1994 mustang gt overheating, please help!

[Blueoval19]

Recently picked up a pristine, two owner completely original 94 5.0. Car was extremely well kept, I test drove it and everything was fine. On my way home from purchasing it, about 30 minutes or so it started to overheat, as soon as I pulled over it started puking coolant and steaming. I did a radiator flush, radiator is new and flows fine, put a new 180 degree thermostat in, opened the screw on top of thermostat and burped it, checked water pump and it's flowing, all fins were in tact and fine, fan was working as well. After I did all that I drove it three or four times and it was fine, no over heating. However my last trip as about an hour and at the very end it started to overheat, I don't get it, it overheats after long rides sometimes, every time it starts to overheat the a/c blows warm, but if it's normal operating temp the a/c is cold? Does it need to be burped again? Is the coolant temp sensor the culprit? Also should add the heater core went and he had it bypassed. Please help me figure this out the car is beautiful condition and I have big plans for it but most importantly I need it to get to and from work!

 

[evilcw311]

Could also be a head gasket.


This message courtesy of crapatalk!

 

[RichV]

Headgasket, water pump, radiator, or thermostat.

If you got a new radiator and thermostat, I'd start with the water pump. You can also have the system checked for exhaust gasses which would indicate a HG failure.

 

[Blueoval19]

I pulled the water pump off, it was spinning fine, all bearings were fine and fins were not broken. Also just randomly overheats after like 4 driving times. That's why I'm thinking maybe another air pocket built up?

 

[Blueoval19]

No coolant oil mixture, no smoke out of exhaust, nothing typical of head gasket?

 

[fran5o]

Dose the coolant system hold pressure?

 

[fran5o]

Also don't forget about the electric fans, could be a ccrm issue

 

[Blueoval19]

Dose the coolant system hold pressure?

Whats the best way to test?

 

[Blueoval19]

Electric fans were kicking on with a/c on, does that mean it's working right?

 

[DFG_magic]

As stated, test the fans. High speed may be working but low speed could be inop. Does the car overheat when you run the AC? Do you notice it overheating when not running the AC? Have the electric fan assembly tested. Both speeds.

 

[DFG_magic]

Electric fans were kicking on with a/c on, does that mean it's working right?

Only the high speed fan circuit runs when running the AC. This is by design to pull cool air through the condenser as well as the radiator. This does not necessarily mean the fan is operating 100%. Low speed needs to activate when coolant temp reaches specified temp the PCM is commanding. This signal is given by the coolant temp sensor based on coolant flow across the sensor. Get your fans tested.

 

[Blueoval19]

As stated, test the fans. High speed may be working but low speed could be inop. Does the car overheat when you run the AC? Do you notice it overheating when not running the AC? Have the electric fan assembly tested. Both speeds.

Yes the car was still overheating with a/c on but then the a/c stopped blowing cold? What's easiest way to test th fan speeds? I'm just confused as to why I drove it a handful of times all around town and no overheating, but then on my last trip I drove about an hour and at the end it started overheating?

 

[DFG_magic]

Yes the car was still overheating with a/c on but then the a/c stopped blowing cold? What's easiest way to test th fan speeds? I'm just confused as to why I drove it a handful of times all around town and no overheating, but then on my last trip I drove about an hour and at the end it started overheating?

Probe power to both circuits with a power probe. The CCRM also contains the relays for the fans and isn't really servicable by most. If the CCRM was bad, it would exhibit similar symptoms as well. There are so many things that could be going wrong it's hard to speculate based on the info. Start by block testing the the engine. You can get a block tester kit at NAPA. That will determine if the head gasket is blown. If it passes the block test, look into other things like the fan, ccrm, and possibly a bad temp sensor causing a false gauge reading. Hook a mechanical gauge up to the cooling system and see the real temp. How does it run when it's "overheating"?

 

[Blueoval19]

Probe power to both circuits with a power probe. The CCRM also contains the relays for the fans and isn't really servicable by most. If the CCRM was bad, it would exhibit similar symptoms as well. There are so many things that could be going wrong it's hard to speculate based on the info. Start by block testing the the engine. You can get a block tester kit at NAPA. That will determine if the head gasket is blown. If it passes the block test, look into other things like the fan, ccrm, and possibly a bad temp sensor causing a false gauge reading. Hook a mechanical gauge up to the cooling system and see the real temp. How does it run when it's "overheating"?

If the high fan is working why would it overheat?

 

[Blueoval19]

Probe power to both circuits with a power probe. The CCRM also contains the relays for the fans and isn't really servicable by most. If the CCRM was bad, it would exhibit similar symptoms as well. There are so many things that could be going wrong it's hard to speculate based on the info. Start by block testing the the engine. You can get a block tester kit at NAPA. That will determine if the head gasket is blown. If it passes the block test, look into other things like the fan, ccrm, and possibly a bad temp sensor causing a false gauge reading. Hook a mechanical gauge up to the cooling system and see the real temp. How does it run when it's "overheating"?

Also can I rule out the coolant temp sensor seeing how as it gets hot and I pull over it starts to steam out of the pressure cap meaning it is actually hot?

 

[DFG_magic]

If the high fan is working why would it overheat?

Low fan comes on first.. If and in fact it is bad, coolant temp is rising without being cooled by the fan until the high temp decides to kick on. By that time, it's already too late and things are too hot. Hope this makes sense.

 

[Chucklz95GT]

Do you have underdrive pullies by chance? My car was overheating and not charging due to underdrives.

 

[lutter94]

Chiming in to follow. Also have high temps with high ambient temps, but the fins are all f'd up. New radiator on the way.

 

[Burninriverdiver]

Check the wiring harness going to your fan as well. Mine had wires exposed and the low fan speed didn't work until I replaced the fan harness (junkyard part for <$5) make sure none of the wires are exposed

 

[Blueoval19]

So I found the issue to by the heater hose bypass. The owner before me used a plastic garden hose t fitting and I believe it was letting air in. I replaced with brass fitting and bled the system and had zero issues since. However now my car overheated yesterday and the fan will not kick on unless I turn the a/c on. Also only sounds like it's the low speed!?!? Any help pleasee