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1986 U1300L 435.11 WDB4351151W134200 Expedition Camper
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30 Posts
Discussion Starter #1
Hi folks,

I’ve been having a hell of a time with on of my hubs. I’m looking for any advice about what’s going on.

I’m in northeast brazil at a campground and have been effectively stuck in this area for a couple months despite various attempts to fix my problem. The campground is nice with a view of the ocean, but i didn’t get a unimog camper to sit parked, i got it to drive. And being in brazil means getting parts is very hard.

So the right rear hub of my U1300L has been running hot and leaking oil. We took it apart and found that the rubber seal was bad and the wear ring was worn. We didn’t have a replacement wear ring, but we did a seal, so we replaced that and also added a spacer ring because the local mechanic though that was the problem.

The new hub worked ok, but was still leaking oil and running 20c higher or more than the other hubs. 90c vs 70c in most cases. I then took it to a Benz dealership truck shop, and they said the silicon sealant job was bad and resealed it. It seemed to work ok but was still running hot and leaking oil somehow.

I had to go to Europe, so i went and got a fully rebuilt hub from Atkinson Vos and also spare parts for a second rebuilt hub just in case. I brought those back with my in the plane.

Getting back to the truck i had that replaced and checked to see that the sealant silicon was covering the whole assembly when we put it on. I put in the oil and drove back to camp. It was maybe 40km… This is where i made a big mistake. I didn’t double check all the bolts were tight myself, and the very bottom one on the hub, the drain bolt was a bit loose. It leaked and the hub was 175c when checked it. Huge mistake, i shouldn’t have gone so far without checking it, i should have double checked the bolts.

When i drained the oil from the hub after it cooled down there was little flecks of metal. But there was still oil in there, i’d guess about half the oil had leaked out while I was driving.

I filled it up, tightened the bolts, and tried a much shorter drive, checking the temp every km or so. The hub was running hotter, 45 c vs 33c on the other hubs, then 70 c vs 35c on the other hubs. And now we’re seeing the oil leak all along the bottom where the hub mounts, so i’m assuming the sealant failed.

I’m wondering if i’m just having bad luck or if i’m doing something wrong. I read Bill Caid’s posts about this, and we’ve gone through the shop manual. Was the sealant we used in all the cases, the same tube, bad? Did i destroy my new rebuilt hub with the careless not double checking the bolts?

The current plan is to take apart the hub, take the old one, and the new parts and try and assemble a new working hub. My big question is if i keep having these problems, am i just missing something, like putting extra grease on the gears or who knows.

Is there something like the sealant which is causing multiple hubs to fail? Could something else be causing it? Or was it just my terrible stupid mistake which caused the second one to fail?

Suggestions for steps to diagnose and fix this?

-evan
 

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Registered
'88 U-1300L, '70 406, '78 406, '78 416 project, '82 406, '57 404, '65 404, '70 404, '68 Haflinger.
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1,849 Posts
Hello Evan,

I can't imagine the frustration you feel with the failure of the second hub. Especially in your situation being on the road and more or less stranded. Glad you are in a good location.

I am no expert on U1300 hubs but have had a few apart. The metal flakes do not spell doom unless you have a bearing flaking off (spalling). I have reassembled a U1300 hub, driven a few miles, and found some flakes. Those flakes, I believe, originated by not having the correct shim in the assembly and the large gear was scraping on the inside of the portal housing. (As you noted, a shim was added by the mechanic, possible strong clue of source of flakes). The bearings were good. I drained and refilled and no further issues. It's important to get those flakes out because otherwise every time you stop for a while, the flakes will settle into the bottom of the large outer wheel bearing and just wait for the bearing to spin again, probably initiating bearing damage.

I'd suggest you evaluate the situation with the internal parts of that hub, just as you already plan. Once you have the best parts back together, and considering the leakage and worn wear ring, consider packing the hub with grease. Not just any grease but NLGI 0 (zero) grease. This type grease goes by other names, like "corn head grease", and is used in farm equipment like high speed rotary cutters on combine heads, and disc mower heads. With the agriculture that goes on in Brazil, maybe you can find that grease. John Deere has their own version. Their description: "Thins to gear oil when working; thickens to grease when resting." One part number is John Deere AN102562.

