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post #1 of (permalink) Old 04-18-2009, 12:51 PM Thread Starter
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Vent line problems

When I restored my CJ7 I ran a common vent hose from both axles, transmission and transfer case through the right frame tube and up to the air cleaner. I used a 1/2" vinyl tube because it was cheap, available and easy to work with. Big mistake. Apparently some gear lube got pushed into it from the back axle. It sat in a low spot until the petroleum ate through tthe vinyl tube. Now I've got gear lube dripping through a hole in the bottom of the frame and onto the rear spring perch.

The real bummer is that the line from the transfer case goes into a T inside the frame tube. It was a first class bear to get it connected working from above with the body off. Now, with the transmission, transfer case and skidplate in the way . . .

EVERYTHING's easy for the guy who doesn't have to do it.
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post #2 of (permalink) Old 04-18-2009, 01:14 PM
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Ooh sounds like fun. Isn't that one of the problems with hooking into a air cleaner? Drawing the fluids up? As well as negative pressure that can draw water in to the case(s)...

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post #3 of (permalink) Old 04-18-2009, 01:55 PM
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Smile vents

yes i think you are correct...............the vent line is something i have been thinking about for the cj8 scramber rear amc full floater project and sent some emails to some other sites and also to a couple of truck builders and they seem to all say it is best to keep the vents for each axle line alone and not to connect them together................the main reason they came back with is that if something was to get into the connected line you would be putting in into all your axles and trans/ cases.............. and could cause a lot more damage than just one axle but i guess if you got one hot enough you would end up with a draw from the other end of the tube and maybe pull lube up into the hose...... dont know for sure but i am going to keep each one with its own vent.....
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post #4 of (permalink) Old 04-18-2009, 06:03 PM Thread Starter
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Quote:
Isn't that one of the problems with hooking into a air cleaner? Drawing the fluids up?
I doubt that's the problem - it would be a mighty severe pressure drop to suck lube up hill that far. I doubt my anemic little 1-barrel six could draw thatmuch air, and I'm pretty good about keeping a good filter in there. Besides, unless air is flowing into the axle somewhere there would be no significant flow through the vent tube to pull the oil along. My guess is that it's oil that got thrown up into the tube by the ring gear, although I still can't understand how it got over the high spot in the frame. I'm going to do some checking tomorrow - had to go to a meeting this afternoon, and now it's Margarita thirty.

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post #5 of (permalink) Old 04-19-2009, 12:53 AM
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He He - you can show your friends your frame leaks oil! Bet they can't top that.


If the pressure in the aircleaner is so low it can "suck" the oil up, then the air induction/filtering system is way too restrictive. It shouldn't even register on a vacuum gauge.

But keeping them separate makes sense - not good to mix fluids, (and any chips, dirt, water etc.) If one one of the items, trans, t-case, axle etc. started having trouble and ran hot it could send the chips to the others. Then not just the one thing needs fixing, everything.

I run the vent line up high into the engine compartment with little in-line fuel filters to keep the dirt out. If oil gets up that high, something's bad wrong.
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post #6 of (permalink) Old 04-20-2009, 02:54 PM
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Quote:
Originally Posted by Jim_Lou View Post
When I restored my CJ7 I ran a common vent hose from both axles, transmission and transfer case through the right frame tube and up to the air cleaner.
I don't 'Restore' anything with the 'Jeep' name on it!

Anyway, when I ran my vents together,
I ran the transmission and transfer case in with them,
Use a Honda Quad CV joint boot to seal up the top of the transmission, drilled/tapped it for a nipple, and now when in deep water, I pressurize the axles, transmission, transfer case, ect so water can't get in.

Came in real handy in the floods last May/June when they asked us to 'Rescue' the old folks and others from the flood waters here!

I had water OVER my dash, and I expected to be buying stock in Valvoline from the amount of fresh gear oil I figured I'd be needing....
But much to my surprise, NO WATER IN ANY OF THE RUNNING GEAR!

Can't say that about three of my gauges, and someone stole my chainsaw, but the running gear was PERFECT!
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Quote:
My guess is that it's oil that got thrown up into the tube by the ring gear, although I still can't understand how it got over the high spot in the frame.
That's easy...
VAPORIZE THE OIL (oil vapor) from heat/slinging in the differentials, and it just condensed/collected on the inside of the tubing, and ran back down to a low spot in the frame....

I'm amazed at the smart guys here that don't know oil EVAPORATES and re-condenses!

Last edited by TeamRush; 04-20-2009 at 02:58 PM.
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post #7 of (permalink) Old 04-20-2009, 04:03 PM Thread Starter
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I doubt that my differential gets hot enough to vaporize much oil. It never goes very fast or very far any more. Last time I check temps was when I thought I heard a bearing grumbling. I was right - the right bearing was shot and it was running about 160. Nothing else was above 60, when ambient was about 45.

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post #8 of (permalink) Old 04-20-2009, 04:15 PM
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Quote:
Originally Posted by Jim_Lou View Post
I doubt that my differential gets hot enough to vaporize much oil.
What kinda diff lube you using? Can you smell it when you open the jug? If you can, you are smelling vapors. It will vaporize at room temperature, just not much. Warm it up and splash it around, and it vaporizes easier.

If I understand how you ran your lines, you built a still. Vapors rose to the high point and then condensed in the low point.

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post #9 of (permalink) Old 04-20-2009, 04:28 PM Thread Starter
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Plain old fashioned 90-weight gear lube. I guess it's possible that there's a little moving around by evaporation, but can't believe that there's much. And the tubes can't be much cooler than the oil in the boxes, so most of the vapor would get all the way out of the tube, I'd think.

Anyway, it doesn't really matter, does it? I'm going to replace the lines with something impervious to oil, and due to the conditions, probably have to run it outside the frame tube. I don't care if some lube eventually gets into it. Only problem would be if it filled it to the top and overflowed into the carb - something that I'm not going to worry about until it happens, and maybe not even then.

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Last edited by Jim_Lou; 04-20-2009 at 04:33 PM.
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post #10 of (permalink) Old 04-20-2009, 07:17 PM
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I think you are confusing “vapor” with the “gaseous state”. There are transition states.

You grease your wheel bearings. Is grease a liquid or a solid?

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