Cbpcop

Vehicle is 98 4Rnr w/2.7 liter 4 banger, 2WD, auto etc. (painfully stock). The issue is that the belt driven cooling fan NEVER disengages (unless it gets somewhere below 60 deg F). Location is south Florida, land of eternal heat. I've read on another forum about disassembling the fan clutch, cleaning it up and refilling with new silicone clutch fluid. Is this an effort that will be worthwhile or is it just too hot down here for that blasted thing to ever disengage? MPG is an average of 15-18 combined. Engine definitely has more power during cold weather with fan NOT running. Don't have the bones to buy an electric fan setup yet.

DailyDrive

What do you mean by never disengages? It's supposed to spin all the time. The real question is, does it always sound like a plane taking off, or just when cranking it up cold, and then it quiets itself?

Cbpcop

Nope! never quiets itself. Pretty much have to file flight plans just to go to work everyday - howls like a banshee!

PismoJoe

Time for a new fan clutch

Cbpcop

Guess the fluid change idea is probably a bust then? It's gonna really suck if I change the stupid thing and get the same result. This last "winter" we actually had temps down into the 40's and it "disengaged" ie didn't run all the time. Same diagnosis? - new fan clutch?

gdutch

I live in Texas, and this summer my fan pretty much howls every time I take off from a stop. That said, it shouldn't be doing that all the time when it gets to be below 70* or so. You might be running hot, which is causing the ECU to keep the fan blowing.

PismoJoe

The fan clutch is not electronic, it is controlled only by temperature. Depending on the temperature, the bi-metallic spring on the front will open and close an internal valve causing the clutch to spin faster or slower

Checking the fan clutch is really simple. When the engine is off and COLD, the fan should spin with little resistance.

DailyDrive

Fan should spin with little resistance only when the clutch is at operating temperature.

Hence why the prop airplane sound when cold.

PismoJoe

I think you have it backwards, you're saying that the fan SHOULD be engaged when it's cold then

TheDurk

I have been bothered by this apparent inconsistency. Here is the answer:

Source: http://www.haydenauto.com/Featured%2...s/Content.aspx

The noise at start-up being there and then going away appears to be the best diagnostic guide to the health of your clutch. I am new to these things--my other cars have been electrics or old fashioned straight mechanical. Other keys are absence of evidence of fluid leakage and excessive lateral play at the fan blades.

PismoJoe

Well I have 2 brand new Aisin OE fan clutches, one on my Tacoma and one on my 4Runner, its 65 degrees outside, haven't been ran today, and they are spinning with very little resistance when turned by hand.

Durk, you're right though, the fan should spin like that for a very brief few seconds at startup, but it should not be engaged fully like I perceived DailyDrive to be referring to. Maybe he meant for a few seconds, I could have misunderstood.

TheDurk

Actually, I think I misunderstood YOU. Anyway, the question of why it engages at start-up is not obvious and I thought worth explaining. And yes, My new OEM Aisin fan does engage at start-up BUT it spins with relatively little resistance by hand--EXACTLY as did the non-functioning 11- year old OEM clutch I took off last week. I checked them side by side and the resistance to turning (cold, obviously as they were on a bench) was light and identical for both. I therefore assert that resistance to hand spinning is not a good method of judging health of your clutch, but start-up action is. My new clutch passed the acid test on the Delaware Memorial Bridge this weekend so I know it's good.

I guess if it was locked up when you hand spun it, or if it freewheels, you could say it was bad, but the fact that it spins with light resistance is no assurance that it is good...or bad....or anything.

profuse007

My 2000 4cyl starts up like an airplane and slows down after 30sec or so. It spins like an airplane when I rev while driving.

Cbpcop

Here's a new one: had a guy who claimed to have worked for Toyota for awhile (insert grain of salt here) tell me they used to do the fan clutch fluid refills using transmission fluid and had good results. I'm a box of rocks on this one guys - does this sound even feasible to anyone? I've been around long enough to know that just because someone does something doesn't mean it's going to work right.