NLGI 0 grease will not leak out of the hub, even with a hub that already leaks lube. This grease is designed to 'set up' when not being physically disturbed. Inside the hub, the portion of grease around the gears and bearings will flow and get carried to the upper gear and bearings, the portion not being disturbed will stay put and not leak out. The second thing you gain with this grease is that flakes of metal tend to get trapped in the stationary grease and cannot fall into the bearing.

I have been running NLGI 0 grease for some time now and have seen portal temperatures drop 15 to 20 degrees. It's hard to compare before and after though. Lots of IMHO here, as you can tell. For sure, this is not a Mercedes recommendation. But, this might give you a work-around on a serious situation.

With this approach you can know you are not running the portal with no lube, either from leakage out, or inward, as with the known problem with U1300 hubs of having the lube migrate into the axle. (review the thread about this).

Good luck,

Bob
 

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BenzWorld UNIMOG statesman
Unimog 404.1 Diesel (sold :( )1995 LMTV 1078
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5,857 Posts
my guess is you may have seveal compounding things with the first being the typical issue of oil getting pushed out venting of the right hub. See http://www.benzworld.org/forums/unimog/1528450-drivers-side-portal-box-vent-tube.html Many in here have noticed extra hot right hubs and the fix proposed by Von has seemed to help many.

My guess is the local temperatures combined with the atomospheric pressure in the area where you are....... is allowing this issue to be more than normal, compunded with existing wear or wear that has occured due to this issue previously. While many have gotten away with moving on by packing with Grease as Hammogger suggest....... at some point you have to do a complete fix. At that time do something like Von's vent show in thread.
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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5,095 Posts
Unimog portal as can run almost dry without immediate failure. You very likely have some key item out of place. Or possibly a damaged portal case. Hard to say from here.
 

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'91 U1250 '02 U500NA
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My 2 Canadian cents...and 1 Polish grosz.
I've rebuilt both of rear hubs in my truck.
I've been watching closely temperatures of the hubs since then.
What I found out, and I'll be always pointing that out, the big factor in raising temperature on your hubs are the brakes.
My rear right hub was running hotter than the left one due to failing caliper.
I had a problem with adjusting gap on the parking pad, so I left it the way it was.
What it does, by extra friction, heats up your rotor, from that, heats up your hub.
Heat evaporates gear fluid that escapes in axle tube, and never returns when cools down due to design of the rear hub.
Less fluid, higher operational temperature, more evaporation.
Eventually seals and plastic mesh mesh in the bearings will melt and we're done.
Yes, I also replaced both rear calipers in my truck, as they both pretty much the same time got seized.
I'm not saying your brakes are the problem, but I want you to be aware of that possibility as well.
 

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1986 U1300L 435.11 WDB4351151W134200 Expedition Camper
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30 Posts
Discussion Starter #6
Thanks for the tips. We got the hub off and there's a lot of metal fragments. We can't figure out how to get the rubber seal off. Ideas?

We'll try and find the grease to put in there. The breaks thing is interesting, might be that the problem was overheating because of both the breaks and the loose bolt. The mechanic that put on the hub which immediately failed wasn't careful at all about the breakpads. They could have been jammed in there and rubbing.

We've got an old failed hub, the one we took out a couple days ago, the new one, and then extra spare parts. Between them all we'll hopefully be able to build out something which works.

Tomorrow we'll take the bus in to the nearest city and try and get parts.

Any idea what we're looking for in terms of the orange silicon sealant? There's a small brazilian unimog forum so i'll ask there for the names. The mechanic who did a poor job used up the last of my sealant and unfortunately i let him go off with the tube so i don't have it.
 

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U1450L DOKA
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9,922 Posts
The Sealant should be relatively easy to
Get right. The Temperature rating is somethinh to
Note, but, other than that, cleaning, degreasing and
Good "Goop" skills are the only requirements.

I would think the other things mentioned would
Be more likely causes before the Gasket
Seal- if you saw oil weeping at the seam, then
Poor prep is probably the cause.

The condition of the Wear Ring is important-
A groove in the wear ring will tend to
Lead to a leaking seal. I have heard of
Shimming the new seal, so that the wiper lands
On an Un-grooved part of the wear
Ring....also filling the wear ring groove with
JB Weld, and sanding it smooth.... But That
Sounds like a temporary fix at best.




