Radiator fluid level going down and trans fluid level going up

wjtstudios

wjtstudios

Hooked
I’ve been battling this for a number of months. My trans was running hot most of the summer to the point where it boiled out of the dip stick hole. I had been checking the fluid level, which was high but didn’t pay any attention to it since the dealership did the fluid swap. After it boiled over I pulled as much fluid I could, 5 quarts, out of the dip stick hole and replaced it with only 3 quarts to the point where was at the ideal marks on the dip stick. Temps immediately when down to normal and drove great. I blamed it on the dealership overfilling it.

Now a month has past, still running cool, but I checked the trans fluid level and is now well above the hot temp marks even after the Jeep has sat for 24 hours. I also checked my coolant level and it was down below the min line.

I was always under the assumption that the trans cooler was trans fluid based and not coolant based and the two systems were separate. All that I can figure is that radiator fluid is finding it’s way into the transmission to have these fluid levels changing. But how is this possible??


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
I don’t see how the two could intermingle. I know some vehicles have the trans cooler integrated into the radiator, but isn’t the JK a separate cooler mounted in front of the radiator. I could be wrong about that since I have a real Jeep with a manual. [emoji23][emoji23]
 
wjtstudios said:
I’ve been battling this for a number of months. My trans was running hot most of the summer to the point where it boiled out of the dip stick hole. I had been checking the fluid level, which was high but didn’t pay any attention to it since the dealership did the fluid swap. After it boiled over I pulled as much fluid I could, 5 quarts, out of the dip stick hole and replaced it with only 3 quarts to the point where was at the ideal marks on the dip stick. Temps immediately when down to normal and drove great. I blamed it on the dealership overfilling it.

Now a month has past, still running cool, but I checked the trans fluid level and is now well above the hot temp marks even after the Jeep has sat for 24 hours. I also checked my coolant level and it was down below the min line.

I was always under the assumption that the trans cooler was trans fluid based and not coolant based and the two systems were separate. All that I can figure is that radiator fluid is finding it’s way into the transmission to have these fluid levels changing. But how is this possible??


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

I don't know how that's possible for the tranny fluid to cross over into the rad - the tranny cooler is independent of it. It's mounted in front of the rad and there are no tranny line connections going into it. Unless there's some lines that I don;t know about. :thinking:

I had this issue with a Pathfinder we had a while ago and it had coolant lines that passed through the rad. The lines ate out and allowed the fluids to cross over and the clutch linings were destroyed by the coolant. But the symptoms were apparent as the tranny started slipping and making rumbling noises similar to what it sounds like when running over rumble strips on the side of the road. Do you have any other symptoms besides the fluid rising?
 
I agree completely. I’m at at total loss here. There are no signs of a coolant leak, no smell.

But one fluid is going up and one is going down and it doesn’t make any sense.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
Ddays said:
I don't know how that's possible for the tranny fluid to cross over into the rad - the tranny cooler is independent of it. It's mounted in front of the rad and there are no tranny line connections going into it. Unless there's some lines that I don;t know about. :thinking:

I had this issue with a Pathfinder we had a while ago and it had coolant lines that passed through the rad. The lines ate out and allowed the fluids to cross over and the clutch linings were destroyed by the coolant. But the symptoms were apparent as the tranny started slipping and making rumbling noises similar to what it sounds like when running over rumble strips on the side of the road. Do you have any other symptoms besides the fluid rising?
Click to expand...

I had exactly the same thing happen to one of my hummers. But it turns the fluid into a strawberry milkshake and that’s not happening.

No other symptoms, shifts perfectly. Temps are at 168 consistently, even on the highway after I swapped the fluid. But something is causing the fluid level to rise. I haven’t done any water crossing since the swap either.

Completely stumped here.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
wjtstudios said:
I don’t believe so. Both, units are sealed and if fluid was coming from the TC, it would struggle to change between 2 and 4 and it’s perfectly smooth.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

Have you traced the lines just to eliminate the possibility of a cross-connection. I can't believe anyone could cross connect the two but dumber things have happened at dealerships.

One other possibility is to drain it again & see if you only get 3 quarts out of it? If you get more than you put into it last time, somehow you have something cross connected.
 
Ddays said:
I don't know how that's possible for the tranny fluid to cross over into the rad - the tranny cooler is independent of it. It's mounted in front of the rad and there are no tranny line connections going into it. Unless there's some lines that I don;t know about. :thinking:

I had this issue with a Pathfinder we had a while ago and it had coolant lines that passed through the rad. The lines ate out and allowed the fluids to cross over and the clutch linings were destroyed by the coolant. But the symptoms were apparent as the tranny started slipping and making rumbling noises similar to what it sounds like when running over rumble strips on the side of the road. Do you have any other symptoms besides the fluid rising?
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Lots of vehicles have a cooler built into the radiator but also an aux cooler in front of the rad for additional cooling. I haven’t worked on a 2015 as he has tho.
 
