Need help on first step - 93 sport engine troubles

[geosnooker2000]

It may be time for a rebuild (who am I kidding, of course it is, it has 320,000 miles on it), but I would like some advice on my first step to diagnose the problems.

1993 Explorer Sport
2WD Manual Transmission
320,000 +/- miles
I am the second owner, got her with 166,000 on odometer in 2000.

History - 2 years ago I was driving in the city in rush hour to a class I could not be late for. About 5 minutes from the University my radiator overheated and boiled out into the overflow tank. It started to run hot. I could not stop. I was within 6 or seven blocks of my parking lot, and I just pushed on to get there. It was weak as a kitten as I pulled in. Barely made it into a parking spot. I knew it was bad. I just let it sit there for the rest of the semester. I had it towed home. Surprisingly, after it cooled down, it ran as strong as an ox. Maybe I dodged any serious damage?

That summer I did my research and decided that I had cracked heads. I bought 2 remans from Alabama Cylinder Head (Look out. They are out of business now). I guess I should have had them looked over by a machine shop, but I am too trusting of a person I guess. I just slapped them on. New head gaskets, new head bolts, new plugs and wires, etc. I thought I did a slow and deliberate job. Cleaned the upper and lower intakes as thoroughly as possible, stuff like that. I fired it up and test-drove it for about an hour. It ran hot. Real hot. Then all of a sudden, something gave way and the temp gauge plummeted down to where it was supposed to be. It ran fine after that for about 2 or 3 months.

Then it started. The temp gauge on long trips would bob up and down, not like before the head change because of heat buildup and pressure release, but with the terrain and throttle changes. Uphill would drop the temp and then start to raise it. Acceleration would lower temp. Chopping the throttle would raise it. Kinda sounds like an ineffective impeller on a water pump? I might mention this was in conjunction with changing out the thermostat several times in order to eliminate that as a possible cause.

Whatever the cause, it was not bad enough for me to do anything about, and soon I was worrying about a far more sinister problem. I started noticing a puff of white/blue smoke on start-up every morning. AND, my mileage dropped from about 21 mpg to around 14-16 mpg. Valve seals? I put the truck on hold, and drove my 1996 EB 4WD instead.

Sadly, due to legal reasons, I don't own that 96 anymore, and need to restore this 93 for my DD needs. I started driving it last January, and just made damn sure I kept enough oil in it. Well, now I am using almost 2 1/2 quarts every tank. There are NO leaks. The driveway is clean. This has to be internal, but it is hard for me to believe I am losing that much oil through a defective valve seal. The engine could be getting 14 mpg because the cylinder walls look like a canyon wall, or the oil has fouled a plug or plugs, or I have a (or several) broken piston rings, or all of these.

If I'm going to rebuild this engine I need to get going. My senior year is fast approaching, and I need a DD within about 45 days. I think it would be a tremendous learning experience to do the work. I have a machine shop that has agreed to boar or hone, and clean the block for $250.

But if I don't actually have to go past the heads to fix this engine and make it run right, I don't want to remove the engine and spend that kind of money on a master rebuild kit.

In short, what is my first move? What do I check 1st, then 2nd, and so on?

Any help would be greatly appreciated.
George

 

[geosnooker2000]

After browsing through Chapter 2D in the Haynes manual, I suppose I need to do a leak-down test. I wonder if my local AutoZone rents that tool out?

 

[arco777]

With that kind of oil consumption, any head work is unlikely to help the issue. If it is for sure being burned, you're going to need to tear down the block.

As for your cooling issue, sounds like a water pump or a blockage in the radiator.

By 320k miles, everything on that motor is going to be getting tired. You could spend a ton of money rebuilding it and fixing all possible failure/wear points, but...

If I were you, I would look into a junkyard motor with lower miles. With as many vehicles as Ford put the 4.0L OHV into, it is not impossible to find a wrecked or blown trans-equipped vehicle with a 150k mile 4.0. A reasonably priced yard should charge you under $300 for a long block with heads included. Swapping the motor into your truck will also not take anywhere near the amount of special tools that rebuilding one will. You should be easily able to swap the truck within 45 days, and at the same time you can easily refresh all the leaky gaskets if desired. A proper engine rebuild may really stress that timeline.

 

[geosnooker2000]

Great ideas! Thanks.
But... a quick search on line has yielded only a few engines, the lowest of which was $400 plus $200 shipping. I will try U-Pull-It in the morning.

 

[geosnooker2000]

@ ARCO7777- Great tip! I called today and they said $200 for a u-pull-it engine.

Now, TO EVERYBODY... can I pull any 4.0L OHV from newer models (chance of less miles on an engine)

Do I need to stick to manual tanny-mated engines, or will any 4.0L OHV with an "X" in the eighth digit of the VIN do?

Also, any tips on pulling an engine from a U-Pull-It lot? I mean, they do not allow jacks. How do you do it without killing yourself?

 

[arco777]

Transmission does not matter to the engine really. Flywheel vs flexplate is the only difference you should see when bolting it in, and that's easily swapped. Technically the cams are slightly different between manual and auto equipped models, but you probably won't notice the difference. Manual cams usually make a bit more torque down low.

Newer model OHV motors should fit without issue but do a forum search on OHV differences to be sure. The intake manifolds are different in some cases, but you should be able to re-use your 93 model upper and lower intakes.

I don't know about U-Pull-It, but at Pick-N-Pull lots they have chain and pulley cranes that you wheel around to whatever car you want to work on, lift the motor, and wheel the crane back to the exit if you need to drop it into your transport vehicle. I'd guess U-Pull-It is similar - people can't be expected to lift motors out by hand! Additionally, it is often difficult to unbolt the motor from the transmission. At a yard you can use the crane to lift both out together, then separate them. No worries about breaking stuff that you won't be needing!

Also a trick I have noticed about the "no jacks" rule. These yards are supposed to pull the factory jacks out of the cars as they come into the yard, but they often miss jacks. For example, Jeep Cherokees have the jack under the rear seat and it's often overlooked. Many minivans have hidden jacks too. Any time I have ever needed a jack at a parts yard (several times) I was always able to find one that the employees missed. Another option is to grab one from near the cashier where they sell them, then go back to the yard with it (don't get seen).

Yard policies vary on power tools; sometimes you can use cordless tools. A grinder and sawzall can be very handy. However if the yard doesn't allow these, what I use is a cordless Dremel. Many times a stubborn brake line or fuel line won't come free and it is far easier to cut it off than to fight with it for an hour. Something to consider.