I have the same problem as the gentleman w/ the '97 4x4 4.6. Intermittent overheating. The water pump and t-stat have both been replaced, as well as the radiator. Some one told me a piece of gasket material from the heater core may be floating around and periodically clogging things. Could this happen? and what’s the fix? Also, someone told the guy w/ the 4x4, that he could have blown head gasket, and to perform a sniffer test to find out.#1. What is a sniffer test? #2. If the head gasket is blown, wouldn’t there be water in the oil?
water in the oil is one indicator of a blown head gasket, the other is during start up is there and excessive amount of white smoke, or when you give it gas does it send out white smoke? either or is a head gasket or a cracked head, also there is a heat leak, that you only lose fluid when the engine is warm,
I see that I neglected to explain a “sniffer test”, all it is, is a simple test that any competent shop can perform for small fee or usually free, and it is a device that literally smells the coolant, and the exhaust, looking for water vapor and coolant in the exhaust fumes, and unburned fuel in the coolant, either says crack or gasket. my other question is were the radiator hoses replaced along with the radiator? if not- they could be collapsing under acceleration – demand, usually the lower one. Now as for gasket material – the only gasket that you engine coolant ever touches is – head, intake, water pump and thermostat – if one of these are out/blown usually shows in a big way, not always though!!! your radiator and heater core are both soldered or plastic crimped – no gasket material what so ever. now for material that’s big enough to plug up you cooling system – unless someone really dislikes you and put junk into your radiator or you have put so much radiator sealer in trying to cheap fix another problem I just don’t see that!!
You have basically three things that pass through the headgaskets, each in its own channel and all seperate; (1) the combustion chamber, (2) cooling fluid passages, and (3) oil passages. A “blown headgasket” could mean a breech between any two of those three things. Typically the combustion chamber will b einvolved, 'cause that’s the passage subjected to the high heat and pressures.
If the breech is between the combustion chamber and the coolant passage (the typical situation), than the high pressures of the combustion will blow high amounts of heat into the water jacket, causing overheating, and the loss of the cylinder’s ability to seal will cause the engine to run uneven, as in a rough idle. In addition, during the intake stroke when there’s high vacuum in the cylinder, the coolant (which is at about 16psi) will get drawn into the combustion chamber and get vaporized, presenting as white smoke out the tailpipe. A breech between the combustion chamber and the coolant will also allow mixing of combustion byproducts and coolant. Each explosion will blow these byproducts into the coolant. That’ll cause crudding up of the coolant visable in the fill hole. It’ll also often cause bubbles to come up out the fill hole (with the radiator cap removed) as the combustion gasses migrate up and out the coolant.
If he breech is between the combustion chamber and an oil passage, the heat from the explosions will cook the oil, and the intake strokes will draw oil into the chambers and it’ll get burned, producing blue smoke and crapping up the sparkplug and cylinder. Since the cylinders produce vacuum on the intake strokes, blue smoke will often appear during deceleration. However, bad valve stem seals are the most common cause of blue clouds, so one should not think a blue cloud on deceleration is a bad headgasket without more symptoms and more testing.
I think in summary you need to have someone evaluate the engine.