Here are some homework assignments. The "Orange"
Stuff is generally a silicone RTV sealant, noted here:

Tech 101 ? How to use the right gasket sealants | Hemmings Daily

And :

http://www.permatex.com/resources/faqs/answers/3-gasketing

The Orange stuff:

http://www.natauto.com/27br-permatex-gasket-sealant.html

Via Amazon ( the website, not the Rio) with comments:

http://www.amazon.com/gp/aw/d/B0002UEOPA?pc_redir=1409138488&robot_redir=1
 

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U1000Ag
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2,446 Posts
Hello rabblerabble, my sympathies ! Not a good thing to endure when you should be having a good tour. I have no experience with hubs, but plenty with oil leaking from the joints between assemblies (starting with 1950/60's British Motorbikes !!!. For this reason, I never use silicon. I find silicon a second-rate solution. I only use the old style Hylomar Blue. It is becomming more difficult to find, but still available from the UK. Unlike silicon, Hylomar never cures, but semi sets and I have never had a leak with it - unlike silicon. Beware of imitations and good luck.
 

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1962 404, 1957 405SH and lots of Landrovers
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All overheating hub failures, over many vehicle types I've worked with and fixed have origionated either with OBVIOUS lubricant loss through a seal but mainly due to binding brakes. Spin the wheel to make sure its free, then go for a short drive and put your hand on the brake caliper / discs on each side of the axle and feel the temperature difference. If need be gently remove the caliper taking care with the pipes,strap it to the axle, repeat the drive and check for "hub" heating.

J
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Best sealant you can use by far it called "Right Stuff". It far exceeds RTV on all fronts.. I sealed a fist sized hole in a LR diff with Right Stuff and a bit of duct tape. The guy ran the truck for 10,000miles without a drip on my field repair. If you can find it, it is the only sealant you should ever need for axle parts.
 

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1981 U1300L
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1,302 Posts
its normal for hubs to run at different temps. a normally functioning differential will not be applying equal torque to both wheels while driving in a straight line. its common for many to not understand how a diff works. . are you measuring the temps at the same place on both hubs with an IR thermometer? i use the MB star on the outside of the hub. a good hub should not require top secret special sealants. like has been stated , a hot hub can have as much to do with a dragging brake as an "about to grenade" gear assembly. in my experience oil migration is generally only problem in the front. if you are not going to do the work yourself , i would council you to watch those that do like a hawk! good luck i'm sure you will beat this problem. remember to check temps often,use magnetic drain plugs, monitor fluid levels at short intervals, especially when cruising at prolonged high speeds.
 

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BenzWorld UNIMOG statesman
Unimog 404.1 Diesel (sold :( )1995 LMTV 1078
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5,857 Posts
atmospheric pressure in the area where you are??? really geo? do they have different air in brazil? lol...oh ya, and get that spell check fixed :smile
spell check...... yeah I agree..... and can't figure out why it no longer works on this site. Works on some sites and not on others. Was not working here even before the recent changes.

Atmospheric pressure..... Maybe am using wrong termonology/science here but thinking was differences in pressures and/or temps based on location can make it easier for oil to work its way up thru the vent. Might explain why some have this issue with the right hub and others don't.
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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Atmospheric pressure or more correctly True altitude or even more relevant Density altitude have nothing to do with oil migrating from hub to diff. All assemblies on a unimog will maintain a similar pressure to the current density altitude. This is unless there is a clogged pipe or a fording system is activated. An increase in oil temperature will push air out in an attempt to equalize the pressure inside and outside the axle assembly.

Regardless this is not relevant in this conversation.

The brake issue is a good one and could be the culprit. A stuck caliper could certainly cause issues. But the metal flakes in the portal are a big tell. It's certainly possible that the gear preload was set to high or any number of possibilities. The leaking issue may also be a tell of to much bearing preload. Hard to tell from here.
 

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BenzWorld UNIMOG statesman
Unimog 404.1 Diesel (sold :( )1995 LMTV 1078
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5,857 Posts
Atmospheric pressure or more correctly True altitude or even more relevant Density altitude have nothing to do with oil migrating from hub to diff. All assemblies on a unimog will maintain a similar pressure to the current density altitude....
The joy of being found wrong is learning something new...... Thanx for taking the time to splain it to me/us.
 

