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Burnt Transmission Fluid Smell when Manually Shifting

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I have been driving my 2017 3.0T pretty extensively shifting via the paddles and on a pretty hot day today noticed the faint scent of burnt transmission fluid. The smell would go away if driving while letting the transmission shift on its own. Anyone have thoughts on this?

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Despite when my PTU had its leak, I never had a burnt transmission smell. I had to get pretty close to smell the fluid's odor meaning it isn't breaking down under heat. Are you smelling it from the inside or outside?

 

If you can, I highly suggest you get under the car and take a look around the PTU housing and connecting shalfs. It's right next to the oil pan and you do not need to remove the under body cover to inspect it.

 

The 3.0T indeed gets atrociously hot and heat has little means of exhausting.

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I smell it inside with windows up as well as outside. The odd thing about it is I was just driving around in a relaxed manner. Shifting around 3,000 to 3,500 rpms and cruising around 1,500 to 2,000 rpms in 5th.

 

Will try to get a look under the car soon.

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I haven't noticed any trans fluid smell either.

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I was driving all day in Sport and manual mode. Anyone else use manual that much?

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I was driving all day in Sport and manual mode. Anyone else use manual that much?

No. Were you driving in the mountains?  I use the paddle shifters more for going downhill than anything else.  Occasionally, if I want to do a quick lane change in slow moving traffic, I'll lock it in low and nail it to get into a gap.  Other than that, I don't find a compelling need to drive around in manual.  The  trans shifts at redline on it's own, so it's not going to improve acceleration times. It might shift a couple of milliseconds  faster than in auto but unless it's a timed run on a track, I don' t think it'll make a significant difference.

 

Maybe you overheated the trans by doing that.  I'd take a look at the fluid to see if it's changed in color.   The 6F55 has a dipstick.  The procedure for accessing it is in the OM under Automatic Transmission Fluid Check.

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No. Just around town. I like the feeling of stretching each gear out a little further than what the car would shift on its own. I think you are right in that it was overheating the fluid a bit. Everything shifts fine so I don't think I did any damage. Thank you for the tip and link on checking the fluid. I'm going to feel it out more driving in auto and if all seems well will just use manual as it was intended which is for occasional spirited driving and going downhill.

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If the transmission was seriously overheated, the car will throw a code and enter limp mode. However like many potential engine gremlins, it does not mean excessive wear is going on unknown to the driver. The transmission will not overheat until the fluid's quality has become so poor in doing its job.

 

To quote from the workshop manual, for the MKZ 3.0T:

 

 

Transmission Cooling Overview

 

This vehicle is equipped with a transmission fluid warmer mounted on top of the transmission and an oiltoair fluid cooler which is mounted on the lower LH side of the vehicle behind the front bumper cover. The cooling system also consists of a cooler bypass valve which is mounted on the rear of the transmission. When the transmission fluid is below normal operating temperature, transmission fluid travels from the transmission to the warmer which uses warm engine coolant to warm the transmission fluid. The transmission fluid then travels to the cooler bypass valve and back to the transmission. When the transmission fluid is at or above normal operating temperature, a valve located in the engine cooling circuit closes, stopping coolant flow to the transmission fluid warmer. The cooler bypass valve opens allowing transmission fluid to travel from the transmission through the cooler and back to the transmission. The transmission fluid cooler transfers heat from the transmission fluid to the ambient air.

 

You will know if the transmission fluid is overheating/breaking down as Mercon LV will be black and really stink bad just from checking via dipstick. Brown means it is managing and Mercon LV changes fast from its red/dark red color, and breaks down faster the more often it is exposed to higher temperatures. If you have a scan tool, you can tap into the transmission temperature sensor for actual degree readings. It should stay between 200 to 220 degrees along any forms of driving after reaching operating temperature.

 

If you are seriously burning the fluid up, then something might be not working correctly with the transmission fluid system given the reasons of use stated (and just a tune is not going to overcook fluids in a daily drive setting).

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Good to know. So I shouldn't be too worried.

I have about 1,600 miles on the car right now. Might I be smelling something from initial break in with the exhaust?

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Using sport mode or manually shifting shouldn't hurt it or cause a smell of transmission fluid.  I would definitely take a look underneath, though, and check out possible leaks from PTU/axle seals or other possible leak points.

 

I use sport mode at the track and also for datalogging my tune.  I also use the paddles when datalogging and the tuner wants to see specific gear and rpm.  I have never had any unusual smells.

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