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Soaring temperatures after transmission fluid change

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24K views 51 replies 21 participants last post by  RustBeltRefugee  
#1 · (Edited)
Been following several threads about transmission temperature and fluid changes. Decided to start a new thread about my own experience.

Based on my sense of the many threads on the subject, I decided to get a transmission fluid and filter change at 75,000 miles. After a few days of driving around town, I got back on the highway. Uh oh. Before the change, the transmission would warm up fairly quickly, and stay in the 200F-205F range during freeway cruising (65-75, cruise control). On long grades it might have hit 210F, and on steep ~10,000' mountain passes I've reached 220F (carefully...). After the change, whoa. Got on a flat freeway, set cruise at 65, and watched temperature climb steadily over the course of about 35 miles/35 minutes, hitting 230F, at which point I pulled off to let things cool at idle before heading straight home. Didn't want to see how high it could go...

Here's the data--coolant and transmission T vs. time. Top panel: normal freeway drive before fluid change, with transmission and coolant temperatures tracking normally. Bottom panel: today's drive, on more-or-less the same stretch of freeway. Hot, hotter, hottest!

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Temperatures over 220F with an empty van, no significant hills, no stop-and-go traffic, cruising at 65 in 45-degree weather. Am I overreacting? Or, should I be on my way back to the mechanic ASAP? (Note: this is the first automatic transmission I have owned in 35 years)
 
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#5 ·
Wow that does look bad! Where did you have the fluid replacement service at? Wondering if they didn't fill up completely, causing overheat?

Would like to know how you collected and graph the data. Very impressive!
 
#6 ·
Captured with OBD Fusion and plotted with my favorite graphing tool Igor Pro! (Yeah, MatPlotLib, I know, I know)

Holy crap. Just looked closely at the invoice and it lists 5 Qt X 1.2 = 6 Qts of Mercon V?!? Hope that's a typo.
 
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#7 ·
I believe it should have LV transmission fluid not V but even so I would not expect that to cause your fluid temperature to rise abnormally.

Here is what the dealertech website states as the correct fluid and filter:


  • Transmission Filter:FT-161
  • Transmission Fluid Spec:XT-10-QLVC

I am concerned about your fluid level being correct for one thing.

Do you know if they used a flushing machine during your service or just drained and filled? Also did they add any other fluids to the transmission pre or post fluid exchange?
 
#8 ·
Paid for them to drop the subframe, remove the pan, change the filter, and replace the fluid. Invoice says "w/fluid exchange equipment." Dropped the van back at the mechanic and talked to them in person. They seemed alarmed by the temperatures (good), but also thought that maybe the 6 Qt. of fluid was due to "some remaining in the transmission even after removing the pan" (uh, 7 Qts.?).

Considering that the transmission has overheated to 230F or beyond at least twice, maybe three times (when not being monitored), I don't think a simple fluid top-off is enough here. Right? The whole point was to get clean, uncooked fluid in place for the next 75,000 miles. The original fluid was apparently in bad shape when removed.
 
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#9 ·
So the torque converter alone holds about 3-4 quarts. Transmission cooler lines and other fluid sitting in the various pistons and what not could make up the difference.

What I am finding odd here is that the wrench light was not set during the overheating event?

I just looked through the workshop manual and it does not give a maximum normal operating temperature or a temperature at which a transmission overtemperature DTC would be set.
 
#10 ·
I googled around for the temperature threshold at which the "service transmission" warning would appear (seen in the previous threads), but found nothing. I pulled off the freeway at 230F to cool down at idle--didn't want to push it further.
 
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#14 ·
OBD Fusion lets you set up logging for each vehicle, and it does it automatically every time you connect, so if you're monitoring on-screen, you know that it's dumping everything to a CSV file for future reference.

It was indeed $800 for the complete job. All three quotes came in around the same, although this was the one place that didn't have to be told about the subframe process to give a correct quote. Still waiting to hear about what the **** went wrong. What seemed like smart preventative maintenance might result in an expensive transmission repair in the near future.

