Friday 16 September 2011

Changing my head gasket..?

did it a couple years ago.. but its been a while i ahve a j30 infinity 1997. for some reason my girl was driving it and it broke down.. come to find out.. it had no water. she also has a hole in the radiator.... bleh lol... but it has a smell.. a smell that i remember to be a blown head gasket. im going to be welding the radiator shut tomorrow when i wake up but if it isnt the radiator. i think it might be the head gasket. is there anyway to be sure its the head gasket.. if so please give me a check off list what to dissconnect.. i know the spark plugs.. spark plug cables. fuel line i think.. and i dont remember what else... thank u and good night il check my answered in the morningChanging my head gasket..?A lot of people forget about smells (probably because they're so difficult to describe) If it's the same smell as before then chances are it's probably the same problem.



If you can get access to a source of compressed air then IMHO the best way to check would be a Leak-down test (it's so much more use than a compression test as it gives it lets you find where, as well as how bad a problem is!)



It's fairly easy/cheep to make your own leak-down tester, the only thing you need to be a bit careful with is drilling the calibrated hole.



Disconnect/unscrew ALL the spark plugs, and uncap oil/coolant caps. Plug the tester into a cylinder and see what the reading it gives. It's it's really low then you've probably got a valve open (or the engine is completely knacked!). You need the valves shut to find out more. If ONE of the driven wheels is off the ground, and car is in top gear turning the wheel will turn the engine/close the valves.



ALL piston engines will leak some air in the test, and you should be able to hear a hiss where its escaping from. If it's a blown head gasket then you'll should get air escaping out of the radiator cap, depending on how the gaskets blown you might get a little coming out the oil dipstick (although that's usually air that's getting past worn rings) Air coming out of exhaust/air means you have leaking valve, or have not shut them. The percentage difference between the gauges show how bad a problem it is.



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Not relevant to your problem but if careful you can find out if the cylinder has a chunk/scratch out of it by lowing the air pressure, and slowly letting the piston descend. (This can be the cause smoking, but is v difficult to spot using a compression test) If there's a scratch the percentage difference between the gauges will increase where the piston rings are on the scratch



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White smoke (steam) in the exhaust would suggest water getting into the cylinder. Doesn't always happen with blown head gasket.
Changing my head gasket..?
Could also do a variant of the leakdown test and connect low pressure air into the coolant system. Where there's a hole, you'll end up getting a hiss of escaping air.

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Changing my head gasket..?
after the radiator is sealed and then its all good to go, put it back in the car and full it with water. leave the radiator cap off then start the car. if its a blown head gasket, the air from the compression of the cylinders will escape through the head gasket crack and shoot out to the radiator. the water/coolant will shoot out high, or it wont shoot out at first and after like 15 seconds a lot of it should be coming out. usually not much comes out! haha
What you are smelling is antifreeze, that could be coming out of the radiator a bad hose or many other places. To answer your question on what all to disconnect, I would recommend that you buy a chilton's or Haynes book for your car.

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