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Old 06-05-2012, 12:05 PM   #1
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Exclamation Problem with Nissan Pathfinder and some Mercedes

I guess this should go here.

My buddy has a Nissan pathfinder (and apparently some Mercedes have the same radiator manufacturer) and he just discovered a major problem with them. Apparently between 80 to 100k miles (his was 101k)the radiator develops a crack at the weld for the automatic transmission line INSIDE the radiator. So radiator fluid starts mixing with the Trans fluid, so the only symptom is the radiator fluid gets a little low but the trans fluid increases. Most people don't ever check the trans fluid so they equait the water loss to evaporation and just keep feeding the radiator.

Meanwhile the trans clutches are not getting the right lubricity and starting to fail, but wait it gets better, there is a trans module inside that if it gets wet (by water not oil) it will rust and fail requiring an entire rebuild just to get to it.

The fix is simple enough either block off the trans lines to the radiator and a aftermarket cooler or some models came from the factory with an external cooler so you just have to block off the radiator one. Then flush the trans 1 to 3 times.

Here's the kicker if your fluid is milky at all or there is rust on the dipstick at all you might get away with just flushing but reports have come back needing a rebuild with in the next year.

Mechanics are recommending if you have a car prone to this then do it now before it leaks. My buddy caught it in time (very little water and no rust yet) but the car in last week needed a new trans at the tune of $3000 instead of $200-400 for the flushes and additional cooler. Take it to a GOOD trans shop this problem is VERY well documented in their trade magazines and on the internet.

Nissan barely admits to it, and says it is not a recall-able item do to the mileage at failure.

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Old 03-31-2013, 09:51 AM   #2
Join Date: Mar 2013
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I have a 2008 Pathfinder with just over 49k miles. I just learned about this and I'm just sick about it! I'm going to check into doing what you suggest. Thanks!

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Old 03-31-2013, 10:14 AM   #3
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My old work van, a 1998 Dodge Caravan, had this happen at around 140,000 miles. I was on my way home from a job site and the tranny started slipping, I checked the tranny fluid when I got home and it was actually puking a tranny fluid/antifreeze mix onto the ground before I got the hood open. My boss had the radiator/tranny cooler replaced and then sold the van a couple months later. I then got a 02 Nissan Frontier CC 4X4, it has 98,000 miles on it now and has had its fair share of issues! My boss is getting a new work vehicle soon so hopefully I will get his 07 Titan CC 4X4 before anything more happens to the Frontier...
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Old 04-28-2013, 09:18 AM   #4
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I've done a little reading on this. Living in Minnesota I'm concerned about blocking off the tranny cooler line that goes into the radiator because it is also used to warm the tranny fluid in cold weather. Is that correct?
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Old 04-28-2013, 04:55 PM   #5
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Yes, that is correct. Water is a better cooling and heating medium than air.

GM engineering states the ideal trans temp is above 150 F degrees, and below 195F. Too low does not allow for a correct flow in the internal parts; too high and the fluid is destroyed.
Dexron IV is rated for 100K miles at a trans temp below 205 F degrees. If you run it at 220 F all the time, it would need to be changed at 50K miles, if you run it at 315 F, fluid will last only 2K miles (Not counting that at extended periods about 260 F will cause seals and plate material to self-destruct.)
However, the temps are accumulative; so that if for a few thousand miles you tow in the summer and hit 240 F does not mean the trans fluid has to be changed at 25K miles.
That's why it is recommended that if you tow, or live and drive in a mountainous area (and other caveats) you change the trans fluid at 50K vs. the normal 100K.
(New GM vehicles since around 200/2009 were shipped with Dexron VI, which is a heck of a lot better fluid than Dexron IV, so that chart is not that accurate since Dexron VI will last longer at higher temps and flow better and lower temps.)

I'll note that this internal cooler failure is not that unusual, and happens a lot to vehicles that are severely off-roaded (vibration is a killer). I actually replaced my radiator at 50K on my H3 just for insurance. And I also have installed an external trans fluid air cooler to help reduce the temps while towing and riding at highway speeds in the mountains.
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Old 06-12-2013, 10:54 PM   #6
Join Date: Mar 2013
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Ok, so not exactly the fix I was looking for, but some bonehead ran the red and took out my front end. Looks like I will be getting a new radiator after all.

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