As if this was bad enough, I also spent the weekend repairing/replacing the front bumper cover on my other vehicle, a Fiat 500. Turns out my long-time neighborhood oil-change guy (or his new tech) got lazy and cut off part of the underbody cover rather than removing the two bolts to lower it. The cut end of the cover got caught on some road debris (that it was there to deflect!), and ended up pulling off the bottom of the front bumper fascia and breaking numerous connectors. 🤜🍆 (BTW, the Fiat can fit inside the Transit if you remove the side mirrors)
 
#15 ·
RustBeltRefugee said:
As if this was bad enough, I also spent the weekend repairing/replacing the front bumper cover on my other vehicle, a Fiat 500. Turns out my long-time neighborhood oil-change guy (or his new tech) got lazy and cut off part of the underbody cover rather than removing the two bolts to lower it. The cut end of the cover got caught on some road debris (that it was there to deflect!), and ended up pulling off the bottom of the front bumper fascia and breaking numerous connectors. 🤜🍆 (BTW, the Fiat can fit inside the Transit if you remove the side mirrors)
Click to expand...
My trophy fake-wife had a Passat with a broken underbody cover, it was a pain to get on and off when I changed the oil. I finally devised a bungee cord system!
I'm happy to say that I'll never need to change the oil on our Fiat, it's a 500e. Good to know I can stick it in the back of the van if needed! I'm assuming a platform on top of the wheel wells? I don't think it would fit between them...
5' tall, 5-1/2' wide, 12' long, so, no.
 
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#22 · (Edited)
Welp, looks like the mechanic is, at best, honorable. The only thing he can think of is a mis-installed filter (@EddieZ) and his transmission rebuild guy agrees, so he’s going to do it all over again (all five hours of labor).

Fluid should be nice and clean after two changes. :rolleyes:
Image
 
#23 ·
RustBeltRefugee said:
Welp, looks like the mechanic is, at best, honorable. The only thing he can think of is a mis-installed filter (@EddieZ) and his transmission rebuild guy agrees, so he’s going to do it all over again (all five hours of labor).

Fluid should be nice and clean after two changes. :rolleyes:
Click to expand...
Yikes - kudos to you that you had the sense to keep an eye on temps - not many would have done that. You probably saved your transmission. Hopefully the trauma was minimal and a fluid swap /correct filter install addresses it and gets you on your way. To his credit - at least he is offering to make good on it - many would not even go that far. Due to your diligence, I doubt any harm was done to the trans.
 
#26 ·
The original 500 had an elaborated engine under cover, with a flexible gasket around the oil pan). Without it, the cooling turbine (a la Porsche) would recirculate hot air from the bottom of the car instead of cold air from the rear hood louvres. Good fun in my old country.
 
#27 ·
I'd be looking at cooler lines pinched or plugged. Low fluid will cause slippage so if you didn't notice any slippage I would say the level is ok, though slippage will cause overheating. This is why I don't like not having a real filler tube and dipstick. Both overfilled fluid and improper installed filter would show bubbles, not to mention overheated fluid would show up as a brownish color. Made diagnosing trans problems much easier back then. I'd like to know where the temp sensor is located that the computer is using for its reference. I use to work on auto trans but not since 1999. Back then torque converters would easily go over 200 degrees and it was normal, it was also the hottest point. A temp reading at other line pressure points would always be lower but I can't say what is normal with todays transmissions.
 
#28 · (Edited)
So the mechanic re-did the whole job, this time using a Genuine Motorcraft filter instead of the "OEM" replacement that gave him trouble on the first pass. Took the van on a holiday shopping trip, and temperatures seemed reasonable at freeway speeds, although I couldn't gather apples-to-apples data because all roads had many stop-and-go segments this afternoon (or stop-and-get-assaulted). The mechanic actually wrote up an extra invoice describing the do-over, and the swap of filter types, so I have documentation of what happened just in case the tranny blows up in six months.

Big thanks to the forum for the advice. I've never owned an automatic transmission before the Transit and have never thought about how such a thing would work.
 
#30 ·
Back to doing longer trips on the open road and... doesn't look normal. Not as dramatic as when the incorrect filter was installed, but:
Image
(Pulled over at 114 minutes to cool)
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(This was dead-flat interstate on a cool evening)

Basically, if I cruise over 65MPH (and I have road trips planned with days of speed limits in the 75-80 range), the transmission temperature creeps up to 210F or higher--even on flat interstate highway. Climb a slight grade or hit rolling terrain at 70+ and I need to stop occasionally to let it cool down. Cruising below 65 is fine. My suspicions about engine coolant temperatures running high are not supported by data. For comparison, I did 20+ days of interstate cruising last summer, before the fluid change, and transmission temperatures were stable at 198-205 at 78MPH for hours on end. In all of these cases, the van is barely loaded, between 6200 and 6900lbs total.

