5.0 overheating - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 32 Old 06-16-2019, 11:11 PM Thread Starter
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5.0 overheating

My 1992 Foxbody has 75xxx miles on it and I barely bought it a month back and everything was going good until I lost a freeze plug and had to have it towed home since then I have replaced the entire cooling system (water pump, radiator,) and ended up just removing the t stat hoping it would help with my overheating problem! No luck the car just overheats and there are no leaks I’ve already changed the radiator cap also .... the oil is clean and doesn’t have any signs of a head gasket issue also I’m on the last step which is changing my fan to electric... any suggestions or questions would help

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post #2 of 32 Old 06-16-2019, 11:13 PM
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Fan clutch?

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post #3 of 32 Old 06-16-2019, 11:54 PM
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does it overheat at idle or highway speed, or both?

is the coolant boiling over?

never run no stat in a street car.....

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post #4 of 32 Old 06-17-2019, 01:07 AM
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If its overheating while just sitting in your driveway, the most likely cause would be headgasket. How does the oil look? Any oil in the coolant?

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post #5 of 32 Old 06-17-2019, 01:39 AM Thread Starter
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Originally Posted by indy2000 View Post
does it overheat at idle or highway speed, or both?

is the coolant boiling over?

never run no stat in a street car.....
overheating occurs when it’s idling sometimes it will run at 3/4 temperature at idle (and continue to rise) and when I drive it around the block it slowly goes back down to 1/2 temperature where it normally sits
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post #6 of 32 Old 06-17-2019, 01:46 AM Thread Starter
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Originally Posted by indy2000 View Post
does it overheat at idle or highway speed, or both?

is the coolant boiling over?

never run no stat in a street car.....
overheating occurs when it’s idling sometimes it will run at 3/4 temperature at idle (and continue to rise) and when I drive it around the block it slowly goes back down to 1/2 temperature where it normally sits and it has no boiling over that I know of... why not run it without a T stat what are the repercussions of this ? Figured for summer it would help the car stay cool... I’m no expert on fans but it spins when te car is idling maybe not fast enough? The oil pressure is all good no signs of a head gasket and I’m not loosing water in the system at all it will stay the same level and still overheat I can see it cycling when the radiator cap is removed... I went to a car meet and was suggested that I bleed the lines due to it being bone dry when I lost my freeze plug anyways I’m not sure how to identify a faulty fan but like I said it comes back down temperature once I get driving a bit the problem starts once the car is not being driven but rather when I’m sitting at a stop light or like a drive threw for a long period of time... hope I’m giving enough evidence I’m pretty new to this !
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post #7 of 32 Old 06-17-2019, 01:48 AM Thread Starter
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If its overheating while just sitting in your driveway, the most likely cause would be headgasket. How does the oil look? Any oil in the coolant?
the oil looks fine I once I had a head gasket issue on my old Stang and the oil was clearly a milky color! I let the car idle in the driveway and it got a little hot so I took it for a drive and it cooled off for the most part
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post #8 of 32 Old 06-17-2019, 01:50 AM Thread Starter
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Fan clutch?
what would be signs of a bad fan clutch ? I’m 18 new to this type of issue on my car but doing my best to learn about it !
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post #9 of 32 Old 06-17-2019, 02:53 AM
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Originally Posted by Aj5.0 View Post
the oil looks fine I once I had a head gasket issue on my old Stang and the oil was clearly a milky color! I let the car idle in the driveway and it got a little hot so I took it for a drive and it cooled off for the most part
If it cools off while driving it sounds like the fan isnt engaging. Like someone else said, i would look at the fan clutch. Does it have a fan shroud? Ive seen people remove them which will cause it to overheat at idle... Also, are you sure its over heating? A bad ground can cause the temp gauge to spike. These cars do not take a lot to get the air out. I usually fill the radiator almost all the way up with the front jacked up, start the car, wait for the thermostat to open up and watch the radiator get sucked down, add water until its full and put the cap on it, add water to the reservoir, shut it off and let it cool down. From that point forward you shouldnt have air but you may need to top the reservoir off once or twice and that should be it.

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post #10 of 32 Old 06-17-2019, 03:03 AM
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what would be signs of a bad fan clutch ? Im 18 new to this type of issue on my car but doing my best to learn about it !
You should be able to turn the fan freely but it should have a pretty decent drag. The fan should also not have any play. you shouldnt be able to rock the fan back and forth (moving one side of the fan closer to the engine than the other). If the fan is really easy to spin and has no drag (going by memory here), very hard to turn or wont turn at all without trying to turn the engine or has a lot of tilting/side to side action you probably should look at replacing it.


