounds we hear are the belts slipping????

It's not really the chirp that bothered me, although I never hear even the slightest chirp from my serpentine belt system at all. What bothered me is that the fan obviously wasn't spinning as the engine started up. There was a good 5-second delay between the time that the engine started and the time that the fan roared to life. After owning my 4Runner for the last 5+ years, I got used to hearing that fan roar upon start-up. It was just really weird to hear it silent.

But the good news is that it hasn't happened again, so maybe it was just an isolated incident. But like I said...I don't like messing around with things that can cause the engine to overheat because a lot of damage can occur when an engine gets too hot. And of course a fan clutch is an integral part of the vehicle's cooling system, so if it even so much as hiccups again, I'm replacing it just as a preventative measure.