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TJ Flat Towing Mystery

rockota said:
Harry already alluded to this... but I understand that a lot of camp grounds don't really make it feasible to use a trailer...
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Harry Johnson said:
Yeah, I own a 16' trailer already. It's easier to find a campsite at rv campgrounds that can accommodate a 27' rig and a spare vehicle than it is to find a site that will fit a 43' rig and spare vehicle. If space isn't an issue, then it goes on the flatbed... shoot, just for the convivence of being able to back up, trailering makes it worth it.
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I saw that Harry has a trailer and uses it when convenient. I know that campgrounds are a pain with a longer rig and like to charge you more. They are a pain in the ass with my toy hauler.
 
Interesting that you post this. My aunt and uncle flat towed her TJ from Sac to Colorado this week and we smelled something too. We were thinking maybe a brake pad dragging or just tire wear. If we smell it again on the way back we will check the fan too. I really don’t think you get enough air flow behind the RV to get it spinning.
 
I have flat towed stuff and had the front diff burp a little bit of fluid out. Old Jeeps do that if they are full or overfull and running higher speeds. Could you be smelling a whiff of gear oil?
 
FordFascist said:
Yes, correct. The point I was making is that the entirety of the wear is occurring on quite possibly the smallest bearing in the entire case. There is no scenario in low range where this bearing is ever spinning that fast vs running at 70MPH.

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Yes, but there is no load. The TC is not handling any power. Just like with a CAD disconnect the spiders are spinning like crazy. No load, no problem.
 
Harry Johnson said:
I thought maybe that as well. I'm pretty familiar with the smell of hot or burning tires, but I did the sniff test around the tires anyway- it's stronger right over the belt when I pop the hood.


The only potential theory I'm working with is the stock fan is spinning while I'm running down the road and "peeling out" on that small section of the belt. I haven't had a chance to test the theory since it occurred to me in the shower last night a few hours after we got back.
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Easy to check. Stick a piece of cardboard in front of the radiator, to block the air flow, and recheck after the next tow.
 
There is absolutely no way there is enough air flow to cause the fan to spool up enough to chirp the belt. That close to the back of an RV, you are essentially in a buffer zone where the air might be flowing TOWARDS the back of the RV, rather than away. You have to be like 15 feet off of the back of the RV to catch significant airstream.
The fan/belt is a red herring.
 
D_JEEPER said:
There is absolutely no way there is enough air flow to cause the fan to spool up enough to chirp the belt. That close to the back of an RV, you are essentially in a buffer zone where the air might be flowing TOWARDS the back of the RV, rather than away. You have to be like 15 feet off of the back of the RV to catch significant airstream.
The fan/belt is a red herring.
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Interesting.

Took the jeep out on the freeway yesterday. Ran it at 70 mph for 20 minutes. No funky smell. So whatever is going on happens while flat towing, but doesn't happen at the same speed under power.
 
Harry Johnson said:
Interesting.

Took the jeep out on the freeway yesterday. Ran it at 70 mph for 20 minutes. No funky smell. So whatever is going on happens while flat towing, but doesn't happen at the same speed under power.
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Could it just be an accumulation of Diesel exhaust fumes from being in the back of the RV slipstream?
 
D_JEEPER said:
Could it just be an accumulation of Diesel exhaust fumes from being in the back of the RV slipstream?
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Front engine, side dump, gasser. Most likely not exhaust. Smell is exactly like when a belt burns up. I haven't had experience with it on cars as much as when the building I work in has one go out for one of their compressors on the roof, or when our last vacuum cleaner used to wear out a belt.

Definitely different smell than tires or gear oil or exhaust.
 
I still say tie rap the fan. Or just sticks 2 by 4 in there to lock it up.

How easy does your fan turn In the clutch? (Like little finger easy?)
 
