Leaking Rear Axle Vent

[Milton]

2009 Mazda B2300
31,000 miles
5 spd manual
Axel: 3.73 gear ratio with a 7.5" Ring Gear

So I crawl under to check the spare tire pressure and once again notice an oil leak around the rear axle vent. It's not new and I can not tell you when it started. I did change the dif lubrication at 21,000 miles. I took some pictures and it appears that it's leaking from the axle vent connection. I can understand the need to vent the axle, but it seems if the vent was working there would be no pressure build up in the axle and no need to leak. So if I pull off the "rubber cup", what will I find? What is the procedure to diagnose and correct the problem?

Rear Axle Vent From Rear

Rear Axle From Above

Rear Axle Vent Hose Clipped

Rear Axle Vent Hose Unclipped

 

[Explorin94]

Pull the hose and the nipple off the rearend and see if any of it is plugged. That is usually the problem when that area is wet like that.

 

[kimcrwbr1]

Is it gear oil and have you checked if the housing is real hot after running high speed for a bit. Run on the freeway for 15 minutes or so and get under it and put you hand on the housing if it is real hot you need to figure out why. Feel by the drive pinion and both wheel bearings. Did you put in the proper gear oil?

 

[85_Ranger4x4]

Pull the hose and the nipple off the rearend and see if any of it is plugged. That is usually the problem when that area is wet like that.

+1, check for something in the hose.

You also might check that you didn't overfill it too.

 

[Milton]

Corrective Action

Is it gear oil and have you checked if the housing is real hot after running high speed for a bit. Run on the freeway for 15 minutes or so and get under it and put you hand on the housing if it is real hot you need to figure out why. Feel by the drive pinion and both wheel bearings. Did you put in the proper gear oil?

Yeah, it's gear oil, the pictures prove that. I have not checked the temp, but I will. The gear oil I used is Amsoil Synthetic Gear Lube SAE 80W-90 so that is not the issue.

+1, check for something in the hose.

You also might check that you didn't overfill it too.

What I did today:
- Pulled the vent host and the "protective cup" (see photo below). On all other photos I've seen, the hose is held onto the vent tube with a worm gear clamp, this one is just pushed over a barbed fitting (see photo below)
- The hose is patent, clean and has zero crud.
- The vent tube is patent, clean and has zero crud.
- So I cleaned everything and reinstalled the hose and protective cup.

My thoughts:
- Everything is so clean I doubt that there is any pressure build up.
- I suppose I could have overfilled it and it leaked because the hose being held onto the vent tube by a pressed fit allowed it to leak.
- So I cleaned everything up so if it continues to leak I can tell.
- If it continues to leak I think I'll remove the protective cup and use a work gear clamp.
- Checking the vent tube patency is another item on the checklist when changing the axle lube.

I'll give a 30 day checkup.

Vent Hose & Protective Cup

Barbed Vent Tube

 

[Rogue_Wulff]

That vent nipple is threaded into the housing. As such, it could be loose and/or leaking around the threads. Removing it, checking threads on both the nipple and axle tube, then sealing the threads may be in order.
Adding a clamp to the end of the hose isn't a bad idea either.

 

[Explorin94]

As long as the hose fits over the nipple with some resistance I wouldn't worry about a clamp. If it is loose I wouldn't worry about putting any sealer on the threads either, just tighten it up. That is a vent and that is all it will ever be. If it continues to leak I would replace the vent hose and change the clip that holds it to the frame. Also check the fluid level and go from there.

 

[Milton]

Follow-up

Just a follow-up. I put ~170 miles on it at 70-80 mph (round trip San Antonio to Austin), no leaks and axles did not heat up. I'll add checking the vent tube patency to my oil change and differential servicing check lists.

Thanks everyone.

 

[alwaysFlOoReD]

I don't understand the use of the term "patent" and "patency". What do you mean?

Richard

 

[Milton]

Patent / Patency

I don't understand the use of the term "patent" and "patency". What do you mean?

patent (pa-tent)
1: protected by a trademark or a trade name so as to establish proprietary rights analogous to those conveyed by a patent : proprietary <patent drugs>
2: affording free passage : being open and unobstructed <the nose was patent with no pathological discharge—Journal of the American Medical Association>

patency (pa-ten-cy)
1: The condition of being open, expanded, or unobstructed.
2: The condition of showing detectable parasite infection.

Blame it on nursing training, I used that term without even thinking.

 

[alwaysFlOoReD]

Its been a while since I ran across a word I didn't know. I don't feel so bad now that I know it's a fairly specialized use of the word. Thanks for explaining,

Richard