Vehicle: son's '88 Ranger, 2wd, 2.9L V6, ~88K miles, everything completely stock

Engine running great, no overheating problems. Drives and shifts fine when fluid at recommended levels. Rear seal is consistently dry so not a source of the leak. Driven for a couple of days, no problems, no leak. On the way home from work (w/o any detectable drips or puddle in work lot), ~2 mile drive, trail of fluid midway home (noticed after driving other vehicle along same route to check), bands begin slipping and delay in engaging after stopping at light, major puddle after parking in front of house. Crawl underneath after putting on stands, leak appears to be coming from vent hole at top of trans. Appears a vent tube at top has come out. Replace vent tube, top off ATF, no problems for 3-4 days, then problems repeats itself.

I've not overfilled the trans, slow and small incremental addition of ATF until at recommended level of dipstick. Run through the gears to make sure everything again shifts correctly, check level, remains fine.

Any ideas? How do I check to see if the trans cooler isn't getting plugged or an air bubble? Lines are in ok shape, not great but no leaks or bulges. Thanks for any help, ---rick

 

No feedback? Can I assume everyone else is as stumped as I am? Is there some sort of clip or retainer that is intended to hold the vent tube in place that I may be missing? Any help appreciated.

 

Have you checked the vacuum line that connects between the intake manifold and the transmission? There should be a metal tube with rubber hose connecting to the manifold and the transmission. I had a case years ago where the lower rubber hose deteriorated and leaked trans fluid near the top of the trans.

 

Thanks for the feedback, ranger pat. It's dark here now but will check it tomorrow after work. Haven't heard anything about the line you mention so will look closely tomorrow.

Is the rubber on the end of the line replaceable with normal vacuum line or is this a factory type part? If a vacuum line, is it more of a breather hose for venting overheated ATF to the intake manifold vs venting to the atmosphere? IMWTK
Appreciate your help, ---rick

 

The hose is replaceable rubber vacuum hose. The vacuum signal goes from the engine to the transmission and is not for venting to the engine or atmosphere.

 

Thanks for the info, ranger pat. Meant to get to this today but had a dead short in my wife's Expy early this morning and that took precedent. Found the short (I hope, cleaning a ground cleared the issues, almost deserves it's own post).

Will look at the Ranger tomorrow. I've got lots of new vacuum hose so hope that resolves it. SWMBO will be driving the ranger for the next week or so while I take the Expy out of town for work next week+. Will report back after she drives it for a couple of days before I leave.

 

It may be a bad pump if automatic

 

In addition;

1) Vent obstructed,

2) Has it been serviced recently? Leaking seal at filter causing cavitation or plugged screen.

Is it a 4S or 5S?

 

Spent most of today working on the truck. Put it up on stands so I could crawl underneath.

Trans cooler checks out ok, took off rubber lines (btw, has an much larger aftermarket trans cooler installed) and blew air through them from my little hotdog compressor and air passed through as it should. Inspected the rubber lines for swelling and interior deterioration and all seems fine.

Traced hardlines all the way back to trans and no detectable leaks (checked while engine running).

The last time the truck did this (I've had it parked for a few weeks) I couldn't centralize any leak source. After topping off fluid, drove it to a good carwash and cleaned the underside of the motor and drivetrain in hopes of having a fresh surface to observe to try to locate the leak. In looking today it appears the fluid is coming from near the back of the motor, all over the back side of both heads and the lower portion of the block (both sides). Top of the motor and trans near the bell housing is dry.

After seeing this I thought of a possible high pressure leak from one of the rigid trans cooler lines along the passenger side of the motor. Had a buddy put the motor under some torque, foot on brake and trans in gear, to see if the motor mounts were broken. All seemed ok, some minor flex of the motor but no visible signs of broken mounts or pinhole leaks in rigid lines when motor is under torgue (thought there might be a pinhole leak in one of the rigid lines when motor worked and motor mounts flexed).

If the pump leaks, will it spray ATF onto the back side of the TQ? If it did, would the now-flung fluid leak out around the metal plate at the front of the bellhousing where it meets the back of the block? Metal plate is covered in fluid from last leaking instance and there is/was evidence of fluid at the bottom of the plate, even a drip still there after being parked for a couple of weeks.

 

KULTULZ: trans serviced about this time last year with new filter, fluid, and added a magnet to the bottom of the pan to pick up/hold any metal bits (just in case and for future inspections). It is a 4 spd auto (3 spd + OD). Vent hole does not appear to be blocked.

 

If the pump is bad it will usually exhaust thru the vent. Have you noticed any leakage through the fill tube?

There have been instances where the front pump seal (OEM) will expand upon excessive heat (fluid) allowing leakage and the seal contracts again after cooling. You go to an aftermarket seal if this is a problem.

When the trans was serviced was the correct fluid used? Is it filled to capacity correctly? It may be overheating without your realizing it. How many miles?

We are just giving guesstimates here as we are not there. If you don't want to get it professionally analyzed, the appropriate FORD SHOP MANUAL will give you a diagnostic sequence.

Hope it is not anything serious ($$$).

 

Its a 29 year old vehicle and probably has been through several owners (and probably isn't on the original tranny unless strangely it had an unusual life and low miles). With that said, who says the tranny dipstick in there now is the correct one for this vehicle that you believe is being filled to the *correct level* (and inadvertently overfilling)?

 

I like the ideas put forth so far but if you have more than one problem, they may be confusing things, so lets jump off the deep end & think/suppose about this some more.

Did this problem come about suddenly after some event?

Have you disconnected the tranny modulator vacuum line connection at the intake manifold & looked to see if it's wet inside with tranny fluid. If it is, the modulator diaphragm has likely ruptured & engine vacuum is sucking tranny fluid into the intake manifold & the engine will burn it.
This can cause the tranny fluid level to drop, the fluid to get hot expand & or boil out the vent.

The modulator is round shaped, on the passenger side of the tranny, about mid way back & up & the cat converter heat shield may have to be moved to pull it out.

If the converter heat shield has been removed, or has fallen off, it can cause the tranny fluid to run hot & leak out the vent if it expands too much, or boils. So make sure all heat shields are in place.

If the modulator diaphragm is bad & must be replaced, make sure it goes back in oriented like the old one comes out.

If the old modulator vacuum line is OEM, it's likely hard & brittle, so replace it, so you get a good tight connection so it doesn't leak vacuum.
Connect the old & new lines together, so to pull the new one into place as the old one is removed.

More thoughts for consideration, let us know what you find.