Turn the by hand and compare that to the amount of effort it takes to fight the wind with your hand out the window. If the fan pulley doesn't move without significant force, no way air making it through the RV, radiator and then exiting the completely AFU airflow management of a Jeep is strong enough to spin the fan enough to make it do a burnout on the belt.

These old bastages have some decent theories though:

Burnt rubber smell in towed Jeep - iRV2 Forums

So a friend of mine and I have the same issue. After towing our Jeeps then detaching and starting we have a burnt rubber smell that last just a short time. He has a newer Grand Cherokee and I had it
www.irv2.com

Or, you know, bring a trailer with you everywhere and stop flat towing your Jeep since it'll probably explode and send shrapnel into a bus of nuns at any moment... :flipoff2:
 
Rockwood said:
Turn the by hand and compare that to the amount of effort it takes to fight the wind with your hand out the window. If the fan pulley doesn't move without significant force, no way air making it through the RV, radiator and then exiting the completely AFU airflow management of a Jeep is strong enough to spin the fan enough to make it do a burnout on the belt.

These old bastages have some decent theories though:

Burnt rubber smell in towed Jeep - iRV2 Forums

So a friend of mine and I have the same issue. After towing our Jeeps then detaching and starting we have a burnt rubber smell that last just a short time. He has a newer Grand Cherokee and I had it
www.irv2.com

Or, you know, bring a trailer with you everywhere and stop flat towing your Jeep since it'll probably explode and send shrapnel into a bus of nuns at any moment... :flipoff2:
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All those people are talking about after they start the Jeep. Harry says he smells it when unhooking the Jeep. (Unless he has already started it be unhooking.) why wouldnt it make the same smell on a trailer? Same road debris. There could be some weird airflow patterns behind a MH. Not hard to imagine air being funneled right at the fan.
 
Rockwood said:
These old bastages have some decent theories though:

Burnt rubber smell in towed Jeep - iRV2 Forums

So a friend of mine and I have the same issue. After towing our Jeeps then detaching and starting we have a burnt rubber smell that last just a short time. He has a newer Grand Cherokee and I had it
www.irv2.com

Or, you know, bring a trailer with you everywhere and stop flat towing your Jeep since it'll probably explode and send shrapnel into a bus of nuns at any moment... :flipoff2:
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I aint skeered, been towing it this way for the last two years, but that still doesn't mean I don't want to know what the heck the smell is from. It's more interesting that all these blue hairs are saying they get the same thing from other vehicles.

So yeah, I went out and I could spin the fan by hand, but definitely not enough to engage the fan clutch... So that's probably not it.

I don't agree with the road grime assertation however, because I noticed the smell as soon as I went to unhook the jeep, long before I started it up.
 
Harry Johnson said:
I aint skeered, been towing it this way for the last two years, but that still doesn't mean I don't want to know what the heck the smell is from. It's more interesting that all these blue hairs are saying they get the same thing from other vehicles.

So yeah, I went out and I could spin the fan by hand, but definitely not enough to engage the fan clutch... So that's probably not it.

I don't agree with the road grime assertation however, because I noticed the smell as soon as I went to unhook the jeep, long before I started it up.
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I'm going to pay close attention to mine this weekend. We're going out to the coast for a couple days and will be flat towing. A lot of the time I'll disconnect out in the road before I even turn into the camp ground just in case I get turned around or something so I'm kind of in a hurry and not paying attention but the place we are going this weekend is a regular place and I have a pull through so I will be towing right into my site.
 
crazybluerider said:
I'm going to pay close attention to mine this weekend. We're going out to the coast for a couple days and will be flat towing. A lot of the time I'll disconnect out in the road before I even turn into the camp ground just in case I get turned around or something so I'm kind of in a hurry and not paying attention but the place we are going this weekend is a regular place and I have a pull through so I will be towing right into my site.
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Take a wiff under the hood as soon as you stop. I started reading through more RV forums and it sounds like some people get it and some don't... I've noticed mine usually goes away within a few minutes of unhooking and parking, but I did have it last and especially long time after towing 280 miles from Truckee, Ca. to Monterey. I could still smell it inside the vehicle when I started it up and drove it to work the next day. After a 10 minute drive into work varying between 60 mph and 25, the smell was gone.