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post #11 of 32 Old 06-17-2019, 09:38 AM
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I agree,it sounds like the fan clutch.Easy fix.The fan spins slowly when the fan clutch isnt engaged.Once the engine reaches a certain temp,the material inside the clutch triggers the clutch to engage and the fan will begin rapidly spinning.You can use a rolled up magazine to barely hold against the fan blades and if it stops the fan blades from spinning,while the engine is cold and at operating temp,this means the fan clutch isnt engaging.If it stops it from spinning only when its cold,but not when its at operating temp,the clutch is ok.Replace the clutch if it stops spinning at both temps.
When you run without a tstat,when the cooling system is functioning properly,it triggers the engine to run cooler than it should and the ecu will run the fuel trim too rich.Run the factory rated temp (192-95) tstat or no less than a 180 tstat.
Check the flat ground strap between the lower intake bolt (rear) or cylinder head (rear) and the driver side firewall.This is the ground for the gauges.This ground being loose,corroded or disconnected will cause the temp gauge to spike when you begin turning electrical accessories on like the heat/ac fan,headlights,etc.
A bad gauge sender will also cause incorrect gauge readings.To check the gauge/wiring,remove the temp gauge wire from the sender (driver,front corner of the lower intake) and touch the metal part (under the wire boot) directly to the engine block with the key on/engine off.The temp gauge should max out.If yes,the gauge and wire are good,which means the sender could be bad if the symptoms lead you away from other cooling system parts being at fault.
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post #12 of 32 Old 06-17-2019, 09:47 AM
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what caused the freeze plug to fall out?
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post #13 of 32 Old 06-17-2019, 03:23 PM Thread Starter
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Originally Posted by indy2000 View Post
what caused the freeze plug to fall out?
it didn’t fall out it just began leaking rapidly when I pulled it out it was rusted over and old looked like the originals
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post #14 of 32 Old 06-17-2019, 03:42 PM
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YOU bought this a month ago

And a frost plug was corroded to the point it leaked out, its not normal to lose a frost plug.

I think your cooling system is full of corrosion and sediment

I would start by reverse flushing repeatedly

You may get lucky and get most out, if not you are looking to replace all the components in the system

Sounds like the previous owner probably did not run correct coolant to prevent corrosion

You still may have blown a head gasket....as well

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post #15 of 32 Old 06-17-2019, 03:45 PM
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Also if one frost plug corroded over to that point, do you think the others are trustworthy?

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post #16 of 32 Old 06-17-2019, 03:52 PM Thread Starter
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Originally Posted by luv2rock View Post
I agree,it sounds like the fan clutch.Easy fix.The fan spins slowly when the fan clutch isnt engaged.Once the engine reaches a certain temp,the material inside the clutch triggers the clutch to engage and the fan will begin rapidly spinning.You can use a rolled up magazine to barely hold against the fan blades and if it stops the fan blades from spinning,while the engine is cold and at operating temp,this means the fan clutch isnt engaging.If it stops it from spinning only when its cold,but not when its at operating temp,the clutch is ok.Replace the clutch if it stops spinning at both temps.
When you run without a tstat,when the cooling system is functioning properly,it triggers the engine to run cooler than it should and the ecu will run the fuel trim too rich.Run the factory rated temp (192-95) tstat or no less than a 180 tstat.
Check the flat ground strap between the lower intake bolt (rear) or cylinder head (rear) and the driver side firewall.This is the ground for the gauges.This ground being loose,corroded or disconnected will cause the temp gauge to spike when you begin turning electrical accessories on like the heat/ac fan,headlights,etc.
A bad gauge sender will also cause incorrect gauge readings.To check the gauge/wiring,remove the temp gauge wire from the sender (driver,front corner of the lower intake) and touch the metal part (under the wire boot) directly to the engine block with the key on/engine off.The temp gauge should max out.If yes,the gauge and wire are good,which means the sender could be bad if the symptoms lead you away from other cooling system parts being at fault.
that’s the problem the car is literally getting hot as hell I can feel that part... no electric components are affecting the temperature gauge - on top of that none of the heater or te ac work nothing blows at all also the hazards work but no turn signals is there a theme here ? Or no connection
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post #17 of 32 Old 06-17-2019, 03:55 PM Thread Starter
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Originally Posted by indy2000 View Post
YOU bought this a month ago

And a frost plug was corroded to the point it leaked out, its not normal to lose a frost plug.

I think your cooling system is full of corrosion and sediment

I would start by reverse flushing repeatedly

You may get lucky and get most out, if not you are looking to replace all the components in the system

Sounds like the previous owner probably did not run correct coolant to prevent corrosion

You still may have blown a head gasket....as well
I have already replaced the whole cooling system what’s the best way to flush the system?... the car has lost 2 freeze plugs both just rusted to the point of leaking and I replaced them (pain in the butt) didn’t pull the motor just worked around it!
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post #18 of 32 Old 06-17-2019, 04:00 PM
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Just for the record those plus are not called frost or freeze plugs. That is not what they are there for. They are used to plug the holes in the block used for casting. They will pop out sometimes when the liquid in the block freezes and sometimes can save the block from cracking. A lot of time the block will crack anyway.
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post #19 of 32 Old 06-17-2019, 04:04 PM
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Originally Posted by Aj5.0 View Post
I have already replaced the whole cooling system whats the best way to flush the system?... the car has lost 2 freeze plugs both just rusted to the point of leaking and I replaced them (pain in the butt) didnt pull the motor just worked around it!
The rust is the worry

What did you replace?

