Exhaust system preventive maintenance

[Kirwin]

I have been following the issues with the 4th generation trucks and that has led me to believe that I might someday have to replace an exhaust system sensor. I bought an extended warranty from Easy Care when I bought the truck from the dealer, but I'm still not sure if the DPF and NOX convertor and their associated sensors are fully covered. The warranty paper work is silent on these components, but does state that the exhaust system is not covered except for the manifold and the turbo. Sag2 posted that if the Ram dealer has a sensor gall in the exhaust and they can't get it out, they replace the exhaust component on Ram's dime. I don't want to have to pay for a new NOX absorber or DPF due to a galled fitting. So at just over 5,000 miles, I decided to remove and reinstall the sensors with a generous dose of Molykote P37 paste. I was introduced to Molykote during my time in the U S Navy submarine service and if you use it, stuff just comes apart, even years later. Its rated for high temperatures up to 2550 F. So I started with the sensor on the pipe just before the inlet to the DPF. There are a total of 5 of these fittings that utilize an 11/16 wrench. I removed each one, coated it, then reinstalled it. These connections came apart easily and the sensor does not turn with the fitting so you don't even have to disconnect the wiring. The next two connections are the up-stream and down-stream pressure connections for the DPF D/P detector. These connections also came apart easily and were done in no time. This left me with the 2 NOX sensors. These are a little more difficult to reach and utilize a 22mm wrench. Additionally the upstream sensor that is located on top of the NOX convertor does not use a separate threaded nut unlike the rest of the sensors. You have to disconnect the wiring and turn it with the sensor to remove it from the welded in bung. The connector mounts to a black box on the inside of the frame and utilizes a yellow lock tab that you just slide down and the wiring connector came apart with a little rocking motion. Once I got it out, it was just like the others and went back together just like the others. Then I went after the 10mm bolts that clamp the DEF injector to the exhaust pipe which, like the other fasteners, were also a potential show stopper. So I removed them one at a time coated them with Molykote and reinstalled them. These bolts in my opinion were the most likely issue in the future as they are common low grade steel bolts threaded into a steel backing plate that as best as I can tell is welded to the inlet of the NOX convertor. I'd suspect that in the future if I hadn't done this, these bolts would most likely twist off. During this portion of the evolution was when Murpy's law struck. I dropped one of the 10 mm bolts into the can of Molykote. Crap, how can I be so stupid. 20 minutes later after finally taking the can apart and removing a good portion of the Molykote, I got the bolt back and on I went. Not a bad job. I did it laying on my back without lifting the truck. Hope this helps. Ken Irwin

 

[JLandry]

Good writeup Ken.

Thanks for sharing it.

John L.

 

[dloughrey]

Very good writeup! Thanks for the information, I be doing this to my truck.

 

[MJWenrich]

I am curious if the Molykote paste is similar to anti seize. Some new sensors already have a coating on them and some anti seize is advertised as sensor safe. Have you found the Molycoat works in those applications? And I thank you for the information on the Molycoat as well. Sounds like a great item to have on the shelf.

Mike

 

[LocoPilot750]

Looks like quite a bit of the Emission system is covered for 5 years 50k. And some is covered 8-80k, I find this on P.20 of the 2014 Warranty Information booklet that came with the truck. The DEF system in included.

 

[Kirwin]

I am curious if the Molykote paste is similar to anti seize. Some new sensors already have a coating on them and some anti seize is advertised as sensor safe. Have you found the Molycoat works in those applications? And I thank you for the information on the Molycoat as well. Sounds like a great item to have on the shelf.

Mike

Molykote P37 is an industrial antiseize paste and is used on steam and grade A clean systems. You can google it and it will show it to be recommended for these type applications. All the sensors appeared to be dry except the forward NOX sensor. That sensor definitely had some type of antiseize on its threads. I was careful to ensure that none of the paste got inside on the actual sensor itself though. I think that would be prudent with any type of antiseize compound.

 

[LocoPilot750]

Does the sensor have to be grounded? Too much stuff on the threads could keep them from making a good ground.

 

[Kirwin]

Does the sensor have to be grounded? Too much stuff on the threads could keep them from making a good ground.

Each sensor is at least a 2 wire sensor. The ground is in the harness for the sensor. So far so good, I don't think that the Molykote will interfere with the sensor operation as long as you don't get the paste on the sensor element itself. It's just like any type of paste anti seize, a little goes along way. Ken Irwin

 

[TimothyLong]

Good write up, Ken! Thanks for passing this on!

 

[Joseph Donnelly]

I used Never Seez on the sensor threads; SAG said they still may seize up over time even with something on them. Also, put some anti seize on the threads of the strap clamp on the tailpipe to the rear trap.

 

[JJPage]

Exhaust maintenance (scheduled)...kind of keeps my fondness to my 03 alive. Can't deny a brand new truck does not appeal to me though.

 

[Kirwin]

I used Never Seez on the sensor threads; SAG said they still may seize up over time even with something on them. Also, put some anti seize on the threads of the strap clamp on the tailpipe to the rear trap.

I'm not sure I know what you mean by the last part "strap clamp to the rear trap"? What clamp are you talking about? Rodger that on that they may still gall, but I at least I have the satisfaction that I did everything in my power to prevent an untimely DPF or catalytic convertor replacement due to a galled sensor fitting on my dime. Ken Irwin.

 

[Joseph Donnelly]

Follow the tailpipe forward. Where it fits into the rear trap's outlet, there is a band clamp about an inch wide holding the tailpipe tightly.