Not inclined to return to the same shop, but I need to get this addressed before any multi-day trips. :-/
 
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#31 ·
Not familiar at all with the tools you use to record the data. Although I have read in a number of comments in the forum of this FORSCAN thing. But it seems you use something else.
Can you share what it is you are using to at least get a csv of data? Any real time charts while logging the data? I assume so since you were aware to pull off and cool things off.

On the Fiat 500 thing, I had (what I believe was called a Fiat 500 at the time) a 1967 Fiat with a small water-cooled motor in the rear. Brakes were drums that look to be taken off a small motorcycle. I think the spec was 25 horsepower on the motor. Had suicide doors on it. It would overheat trying to go up any kind of extended highway hills. I used to have to carry some spare water.
But I bought it for $100 while eating pizza when the guy pulled up and it had a for sale sign on it. It was pretty cool. It got a consistent 47 mpg.
 
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V
#33 ·
Well this is frustrating even for me just reading it! I can only imagine how you feel. I just don't understand these super hot transmission temperatures. I know it's not the same thing, but my E-350 (when running at 15,000# GCWR up hills in hot weather) wouldn't get much over 205ºF on the transmission. I thought that was hot and so put on a larger transmission cooler (in place of the OEM Ford one). Now I can't make it break 200º even if towing heavy on the surface of the sun (or what passes for that, i.e Mohave mountains in summer).

It just seems crazy that the Transit transmission would have to run so hot (even in benign conditions and even before yours got worse). Heck, I only have three gears (plus overdrive). How can't it be cooler when you have so many more to choose from, your transmission is like a 30-year-newer design, and your van is practically light as a feather (6,xxx#)?

Another question I have (this was touched on above so not a total tangent): Is there no way to change the transmission fluid the way we used to where you would essentially remove a hose and then allow the old fluid to flow out into a waste bucket while at the same time new fluid was being sucked in? That would allow changing it all but is that not valid on the Transit?

I really want to get a Transit to replace my ol' E-350 -- and I know nothing's perfect -- but I'm feeling a little shaky about spending $60k and possibly having it be delicate or tempermental. Guh.

Back to your specific issue though: What the heck? Obviously it must have something to do with that initial service.... but what? I wish I understood it better so I could help you sleuth it.
 
#35 ·
Rather than give TFGs a third chance at destroying my transmission, I instead took it to Schucks Transmissions in Dublin, CA. Great experience. Not only did the service writer document the full set of data, but the senior mechanic came out during drop-off and had a nice long chat with me about exactly what was happening. He didn't want to do another $800 subframe removal, so instead did a transmission fluid flow test. This registered >5 gal/min, deemed normal. Decided no further work needed to be done at that moment. But somehow, afterward, the overheating issue disappeared! Drove several familiar routes and noted that temperatures were normal again--10F to 15F below the previous "hot" values while cruising, and no soaring temperatures during long uphills. Committed to a road trip up US 101 to the North Coast and had no problems, no overheating, no need to stop on freeway grades. Maybe the flow test dislodged a blockage? Maybe the TFGs overfilled the transmission and Schucks refilled it correctly? I don't know...
 
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#36 ·
The pancake style heat exchanger Ford uses is just enough for a Toyota/Honda transmission but for sure causes issues later on. They mounted it next to the radiator and the coolant flow is BEHIND the thermostat which means the engine has to be at OT before the transmission is cooled, even as the transmission overheats. I've gotten vent puking transmissions from almost every contractor that hits the ground running on a cold start in the morning! The fins distort from improper heat transfer and then the debris builds up in the gullies. The more buildup, the hotter the transmission will get. Despite a picture just imagine a flanged end pipe inside that cooler that doesn't allow fluid to fully flow past it and instead creates a sort of back-wash effect where the debris is just sloshing around inside the cooler. These units need to be flushed and then back-flushed with a HOT transmission flush machine so if the DEALER doesn't know that nor the fluid type specifically then RUN to one that does or any reputable transmission shop for that matter. Ford Dealers that don't have this equipment may not have opted in to the new regime for these Transits and Transit Connects, which means they're as good as toast because those guys didn't get the training either. I'm surprised they took you at the first dealer, usually they turn customers with transits away if they have too many issues. Seen a lot of body wiring harness issues, surge tank caps (hint for transit owners : If the small plastic pipe to the degas bottle pops or your engine is overheating, replace the surge tank cap when cool. Every cap tested at my shop pops off at 25 psi or above, Spec is 21 psi) Rotted ECM connections causing EVAP faults. The trailer light module being near the aft end of the driver's footwell. If you're infotainment stuff stops working, check to see if that module is nice and green! 3 10mm bolts, be careful with the trim panels, access is right there through the door with 5 T-25 torx screws holding it in. Yes the module sits like that once you're inside. Hope that can help a bit.
 
