98 Expedition - Disappearing ATF Fluid

[Fitz98]

I have a 98 Expedition 5.4 4x4 with a 4R100 tranny. Over 200k miles on tranny.
Recently the truck was stalling while shifting in reverse and also shifting to low gear. The truck drops in RPMS and sometimes stays running and sometimes stalls.
The transmission fluid was low, no reading on the dipstick. I added a 1/2 quart that I had on hand and it did not do it.
2 days later it is starting to show same symptoms again, I still need to add more fluid to bring the level up where it belongs.
I don't see any obvious leaks around pan gasket or rear seals on tranny and no stains in my driveway.
My question is, where could my fluid be going? Other areas to check for leaks?

 

[WobblyElvis]

You may have a transmission heat exchanger in one of the radiator end tanks. It's possible it's leaking into the radiator fluid but you'd probably notice that.

 

[Trav]

Check the transfer case level. 2 seals would have to be leaking but it happens, cooling system may be full of oil also as someone posted.

 

[bdcardinal]

Originally Posted by Trav
Check the transfer case level. 2 seals would have to be leaking but it happens, cooling system may be full of oil also as someone posted.


I was just about to post this. Common to see missing ATF end up in the transfer case.

 

[Fitz98]

Just checked the coolant.
It is not overfull, but is pink and milky color. I am leaning towards radiator problem.
2 questions
1) does this problem go backwards as well? Will I need to change transmission fluid?
2) Why would my coolant level not be overfull?

 

[Trav]

It sure can and you will loose the transmission, fluid changes wont help, the damage is done. Stop driving it now, disconnect the lines going into the radiator, cap them and change that radiator now.

 

[wag123]

Originally Posted by Trav
It sure can and you will loose the transmission, fluid changes wont help, the damage is done. Stop driving it now, disconnect the lines going into the radiator, cap them and change that radiator now.

+1
This was a MAJOR problem that Nissan had in the mid 2000's. Many thousands of Nissan automatics failed because of this exact problem. After you replace the radiator you need to find someone who has the machine to do a full transmission coolant line fluid flush, then hope for the best.

 

[AZjeff]

Originally Posted by Fitz98

It is not overfull, but is pink and milky color. I am leaning towards radiator problem.


In the 05-09 4.0 V6 Nissan Xterra world that's called SMOD.

Strawberry Milkshake of Death. Terminal.

 

[nthach]

Originally Posted by Trav
It sure can and you will loose the transmission, fluid changes wont help, the damage is done. Stop driving it now, disconnect the lines going into the radiator, cap them and change that radiator now.

++

glycol dissolves the friction plates in the transmission. Besides a new radiator, you will need to replace all the coolant hoses and degrease the cooling system(ideally with phosphated Cascade, but regular dishwater detergent/TSP/Shout will also work) if you want to do the job right. You will also need fluid hoses between the radiation and tranny as well.

Once a transmission is contaminated with coolant, it's only a matter of time before it completely fails.

 

[Fitz98]

Hopefully got the problem early enough, sounds like things can get pretty serious in a hurry.
I will inspect tranny fluid when I remove coolant lines, hopefully it did not go into transmission.
Now comes the question about flushing the cooling system and getting any residual oils from the cooling system before any other problems can arise.. Anyone know a good process and product to use to flush the transmission fluid contamination from the cooling system?
I am guessing about a quart or 2 of cross contamination, since the transmission was working reasonably well after adding 1/2 quart, and started to see the fluid on the bottom of the dipstick after adding 1/2 quart.
Any concerns about cooling system seals and hoses with that amount of transmission fluid diluted in the cooling system. Seems like the problem is about 1 week old.

 

[Fitz98]

I would imagine that it would be best to remove transmission lines and flush the system before putting in the new radiator so not to contaminate the new radiator.
Anyone know the size plugs and caps I would need to do this for the transmission lines and radiator threaded holes?

 

[Trav]

Just use a piece of plastic cap or a plastic bag zip tied on the line to prevent anything getting into the line while the radiator is out not to drive it.

 

[Fitz98]

Sounds good for disconnecting the transmission lines during down time, but what about when flushing the cooling system on the radiator side and also wouldn't the transmission lines get pressurized? I am thinking I should flush the system before changing the radiator to keep the contaminates out of the new radiator.

 

[Trav]

Is the transmission fluid peptobismal looking or still red? Connect a hose between the 2 cooler lines and clamp them to run the engine for flushing,

 

[Fitz98]

In this picture, the pink is the engine coolant, the dark red is from the transmission cooling resevoir

 

[mattd]

Definitely not good. Stop driving it until you fix it unless you already have.

 

[Fitz98]

I went to a local reputable transmission shop to show him the transmission fluid (and coolant) sample. The best mechanic in town uses him for all his tranny work. He said that the fluid still looks good and that if there was any coolant in it, it would be very noticeably pink as well. I wanted to schedule a transmission flush and a filter/fluid change. He said that while he would be happy to take my money, he would not recommend it. He says that more often than not on high mileage transmissions, the detergents free up contaminates in the transmission and ultimately some of it will find its way into internal parts and create problems. He gets a lot of vehicles come back after flushes. His advice was to just leave it alone and if it isn't broke, don't fix it. Anyone with experience in this having done transmission flushes?

 

[The_Eric]

Just change the fluid and filter, pull the drain plug on the torque converter if equipped or if it doesn't have a plug in the converter, fill it with fluid and pump the old out the cooler line.

 

[Fitz98]

Well....that was an utter disaster. I uses hose clamps to attach a clear hose to the 2 transmission lines to bypass the radiator transmission cooler to do a cooling system flush before putting in the new radiator. I was trying to avoid contaminating the new radiator.
Started up the truck and in a very short period of time about 1 quart of transmission fluid blew EVERYWHERE. I think it just leaked around the hose clamp, can't see where else it could leak. It was on my boat, on my other truck in the drive, on my Expedition and all over the engine compartment and all over my drive way. That must be some pressure that transmission pump makes.
I took out the thermostat and blew out all the old cooling system with a portable blower, I am going to draw a vacuum on it and put in the new radiator and do a flush with the transmission lines hooked up.
That was a 2 hour cleanup with simple green.