E92 M3 DCT Overheat!

Helmsman wrote

Good input. Quite a few things done though, any idea what was the actual issue?

From everything I gathered and after reading transmission temps, we came to the conclusion of a failing temp/revolution sensor. Fluid was not low, clutch pack and clutches showed no signs of warp or excessive heat/friction outside of normal range. A good starting point would be to look at the the DCT thermostat and address if that is failing as Bimmerworld states that is a very potential culprit as well : https://www.bimmerworld.com/Cooling/Oil-Coolers/DCT-Transmission-Oil-Thermostat-E9X-M3-DCT.html

TheGr33k wrote

From everything I gathered and after reading transmission temps, we came to the conclusion of a failing temp/revolution sensor. Fluid was not low, clutch pack and clutches showed no signs of warp or excessive heat/friction outside of normal range. A good starting point would be to look at the the DCT thermostat and address if that is failing as Bimmerworld states that is a very potential culprit as well : https://www.bimmerworld.com/Cooling/Oil-Coolers/DCT-Transmission-Oil-Thermostat-E9X-M3-DCT.html

Got it. Replaced the Tstat earlier. The Clutch temp (revolution) sensor is the one occasionally going up and down. Seems to stabilize when driving a bit harder/revving up which makes me wonder about the fluid/spray supposely cooling the clutches (did you by any chance see what that looked like inside mate?). Will top up fluid during the week, see what happens.

I'm wondering, is there a way to bypass the DCT fluid thermostat? To have it permanently open so that fluid flows to DCT cooler 100% of the time. I live in a hot climate so warming up the DCT fluid is not so important.

Redd wrote

I'm wondering, is there a way to bypass the DCT fluid thermostat? To have it permanently open so that fluid flows to DCT cooler 100% of the time. I live in a hot climate so warming up the DCT fluid is not so important.

Foolish IMO. The thermostatic control is desirable. It's easy to access, easy to replace, not an expensive part. Retain it.

deansbimmer wrote

Foolish IMO. The thermostatic control is desirable. It's easy to access, easy to replace, not an expensive part. Retain it.

Yessir... 😅

TheGr33k wrote

From everything I gathered and after reading transmission temps, we came to the conclusion of a failing temp/revolution sensor. Fluid was not low, clutch pack and clutches showed no signs of warp or excessive heat/friction outside of normal range. A good starting point would be to look at the the DCT thermostat and address if that is failing as Bimmerworld states that is a very potential culprit as well : https://www.bimmerworld.com/Cooling/Oil-Coolers/DCT-Transmission-Oil-Thermostat-E9X-M3-DCT.html

So turned out 0.3 liter was possible to squeeze in i.e. box was full so there goes my final hope out the window. Temp sensor continue to act. To make it clear I got the code and limp on my way from the shop....

They quoted 2k usd to drop the box and replace the sensor and while in there one of the hoses to sort a tiny leak. Might be my next action but will try a adaptation reset for the fun of it first.
Again box have done 40k calm miles so continue to refuse to believe the clutches actually slip.

If you’re in SoCal, I can refer you to the shop I had drop my DCT and replace rhe RPM/temp sensor as well as fully reseal the transmission and reinstall it. Veryyyy fairly priced for outstanding work.

TheGr33k wrote

If you’re in SoCal, I can refer you to the shop I had drop my DCT and replace rhe RPM/temp sensor as well as fully reseal the transmission and reinstall it. Veryyyy fairly priced for outstanding work.

Located in Stockholm so a bit too far off.... Thx anyway.

TheGr33k wrote

From everything I gathered and after reading transmission temps, we came to the conclusion of a failing temp/revolution sensor. Fluid was not low, clutch pack and clutches showed no signs of warp or excessive heat/friction outside of normal range. A good starting point would be to look at the the DCT thermostat and address if that is failing as Bimmerworld states that is a very potential culprit as well : https://www.bimmerworld.com/Cooling/Oil-Coolers/DCT-Transmission-Oil-Thermostat-E9X-M3-DCT.html

FYI had the rpm/temp sensor replaced, it was the issue here as well.

That’s great to hear man! I can see these RPM/temp sensors giving out over time as they are starting to and this could save people’s tons of money in diagnostic and troubleshooting costs/time. I am still going strong since my replacement as well with zero issues.

TheGr33k wrote

If you’re in SoCal, I can refer you to the shop I had drop my DCT and replace rhe RPM/temp sensor as well as fully reseal the transmission and reinstall it. Veryyyy fairly priced for outstanding work.

What shop?

TheGr33k wrote

That’s great to hear man! I can see these RPM/temp sensors giving out over time as they are starting to and this could save people’s tons of money in diagnostic and troubleshooting costs/time. I am still going strong since my replacement as well with zero issues.

Most frustrating was that the main bmw dealer didn't diagnose it while I was still under warranty - insurance so would have been paid work for them i.e. complete ignorance - only after I got Protool and diagnosed myself I could guide (another) dealer on what to do. $2k job buy still happy it was the sensor.