Okay guys, I read the other thread, but bear with me here.

I have a 99 3.4 limited 4x4. About 3 weeks ago I was pulling a car on a trailer (5000lbs give or take a few hundred) on the interstate in stop and go traffic. I looked down at my gauge cluster when my friend said that he thought he heard knocking (I was checking to see if i had a c/e light on) and noticed the temp gauge was up toward hot. Luckily, traffic broke and we got moving. I cranked the heat on, and rolled down the windows and it cooled back down to normal. I took it as a fluke, added about a quart of water too the coolant resevior and called it a day. Fast forward to this weekend. We were camping, my buddy was in his time bomob 88 V6 and I was in my 99. I told him to watch his coolant temp, b/c slow going up steep stuff can get one hot. I then noticed mine was the one getting hot. Just I cranked the heat all the way up, but couldn't really do much good without getting some air through her, so I picked up the pace to about 30mph on the dirt roads to cool it down. I got out of the truck, popped the hood, left the heater on (the temp gauge was still about 3/4 the way up) and then i looked under the hood. The hood was nice and cool, everything seemed normal. I grabbed the throttle cable and reved it up a bit. And I noticed the fan didn't turn any faster when I revved it up. You would think with a truck running hot the fan would kick in and cool it down. But this wasn't the case. The fan was basically free-wheeling. Now I KNOW the fan works, b/c as you all know when you start your rigs in the morning, the fan runs for about 20 seconds and your rig roars. It has plenty of resistance on it, so I know it's working. I'm wondering if there's any sensor that tells this clutch when to engage, because if there is, I'm thinking this may be the problem. It COULD be the thermostat, and I went and bought one just in case. But finding the thermostat housing down on the block doesn't make me too hasty about changing it out before asking some of you guys about this fan issue.

So bottom line is, normal hwy/city driving I never have any trouble (remember temps are in the low 70's when this happens, I'd hate to see it in the upper 90's here in a few months) but when going slow and stressing the motor (hills/trailers, etc.) the engine will overheat. I'm leaning more toward the fan issue, b/c if it were the thermostat, even running down the hwy empty it should overheat, b/c the cool water in the radiator isn't allowed into the block.

 

It sounds like the fan is still working fine and that you just stressed the engine (ie running it at max load and very low speeds). Mine did the same thing coming out of Arizona (even to the point of almost boiling over the radiator) but it still ran fine when unloaded. I think if you are worried about that too much you might consider trying a dual electric fan setup. Sounds like it is otherwise working as it should. These trucks just don't tow heavy loads all that well at all.

 

Well, can you explain why it shouldn't be able to idle around dirt roads in low-mid 70 degree weather WITHOUT the a/c on? Truck wasn't loaded then. By idle i mean 1st - 2nd gear (10-20 mph). My friends 3.0 V6 in his old 88 beater had no issues at all.. nor would/should any vehicle in those conditions unless it was on it's last leg (not implying that mine is but... you know what I mean.) I know there's a problem, I just don't know exactly what it is. I went ahead and changed the thermostat, just to get rid of that variable, but like I said, I rarely have this problem when not at low speeds or otherwise putting a bit of load on the truck.

 

The fan works with internal fluids heating up and cooling, so you can rule out electrical in that regard. Will the fan spin when the motor is hot and you shut it off?

I have two extra fans that I would sell for cheap if it gets to that point.

I would also look into a clogged radiator, bad WP, or some type of sending unit problem.

Has it leaked or used any coolant that you are aware of recently?

 

If I understand your question, you're wondering if the fan spins after I shut it off... no. That's impossible without an electric fan... right? Or do you mean when I restart the truck? When I restart it, yes it spins for the usual 20 seconds at the same speed as the engine rpm, then slows back to the normal fan speed after that.

 

No, I mean by hand. If the fan is working properly, you will NOT be able to spin it by hand with the motor hot.

 

same problem here! Im trying to get it fixed before the summer gets here.

Runs great while moving but If I let it sit for a bit, the temp gague slowly rised up to the red mark....

So far I've changed the thermostat, flushed the system, new radiator cap, and a new fan clutch.....

I noticed that the fan clutch is working just the same as the old one. when its cold there is a little bit of resistance but after the engine is hot, The fan will free-wheel..... Could I have got a bad fan clutch???

95 4runner 3.0 5-speed..

 

i had a similar problem, i took in to see my mechanic who is an ex toyota dealer mechanic, and he advised me it was my fan clutch...he mentioned that was a common problem with 3rd gens...i bought one and replaced it. NEVER had a problem again...ps i changes the thermostate just to be safe aswell...nice and cool under pressure since.

 

That's probably it then.... it's strange how it works just fine on startup. I kinda thought this might be the issue. Anyone have a hookup on the part for this, or is it just a gouge at the dealer?

 

I have two fans, one has 70K and one has 50K. To be honest, I am not sure which is which. Let me know if you are interested. I am sure we can work something out.

Have you tried local wrecking yards?

 

Well, no I haven't, but I wouldn't trust them anyway. How much do you want for your fans? Can you just sell the clutch, or is it a one peice part? My fan blades are in superb condition. I'm going to give it the test today. SO you're saying that you should be able to spin the fan fairly easy when the truck is cold, but once it's warmed up it should be difficult to spin? How difficult exactly. Because when it's cold and i give it a good whirl, it only spins about 1/5th of a revoltion... basically turns 1 fin worth of turn.

 

Well, my understanding is the following:

Cold: Spins a little by hand, but not very easily (hence the reason you hear a roar at start up).
Warm: Fan should spin freely.
Hot (norm op temp), engine sits for a second: Fan should be difficult to spin, if at all.

I don't think the fan blades can be safely separated from the clutch. I think the clutch is integrated somehow, but I would have to look.

How many miles do you have? This seems like pretty rare problem on the 3.4.

 

115kish.

 

I posted this in the 2nd gen overheating thread, but since I have a 3G, I think it applies here, and would be benefitial for people searching the archives later... I'll paste what I posted there...

W3S had a good idea...

I took some folders, taped them vertically (one on top of the other), and stacked them 3 wide across the front to prevent any airflow (they went between the a/c condensor and the radiator). I then shut the hood and started driving. First 2 minutes nothing. So i dropped it to 2nd gear (30mph). Still nothing, so i dropped it to 1st gear going about 20-25 mph on the streets around my nieghborhood. I then started to see the temp gauge rise. I would really hammer it up to about 5k rpm and I could literally see the temp gauge go up. So i held it about 3/4 high the whole way home by going into higher gears and letting it cool and staying in low gear for heating up. So i get home and i pull the folder out and i notice the fan is working just fine - as i rev the engine, the fan revs up too: GOOD!

So i get it back to normal operating temp, the fan has gone off. So I try again, this time, not moving. I stick the folders back in there, and turn on the truck. I rev it up a few times and I start to see the needle climb. (You have to have the hood down I found, or else all the hot air escapes). It got about 3/4 the way up and the fan was working great (just no air could pass through). So I removed the folders and reved her up to about 2-2.5k and she started cooling immediately. The fan I found is actually very accurate. My needle when running "normal" sits just below the 1/2 way mark on the temp gauge. The fan did not shut off until it was exactly at it's normal spot just below the 1/2 way mark on the temp gauge. So those wanting to test their fans might try this method. So now that I've replaced the thermostat, and affirmed that the fan is indeed working, hopefully it won't overheat again. If it does, the next step will be having the radiator cleaned professionally.