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BigJimnyMeet (North) 2024 (12 Jan 2024)


BigJimnyMeet 2024

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Stock diff breathers - how d'you know they're working correctly?

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13 Nov 2023 15:10 #252095 by Atheling
Daft Q prob - the caps rotate (one was seized and freed it up) but don't feel 'springy' on depressing them. Is that right? Not planning on much wading, more like foot deep Wilts puddles. 

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13 Nov 2023 17:12 #252096 by 300bhpton
I think they are like the breathers on a Series Land Rover. A little pressure style valve cap, that can vent excess pressure. If you plan any sort of wading I'd be tempted to fit extended breather pipes however. While the cap should close, if stuck open or rapid cooling of the diff due to be submersed, they can act as a vacuum and suck in water.

If they are stuck closed I'd expect an oil leak due to pressure build up.
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13 Nov 2023 17:44 #252098 by Atheling
Thanks for your response. Yes I had a diff oil leak with the seized cap.
I wondered whether the stock breathers should feel springy to the touch? - as mine aren't really. Wanted some idea of whether they were operating ok.

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13 Nov 2023 19:54 #252101 by Roger Fairclough
Yes, they should feel springy even to a light touch, but remember they are as technically advanced as a chocolate fire-guard. You are far better off with diff. breathers using pipe and hose.

Roger
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13 Nov 2023 20:58 #252104 by Atheling
Haha! So I don't think they work. I'll do the extended breathers then.
Thanks all.

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13 Nov 2023 21:24 #252106 by 300bhpton
I haven’t looked at the ones on the Jimny. But I’d be surprised if they are springy. As I understand it they operate like a valve. So under pressure would open and be closed without pressure. If there is any spring it would be pulling them open, not pushing them closed. Happy to be corrected if I’m wrong though.
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13 Nov 2023 21:44 #252107 by Roger Fairclough
They are a valve, but in reality it is cheap and nasty. In essence it is a light spring keeping a soft plastic disc in contact with a tube. As pressure builds up inside the diff. housing, the disc is lifted off the tube and excess pressure is released. When you stop and the pressure drops, the spring pushes the disc down onto the tube. The problem is that the disc is probably open when you go through deep water and the water will pass the open disc and flood into the housing. Most deep fords are usually short in length so the cold of the water will not have enough time to cool the diff. and lower the pressure to allow the spring to close the valve. Plus, over time, crap gets inside the outer tube and the seal is ruined and the thin steel of the spring is destroyed by corrosion.

Roger
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13 Nov 2023 22:56 #252114 by yakuza
For some reason mine do what they should, or as Roger say only short bath so not cooled enough to suck the water in.
Have never seen gray oil with signs of water when servicing my driven cars with water level on the bonnet.

But I have had parts cars with Grey sludge in diff and transfer.

Norway 2005 Jimny M16A VVT, 235 BFG MT, 2" Trailmaster, ARB rear lck, 17%/87% high/low gears.
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13 Nov 2023 22:57 #252115 by Lambert
If you are going through water any deeper than the bottom of your wheels on anything like a regular basis you really want extended axle and transmission breathers, a kit and the time taken to fit it is much cheaper than fixing a damaged drive train.

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
ADOS Attention Deficit Ooooh Shiny!
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14 Nov 2023 06:04 #252117 by yakuza
Oh no doubt about that Lambert, Just thinking how strange it is that I never had any mishaps yet.
Never intend or plan to dive either but then it just happens 1000km from home.
Got hoses and everything ready too, just needs to get done.

Transmission cases on my car have original breather hoses up to a higher point on the fire wall.

Norway 2005 Jimny M16A VVT, 235 BFG MT, 2" Trailmaster, ARB rear lck, 17%/87% high/low gears.
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14 Nov 2023 15:43 #252121 by jackonlyjack
Make your own for around 15 quid
1/8  BSP tap 
1/8 elbow to 6mm push fit pneumatic connector
6mm outside diameter pneumatic pipe  all parts available on eBay
Pop of original breather cap pull out spring then tap the hole
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