Q: Showing signs of a blown head gasket.

asked by on February 14, 2017

Truck overheated this morning, engine died. Radiator was bone dry. I had some bottles of water with me, so I poured that in once it was cooled off. Was able to crank the truck up and bring it to a gas station down the road where I was able to fill the radiator. Showing signs of a blown head gasket (overheating, tons of smoke coming from tailpipe, water shoots out of radiator when I fill it up), but when I checked the dipstick, the oil seemed perfectly fine. I just changed the oil last weekend, so I don't know if that has something to do with it. I would think that I should still be able to see something in the oil if it is a blown head gasket. Also, while I was driving back home from the gas station, the smoke stopped coming out. It seems to only smoke when the engine is cool, but there is a definite smell of coolant when it is smoking. Just trying to figure out if there's anything else it could be besides the head gasket.

My car has 209000 miles.
My car has an automatic transmission.

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If there is a head gasket leak, as the engine heats up and expands, that may be sealing the leak somewhat and that would explain your experience. Based on what you are describing, it certainly sounds like a break at the head gasket is likely and/or you could have even gotten cracks in the head or block. All the possibilities would be investigated on disassembly. Overheating will often ruin the thermostat, of course ensuring (or at least contributing to) continued overheating even if nothing else (like a head gasket) is wrong and the coolant level is restored. To get to the bottom of this there are a couple strategies. You can check for exhaust gas in the coolant, you can check for cylinder leakage using a leak down tester and you can see if there is coolant loss as you drive the car. If there are no external leaks, and yet you have coolant loss, that would be a sign of a head gasket leak.


As far as resolving this, if you do attempt a repair keep in mind that cylinder head gasket replacement requires strict adherence to Factory Service Manual specifications particularly regarding block and head flatness. Overheating tends to warp these surfaces and consequently the head and block have to be carefully measured before gasket replacement is even contemplated; these surfaces have to be flat within .002 inches, which is one-half the thickness of a human hair. Also, head bolt replacement and torque sequence, surface preparation (surfaces have to be perfectly smooth and mirror-like before gasket is applied), and so forth, are all critical. Unless the conditions are perfect, leaks are actually common. That’s why a lot of shops won’t do the work because it takes too much effort. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine overheating diagnostic and the responding certified mechanic will identify the problem and estimate a repair strategy to get your car running again. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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