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post #20 of 32 Old 06-17-2019, 04:14 PM Thread Starter
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Also if one frost plug corroded over to that point, do you think the others are trustworthy?
no they are probably all going bad but no leaks so far
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post #21 of 32 Old 06-17-2019, 04:15 PM Thread Starter
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I have already replaced the whole cooling system what’s the best way to flush the system?... the car has lost 2 freeze plugs both just rusted to the point of leaking and I replaced them (pain in the butt) didn’t pull the motor just worked around it!
The rust is the worry

What did you replace?
they rusted to bad they leaked
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post #22 of 32 Old 06-17-2019, 05:22 PM
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HUH?

What in the cooling system did you replace?

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post #23 of 32 Old 06-17-2019, 05:59 PM Thread Starter
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HUH?

What in the cooling system did you replace?
water pump, radiator, thermostat , radiator cap
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post #24 of 32 Old 06-17-2019, 07:49 PM
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all stock replacements?

not thick oversized rad?

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post #25 of 32 Old 06-17-2019, 08:48 PM
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Are you certain that the gauge is correct and the car is actually over heating? I had an issue (two years ago?) where I flushed the radiator and due to overheating issues afterwards, I assumed I had a bubble in the system. Turns out the gauge was just wrong and only read as overheat if I had my headlights on. Some form of electrical problem.

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post #26 of 32 Old 06-17-2019, 09:22 PM Thread Starter
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Are you certain that the gauge is correct and the car is actually over heating? I had an issue (two years ago?) where I flushed the radiator and due to overheating issues afterwards, I assumed I had a bubble in the system. Turns out the gauge was just wrong and only read as overheat if I had my headlights on. Some form of electrical problem.
yes I’m sure it’s overheating the motor gets very very hot and the gauge slowly climbs no spikes
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post #27 of 32 Old 06-18-2019, 08:23 AM
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Quote:
Originally Posted by Aj5.0 View Post
yes Im sure its overheating the motor gets very very hot and the gauge slowly climbs no spikes
Just out of curiosity, where is your timing set at?

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post #28 of 32 Old 06-21-2019, 02:10 PM
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sounds like air trapped in there to me
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post #29 of 32 Old 06-21-2019, 07:41 PM
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Do you have the correct water pump? Reverse flow pump is the right one . Had that issue before, a standard flow pump was in the box instead of reverse flow.

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post #30 of 32 Old 06-22-2019, 02:40 PM
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Since it cools off at speed, I'd say bad fan clutch. Run the car til it's really hot...not overheating. Then turn the car off and try to spin the fan. When it's hot it should pretty much be locked up to the water pump.
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post #31 of 32 Old 06-30-2019, 10:46 AM
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Definitely want to reverse flush at the very least if you had two plugs rusted out, all that rust and sediment or whatever other pollutants are floating around in there could damage your brand new parts.

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post #32 of 32 Old 06-30-2019, 11:51 AM
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I just skimmed through all of this and I feel that a part could be missing.

On the 5.0 Foxbodies, there is a "Air Deflector" located under the Core Support. Without it, a Fox will tend to overheat, yes, even at speed. It is made of Black Plastic and kinda resembles a piece of angle iron going side to side.

Also, I saw some posts that complained about "Mis-Reading Gauges". This is most likely due to a faulty ground of the Dash Wiring Harness near the Battery. This Ground goes to the Dash Harness, the Chassis as well as the Negative Side of the Battery. This Faulty Ground may/can also cause some but not all of the Gauges to Fluctuate Wildly sometimes. If it does not spin at all, it is either a non-clutch type fan or it has a fan that has "Frozen Up". Replace it (Either way).

To test a Fan Clutch: It should be made of Yellowish Plastic. Engine Off. Try to "SPIN" the fan with your hand in either direction. If it spins freely, replace it. If it does not move easily and stops rather quickly after you let go of it, it is good.

If you have just ONE Block Casting Plug go bad, replace all of them and I recommend using Brass Replacements (if I remember right the Part Number is P28C). Aslo, use Permatex Tack on the edges of the relacements and make sure to clean the block "holes". While you have them all out, use a high pressure hose and try to get any Gunk out of the engine block. A SOCKET that just fits inside the edges of the plug will suffice for an installation "tool".
Remember too, there are Casting Plugs on the Front and Rear of the heads too. Those are the same size of "Hole" but take a "Shallow" Plug. If you go here, it would be easier to just pull the engine at that point.

Keep in mind too that you may have "Weak Head Gaskets" and those will still cause overheating without the "Milky Oil" tell tail sign.

Jon

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Last edited by Jon Evenoff; 06-30-2019 at 12:26 PM.
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