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Can Marvel Mystery oil help a 79 F-100 running on 5 cylinders

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Can Marvel Mystery oil help a 79 F-100 running on 5 cylinders

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  #1  
Old 02-08-2012, 02:58 PM
Ki-Adi-Mundi
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Can Marvel Mystery oil help a 79 F-100 running on 5 cylinders

My 1979 F-100 has a 302 and is only running on 5 cylinders. I want to see if I can reawaken this engine. Iv tried new spark plugs and wires and that didn't help. Then a compression test revealed that these three cylinders don't have compression.

I have never used Marvel Mystery oil so I was hoping someone on here could offer some guidance. How much should I pour in each cylinder? and how long should I let it sit? Any other tips would be great.


Thanks
 
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Old 02-08-2012, 03:09 PM
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Unfortunately, no. I'm afraid the only thing to bring those cylinders back to life would be either a valve job or worse, new rings. Pull the valve covers and see if all looks OK. You might have a bent push rod. I had a 460 that was running on 6 cylinders, it sounded beastly but after taking the intake manifold off, I found a lifter laying in the valley that had grenaded. Cylinder #2 to be exact. Otherwise the M.M oil wont hurt a thing. I had a jug of it floating around my garage so I poured it into my 97 T-Bird and the rest into my truck. I really haven't noticed any difference one way or the other nor have I heard anything bad about it.
 
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Old 02-08-2012, 08:07 PM
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mystery oil helps a lot of stuff but i dont think it'll help that problem.
 
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Old 02-08-2012, 08:25 PM
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If you don't have compression, you've got something along the lines of burnt valves, a hole in a piston, etc. Nothing in a bottle is going to fix that.
 
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Old 08-14-2012, 06:28 AM
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Thanks for the help on this one. The strange thing Is this truck runs ok, idles fine but of course has very little power which means no "peeling out" or taking off in a hurry. It does not smoke except occasionally on start up. I'm going to check the push rods next.
 
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Old 08-14-2012, 12:05 PM
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If you have absolutely no compression on 3 cylinders, the motor is in bad shape. There are a lot of possibilities, but I do have a question - which cylinders are bad/dead? If there are two cylinders adjacent to eachother without compression, there's a chance that the head gasket is bad as well.

Things to check: (In order from easiest to hardest)

1) Remove the valve cover. Look to make sure none of the valves are sticking open. You can tell by looking down the line of rockers and making sure that none of them stay "down" as you slowly rotate the motor by hand.

2) With the valve cover off, and after you've made sure that no valves are sticking open, check to make sure that all of the valves *are* opening (and then closing) as you rotate the motor over by hand. An intake valve not opening could be caused by a bent pushrod, as was already stated - you'll know it's a bent pushrod if it's not firmly seated between the lifter and the rocker arm. If it's loose, there's a good chance it's bent. However, I had a dead cylinder in a 4.0L Jeep motor (also with no compression) caused by a bad cam lobe. If the air and fuel can't get into the motor, they won't have compression. If you spin the motor over and a valve doesn't open (sometimes it'll take two full turns of the crank to see one valve open), but the pushrod is still seated properly, you may have a bad cam lobe. This isn't as likely, especially if it's a stock Ford camshaft.

3a) Take the spark plugs out. Yes, all of them! Re-check the compression numbers, and write them down. Then, take an oil can and squirt a few pumps of oil in the cylinders that are reading really low. Re-check the compression immediately. If the compression is significantly higher after squirting some oil in the bore, then the piston rings are worn out in that cylinder.
3b) You can also squirt oil into the "good" cylinders and re-check - if the numbers are significantly higher in the good cylinders, then the rings are worn out and the motor's going to need a rebuild or replacement sometime in the future.

4) After checking #3, if you see that two of the cylinders with no/low compression are adjacent, it could be the head gasket. You may also find that the oil in the truck is brown and/or foamy after driving it, or you may find that there is brown "yuck" in the radiator/coolant. Either is a sign that one (or both) of the head gaskets is bad. This is also more likely if the truck was overheated prior to the problem developing.

5) If the valves/pushrods all look good and are working properly, the oil trick doesn't help, and the head gasket has been eliminated as the source of the problem, you need to check for physical damage to the pistons and block. This is easiest with the cylinder heads removed, but if you have a bore-scope, you can drop it down the spark plug holes and look for holes in the piston or scoring of the cylinder walls. This is pretty rare, unless you run the motor on really bad/old gas, or the timing is way off and the motor is pinging/knocking/detonating. This may also be the case if the motor sat for a long time (we're talking years) and the cylinder walls rusted before the motor was re-run.

I put #5 after #4, simply because you can check for evidence of a head gasket failure without pulling the head (though there's no way to tell for sure!), but you can't do #5 without pulling the head or dropping some bucks for a bore-scope.

Your problem may be any one of these, or even two of them. Or three - you won't know until you start going through the motor and eliminating possibilities.

Good luck! Hopefully it's just a few bent pushrods!
-Brad
 
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Old 08-14-2012, 04:47 PM
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Old 08-15-2012, 07:06 PM
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Thanks! I'm going to do this in the next couple of weeks. At least I don't have to depend on it everyday since it's a work truck / drive around in the woods for fun truck. I seldom put it on the road. I'll let y'all know how it goes.

Tanks again
 
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