4Xtruck

I've owned this 1997 2.7 Tacoma for almost 3 months. I've done a lot of work to get this truck in good mechanical shape. During this time, my check engine light went on twice. On both occasions, I overfilled my tank with gas and then drove 10 miles home. The next morning, I experienced rough idling for about 2-3 seconds when I started the truck, then everything smoothed out, but the P0304 code was thrown (misfire in cylinder #4). The CEL resets easily. This truck purrs like a kitten and the temp gauge stays on the cool side at all times. I don't burn any oil. This doesn't happen if I drive 15 miles after filling up the tank. Gas mileage is excellent (compared to my old 22re). I do notice that my coolant slowly goes down, and I can't find any leaks. There is no coolant in the oil. I'm thinking the problem may be a small leak in my #4 injector or a leaking head gasket. I'm in the process of building a leak-down tester to check for a potential head gasket leak.

Has anyone experienced these symptoms before? Do you have any other suggestions of something to check, other than what I've already mentioned? Any and all help would be appreciated.

tantacoma

Hopefully, the slow coolant leak may be due to a pinhole in the upper part of the radiator (venting steam instead of liquid). This happened to me once.

4Xtruck

I hope that is it. Would that need a pressure test to prove?

tantacoma

In my case, I was able to see the small jet of steam coming out from a small hole in the upper part of the radiator. I had to run the car and get it to normal operating temperature. If the rad cap is working properly, there should be about 14psi in the cooling system, pushing the steam out.

4Xtruck

After doing a leak down test, I can't understand how this truck runs so well.

Cylinder #1 showed a drop from 100PSI to 20PSI, with much pressure coming out of the exhaust pipe.

Cylinder #2 showed a drop from 100PSI to 0PSI, with air coming out of the throttle body (I could hear sounds in the exhaust pipe, but there was no air coming out).

Cylinder #3 showed a drop from 100PSI to 0PSI, with air coming out of the throttle body (I could hear sounds in the exhaust pipe, but there was no air coming out).

Cylinder #4 showed a drop from 100PSI to 0PSI, with air coming out of the throttle body, exhaust pipe and radiator. This must be the cause of my loss of coolant and P0304 code.

I'm sensing the head gasket is bad and the head needs to go to the shop to have the valves re-worked. Since the truck runs so well, I'll put this on hold till next summer. Any other suggestions any of you might have?