Oddly, the 96 blazer im running is liking to overheat and can suck down a full load of 50/50 antifreeze in about half an hour.... no leaks to speak of. What could be the problem?

Heater coil?

 

Is it smoking? Ya might be consuming it. Gasket leak somewheres.

 

Hey,

1st off - Don't continue to drive it. If you're lucky it may only be intake gaskets but if it progresses, you could take out the head gaskets or crack the head. Have you checked your oil???

Bob

 

Like I said in the original post, NO LEAKS anywhere. Oil is fine, recently changed and nothing to suggest a failed gasket anywhere. No smoking either. Which is why I'm thinking heater coil... it is a possible solution correct?

 

Well, you statement on "NO LEAKS anywhere" and the fact that you are loosing coolant conflict with each other. If you are loosing coolant, you have a leak. If your heater core was leaking, you would smell antifreeze inside. If you have a blown headgasket, which is allowing coolant to get sucked into the cylinders, it would just get blown out the exhaust.

Now with the amount that it is going through. Are you saying that it's draining out the entire radiator in a half an hour? That is a HUGE leak somewhere along the way. If it is going through this much coolant and if a head gasket is the culprit, then you should be able to see signs of this on the plugs. You should also notice a stumbling or misfire on one or more cylinders (depending how bad the headgasket is).

I would pull your plugs and check them. Signs of a coolant leak into the combustion chamber should be a white, flaky coating on the plugs if the fuel/air mixture is actually igniting. If the cylinder is misfiring, then the plug should be wet.

You could also verify the integrity of the head gasket by doing a compression check.

 

sectshun8,

I had a similar (exact?) situation, I chased the problem for over a year. It seemed to get worse in the winter, so I was thinking it was a thermal expansion problem with the plastic tank radiator/hoses or something. First, I replaced ALL the coolant hoses, radiator cap, and thermostat. I thought all was good until the next winter when the recovery bottle continued to slowly go down. I then convinced myself that the radiator tanks were slowly weeping and I just couldn't see the leakage, I replaced the radiator. I kept an eye on the recovery bottle and again I thought all was good. Then, one day, on a short ride home from work, the temp gauge starts going above normal, osilates, drops back, and keeps repeating. I checked the recovery bottle - still full and check the rad - super low. I filled up the rad and went in the house. At that point, I started thinking..... I checked the oil.... Milkshake and overfull! I dove into replacing the intake gaskets expecting to have to pull the heads. Lucky for me, I didn't have to.

As for your situation, my guess (since I'm not there) is that when you filled your rad after it being empty, there was an air pocket that burped when your thermostat opened. It therefore allowed the coolant level to drop. If you were actually loosing coolant that quickly (and it wasn't in the oil), there would have to be a trail somewhere (out the water pump weep hole, out the drain tube below the heater core on the passenger side, on the passenger side floor, smoking like mad (head gasket/cracked head or block), or a puddle underneath). In my case, I think the leak was so small, that as it leaked into the crankcase and the engine heated up, it was just vaporized out the exhaust. It probably smoked slightly but I didn't notice it. At the time I replaced the gaskets, my '96 Blazer had about 118K on it. The 4.3 is notorious for intake gasket leaks. Some say it's related to Dex-Cool but thats a whole other debate! I switched over to 'normal' coolant at about 60K. For what its worth, if I was doing the work myself, I personally would much rather do the intake gaskets than the heater core.

Good luck and let us know what you find,

Bob

 

See my related post under "DEX-COOL". I chased a similar leak for about a month. While a couple of quarts leaked out of the engine, I got only a couple of drops on the garage floor, and could find nothing on the underside of the engine. My best guess at this point is it is a leak off of the intake manifold, where Blazer w/ 4.x litre Vortec engines is so susceptible. The marks on the garage floor are definetely in line with the rear of the engine, and there is no trace around radiator, heater hoses, water pump, or radiator hoses. Also no trace in the oil. It is leaking off the backside, and only when the engine is running outside on the road. I can't find any leaks from an idling engine.

A heater core leak would end up on the passenger side floor inside the truck.