ditching the fan clutch - discuss (1 Viewer)

[semlin]

met up with Gold Boy a BJ74 owner today and noticed that he had switched out the fan clutch for a fixed unit sold in saskatchewan for the mine trucks. It looks to be a bolt in for the 80 although depth is uncertain. i am curious what people think of this or the idea of an aluminum spacer to move the fan clutch closer to the rad . the logic that the fan clutch temp sensor is not trustworthy is interesting to me because the behaviour of my truck reminds me of a vehicle with a bad fan clutch (even though it is brand new).

Apart from replacing my rad I have replaced everything and there are no remaining "stock" options to cool my truck further yet it runs hot according to my raventai modded gauge even in town (by hot I mean mid 190s and often up to 200 on the highway in cold weather). i towed an m101 trailer over 400 miles thiss weekend over a lot of 8-10% grades. i will easily and quickly pop up in temp on grades at highway speeds. I can easily go to 210 on even short steep 8-10% grades with no ac in cold weather. that is not overheating YET but i do not think i would want to attempt the same thing in 100 degrees weather with a/c on. the rad does not appear blocked in the least. i have no sludge. what bothers me is the truck sheds the temp fast on downhills but has a "memory" so that once it gets up there in temp it stays up there even if it cools right down between climbs.

anyway, interesting to see what others are doing.

https://forum.ih8mud.com/showthread.php?t=81292&highlight=fan+clutch

 

[Rich]

That is a viable alternative. Idealy the fan would be replaced with one designed to operate without failure at max engine rpm. The factory fans likely are not.

Years ago I had a clutch lock up while on highway (road trip, towing boat, return trip from Florida keys) in a Ford van with 460 engine. Was in the middle of the boonies in Virginia on a Sunday morning. Clearly the metal fan was never intended to operate at full speed. It roared like a jet engine. It was almost impossible to carry on a conversation the noise was so loud! Lucky for me the at the very next exit, still in the middle of the rural country side, there was an autoparts store (and nothing else for miles around) it was open, and they had a replacement fan clutch.

What you give up with a fixed fan is a bit of fuel milage, as the fan will be turning at engine rpm whether you need the extra cooling or not.

 

[MaddBaggins]

I believe you would need to upgrade the fan to something much stronger. I have heard stories of fan blades flying apart shooting thru the hood and rad. Not sure how the 80 fan would like that constant high rpm.

 

[RavenTai]

If you are going to ditch the clutch you need a flex fan, and not the dinky ones you see in parts stores, one with deep scoop blades that flatten out at higher RPM.

you will still loose some power and milage,

a full RPM factory fan will loose a lot of power and might not hold up to the force, our 1FZ will turn a lot more R's than a diesel.

 

[Cube Dweller]

Semlin, have you checked your timing? Running advanced can cause it to run hot. Apologies if this is a repost suggestion.

 

[semlin]

thanks. it is recently set correctly. i agree running lean is a suspicion but if it is running lean I can't figure out how. new fuel filter, FPR, freshly cleaned injectors, air filter clean (I'm going to replace it anyhow), egr all rebuilt

as i'm typing i realize i meant to check my pair valve to see if it is running right. i guess that could mess with the 02 sensors.

 

[FJ40_owner]

I run a heavy 6 blade fan with no clutch. My Rad mad told me to install a spacer so that the fan is aligned with the shroud. I asked about the fan being closer to the rad. He was emphatic, "just even with the shroud." I purchased spacers from Summit, they have all sizes.

Good luck

Jim

 

[semlin]

jim, is that on a 40 or an 80? where did you get the kit?

 

[CJF]

thanks. it is recently set correctly. i agree running lean is a suspicion but if it is running lean I can't figure out how. new fuel filter, FPR, freshly cleaned injectors, air filter clean (I'm going to replace it anyhow), egr all rebuilt

as i'm typing i realize i meant to check my pair valve to see if it is running right. i guess that could mess with the 02 sensors.

Do 93's have an Air Flow Meter like on the 3FE's, or the fancier Mass Air Flow sensor like on later models? Opening up the AFM to adjust mixture has recently become surprisingly popular on the 3FE list, with some folks even doing it seasonally to adjust for changes in fuel (oxygenated, etc.).

