Visco Fans and falling off parts...

[VerMonsterRV]

Well, I have been chasing my tail with an annoying rattle but it finally became clear today. Checked various heat shields, bolts and exhaust fittings. Plus I just did the turbo swap and radiator upgrade so I always doubt what I did first, so double check everything there. I even checked the valve clearances in hopes that was it. But it ended up being the visco fan. There is a round perforated disc held on with 4 screws on the front of the fan (nice and hidden when the radiator and fan shroud are installed), well currently on our truck that disc is held on with a single screw. Allowing that disc to swing around as the fan spins. The picture below is off the web as I have yet taken the time to get in there and fix it. I know it is this plate as when I spin the fan from below I see it peeking around the edge of the fan, clanking away.



So, if I can't find some replacement screws (not likely as we are in Redwoods NP) does anyone know if I can just remove this plate (hey there is only one screw in it) and run it for a bit without it until I get to a place with replacement screws? Anyone know the purpose of this plate?

 

[DiploStrat]

Stephan question.

FWIW, we had a defective fan on our truck. Took several valve adjustments to find it. We stayed with a pure mechanical fan.

 

[Sitec]

Those will be countersunk M4 or M5 screws... Over here hardware stores have those small over priced grab packs with 4 or 5 screws/bolts for $10 or more. You might find what you need. No idea what that plate does tho! Ours has a working viscous fan, so it is staying. Running a solid fan will make the fuel consumption go up a surprising amount.

 

[VerMonsterRV]

I did a bit of digging around including bothering Stefan again. Problem is he just knows too much about these trucks. In my digging I found replacement aftermarket fans without this plate. Apparently this plate somehow protects the bimetal chunk that helps tell the temp. I will search out the screws but for now I will run without it. Fan still works as normal. With the plastic shroud and radiator right in front of it I am guessing a rock would have to go through the intercooler and radiator before it could get to this bit of metal. My guess is I would notice if something like that happened. Not sure if it was put on the fan for engines that were a bit less protected from frontal stuff. I reached up inside the fan shroud and was able to remove the last screw, now I can move onto finding the next rattle...

 

[joeblack5]

That m4 / m5 screws are available at Lowes. Hardware section. Probably even on stainless. Not sure if you can get a screw driver between the radiator and the protection plate? I would go with an Allen or hex head.. or leave it of altogether..
Lucky it did not come loose and catapulted into you radiator by the fan blades..

Johan

 

[VerMonsterRV]

That m4 / m5 screws are available at Lowes. Hardware section. Probably even on stainless. Not sure if you can get a screw driver between the radiator and the protection plate? I would go with an Allen or hex head.. or leave it of altogether..
Lucky it did not come loose and catapulted into you radiator by the fan blades..

Johan

Thanks, and a few more miles and it would have. Would've been particularly painful since I literally just upgraded the radiator!

Well, on the topic of parts falling off. This plate wasn't our rattle ?. Yup, first drive and the rattle was still there. But... I think I may have found the problem.



That there is the passenger side engine cradle bolt. Yeah, it is completely loosened and just resting there. Little tight to get in there but I was able to get a ratchet in there. Of course I put on a liberal coating of locktite. Man I hope this is the rattle (but either way I am glad I found it).

 

[RoamIt]

Hopefully that's it! "engine cradle bolt" sounds important
I'd absolutely call the search for the rattle a win already.

 

[Joe917]

Being in tune with your truck's noises is key to catching problems early.
We were driving out from Wrangle st Elias following a friend in his MAN. We were clipping along at a good pace and at one point I heard a pretty good clunk from below. Sounded like a good sized rock in the wheel well. we had to stop where a mudslide had buried the road 3 or 4 feet deep. I left the truck idling to cool as we walked forward to investigate. 5 minutes later I went to shut the truck off and the temp had climbed over 100C. I immediately shut down and crawled underneath.
The cause of the clunk was a catastrophic viscous fan failure. The fan mount has a heavy rubber connector that isolates vibration. the rubber bond had failed and allowed the entire spinning fan to separate. Apart from one curved track through the radiator cooling fins there was no damage and the fan was stuck in the shroud. It took some time to pull the fan out but by then the road had been cleared.

