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It appears that my transmission cooler lines have been cut and rigged back in a u. And what is these other cut lines and missing wireing for? 03 Passat 1.8t
 

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I don't think those lines are for the transmission, is this a manual or an automatic car?

Either way, I believe that is the power steering "cooling line" that is looped back with rubber hose. There is typically a steel u shaped tube that sits behind the bumper, if the car sees salt that tube will rust out and leak. I assume the PO just cut it and replaced it with rubber hose after that happened.

That part isn't terribly expensive so I suggest you replace it so it can be secured properly and so you don't risk the ends blowing off.

The wiring you are missing is for the oil level sensor. You should be seeing some type of fault with that completely disconnected and, if you arent, thats a tad concerning.

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It could be any number of reasons. An accident that damaged the hoses, a bad radiator or the owner wanted to run an external trans cooler. The loop does look like it's the p/s cooler but it's hard to tell from the pics.
 

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Some information about the car would help.

The connector on the bottom of the oil pan is the oil level/temp sensor.
It might be rom another car, if your car didn't have one, it would not have the wiring.

The PS cooler might have been rusted or otherwise damaged and bypassed.

Maybe your car was auto and is now manual, this would make the ATF cooler hoses redundant..
 

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@Tomvw right. The oil pan confused me for second. The 2003 does not have a level sensor. That would be a replacement pan off an older Passat.
 

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@Tomvw right. The oil pan confused me for second. The 2003 does not have a level sensor. That would be a replacement pan off an older Passat.
My Girls 02 doesnt have a Oil level Sensor either. With no code. Ive assumed. It didnt come with one. my 01 tho does have a oil sensor haha. Definitely are the P/S lines in the pic tho in a few. You can see the trans lines running along side the radiator
 

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Discussion Starter #7
So the bottom lines are for the power steering.. what is the other lines for that have been siliconed?
 

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So the bottom lines are for the power steering.. what is the other lines for that have been siliconed?
Those are the transmission cooler lines leading into and out of the radiator.

As I believe has been suggested, the may have redirected those lines to an aftermarket trans oil cooler. Look in at the front at the radiator through the upper and lower grille. See any smaller radiator in front of the A/C condenser and radiator?

This pic shows the lines redirected around the front of the radiator, it seems.
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Clearly the factory cooling lines are bypassed.
You can see the external cooler through the front grille.



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Kind of a side-topic, but aftermarket transmission ATF "coolers" are generally a bad idea on a Passat, in my opinion. First, you actually should want the ATF to get hot enough to drive out moisture that might get in through the breather, or when the transmission is being serviced. Secondly, the torque converter's lock-up feature means that the slippage, which generated so much heat in earlier designs of automatic transmissions, is mostly gone.
 

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Kind of a side-topic, but aftermarket transmission ATF "coolers" are generally a bad idea on a Passat, in my opinion. First, you actually should want the ATF to get hot enough to drive out moisture that might get in through the breather, or when the transmission is being serviced. Secondly, the torque converter's lock-up feature means that the slippage, which generated so much heat in earlier designs of automatic transmissions, is mostly gone.
Good points.
I think automatic transmission has thermostat that opens up when it reaches the operating temperature. And i believe in our ZFs, it is around 45C (113F). Regardless, the transmission should presumably run at operating temperature thanks to the thermostat.
I installed that big a$$ external cooler and as the winter arrives in south, the transmission runs 20-30F cooler than 80, which was what o would measure when the factory cooler was working. Still driving Ok. I am going to start a thread about transmission running at much cooler temperatures.

I am not sure what you mean by the lock up feature is gone at cooler fluid temperatures. I am not too informed about automatic transmissions.

@cchief22 knows more about those trannies than a ZF engineer.


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I am not sure what you mean by the lock up feature is gone at cooler fluid temperatures. I am not too informed about automatic transmissions.
You got things a little backwards there, sir. ;)
In The Olden Times...... a torque converter had no locking clutch - it always had some slip to it. Slip = heat - and, a lot of it.
Because a more-modern auto trans can lock the torque converter whenever 'slip' isn't needed (read: any time that the car isn't at a standstill, basically), the transmission generates a lot less waste heat than did an Old School automatic.
IIRC, a 5HP- locks the torque converter from 3rd gear on up (might be 4th. Need to re-read the docs. Pretty sure that it's 3rd.)

