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Volkswagen Passat: 1998-2005 (B5) transmission overheating


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Last Post: Dec 11, 2013 6:57 PM Last Post By: tcovenant2000
ASULWER

Posts: 7
Registered: 12/04/13
transmission overheating
Posted: Dec 4, 2013 1:32 PM
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I have posted this problem to two other sites and not much help from either. i am trying this one to see if someone can help me.

First the problem: when i first start my 2001 Passat GLX V6 2.8 Car the transmission shifts fine. After i have driven it for awhile, say 30 miles, my car will shift at higher RPM's than normal, normal is around 2k-3k, abnormal is closer to 4k. I thought the transmission output rpm speed sensor was the problem as this is a shifting issue. i replaced that which was by removing the oil pan on the transmission. while i had that removed i also replaced the filter and gasket. still the problem remains. I hooked my vag-com to my car and no trans codes come up, BUT i noticed that the problem with the shifting occurs when the trans temp makes a sudden jump from 92 deg C to 155 deg C. I replace the trans fluid with the following product from Advanced Auto Parts

Castrol Import Multi-vehicle (ATF) Automatic Transmission Fluid

I have read other places that this will work. Also note that problem occurred BEFORE the trans fluid was changed so i do not think that this trans fluid is the problem. Advanced auto parts states on their website that this fluid will work with my car. Any ideas on what else i can do to narrow down the problem?

I have includes the vag-com log that i saved from VCDS, as you can see no codes from the trans. As you can see from the CVS file, also included, the temp jumps from 92C to 155C
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: transmission overheating
Posted: Dec 4, 2013 9:33 PM   in response to: ASULWER in response to: ASULWER
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The temp can't "jump" from 92C to 155C just like that. It is a fluid. There is only so much heat being produced. The problem appears to be the temp sensor itself. Beyond that I can't say more.

Thomas
ASULWER

Posts: 7
Registered: 12/04/13
Re: transmission overheating
Posted: Dec 4, 2013 9:55 PM   in response to: tcovenant2000 in response to: tcovenant2000
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how can i test the temp sensor? is there one for the transmission? its the one located when i take the trans oil pan off right?
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: transmission overheating
Posted: Dec 5, 2013 6:38 PM   in response to: ASULWER in response to: ASULWER
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Hopefully someone will post an answer. As I said, I don't have one. I am an electronics guy by trade, not a mechanic. I know virtually NOTHING about transmissions of any sort. I do know, however, that if there's a temperature readout on VAG then there is a temperature sensor. If that sensor is showing the temp going from 55 to 192C in no time, then the sensor is suspect. Actually, I'd say it's more likely you've just got a bad connection.
I don't know what the TCU will do when this happens...but I doubt it's a coincidence that the shifting gets funny when the temp is showing impossibly high. I would venture to say that, with the possible exception of the exhaust manifold, nothing in your engine even gets to 192C.

Thomas
ASULWER

Posts: 7
Registered: 12/04/13
Re: transmission overheating
Posted: Dec 5, 2013 8:38 PM   in response to: tcovenant2000 in response to: tcovenant2000
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you have the temps wrong, its 92C to 155C
ASULWER

Posts: 7
Registered: 12/04/13
Re: transmission overheating
Posted: Dec 5, 2013 9:17 PM   in response to: ASULWER in response to: ASULWER
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sorry i incorrectly stated the temps. in the included CVS file you can see that the temp moves up slowly until it reaches 96C then jumps to 152C and stays in the 150's. I believe its going into limp mode when this high temp is reached.
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: transmission overheating
Posted: Dec 6, 2013 6:34 PM   in response to: ASULWER in response to: ASULWER
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Whatever. I very much doubt that your transmission temps are reaching 152C either. That's over 300F. Things burn at that temp!

I would check all the cables/wires going to the transmission. Likely the problem is there.

Thomas
ASULWER

Posts: 7
Registered: 12/04/13
Re: transmission overheating
Posted: Dec 6, 2013 8:14 PM   in response to: tcovenant2000 in response to: tcovenant2000
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VCDS reported those temps. could be that the temp sensor is bad, or something else bad. i am not sure what the problem is here or where to begin. If you look at the CVS file that is included you can see the temps that VCDS reports.
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: transmission overheating
Posted: Dec 7, 2013 11:13 AM   in response to: ASULWER in response to: ASULWER
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Again:
1. There is no freaking way your trans fluid is hitting 150C or anything close to that.
2. The temp sensor is mis-reporting.
3. Check ALL wires and connections going to trans.

Beyond that I cannot help.
Thomas
ASULWER

Posts: 7
Registered: 12/04/13
Re: transmission overheating
Posted: Dec 7, 2013 2:45 PM   in response to: tcovenant2000 in response to: tcovenant2000
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would this cause it to go into limp mode? at least this is what i think i am experiencing with the weird shifting. might think something is wrong with the reported temps and is going into limp mode?
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: transmission overheating
Posted: Dec 8, 2013 11:49 AM   in response to: ASULWER in response to: ASULWER
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That would be my guess. I don't know much about transmissions...but I know that if the fluid is being circulated faster it will cool better. Given that, it would make sense to me that the trans would want to shift later and at higher RPM's in order to keep the fluid circulating faster.
Thomas
Francis at Bent...

Posts: 30
Registered: 11/13/13
Re: transmission overheating
Posted: Dec 11, 2013 8:22 AM   in response to: tcovenant2000 in response to: tcovenant2000
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Hi I looked at your table and saw the sudden temp rise. You are correct your vehicle is likely in a limp or protection mode. The high RPM and hard shifting are likely representative of the car minimizing torque converter slip to control what it sees as high temperatures. While not exact, if you have access to a infrared laser thermometer (the kind you point and aim with a laser) you can look for a spot on the oil pan or a cooler out line, any where that will transfer the fluid temp as closely as possible, and take a temp reading there. As stated this is not exact but could give you an approximate reading of what the fluid temp is when the problem occurs. You can then compare this to what your scanner is showing to possibly narrow the problem down to a problem with the sensor or circuit.
ASULWER

Posts: 7
Registered: 12/04/13
Re: transmission overheating
Posted: Dec 11, 2013 10:04 AM   in response to: Francis at Bent... in response to: Francis at Bent...
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it has been really cold lately, 10-20F, which causes the car to not act up. i have had difficulty getting the car to act up because it cold here. when it warms up again then the car will do its thing.
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: transmission overheating
Posted: Dec 11, 2013 6:57 PM   in response to: ASULWER in response to: ASULWER
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Increased outside temperatures cause more problems with intermittent connections. Again, these symptoms fit with connector/wire issues.

Thomas

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