 

[VerMonsterRV]

Hopefully that's it! "engine cradle bolt" sounds important
I'd absolutely call the search for the rattle a win already.

I guess if you mean "important" as to keeping the engine connected to the truck, then I think I agree with you ?. Yup, definitely a win. Now onto the next rattle.

I am also planning, once the weather cooperates, to spend a bit of time poking around to see if I can find any other loose bits. Guess all the shaking from rougher roads is loosening things up a bit.

Plus, with @Joe917 's comment I am considering carrying a spare fan.

 

[VerMonsterRV]

Oh, and I want to give credit where credit is due, once again Stefan the magician suggested these bolts might be an issue. The man literally has forgotten more about these trucks than I will ever know.

 

[Neil]

Interesting thread about viscous fans.

Out of interest, how often do you think they actually engage.

I have never seen my running, but I have heard it kick in on a handful of occasions when I have been crawling over the Andies at high altitude and my tempreture has crept up a little . I am.pretty sure that sitting on the highway at top speed all day it never kicks in .

If I idle the vehicle for long periods the tempreture doesn't climb enough to kick it in. I have often wondered if its even working correctly , but my temp has never got too high .

I know that the fan on the 1017 has a handy big nut on the back of it that if you turn it 90 degrees it locks the fan drive rigid and bi passes the viscous coupling . I assume this feature is common on all our models

Neil

 

[RoamIt]

So what would be the down side of electric fans with a adjustable thermostat and a manual switch? The upsides would be less parasitic drag on the engine and being able to shut off for water crossings.

 

[VerMonsterRV]

I can hear our fan wind up when the engine is under load and once the load decreases it returns to the freewheel state (it always spins when the engine is running, just not "engaged"). This is just a guess but I think maybe in the intercooled trucks the fans run more often. The intercooler is mounted directly in front of the radiator, obstructing direct airflow. Plus the air exiting the back side of the intercooler is warmer than the ambient air temp, which then hits the radiator. I also know this, we replaced our radiator with the Nissens one that crossed to the OEM part number. The fan ran more frequently. I have just now again replaced the radiator with a Nissens one that cross references to the OEM one on the 240hp engine. Thicker core and way better cooling = less fan running.

Interesting thing about visco fans, is as far as I can figure out, they are not directly temperature controlled by the actual engine temp. Just the ambient air temp in front of the fan. It seems that when we drive in higher cross winds the fan runs more. Guessing less air flow through the radiator causes the air in the fan shroud to increase.

Idling I have never had the fan come on, but I rarely idle the engine for any length of time.

About electric fans, I was thinking of going down that route if I went with a custom radiator (really want a heavy duty all conditions cooling system). Trick is finding a 24v one made for medium duty trucks. They didn't seem real common.

As a side note about the cradle bolts. Stefan knew about this possibility as his had also backed out. Given that, I would recommend (at least any LN2 owners) giving a quick look. Not sure how the other model engine cradles are bolted to the engine, hopefully a bit less prone to backing out.

 

[Joe917]

The big nut is to lock the fan in the event of overheating due to the fan clutch not working, this is the normal failure mode.
You can't carry spare everything Jon. The viscous fan is a heavy part.
Our fan (actually somebody else's fan as we just sold the Heffalump) comes on on climbs and city driving. The fan can be had from Terry Lee or Pacific Power Group among others.
The problem with electric fans is they are electric, I prefer a mechanical system. There is less parasitic drag with the viscous fan, that is the point.

 

[Sitec]

Ours cut in a few times when I was hauling the retaining wall rocks home (at the begining of this thread)... 40 deg days, an overloaded truck and some steep climbs had us in second gear at almost full revs with the fan howling! Truck stayed cool. The same couldn't be said for the occupants though!!


Seems an age ago... There's a house there now!