New long block!

[JR]

I've been having problems with the engine in my Dodge Dakota overheating. I sent it to the Dodge dealership, where they changed the radiator cap, then closed the doors for good.

I sent it to the Jeep dealership, where they now do Dodge warranty repairs, and they changed the radiator cap (yes, again!). Somewhere along the way I had replaced the thermostat twice (I'd like to get my hands on the knucklehead who designed this engine with the thermostat located on the bottom of the block!).

I took it again to the Jeep guys, now with about 45K on the odometer. They wanted to give it back with no trouble found. I had a pleasant chat with the manager, who was very reasonable. He suggested to the service writer that the actual engine mechanic take a look at it. Apparently I had been stuck with the "driveability" guys doing the work. Engine mechanic takes a few days to tear into into it, and promptly declares it needs a new long block. Visible scoring on the #5 cylinder and implied head problem.

Two days later I was out the door for only $145 for plugs, oil, coolant, etc. A warranty finally worked out for me!

JR

[Uncle Cracker]

A warranty finally worked out for me!

Glad it did... Most of them are just worthless paper.

[mpc]

I'd like to get my hands on the knucklehead who designed this engine with the thermostat located on the bottom of the block!

JR

Bet that engine has a "reverse flow" cooling system. In the "old days" cool radiator water was pumped from the bottom of the radiator, into the engine block. From there the now-warmed-up water went to the cylinder head and intake manifolds. The idea was to WARM those parts to keep the air plus atomized fuel mixed properly but not let them get too hot either. Air+fuel flowing through a cold intake manifold pipe/runner wants condense the fuel out (think of morning dew on your lawn) so warming those parts helps keep the fuel suspended in the airflow. Also, for winter states, that heat keeps any humidity from condensing out or even worse keeps it from freezing. Private airplane pilots are familiar with "carburetor heat" controls for this same reason - gotta heat the carb up somehow on those air cooled airplane engines. (by directing some exhaust gasses near/around the carb or through a heat exchanger that bakes the air going into the carb.)

Anyway, with modern port fuel injected engines, gas is sprayed directly into the cylinder's intake valves. So there is no gas in the intake manifold to condense out... ergo it's not as necessary to heat it. Just keep it above freezing temps. So car makers now run the cooled radiator water to the cylinder head first (it's not really cold water, it's just cooler than the water coming out of the engine) and then to the engine block. This keeps the cyl head cooler than the old designs... and that allows higher compression pressures. Higher compression = better thermodynamic efficiency ==> more horsepower and better MPG.

And it also means a thermostat located at the "outlet" of the engine which is now down low. Of course the manufacturers could spend a few extra bucks and use a remote mounted thermostat to make it easy to replace... but we know they care more about assembly costs than maintenance costs.

Anyway, good for you that you (finally) got a proper long block replacement. Now find a way to get a new transmission out of them to really reset the mileage on your pickup!

mpc

[JR]

Great explanation, MPC. Thanks!

You're right, though, it's a maintenance headache. I didn't have a maint. manual, but I thought "How hard could it be to replace a thermostat? 20 minutes, tops." When I found it on the bottom, I couldn't believe it. I called my buddy over. He and I both worked in gas stations when we were kids. I made him go through the same process I did in order to find the elusive thermo.

After cursing for a good bit, it took us an hour to do the deed, and it was a mess.

It's running well, so I'm happy.

JR