AWD Odor from PTU on 2007-2015 various vehicles, re:SSM 45053

BrunoWilimek · September 15, 2015

The SSM reads: 2007-2015 Various Vehicles Equipped With All Wheel Drive - Propane, Or Natural Gas Odor During Idle Or Low Speed Driving

Some 2013-2015 MKZ vehicles equipped with a 3.7L, 2007-2014 Edge, 2007-2015 MKX, 2011-2015 Explorer, 2009-2015 Flex, 2010-2015 MKT, 2008-2015 Taurus, 2008-2009Taurus X, 2009-2015 MKS, 2007-2012 Fusion/MKZ, and 2007-2011 Milan vehicles equipped with a PTU may exhibit a propane, or natural gas odor from the HVAC systemafter driving the vehicle for 20-45 minutes. This odor, if present, is most noticeable while idling or during low speed driving. Inspect the PTU for fluid leaks and repair any leaks per Workshop Manual Section 308-07B. If odor is still present after the leak repair and cleaning, replace the PTU and vent hose, if equipped. For vehicles with no leaks and odor present, replace the PTU along with the PTU vent hose, if equipped. Refer to Section 7 of the SLTS manual for the appropriate labor operations. My question is has anyone investigated this issue further? The reason I ask is that my 07 Edge has the odor from the PTU, but no leak. I replaced the PTU in a 2010 Flex for the same issue and since the old PTU did not have to be returned for a core, saved it and cracked it open to see what was inside. The only external difference from the old PTU to the new one was a drain plug has been added to the new unit. The fluid inside the old unit had turned into a black gooey sludge, but I don't see any other faults inside the old PTU. The fluid specified is 75W140 gear oil. When I checked the fluid in my own PTU through the fill plug, it was the same black goo as the Flex. other than the odour, though, it works well, so hesitate to mess with it until I have to. Anyone got any input on this?

Matt Saunoras · September 15, 2015

You may want to flush that black goo sludge out and make sure fresh axle lube is present. You'll probably have to pull the PTU to do this but on my own personal vehicle I'd think it would be worth it.

There is a recent post on the FMC boards about this, some guys think 75w-140 isn't heavy enough fluid for the stress the PTU endures

cbriggs · September 16, 2015

I put a ptu in my 2010 flex for this concern, stinky like a propane leak at idle, and black goo in the ptu. Smell is gone. I think the issue is more the fact that it only holds 1/2L of fluid. Maybe the drain plug is to introduce a maintenance interval and prevent the fluid from breaking down. I know I will be replacing the fluid in mine once in a while now.

Brad Clayton · September 16, 2015

I had the same issue on mine and the axle seal was leaking trans fluid, so I took the opportunity to drain the unit on vehicle while I replaced the seal set. I just removed both inner and outer seals and tipped the car on it's edge with one side of the lift so the ptu gear oil could drain out as much as possible. I refilled it with fresh 75w 140 and was good to go. I couldn't afford to replace that unit so I wanted to take care of it as best as I could. That was at 70k, I just serviced the car last week with 155k on it now and the fluid was nice and thin but black. Them little units take a beating for sure and we drive the wheels off the thing to begin with.

batmantech · September 16, 2015

The ford message board has a small topic on this going now. It is topic "PTU black fluid".

Look like the guys are drilling and installing a drain plug.... I guess there are pictures on ford technician facebook page.

BrunoWilimek · September 17, 2015

Thanks, guys. I was thinking along the lines of draining and re-filling, but am worried that the black goo can't be completely flushed out. The one I took apart to see what's inside took lots of scrubbing in the parts washer to get that sticky crud rinsed out. I wonder what could be temporarily run in the PTU to release it and then drain it without causing any damage to the bearings? I also can't justify spending a few hundred bucks on a new unit.

cbriggs · September 21, 2015

I would try ATF. Drive it gently for 20 or 30 km to get it warm and see if that will clean it up? Mine still had powertrain warranty when I replaced the PTU (85,000km), but to make sure it lasts off warranty I will be servicing it regularly. Adding a drain plug if not equipped would also be great idea. I have done that on a few front diffs to avoid having to pop the pan for a simple fluid replacement.

BrunoWilimek · October 2, 2015

Thanks, Chris. I will try that when time permits.

BrunoWilimek · December 17, 2015

Well, I followed your tips and drilled a drain hole, after inspecting the insides of the unit I replaced in the customer's Flex. After you remove the heat shield over the exhaust pipe, there is a flat area at the bottom of the unit that is accessible to drill and is between the gearset, so will not hit any internal components when drilling. I had a 1/8 NPT tap, so carefully drilled a hole when the fluid was warm, then tapped hole, allowing black fluid to drain and flush out chips. Then used a funnel with a length of hose over the top of the engine, wire-tied away from the catalytic converter and into the PTU. I added the appropriate amount of Mercon V and drove slowly and carefully around the dealership and area for several minutes to circulate the fluid. I drained that and repeated twice more, until the fluid started to look more reddish than black, then drained it again and added 75W140 and repeated the drive cycle, then drained and filled a second time with the gear oil. No more smell. Thanks again for your ideas. :notworthy:

mchan68 · December 17, 2015

That's a lot of draining and filling though. I personally think more frequent fluid change intervals of all its half litres would probably go a long way.

forddieseldoctor · December 17, 2015

Well, I followed your tips and drilled a drain hole, after inspecting the insides of the unit I replaced in the customer's Flex. After you remove the heat shield over the exhaust pipe, there is a flat area at the bottom of the unit that is accessible to drill and is between the gearset, so will not hit any internal components when drilling. I had a 1/8 NPT tap, so carefully drilled a hole when the fluid was warm, then tapped hole, allowing black fluid to drain and flush out chips. Then used a funnel with a length of hose over the top of the engine, wire-tied away from the catalytic converter and into the PTU. I added the appropriate amount of Mercon V and drove slowly and carefully around the dealership and area for several minutes to circulate the fluid. I drained that and repeated twice more, until the fluid started to look more reddish than black, then drained it again and added 75W140 and repeated the drive cycle, then drained and filled a second time with the gear oil. No more smell. Thanks again for your ideas.

Did you happen to get a picture of where you put the plug?

BrunoWilimek · December 18, 2015

I will take pictures the next time i get it on a hoist. Thought of that after it was too late.

BrunoWilimek · December 18, 2015

That's a lot of draining and filling though. I personally think more frequent fluid change intervals of all its half litres would probably go a long way.

Now that it has a drain plug, I am going to change it at least once a year. Couldn't do it before now.

BrunoWilimek · December 19, 2015

I have posted these pictures to show the PTU I used for reference when determining where to add a drain plug to my PTU. The factory location mentioned is where the unit to replace this one had a drain plug and was the only external difference to the original unit. Note that when the PTU is installed in the vehicle, the factory plug location is not the lowest spot on it, the area I chose is below this and the lowest point is actually slightly lower but is at the position of one of the gears and therefore not a good spot.

cbriggs · December 21, 2015

Awesome, glad it worked out. I have a flex ptu and an edge ptu that were both replaced for black fluid. I am thinking I may tear them apart, clean them out and inspect them, might be able to sell them in the future.