I don't know much about glasspacks or how they do on Dakota's, but there are some things you and your dad can do to help out the 3.9. A Dakota with a 3.9 really is underpowered for is weight and size, and like Primus said you get used to it. You can start with a good tune-up, plain old copper core Autolite 3923 plugs work best in the 3.9. You can get them for about $1.50 each at Walmart, a little more at parts stores. Be sure to ask for and get plain 3923, not AP 3923. AP's are platinum and you don't need them. The distributor cap and rotor button with brass contacts work very well also in the 3.9, Napa part # MO 26 and MO 28. I personally like the Belden premium spark plug wire set from Napa, they are great quality and better than OE. They cost about $35.00 at Napa stores here in Florida.

While you are running down the coolant leak and flushing the heater core, change out the stock 195 degree thermostat for a 180 degree one. The PCM will think the engine has not quite reached operating temp and will advance the timing just a little. It's enough to give a mild boost in power and will help eliminate any preignition pinging, if you have any. The downside is your MPG might suffer. Don't use a cheap no name or store brand thermostat. The Napa Super Stat or Robert Shaw thermostat is best and well worth the few extra bucks. In my Dakota, a 180 tstat combined with a V8 TB from a 318 motor actually improved my MPG. Even the Dodge engineers did a study and found that the Magnum engines perform better at 182 degrees, but they had to go with a 195 thermostat to meet Federal emissions requirements. I think they did another study and found that the Magnum engines do better with copper core spark plugs too.

Something else you can do to help power at least in the 1500 to 2500 RPM range is to swap out the V6 throttle body for a V8 throttle body. The V8 one has larger bores and will get more air into the combustion chambers. Lots of us have done that and it has worked pretty well. You can find a V8 TB at a junk yard or online, for about 65 to 100 bucks. Be sure to get the throttle cable from the donor truck if the linkage connectors are not the same as yours, or just get the cable for the donor year model from the Dodge dealer.

You can also remove the rubber flap from the right side of the radiator between it and the passenger headlight, and pull off the plastic elbow from the air intake box. Both are restrictive to air flow. In my own Dakota I went a step further and took a Dremel tool to the front of my air box, and cut a larger opening in it. Doing that and using a good quality regular non-oiled paper air filter is every bit as good as an expensive cold air intake, at least on my truck it is. It just howls a bit when you floor it as in going up hills or passing someone.

You might also get a volt meter and test the center wire on the MAP sensor. If it's less than 2 volts at idle, replacing it may help the power problem. I think that's the way to test it. A Haynes book will tell for sure. There's a really long post on here from last summer called "MPG and Power problem solved" or something like that. Several of us took that guy's advice, got new MAP sensors and better performance out of it. My own MPG didn't really improve that much from it, but it helped on the butt-dyno. Autozone had the best price on it here, about $65.00.

Some here have gotten better performance from their 3.9 by using all synthetic fluids for oil, transmission and the differential(s). I just use regular Valvoline conventional 75W90 gear oil in mine, and Valvoline or Napa brand 10W30 conventional motor oil. I have never really bought into the synthetic oil thing, and I change my oil every 2800 to no more than 3000 miles. I have to use synthetic fluid in the transmission though, Pennzoil Synchromesh is what I use but I have a 5 speed NV3500. The manual trans fluid at the dealer is $16.00 a quart, Synchromesh is about half that and is the same fluid.

At 85,000 miles I replaced both of my upstream O2 sensors strictly as a maintenance item, they cost about $30.00 each from www.ntk.com (www.sparkplug.com). If you replace yours use NTK or Dodge OE. Don't use Bosch, they do not work well with Magnum engines. My truck ran some better with new O2's and a new MAP sensor. There is no need to replace the downstream O2's unless you have a code for it. They don't really do much.

Others here have put on aftermarket exhaust and said it helped power. Others have done that and put in 1.7 roller rocker arm sets and said it really helped. The 3.9 may not be the fastest thing on the street, but they are reliable as long as you take good care of it. For a V6 they are adequate and get fair gas mileage in a 3000 pound truck. Mine averages about 18 in mixed city and highway driving. One thing that I found helps mine is I give it a dose of Gumout Regane about every 5000 miles. It helps keep the fuel system clean and helps out on MPG, and my truck runs better with it. I'm thinking of trying some Marvel Mystery Oil in the gas tank soon though, I have been researching it online and a lot of guys have had good luck with it.

Good luck with yours and your dad's truck. Post here if you need more info.

Jimmy

 

Jimmy,

First of all I want to thank you for taking the time to write all that. That must have taken you an hour to do. Thank you very much!

Secondly, and not to sound unappreciative, but I have a few more questions. I got the Dodge back from the local garage and the Dodge is blowing hot air now. Thank God! What the garage did was flush the Heater Core. They were told to flush both the Heater Core and the Radiator but they didn't. Should I flush the radiator also?

Am I going to have to have the Heater Core flushed every few months? How often does this problem typically arise in a Dakota? This is a common problem with these little trucks and I would like to know just how often I have to look forward to flushing the Heater core.

Thanks a lot everyone! Thanks again Jimmy.

 

Glad to know you got it fixed. I'm no expert but if the coolant has not been flushed and it's 10 years old, I would most definitely flush it out. At that age if the radiator hoses and radiator cap are original I would definitely replace them too and use all new hose clamps. While you are at it replace the bypass hose at the water pump too, but it may be difficult to remove if it is the original part.

I don't know why the heater cores in Dakota's sludge up. Personally I think it's from not changing the coolant out on schedule and there is a reaction with the metal composition if the core itself that causes the coolant in the core to turn to Jell-O. Green antifreeze really should be changed out and a complete flush done every 2 to at the most 3 years. Around here you can get a power flush done on the radiator and cooling system done at most shops for about 60 or 70 bucks. It's done with a flushing machine and works well. They also add a chemical flush/cleaner treatment to it too.

Glad your truck is fixed. If anything else happens post here, there are a lot of knowledgeable guys here who can help.

Jimmy