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1957Hedgehog's avatar
1957Hedgehog
Explorer
Mar 13, 2017

Help Identifying Leak Under MH?

Howdy. New to the forum. Appreciate any help identifying a leak I'm seeing under my MH before I haul it in for maintenance. Disclaimer: I'm not a motorhead so very limited ability to service major eng/trans issues. Thanks for understanding :-).

2004 Nat'l RV Dolphin, 60000miles, W-22 Workhorse, GM Vortec 8100, Alison 1000 Trans. We've had it 5 years. Used to tow a 2004 CRV, now towing 2014 Jeep Wrangler. Both currently sitting in our driveway. Last trip over Christmas (GA to MS), noticed small leak when we got home.

Leak is centerline from a pan just aft of front tires. Fluid is heavier than water but not greasy like oil with no real odor I can smell, small amounts seem to spread out but not evaporate, and I'm not able to tell the color easily.

Are we looking at a trans, brake, or landing gear problem maybe?

Thanks again. Cheers,
Walt
Class A

15 Replies

  • Gjac's avatar
    Gjac
    Explorer III
    Mar 14, 2017
    1957Hedgehog wrote:
    rgatijnet1 wrote:
    In that area the transmission can leak around the small red filter, where the oil cooling lines come out on the passenger side, as well as at the lower pan gasket.
    You may have to get underneath and clean everything to find the exact location of the leak.
    As mentioned, I would try tightening the pan bolts an extra 1/2 turn. You do not want to over-tighten them which may distort the pan and make it leak more.


    Yes, sir, thank you. I'll check that area as well. From what I saw, at least 1 of the pan bolts had a drop on the head. And there was a drop at the bottom of the pan near the drain bolt. I do have a torque wrench so I'll check the Allison manual first before tightening.
    Have you ever had the fluid changed by dropping the pan? If so how long ago? There is a sequence to torquing the bolts also. The last time I changed my fluid I used the new rubber gasket that came with the filter kit because the OEM filter was 20 years old and looked stiff. That was a mistake I could not get the pan to stop leaking with the new gasket. The original gasket had steel inserts around each bolt hole that prevents the gasket from deforming when bolts are tightened. After a week of trying to re torque the pan bolts run engine and checking for leaks I put the old gasket back on and all was well again. Just make sure the leak is not coming from above the pan gasket and running down the sides to the bottom. Good Luck and welcome to the forum.
  • 1957Hedgehog's avatar
    1957Hedgehog
    Explorer
    Mar 13, 2017
    rgatijnet1 wrote:
    In that area the transmission can leak around the small red filter, where the oil cooling lines come out on the passenger side, as well as at the lower pan gasket.
    You may have to get underneath and clean everything to find the exact location of the leak.
    As mentioned, I would try tightening the pan bolts an extra 1/2 turn. You do not want to over-tighten them which may distort the pan and make it leak more.


    Yes, sir, thank you. I'll check that area as well. From what I saw, at least 1 of the pan bolts had a drop on the head. And there was a drop at the bottom of the pan near the drain bolt. I do have a torque wrench so I'll check the Allison manual first before tightening.
  • rgatijnet1's avatar
    rgatijnet1
    Explorer III
    Mar 13, 2017
    In that area the transmission can leak around the small red filter, where the oil cooling lines come out on the passenger side, as well as at the lower pan gasket.
    You may have to get underneath and clean everything to find the exact location of the leak.
    As mentioned, I would try tightening the pan bolts an extra 1/2 turn. You do not want to over-tighten them which may distort the pan and make it leak more.
  • 1957Hedgehog's avatar
    1957Hedgehog
    Explorer
    Mar 13, 2017
    rgatijnet1 wrote:
    When you checked the transmission fluid was it with the coach sitting level, with the engine running, in PARK? This is to be done ONLY after the transmission is warmed up and has been shifted through all of the gears and has been left to rest for a minute or so with the engine running in PARK. Make sure that you set the foot brake before you go out to check.


    Yes, sir, did exactly that in a rest area enroute home. Leak was so small while camping was hard to tell if it was a new or old spot. At rest area noticed fresh spot, cranked it back up, ran it through the gears (had to do this for a former toad), left it running and warm, checked fluids. Dip stick good. Now spot is bigger in my driveway.
  • 1957Hedgehog's avatar
    1957Hedgehog
    Explorer
    Mar 13, 2017
    mfox20 wrote:
    Might be as simple as tightening the pan bolts.


    Thanks, I'll try that next. Checked the drain bolt, its tight.
  • rgatijnet1's avatar
    rgatijnet1
    Explorer III
    Mar 13, 2017
    When you checked the transmission fluid was it with the coach sitting level, with the engine running, in PARK? This is to be done ONLY after the transmission is warmed up and has been shifted through all of the gears and has been left to rest for a minute or so with the engine running in PARK. Make sure that you set the foot brake before you go out to check.
  • 1957Hedgehog's avatar
    1957Hedgehog
    Explorer
    Mar 13, 2017
    Thanks for the quick replies, guys, appreciate it. Not easy to get under (bad back), but did it, wiped area, and guess I missed an important "clue" last I looked. Pan is stamped "Allison" and white paper test shows red fluid. Don't I feel the fool. When I first found the leak it was a warm engine after returning from camping in MS. I immediately checked fluids including trans which was in the correct "Hot Eng" range of dipstick making me think other than trans fluid leak.

    Midnightsadie, thanks for the Mobil Tech suggestion. Before I call my guy in, does this pan have a gasket that's DIY to replace? Anyone ever done it? Any tips? Thanks again.
  • rgatijnet1's avatar
    rgatijnet1
    Explorer III
    Mar 13, 2017
    On the 8.1L engine with the Allison transmission you have TWO sets of blue cooler lines coming from the rear up to the radiator. The blue lines on the driver's side carry engine oil to be cooled by the radiator and the blue lines on the passenger side carry transmission fluid to also be cooled by the radiator.
    There are also brake lines that converge in that area along with hydraulic fluid from your levelers.
    Now if you throw in radiator coolant and window washer fluid, along with condensation from the AC unit, you can see that you have a lot of fluids that can start to drip by the front wheels.
    I think it is important that you collect some of the fluid on a white piece of paper and then try to identify it. It could be important or insignificant in the operation of your coach.

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