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U1450L DOKA
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If he is at a campsite above and with a view to the beach,
The atmospheric pressure is about as high as it gets on this
Planet, theoretically.
The higher the average existing air pressure ( MSLP -Mean
Sea Level Pressure, as an index ), the more any contained
Vessel (portal housing) has to work to overcome the
Seal in order to leak.
On the summit of Mt. Everest, in theory, a Unimog that
Leaks at sea level, will leak more readily at the Summit.
Thankfully, we don't have to worry about a Unimog on the
Summit of Everest, even a cardboard Replica of one.It is too
Much work to haul toys.
As has been stated, the local atmospheric pressure has
Almost zero to do with leaking or migration of Oil on a Unimog.
The leaks will be due to mechanical conditions, not atmospheric
Ones.
Oh, and there is just as much AIR (Oxygen) on the summit
Of Everest as there is on the Beach in Brazil- it is just at a
Much lower pressure.
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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5,095 Posts
If he is at a campsite above and with a view to the beach,
The atmospheric pressure is about as high as it gets on this
Planet, theoretically.
The higher the average existing air pressure ( MSLP -Mean
Sea Level Pressure, as an index ), the more any contained
Vessel (portal housing) has to work to overcome the
Seal in order to leak.
On the summit of Mt. Everest, in theory, a Unimog that
Leaks at sea level, will leak more readily at the Summit.
Thankfully, we don't have to worry about a Unimog on the
Summit of Everest, even a cardboard Replica of one.It is too
Much work to haul toys.
As has been stated, the local atmospheric pressure has
Almost zero to do with leaking or migration of Oil on a Unimog.
The leaks will be due to mechanical conditions, not atmospheric
Ones.
Oh, and there is just as much AIR (Oxygen) on the summit
Of Everest as there is on the Beach in Brazil- it is just at a
Much lower pressure.
Ok, I'm trying to follow you but I don't think I can even though ultimately you agreed with me.

So a perfectly good mog is loaded on a plane and flown to max altitude. The "pressure" on the seals is no greater and no less than when at sea level. This excludes the effects of gravity etc.

Basically stating that a glass of water carried to the top of Mt Everest should not have any more or less pressure applied to its walls than at sea level (in super plain terms as I am sure there is some other random force that kicks in on a molecular level) This is because the pressure inside the glass and outside the glass is equal just as it is at sea level. This is also the case if you dropped a glass of water to the bottom of the Ocean. The glass would not shatter at the bottom of the ocean.

Now if you were to fill the same glass up with water and seal the top of the glass so that neither water nor air could escape the glass then the glass could theoretically explode at a certain altitude or implode at the bottom of the ocean due to a difference in pressure inside the glass and outside the glass.


A Unimog axle example would follow the same results of the open glass of water. The seals on the Unimog are mechanical and do not rely on pressure to remain positive. In fact you could take a Unimog axle into space and it would be no more or less likely to leak.

A leaky portal is either related directly to damaged seals or surfaces or poorly seated/damaged case mating surfaces.
 

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U1450L DOKA
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Doka TD - regarding the PM.
Yes we agree:
If the box leaks, the seal is faulty. The air pressure Is not
The issue.
I'd say that the Cavitation theory, wherein the
Reduction gears in the portal boxes 'whip up' the oil to the
Point that it migrates up the vent tube, does indeed involve
A pressure differential. In theory, the rotation of the gears
Acts as a pump, increasing the local, internal pressure
In the portal box, sending the oil upstream, up the Vent
Tube, and out of the portal box. The viscosity of the oil
Is also a factor- encouraging the oil to "hang together"
And climb up the tube, more than a less viscous fluid
( Water, for example) would do.
Because all four of the portals on a Unimog do not
Seem to exhibit the exact same tendency for oil loss,
I suspect the issue is a little more complex than straight
Pumping / pressurization based on Gear Rotation.
Even then, it is not a closed system, as the vent tube
Is open to the local atmosphere.... Via the differential, which
Is also vented.
Anyway: we agree : Mt. Everest or the bottom of the ocean,
A leaker is a leaker.
 
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