Higgy

I'm a little confused.. you have an 08 and can get a blink code off the dash? What engine is in that truck? An 08 should have an MP engine which does not use blink codes. Not that I am aware of, anyway.

I would imagine it is because your engine is typically under constant load when your rolling on the highway. City driving would give it time to recover at stop lights and what not. If I were you I would drain your coolant, put a new set of t-stats (can't hurt) in it and take a look at that screen that MackPro was talking about. If you do pull your t-stats, you can test them in a pot of water on the stove and a thermometer in the water. I think they are supposed to start opening at about 170 and be fully open at 195 or so. Can't remember exact temps.

I'll chime in here. I just joined this forum and I feel like I'm posting all over the place.. as if anyone cares what I have to say... I like the mDrive, also known as Volvo iShift. The only difference that I am aware of is that Volvo uses a shift knob mounted next to the driver's seat and Mack has a dashboard mounted shift pad. They pull hard. They do get good fuel economy. A week or so ago I happened to check the fuel trip history on a Volvo VN with an iShift and 475HP D13 (which is a green MP8) and according to the ECM it was getting 8.1mpg. It's kinda cool to sit there and do nothing except hold the throttle on the floor and let it do it's thing. I have only driven one mDrive so far but with a Volvo you can you can hold down the engine brake switch and slow to a crawl from 65mph just hitting that one switch. It works smooth. I think it is the smoothest operating automated truck transmission ever. It's years and years ahead of any Eaton Autoshift that I know of. Maybe Eaton has something in the works, I don't know. They better if they intend to compete with Volvo. The iShift has been in the Volvos for several years now and I do not remember seeing a major iShift failure come through our shop. The only times I can think of an iShift with a problem in our shop were just air leaks from around where the ECU mounts on top of the case and we've replaced a couple iShift ECUs. The only campaigns I can remember on it were just software updates. It's pretty cool to see inside because you look down inside the case and there's not much there. It's a single counter shaft design. I still would not have one if I was an owner operator. This should be an interesting read if you are interested in the mDrive. Someone please let me know if this file doesn't work. It was too big to upload so I had to compress it. mDrive - Design and Function PV776-88979192.zip

mDrive design and function PV776-88979192.zip

..and don't forget to drain your tanks daily. I know most people almost never do this. I'm sure it helps after a compressor failure.

Yep.. change that dryer cartridge.

Pull the harness wires out as much as you can and check them real good. Could be a bad spot in the wires causing intermittent open. It is also possible that when you stuck the paper clip in the female connector terminals that you spread those terminals out to where they are now making poor contact. You could pull a male terminal out of your old sensor connector and stick it in the female side. The terminals should have a decent drag on them to be making good contact.

The black smoke may or may not be related, could just be a boost issue causing the smoke. Trucks are hard to fix over the internet.

So from what I understand, it is not actually overheating. Your fan is cycling excessively to keep it cool? By excessive I mean on/off/on/off/on pretty quickly.. right? This is usually caused by poor airflow across the radiator for one reason or another. Your fan is working hard to keep it at temp. I know you said you have a new CAC and Rad in there. Check for anything that would cause poor airflow like the radiator fins plugged with dirt, fan clutch itself may be weak, make sure belts are in good shape, tensioner allowing belt to slip on fan pulley, fan shroud missing or broken, . Also possible you could have an internal cooling system restriction such as stuck closed t-stat. Macks seem to have a lot of casting sand in the block that has been known to cause internal restrictions after the engine gets some hours on it. I have seen this sand crap plug the elbow fittings for the bleed lines to the surge tank and cause running hot complaints. This is also another reason that screen is in front of the oil cooler inlet. Make sure the weep hole in the water pump is not leaking, if it is, change it out. That's about all I can think of. Good luck to you, sir.

If they put a new y hose on it, they almost surely checked the screen, it basically falls out when you pull that hose down. I would not throw that screen away. If it's dirty or broken (sometimes they get so plugged the top gets pushed out from the pressure) it should be replaced. That screen is there to protect the oil cooler core from becoming plugged with trash. Not a bad idea to replace the thermostat. Do you have any other symptoms? Does it push coolant from the radiator cap or from the pin hole in the center of the expansion tank cap? If you have been adding coolant and can't find any external leaks, you should pull the piping off the egr cooler and have a look down those pipes as shown in the service bulletin posted above.

Did you put a fat pea size drop of silicone at the four corners of the block where the flywheel housing meets the rear and the timing cover up front? If you don't seal those four seams, it will leak.