Ddays said:
Have you traced the lines just to eliminate the possibility of a cross-connection. I can't believe anyone could cross connect the two but dumber things have happened at dealerships.

One other possibility is to drain it again & see if you only get 3 quarts out of it? If you get more than you put into it last time, somehow you have something cross connected.
Click to expand...

I think if they had crossed the lines it would have toasted the trans like it did on our other vehicles a long time ago. They did the fluid and filter swap 16 month ago at 50k. It’s now at 78k and It hasn’t been to the dealer since.

I replaced the radiator and thermostat in the spring, but there’s no way of combining the systems in that process.

IMG_2182.jpg

Here’s a picture of the dip stick. When I refilled it last month, it was right in the middle of the two lines. Now it’s above the step on the stick.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
wjtstudios said:
I think if they had crossed the lines it would have toasted the trans like it did on our other vehicles a long time ago. They did the fluid and filter swap 16 month ago at 50k. It’s now at 78k and It hasn’t been to the dealer since.

I replaced the radiator and thermostat in the spring, but there’s no way of combining the systems in that process.

View attachment 336415

Here’s a picture of the dip stick. When I refilled it last month, it was right in the middle of the two lines. Now it’s above the step on the stick.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

When you fill it you are making sure it’s at operating temperature, or stone cold temp, and on flat level ground?


Also only way they could share is if the trans cooler is built into the radiator. If the radiator and cooler are cracked at their separation points then they would be able to transfer the fluid between the two
 
cozdude said:
Lots of vehicles have a cooler built into the radiator but also an aux cooler in front of the rad for additional cooling. I haven’t worked on a 2015 as he has tho.
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I can;t speak on the 3.8 setup, but the 3.6 has no connections other than the two rad hoses. The cooler unbolts from the front of the rad and has two hard lines that kind of hold it in place. Those lines aren't connected to the rad at all.

wjtstudios said:
I think if they had crossed the lines it would have toasted the trans like it did on our other vehicles a long time ago. They did the fluid and filter swap 16 month ago at 50k. It’s now at 78k and It hasn’t been to the dealer since.

I replaced the radiator and thermostat in the spring, but there’s no way of combining the systems in that process.

View attachment 336415

Here’s a picture of the dip stick. When I refilled it last month, it was right in the middle of the two lines. Now it’s above the step on the stick. .


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

Is it possible there was somehow more fluid in it than you realized? Could you pull some fluid out of it again & see if it goes back up? That fluid looks brand new - agree there can't be coolant in it
 
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cozdude said:
When you fill it you are making sure it’s at operating temperature, or stone cold temp, and on flat level ground?
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Both. Brought it up to cold at first. Ran it, up to operating temp and checked it an it went to mid to high as it should. My garage floor is dead flat. Over the last month, I’ve been a bit obsessive checking it and it had been holding, but after running to Windrock and back and then a hard week of miles last week it’s gone way back up.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
Ddays said:
I can;t speak on the 3.8 setup, but the 3.6 has no connections other than the two rad hoses. The cooler unbolts from the front of the rad and has two hard lines that kind of hold it in place. Those lines aren't connected to the rad at all.



Is it possible there was somehow more fluid in it than you realized? Could you pull some fluid out of it again & see if it goes back up? That fluid looks brand new - agree there can't be coolant in it
Click to expand...

I’d agree that it could have been my error but
I’ve checked it to many times at both hot and cold since the swap. It’s definitely gone up considerably over the last 10 days.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
wjtstudios said:
Both. Brought it up to cold at first. Ran it, up to operating temp and checked it an it went to mid to high as it should. My garage floor is dead flat. Over the last month, I’ve been a bit obsessive checking it and it had been holding, but after running to Windrock and back and then a hard week of miles last week it’s gone way back up.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

Your checking it with the engine running and in neutral or park. I assume you are but just making sure cause that make a big difference if the motor is on or off
 
Now I am running amsoil trans fluid verse oem. I don’t see that being an issue. But maybe?


2015 JKUR AEV JK350
1985 CJ8 Scrambler
 
wjtstudios said:
Now I am running amsoil trans fluid verse oem. I don’t see that being an issue. But maybe?


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

As long as it’s ATF+4 which is what the mopar blend is then your fine. Brand doesn’t matter just needs to meet the factory requirements
 
wjtstudios said:
I’d agree that it could have been my error but
I’ve checked it to many times at both hot and cold since the swap. It’s definitely gone up considerably over the last 10 days.


2015 JKUR AEV JK350
1985 CJ8 Scrambler
Click to expand...

Too bad this wasn’t your gas tank refilling itself [emoji23]


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