Coolant Loss from the Lower Intake Manifold Gasket

Contributed by Ken Hayes

If you can't find your coolant leak, here is another place to check I was experiencing a progressive coolant loss that started about three months ago. After reading many Internet posts about cracked heads and blown head gaskets, you could imagine my fear about finding and correcting my coolant leak. My 92 4.0L had a running leak that appeared to be coming from above the engine mount on the passenger side. I corresponded with a mechanic and inquired about a possible freeze plug problem - hopefully instead of the head gasket. He told me that there was a freeze plug above the engine mount. I inspected the freeze plug and found no problems. Still suspecting the worst, I decided to check other Internet posts for coolant loss problems. One lady had a similar problem coming from the intake manifold gasket.

I crawled under my Explorer (for the 15th or 20th time) and found one drop of green antifreeze on the bottom side of the front protrusion of the head. Further investigation (OK, a great deal of time under the Explorer with it running and off) found that the coolant apparently was leaking down the front side of the engine, dripping off the oil pan stud on to the transmission cooling lines, running down the cooling lines to the bracket behind the engine mount, and dripping to the ground from there.

I spent $80 at Autozone for the valve cover gaskets, RTV, intake manifold gaskets, and a cheap torque wrench.

I followed the Haynes manual to the letter (well almost). I started at 10:00 AM and finished at 6:30 PM with one 30 minute break for lunch. Not complicated, but a great deal of stuff to remove. I found a crack in the lower intake manifold gasket at the front water port on the passenger side. Also, I found corrosion on the rear water port locations of the gasket. This repair solved the coolant loss problem and that of my leaking valve cover gaskets and oil coming from the intake at the front and rear of the vehicle.

Almost everyone knows this but - If you attempt this repair, I recommend the following:

1 - Be careful with all connectors, especially the fuel injectors. The plastic will become brittle with time and temperature. I broke three of my snap hooks. Go ahead and unplug the main connections by the alternator for the fuel injector and sensor wire harness. This will allow you to flip the harness out of the way when needed. The Haynes Manual I have does not illustrate this, it will come in handy.

2 - Don't try to keep the alternator on and perform this operation. You need the space. Especially at the heater hose clamp.

3 - Go ahead and remove the thermostat housing. You might want to replace the thermostat any way.

4 - Be sure to form the new lower intake gasket. The new gasket will be stiff. Form and mate it to the heads and valley after cleaning and before placing the RTV.

5 - Cover all openings to prevent gasket material from entering.

6 - Original valve cover gaskets will require some manhandling to clean away. Do one side at a time.

7 - Get the Haynes manual and follow the RTV instructions to the letter. You will understand this when you have the engine apart.

I was losing about a cup a week and then a cup a day. My repair was successful. No more leaks. I just wish I took some pictures to show everyone the crack in the gasket. It's unbelievable how small of a crack can cause so much headache.

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Added February 10, 2000