Curtis

 

[Tools R Us]

The bimetal spring that engages the clutch senses the air temp in the shroud, it's designed to work that far from the radiator. Earlier trucks that have solid fans have different pulley ratio driving the fan slower, the fan clutch is designed to always slip, so they are driven faster. If you drive a clutch type fan at full speed you run a big risk of it coming apart, violently and taking a bunch of expensive parts with it.

 

[Gold Boy]

violently and taking a bunch of expensive parts with it.

I know that this can happen and does happen, particularly with cheap aluminum after market fans.

But it has never happened to me. I have also had SBC with a steel flex fan and have taken it to way over 4000 RPM with no problems.

I have not changed any pulleys, and I am using the stock fan.



Now this may sound strange.... But sometimes the more I rev her the cooler she gets.

 

[mabrodis]

While troubleshooting some high-engine-load overheating on my '97 I took out the fanclutch and made it a non-fan-clutch by drilling through it and putting two bolts, so the fan just spun at engine speed all the time. I drove that way for a few weeks (still have the "clutch" I think...), it worked great to cool the engine, it was a bit loud, sounded very airplane-ish when you revved it up at an intersection, but I hit ~5000 rpms on a 97's plastic fan with no problems at all. I would only be concerned with the power loss, I wouldn't worry about the fan's strength, assuming the fan is not already suspect/cracked, etc...

 

[mabrodis]

Now this may sound strange.... But sometimes the more I rev her the cooler she gets.

I've seen that before, from what I've seen it's usually because at an idle/low-rpms the engine is idling so low there is almost no air movement AND almost no coolant movement. I remember years ago at a gas station we were in some 1-ton truck that was idling and getting hotter and hotter, started spewing coolant out and my dad hopped in and revved it up for about 15 seconds and sure enough, temp needle came way down, stopped spewing, etc...just needed more airflow and more coolant movement...

 

[bigbrowndog]

If it was better, as it's obviously cheaper don't you think Toyota would have stuck with the solid fans they had in the begining? All the other companies also.cheers

 

[e9999]

If it was better, as it's obviously cheaper don't you think Toyota would have stuck with the solid fans they had in the begining? All the other companies also.cheers

well, a lot of corporate decisions nowadays are likely driven by corporate economy standards. From what I read, there is great pressure to cut down 0.1mpg here and there to meet the cutoffs, so who knows...

 

[bigbrowndog]

well, a lot of corporate decisions nowadays are likely driven by corporate economy standards. From what I read, there is great pressure to cut down 0.1mpg here and there to meet the cutoffs, so who knows...

True, but my H.S.V. was developed as a performance car at nearly double the price of the standard car and they chose to run the viscous fans until a sufficiently strong set of twin thermos were developed 4 or 5 years later. Beauty there they can run at full revs while stationary or stuck in traffic or run on a timer after shut down. The standard fan is not designed to run at high revs like the origional steel fans were with less blades and less pitch. just my thoughts.

 

[IdahoDoug]

Semlin,

I think your rad may have some previous owneritis in terms of sludging at the bottom. We've had reports here of at least one 80 rad with no visible sludge from the cap hole (can't really see much here in truth, ya know) being cut open and finding large amounts in the bottom. I just have to think that's your issue, and before you start off into unknown modification territory for the cooling system, I'd consider a radiator.

DougM

 

[MTNRAT]

Semlin, the rad boss the rad. Go with the 94 3 row brass from cdan. If you have done everything else that is it. My old rad had no visible sludge at all. Changed it out and bingo, AC full cold, pulling a 3500lb boat up the Cochahalla in 90 degree heat.
Cheers,
Sean

 

[landtank]

but has a "memory" so that once it gets up there in temp it stays up there even if it cools right down between climbs.

This is exactly how my truck was behaving. Once it got to a certain temp it would just sit there.

So initially it would be at 180*, then I'd climb a hill and it would move up slightly and then just sit there. Some acceleration or another hill and it again would move up slightly and then sit there.

This has all been taken care of with a simple tweak to the fan clutch.

And I have new everything, including the 3 row brass rad.

 

[semlin]

since posting this thread i've decided to try modifying the blue fan clutch first. switiching to my old fan clutch definitely helped a little.

i agree the rad could be it but i have never had even a teaspoon of sludge in the overflow. fan clutch first then rad.