6.9l temp sendin unit gone?
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6.9l temp sendin unit gone?
well i dont know exactly whats wrong with my old girl but either the temp sendin unit is gone or i have a blown head gasket my temp gauge loves to mess around with me itll say one min its at the a or l in normal then drop down near the n and o but also she has run dry of antifreeze and i just seemed to stop runnin dry i use a hand pump to pump excess antifreeze from overflow tank back in he radiator and then its gone as soon as i drive it and the temperature gauge goes crazy i dont know what exactly is wrong with the old girl but id like to keep her runnin here for a bit longer
Logistics Pro
Joined: Sep 2010
Posts: 4,411
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From: Victor, MT
These are possible problems of your engine:
Blown Headgasket(worst case scenario)
Thermostat
Cracked Block cause you have an 84 6.9l...which the early blocks are known to crack at the blockheater freeze plug...do you use the block heater?(absolutly worst case)
Leaking radiator
Temperature sending unit
Start with the simple things, new Motorcraft or Internation Thermostat, then go from there, check your radiator for cracks, Then if you have a block heater, trace the plugin to the back of the block and see if its cracked...
Blown Headgasket(worst case scenario)
Thermostat
Cracked Block cause you have an 84 6.9l...which the early blocks are known to crack at the blockheater freeze plug...do you use the block heater?(absolutly worst case)
Leaking radiator
Temperature sending unit
Start with the simple things, new Motorcraft or Internation Thermostat, then go from there, check your radiator for cracks, Then if you have a block heater, trace the plugin to the back of the block and see if its cracked...
Postmaster
Joined: Feb 2011
Posts: 3,560
Likes: 1
if the gauge reading moves that far within a few seconds, you're either low enough on coolant that the sensor is in the air half of the time, or your sensor or wiring is bad, causing the gage to sometimes get the right signal and sometimes not.
if you're low on coolant, gotta figure out where its going. aune mentioned many of the common places it goes, but also check hoses, heater core, etc. if your radiator has never been replaced, its a likely suspect, as this is about the age where they normally give up the ghost. coolant usually leaves some distinctive stains on the radiator, its hard to miss if you look close.
once you've been through all the basics, it might be time to start looking for problems like a head gasket
if you're low on coolant, gotta figure out where its going. aune mentioned many of the common places it goes, but also check hoses, heater core, etc. if your radiator has never been replaced, its a likely suspect, as this is about the age where they normally give up the ghost. coolant usually leaves some distinctive stains on the radiator, its hard to miss if you look close.
once you've been through all the basics, it might be time to start looking for problems like a head gasket
Postmaster
Joined: Feb 2011
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b-uno, i guess you could try, but i wouldn't expect it to last very long. keep in mind the heating-cooling cycles, the vibration, and the coolant under pressure behind it. if you know a guy who's good at welding cast iron, he could weld it for you, but thats a job for a very experienced man, as one mistake will condemn your block
Senior User
Joined: Sep 2008
Posts: 318
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From: Portage Des Sioux, Mo
If it was a cracked block the antifreeze would not end up in overflow tank, unless it is into combustion chamber. Then you would probably see it as a cloud in the exhaust and have hydrostatic lock next time you start it after sitting right amount of time. I think that is what killed my old engine. If you are lucky you have the same problem I had (with second engine). Bad (new) radiator cap. The 6.9/7.3 need a higher than normal pressure cap about 12-15 PSI. The bad cap came with new radiator and kept blowing antifreeze into overflow tank. I was afraid my new engine had a cracked head. I put the old cap back on and have not had a problem since. If the antifreeze keeps getting that low it could cause the gauge to bounce also.
Lets hope it is that simple for you.
Lets hope it is that simple for you.
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Senior User
Joined: Sep 2008
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From: Portage Des Sioux, Mo
If you do have a crackand are going to use JBWeld, grind a small v the length of crack before using it, it will need something to get ahold of, Don't go all the way through though. I have seen a marine mechanic use sealant and a plate fastened to the side of a generator to seal it after it cracked because someone forgot to winterize it. It was a fresh rebuild too.
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Joined: Mar 2012
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alright well i filled the radiator completly full of antifreeze two days ago and normally it would've been actin up again but it didnt its still sayin the temp is round n or r and ive been drivin it normal so idk exactly what that means
Senior User
Joined: Sep 2008
Posts: 318
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From: Portage Des Sioux, Mo
One other thing I did not think of. If the radiator is partialy clogged the water pump could force antifreeze out past cap and into overflow. Depending on how bad it could only be at higher RPM but enough flow at lower RPMs to handle the flow. You should be able to get a clue on that just by looking in top of radiator and seeing what the tubes look like.
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