#37 · (Edited)
jones.mstruck said:
The pancake style heat exchanger Ford uses is just enough for a Toyota/Honda transmission but for sure causes issues later on. They mounted it next to the radiator and the coolant flow is BEHIND the thermostat which means the engine has to be at OT before the transmission is cooled, even as the transmission overheats. I've gotten vent puking transmissions from almost every contractor that hits the ground running on a cold start in the morning! The fins distort from improper heat transfer and then the debris builds up in the gullies. The more buildup, the hotter the transmission will get.
Click to expand...
Funny that your post comes two days after I started noticing higher temperatures on my usual "commute" up Carson Pass (+7,990'). Part of it is that dry roads mean I'm climbing faster/more aggressively, but still, I used to be able to do much steeper roads with temperatures under 210F, while now I'm seeing 225F and very slow cool-off if I do pull over. Not "soaring" but clearly warm.

Might go back to Schucks and ask about the flushing process you describe.
 
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#38 ·
Was worried about lack of lock-up in the torque converter (explanation for overheating during flat freeway driving), but the forum comes to the rescue again with this excellent old thread that explains lock-up in detail: P0741 Torque Converter Clutch Circuit Performance or...

Did a big mountain-pass drive over the holiday weekend in very hot weather and had inconsistent behavior. Running hot on the flats, not running hot during a 4,000' climb, and several times when the engine and transmission temperatures seemed unrelated (i.e. engine up to 198F, but transmission stays cold for ~45 minutes until I drive hard/climb). Posts #27 and #36 make a lot of sense, if the flow between the two is impeded you can't know where the heat will go.
 
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#39 ·
So I gathered some more data. Had a feeling I was about to have a "hot" morning, so I logged engine and transmission temperature for 40 minutes of flat, easy driving. WTF?

Image

Really does seem like there is minimal thermal exchange between the engine and the transmission. Shouldn't the engine warm the transmission once the engine temperature passes 180F? Lost connection to the logger, but a gentle hill climb at 45-50 minutes sent the transmission temperature up to 220F while the coolant never passed 202F. Then, I stopped, took a lunch break, and continued on the drive... and the transmission stayed under 210F, even with 4,000' of climbing Sonora Pass. Huh. The idea of intermittent clogging of a heat exchanger proposed above seems plausible, like a cycle of warm-up/cool-down "fixed" the initial flow problem.

Although I kept the transmission under 220F for the mountain pass, I did notice rough shifting for about 15 minutes after the climb. Do you need to re-check fluid levels after an overheat?
 
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#40 ·
RustBeltRefugee said:
Really does seem like there is minimal thermal exchange between the engine and the transmission. Shouldn't the engine warm the transmission once the engine temperature passes 180F?
Click to expand...
If the transmission cooler is outside of the radiator, then I would think the answer is no.

OTOH, my Honda Accord has a transmission cooler (in this instance it is more correctly called a heat exchanger) inside the radiator, so what you asked would indeed happen.
 
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#44 ·
Wait until it starts leaking, There are a number of reports here as well as a TSB on this. Transmission fluid and coolant mix together. It is mounted near the bottom of the radiator as I recall from past threads.
 
#45 ·
For what it's worth, I would postulate from your chart that the trans thermostat that sends fluid through the cooler opens around 155 degrees.
Flat plate coolers/heat exchangers are very, very efficient and hence very small.
Do you ever see significantly higher trans temps than engine coolant temps? If not you can probably find another issue to worry about.
 
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#46 ·
pbethel said:
Do you ever see significantly higher trans temps than engine coolant temps? If not you can probably find another issue to worry about.
Click to expand...
Since the botched maintenance that started this process, yes, the transmission temperature is higher to much higher (10F-20F) than the coolant temperature when driving on moderate grades or at high cruising speeds (empty van, <6000lbs). If the key to transmission health is keeping the temperature below 225F, then regular roadtrips are going to kill me. The key thing I've noticed is that the transmission often cools very slowly when parked at idle, or when driving slowly on the flats, and increasing engine RPM does not help.

Perhaps having the new reputable shop drop the subframe and redo the filter/flush for ~$800 might be worth it at this point.
 
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