Trans fluid from HMMWV air cleaner?

[Gear Report]

What can cause transmission fluid to leak from the air cleaner?
1987 M1038, 6.2, 3 speed


When it first happened a few weeks ago I assumed it was the "transfer case vampire" and bypassed the t-case cooler loop. So, I know it can't be that.
What else could it be?


Also, no idea if related or not, but I've noticed the past week or so that the first time the HMMWV is driven for the day it takes a minute for the transmission to warm up and start working. ie. I put it in R and the engine revs, but no movement. So, I hold the brake and cycle through 1, 2, D, N, R, stopping for a couple of seconds on each. Maybe it works when I get back to R. Maybe I have to go through them again. Once warmed up it appears to operate as it should.
I checked trans fluid and it was a 1/4" high on the dipstick, so syphoned some out.
Ideas?

 

[Action]

if the fluid is too low, it wont move. Was it warmed up and engine running when you checked the level? you may have not needed to take any out...

 

[Retiredwarhorses]

Trans fluid is only in 3 components, trans, tcase and PS pump...the PS pump is only vented on Marine corp trucks.
all vents terminate to the air filter box...are you sure it's ATF? A bad fuel pump diaphragm will leak to the filter as well.
your trans issues are not good....it is not normal.

 

[Retiredwarhorses]

If you really want to know where it's coming from, disconnect the vents going to the trans and tcase...it will leak out of the affected component. It's also possible you have residual fluid still in the line....did you open the tcase fill plug and drain out the excess if you in fact think the cooler loop was broken? If you didn't, it's waaaay over full and still venting out.
also, blow out the vent lines...but be careful, low pressure.

 

[Gear Report]

if the fluid is too low, it wont move. Was it warmed up and engine running when you checked the level? you may have not needed to take any out...

I am now questioning whether it was warm enough. Will check after I drive it next.

 

[Gear Report]

are you sure it's ATF?

Yep. It is pink.

 

[Gear Report]

If you really want to know where it's coming from, disconnect the vents going to the trans and tcase...it will leak out of the affected component. It's also possible you have residual fluid still in the line....did you open the tcase fill plug and drain out the excess if you in fact think the cooler loop was broken? If you didn't, it's waaaay over full and still venting out.
also, blow out the vent lines...but be careful, low pressure.

I am hoping it is residual fluid in the vent line.
When it first started dripping trans fluid under the air cleaner I determined the t-case cooling loop was leaking by checking t-case and finding an extra quart+ above the fill plug. I let it drain until it was at the fill plug.
I will disconnect and blow out the vent lines this week.

Thanks for the ideas, guys.

 

[Bulldogger]

Off road diesel is pink and oily too. But I'm sure you know what's in your fuel tank.
Bulldogger

 

[Gear Report]

Off road diesel is pink and oily too. But I'm sure you know what's in your fuel tank.
Bulldogger

Yep. I can't get off road diesel. My fuel has a yellow tint.

 

[tomcata3]

I talked to a hmmwv mechanic and he point out that the vent line for the hubs had to be separated from the transfer case and the transmission , there is a tm for this. if you drive fast it can pull the fluid up into transmission then to the air cleaner. check your hubs. I ran a new line to separate the hubs and connect it right before it goes into the air cleaner

 

[Retiredwarhorses]

I talked to a hmmwv mechanic and he point out that the vent line for the hubs had to be separated from the transfer case and the transmission , there is a tm for this. if you drive fast it can pull the fluid up into transmission then to the air cleaner. check your hubs. I ran a new line to separate the hubs and connect it right before it goes into the air cleaner

never heard od of such a thing, Hummer H1's have same vent setup as HMMWV and never an issue in over 20yrs.

 

[Gear Report]

This is odd.
Pulled the fill plug on the t-case and got about a quart of fluid out of it.
After bypassing the t-case cooling loop a couple of weeks ago the fluid in the t-case was level with the bottom of the fill hole.
... and I checked the transmission after driving yesterday and it was about a quart low.

The parts TM shows the trans and t-case in separate illustrations. I can't wrap my head around how they connect. Is there a seal between the trans and t-case that is leaking?

 

[tomcata3]

there is another tm saying to run a new vent line for t-case. you need to separate the transmission vent line form the t-case vent line

 

[Retiredwarhorses]

This is odd.
Pulled the fill plug on the t-case and got about a quart of fluid out of it.
After bypassing the t-case cooling loop a couple of weeks ago the fluid in the t-case was level with the bottom of the fill hole.
... and I checked the transmission after driving yesterday and it was about a quart low.

The parts TM shows the trans and t-case in separate illustrations. I can't wrap my head around how they connect. Is there a seal between the trans and t-case that is leaking?

There is no way you would get that much fluid from the trans to tcase at the mating area, the seal on the forward shaft even if it failed would not allow that much fluid to flow. Unless maybe the seal is gone, highly unlikely.
please post a pic of your cooler bypass you performed....you still have your trans dumping fluid into the tcase.

the venting is easy and the same on every Hmmwv...there is a vent line from the trans and tcase that come together at a "tee", then routes to frame rail vent line, the frame vent line is coming from the rear diff and geared hubs...this continues on to the front to join the front diff and hubs, as well as the fuel pump, then "tees" off to the air cleaner housing.

 

[Gear Report]

Ok. For now I'll monitor and assume that I somehow screwed up the t-case fluid level when I did the t-case cooler bypass.
I think the transmission being low was my mistake after syphoning some fluid out after checking it when it wasn't fully warmed up. Coincidence that the t-case was high by the same amount the trans was low.

 

[Gear Report]

please post a pic of your cooler bypass you performed....you still have your trans dumping fluid into the tcase.

2 loops

 

[Gear Report]

This past weekend I dropped the transmission pan and changed the transmission filter. Someone PMd me that the delayed transmission engagement could be a bad o-ring on the transmission filter pick-up tube. The o-ring was intact, but hard. I replaced that o-ring and it appears to have solved the delayed engagement issue. I had noticed before that when checking the transmission fluid after a drive the fluid was pretty bubbly. After replacing the o-ring it is not. So, hoping that this internal pick-up tube suction issue was creating an internal pressure imbalance that caused fluid venting. Haven't had any further venting since replacing the o-ring.

I suspect the t-case was getting fluid via the vent line from the transmission.

I'll make sure the t-case fluid level is correct and check it frequently to be sure it isn't changing. If it is, then I'll isolate the vent lines.

 

[Action]

The transfer case can get extra fluid in it from a cracked cooling loop inside of it.

 

[Gear Report]

The transfer case can get extra fluid in it from a cracked cooling loop inside of it.

Yes. Already addressed near the beginning of the thread.