Long story short: That external cooler may actually over-cool the transmission, because VW & ZF are relying on the engine cooling system to:
-get the transmission to operating temperature as quickly as possible
-remove waste heat (as necessary) from the transmission
-maintain the transmission at nominal operating temperature.
That external air-to-oil cooler throws all of that out the window.
 

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You got things a little backwards there, sir. ;)
In The Olden Times...... a torque converter had no locking clutch - it always had some slip to it. Slip = heat - and, a lot of it.
Because a more-modern auto trans can lock the torque converter whenever 'slip' isn't needed (read: any time that the car isn't at a standstill, basically), the transmission generates a lot less waste heat than did an Old School automatic.
IIRC, a 5HP- locks the torque converter from 3rd gear on up (might be 4th. Need to re-read the docs. Pretty sure that it's 3rd.)

Long story short: That external cooler may actually over-cool the transmission, because VW & ZF are relying on the engine cooling system to:
-get the transmission to operating temperature as quickly as possible
-remove waste heat (as necessary) from the transmission
-maintain the transmission at nominal operating temperature.
That external air-to-oil cooler throws all of that out the window.
What about the internal thermostat that regulates the tranny temperature? It regulates the temperature regardless of how fast the fluid is cooled. Right?

So, if the thermostat opens at 50C, it will take 30 second for the fluid to get back to 50C with larger external cooler as opposed to 1 minute with factory installer cooler.

I observed the way engine coolant is regulated. On highway, thermostat opens at 95C, and in 15-20 seconds, it drops to 90C, at which time the thermostat closes until it reaches 95C again. If I used a larger external cooler, the fluid is cooled much faster but will still stay at 90C due to the thermostat.

That’s to say, the type of cooler is relevant for how fast the fluid is cooled.

That’s my understanding.


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In The Olden Times...... a torque converter had no locking clutch - it always had some slip to it.
You are practically 100% right, but Interestingly, there actually was one of the earliest automatics that did have a lockup clutch, made by Packard. The "Ultramatic" was introduced in 1949 and made only a few years, as Packard soon went out of business. I've got an old copy of a 'Motors' shop manual, and was surprised to see a clutch disk as part of the Ultramatic torque converter.
 

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What about the internal thermostat that regulates the tranny temperature? It regulates the temperature regardless of how fast the fluid is cooled. Right?

So, if the thermostat opens at 50C, it will take 30 second for the fluid to get back to 50C with larger external cooler as opposed to 1 minute with factory installer cooler.

I observed the way engine coolant is regulated. On highway, thermostat opens at 95C, and in 15-20 seconds, it drops to 90C, at which time the thermostat closes until it reaches 95C again. If I used a larger external cooler, the fluid is cooled much faster but will still stay at 90C due to the thermostat.

That’s to say, the type of cooler is relevant for how fast the fluid is cooled.

That’s my understanding.
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The question is, is there actually a thermostat in the trans? I don't know, but I would be surprised if there was one.
 

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What about the internal thermostat that regulates the tranny temperature? It regulates the temperature regardless of how fast the fluid is cooled. Right?

So, if the thermostat opens at 50C, it will take 30 second for the fluid to get back to 50C with larger external cooler as opposed to 1 minute with factory installer cooler.

I observed the way engine coolant is regulated. On highway, thermostat opens at 95C, and in 15-20 seconds, it drops to 90C, at which time the thermostat closes until it reaches 95C again. If I used a larger external cooler, the fluid is cooled much faster but will still stay at 90C due to the thermostat.

That’s to say, the type of cooler is relevant for how fast the fluid is cooled.

That’s my understanding.


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There is no thermostat in the Passat transmission.
There is a temp sensor which is monitored by the TCM, if the temp goes above a certain level, the TCM sends a message to the ECM to reduce power.

The coolant thermostat doesn't work as you described.
When highway driving, the thermostat is partly open all of the time, it varies within the thermostat range as required.
 

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There is no thermostat in the Passat transmission.
There is a temp sensor which is monitored by the TCM, if the temp goes above a certain level, the TCM sends a message to the ECM to reduce power.

The coolant thermostat doesn't work as you described.
When highway driving, the thermostat is partly open all of the time, it varies within the thermostat range as required.
I would imagine if there would be a thermostat, on a cold engine you wouldn't be able to see any fluid shooting out an opened cooler line. But that is definitely not the case. It shoots out a LOT of fluid.


On another note, does anyone know the temperature that a w8 external trans cooler opens at?
 
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