legacycentral bbs

Anybody know a good method of testing a water pump? Just bought a '97 GT sedan (cheap!) to play with and the previous owner said it got kind of hot a couple of times. Today I put a new thermostat in it and flushed the engine and radiator really well with the hose, seemed to have good flow through both. Let it idle in the driveway for a little bit and the gauge leveled out right in the middle. Took her for a spin and after about two miles the temp started rising like crazy. Had to limp home with a combo of coasting with the engine off and occasionally just sitting and letting it cool down for a few minutes.

Does it make noise or leak from the weep hole at the bottom? That's all I know of. You might have a bad head gasket.

Nope, no noise or weeping. I've never quite understood how a bad head gasket causes overheating, can anybody help explain that?

I think it causes overheating because it usually burns up coolant in the cylinders and/or mixes the coolant with the oil and that doesn't cool your engine very well and I doubt coolant lubricates your engine that great either.

Also air from combustion gases can get into the cooling ducts, displaces coolant, and blocks flow.

Bubbles in the overflow bottle......... I wonder what percentage of ej25d engines have had head gasket failure.

That's a head gasket, then. What seems to happen is that the air gets trapped in the pocket by the water pump impeller, blocking flow. It gets progressively worse, especially at a steady speed. A limp-home method would be to remove the thermostat and stop every so often to squeeze the rubber hoses to displace the air. Only works for so long, but it could mean the difference between getting home/mechanic or waiting and paying for a tow.

Typically if it doesnt overheat when idleing, but it does when its driving, and is a manual (some models/years have trans coolers built into the rad) then its a headgasket or a leak in the system such as a rad. cap, or hose.

But, (if its an auto and the cooler is built into the rad) the possibility of having low fluid, a bad tq converter or burnt clutches will skyrocket the temp of the fluid that transfers into the radiator. You obviously wouldnt see this case unless you were driving.

Most likely its a blown head gasket. Best option to check is to do a leakdown test (which could also lead you to bad rings/valve seals with higher mileage) which will tell you which cylinder is blown or between which cylinders. You could also do a compression test.