Engine Overheated Then Started Knocking Really Loudly :/

southern_boy

New Member
Apr 6, 2010
20
0
1
Texas
Been gone a while guys but I am back but unfortunately with problems and worry. I drove my 67 around and before I knew it my temp was skyhigh and I pulled over to see what was going on and my 289 started throwing up it's coolant from the overflow hose and from under the Cap. So I let it cool then I hurried the old girl home. But as I arrived the poor girl started knocking and clanking like no other. I hit get parked and shut her off and she continued to run clacking and clanking and rattling away I had to cycle the key a few times to get her to go down. But the knocking was that of nightmares. The overheating I found was caused by the shop using a gob of gasket sealant on the thermostat gasket that then got into her thermostat clogging the poor girl up. I haven't started her since worried about the clanking noise. What was it and is she going to be ok without another rebuild?
 
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Well it could be that you've already done the damage and starting it back up is the only way to find that out. Sometimes overheating in itself will produce weird noises. Your thermostat for instance could have been "popping" open and closed (binding) making some of that noise. It also could have been that your cylinders were so hot that your fuel was preigniting. First will it still rotate? If so you'll need to start it up again paying attention to your oil pressure and looking for any smoking. Of course if still knocking or if smoking you'll have your answer. Even if it doesn't seem that there is any damage I would also do a compression check to see if you possibly warped a head and blew a head gasket. Check for water in your oil and or bubbles or oil in your coolant.
 
Ok where's the sticky on how to do a compression check, and to check both of those would I just drain them both? And if there is one or the other what does that mean. Also what's the chances she will come through this without any problems?
 
No need to drain anything yet. Pull your dipstick and look at your oil, to see if it looks milky or has any abnormal look or smell to it. Check your coolant for any floating drops of oil. When you start it up, pop the radiator cap before it warms up and look for any continuous bubbling ( you may even get a slight smell of exhaust with the bubbling).

Compression check is fairly easy and you can rent a compression gauge at autozone for free. Remove all of your plugs and thread the compression gauge hose into the spark plug hole. Crank the engine several revolutions until the gauge quits increasing in pressure. Write down the pressure and repeat for each cylinder. Your looking for low pressure in one or more cyls. Compare them all and see if any are a lot different from the others.
Low pressure in one or more with continuous bubbles in the coolant would be blown head gasket between the cyl and water port (or cracked head or block)
If two cyls that are next to each other have low pressure then that would indicate a blown gasket between the two.
Low pressure with continuous smoking out the exhaust would be bad rings.
If the exhaust smokes only at start up but then goes away that would indicate bad valve seals

No way to bring back bad fuel but depending on how bad it is you could siphon some out of your tank and mix fresh fuel with it. That is if its not real bad. Does it have a varnish smell to it? You can and should also get a can of seafoam and mix some in your tank to clean things up.