I am starting to wonder if it's rubber "roost" from the motorhome's tires, or maybe brake dust from my brakes since we dropped a lot of elevation? Either way, maybe those little particles don't have to heat up to smell and they're just everywhere after towing.
 
Harry Johnson said:
So yeah, I went out and I could spin the fan by hand, but definitely not enough to engage the fan clutch... So that's probably not it.
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Spinning the fan by hand was just to verify that wind could do it. The way a fan clutch works is it gets harder to spin as it gets hot. That heat usually comes from the radiator or from the waterpump and general under hood temps. In a towing situation, I wonder if the spinning generates its own heat. Maybe it starts getting so hard to spin, it either spins the pulley or just transfers heat to it and cooks thebelt in one place. You said you felt the belt, have you felt the water pump pulley?
 
Your front diff breather is right at the radiator on the passenger side. Your tranny breather is on the firewall near the brake booster. I would take a wiff of each of those to see if one is more pungent and the other.:idea:
 
Stingray said:
Plus the belt would have to be pretty loose.
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Which would then be obvious as soon as you started the motor.

Harry Johnson said:
Take a wiff under the hood as soon as you stop. I started reading through more RV forums and it sounds like some people get it and some don't... I've noticed mine usually goes away within a few minutes of unhooking and parking, but I did have it last and especially long time after towing 280 miles from Truckee, Ca. to Monterey. I could still smell it inside the vehicle when I started it up and drove it to work the next day. After a 10 minute drive into work varying between 60 mph and 25, the smell was gone.

I am starting to wonder if it's rubber "roost" from the motorhome's tires, or maybe brake dust from my brakes since we dropped a lot of elevation? Either way, maybe those little particles don't have to heat up to smell and they're just everywhere after towing.
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I think this is the culprit. Quit doing burnouts man.
 
I'll most likely never flat tow but I'm curious to find out what is going on. :grinpimp:
Wouldn't a fan slipping on the belt destroy the belt in a hurry?

And if it doesn't smell when towing it on the trailer then I think it's quite safe to say the fan is not at fault.
 
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Sure you're not smelling PS fluid? Maybe burnt PS fluid?

I know its far fetched, but having the steering cycle without the pump running could be pushing PS fluid or at least the smell out of the cap. And likely when you pull over and park the steering just got done being cycled quite a bit.

Thing might also be death wobbling like crazy back there
 
Harry Johnson said:
Got a 98 TJ that we occasionally flat tow behind our RV. It works great BUUUUT... Nearly every time I do, it smells like the serpentine belt is burning when I go to unhook it from the back of the RV. Everything else seems to be fine and it fires right up and runs down the road with no issues after. The smell is gone after that first drive. I've touched the belt after towing and it's not hot. The burned belt smell is stronger if I open the hood and stick my nose over the belt for a sniff test.

I follow the instructions in the manual for flat towing: Key turned, but not on, transfer case in neutral, manual transmission in gear (I usually use 4th because the idea of the transfer case popping out of neutral at 60 mph terrifies me).

What the heck is going on?
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My dad experiences the exact same phenomenon flat towing his Grand Cherokee. I don't know if it is from the RV tires, exhaust, road grime, etc. First time you get in it in after flat towing it has a "burnt rubber" smell but goes away after the vehicle is run. We always attributed it to the layer of dirt, rubber, diesel exhaust, etc. from the motorhome. He's been flat towing for 25+ years...
 
Coyote said:
All this talk of a slipping fan, won't that happen on a trailer also? I'm going with the road debris on the exhaust.
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Won’t the road debris happen on the trailer also? The airflow could be different in both cases. Has the OP confirmed the smell before running the engine?
 
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