Weird temp gauge bobbing and coolant loss

[geosnooker2000]

Hey guys, I've got my 4x4 '96 EB 4.0 up and running from a 2 year hiatus. It was running like crap, so I changed the plugs and wires, and it ran even worse. It went from 18 -19 mpg on the hwy down to about 14mpg. So I thought "what would I have done in changing the plugs and wires to make it worse?"

To cut to the chase, nothing. It was corrosion build-up in the coil unit. I replaced it with a new one from Auto-Zone, and it gets 22mph now. The best it's ever performed.

The problem is...... It's loosing coolant, and I can only guess it's going out the tailpipe. There are no obvious leaks anywhere else. AND, my temp gauge is bobbing from 1/4 to 1/2 once it warms up. I figured that could possibly be fixed with a new thermostat. But I doubt that has anything to do with the coolant loss. It is possibly an indicator that it is happening, but it's not a cause, is it?

For some reason it's not forcing gasses into the coolant system like my '93 did last year. (on my '93 sport, it would force gasses into coolant system, blow past the radiator cap and burst out of the overflow....... then it would overheat) This '96 is just loosing coolant and I don't know how to tell where??? And as I said, it's not overheating, it's just fluctuating from low to medium.

PLEASE don't let it be a blown head gasket PLEASE!!!!!!

What do you guys think? any ideas?

 

[FIND]

Well, you could have a bad intake manifold gasket if you were actually leaking coolant into your intake, but, a slow leak elsewhere is not always obvious. Your gauge problem could be caused by air bubbles in your coolant system or a bad sending unit. Good luck with it.

 

[geosnooker2000]

Well, you could have a bad intake manifold gasket if you were actually leaking coolant into your intake, but, a slow leak elsewhere is not always obvious. Your gauge problem could be caused by air bubbles in your coolant system or a bad sending unit. Good luck with it.

You say that as if it WOULD be obvious if it were leaking into my intake. Is it? What do I look for?

Not a bad sending unit, as the heat blows hot when the gauge drops, and then not-so-hot when the gauge is rising, indicating that something IS restricting the coolant flow and then releasing it, over and over again. Could something besides the thermostat do that? Like maybe a water-pump going bad?

 

[windsors03cobra]

Head gasket all day long, I would also have the heads checked for cracks and milled.

 

[geosnooker2000]

Head gasket all day long, I would also have the heads checked for cracks and milled.

Then how come I'm not getting boiling over pressure into the radiator?

 

[FIND]

A leak in your lower intake manifold may not always be obvious either. If you suspect a head gasket or intake manifold leak, pull your plugs and check them, though, you are correct. Normally the head gasket leaking in such a way that it goes into the combustion chambers and not the oil would cause bubbling in your radiator.

 

[drbenz]

If you can't see a leak it's time to pressure test the cooling sys and check for a leaking head or gasket with a block tester. A local shop can do that for you if you (likely) don't have the tools yourself. It's a lot better than guessing.