My work van has developed a small coolant leak and it's draining down into the driver side spark plug wells. I can see it coming from right behind and below the thermostat housing.

Has anyone done this job, is it something that I as a fairly capable mechanic can tackle on a weekend or is it not possible to do in a driveway?

I'm guessing I can remove the intake with the fuel rails on it and swap those over on a bench to make that part easier.

 

I had vans develop this and replacing spark plugs and coils on the misfiring cylinders actually stopped/slowed the leak to where it wasn't an issue for a long time. I think there may be a very small leak which over time shorts out the plug causing that part of the engine to run cool and exacerbate the leak because of uneven heating. I honestly had vans doing exactly what you described and was able to run them without problem for long periods of time by simply replacing the plug and coil. That said, I also had a couple of them get so bad that I had to change the manifold gasket.

You can do it in a driveway on a weekend, but don't plan other activities that weekend. It's a bit involved. I wouldn't recommend for a novice, but intermediate and above should be ok. If I recall correctly, I pulled the fuel rails off the top of the injectors to get it out of the way and might have pulled injectors out. That's not difficult. It's just all the little stuff you have to mess with.

 

Thanks for the reply - I think it's been leaking very slowly for a few months, but I was passing someone on a 2-lane highway not long ago and it suddenly dropped a cylinder. I changed the plugs thinking there was one bad or fouled since they had 120,000+ miles on them as well as getting a #6 misfire code, and found that well full of coolant.

Just looking at the new manifold, it doesn't look too hard. If I can remove it with the fuel rails on it, it should be easy to swap over. I did find one video where the guy just gave the pointers and showed footage of the engine with the manifold off - he didn't even remove the coils, just unplugged the wires.

 

So this turned out to be a lot less of a chore than I expected. I figured I'd share some things I learned.

1) It wasn't a 5.4, it was a 4.6, didn't realize it until we had the manifold almost completely loose.

2) The manifold wasn't cracked, just the gasket.

The one thing that would have stopped the job would have been the EGR tube, and it took two of us to break it loose at the valve. I soaked it with PB Blaster and it got to soak for an hour, and I coated the threads liberally with anti-seize before reassembly. There was no accessing the fitting at the manifold, but once it was loose at the valve and the bracket unbolted from the plenum I could flex the pipe about 1/8", turn the valve a 1/4 turn and it came out very easily.

We removed the fuel rails while it was on the engine, but it wasn't necessary. I reassembled them on the manifold and they didn't get in the way at all on installation. The fuel line has a quick disconnect, which I made a tool for out of a plastic conduit fitting.

There was a LOT of debris around and under the manifold. A rock about 3/8" fell into one of the spark plug wells, which would have caused a much worse problem if it had fallen into the engine. We should have blasted it thoroughly with compressed air first.

The manifold came out from the rear (It didn't look like it could come out the front without removing the grill and radiator), the only thing really in the way was a tube pointing up from the coolant crossover. I just had to unbolt it from the back of the engine and it dropped down.

We used the Dorman manifold, which I would not recommend. It was a nice complete kit and it's supposed to be a better design to have fewer problems, but the whole thing was a good 2" shorter which is what I think has noticeably cut down on the power. It runs fine overall but the top end is about gone.