engin running hot on 1996 cbra

[clubcart84]

1996 cobra runs hot. fan not coming on at 200 degrees. if I unplug from the fan at the sensor the fan comes on. the sensor is new. the thermostat is new and also new 3 row alum radiator. I started to burp the air at the crossover and notice constant air bubbling at the crossover in a funnel filled with antifreeze. rev the engine and the bubbles increase. Head gasket???

 

[evilcw311]

Head gasket wouldn’t keep your fan from coming on.


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[clubcart84]

yea just one of the things going on. any idea what would keep the fan from coming on? new sensor and when I unplug the sensor the fan starts on low speed and then goes to high. Would the bubbling indicate head gaskets

 

[evilcw311]

Bubbling can either show blown head gasket or that you’ve still got air in the lines after changing your radiator.

Sniff the coolant when it’s hot. Does it smell like exhaust??


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[clubcart84]

coolant does not smell like exhaust. oil looks clean. opened the crossover and refilled it. going to let sit open for 4 hours like I read on a burp search fill and install plug and bring up to temp. going tp unplug sensor to allow fan to run, if I can keep it cool I will start chasing the fan problem

 

[clubcart84]

I have read a lot of threads on pulling heads. any thoughts on pulling heads with motor in car, It has long tubes and I need to replace them as well. I can do ether in or out, Have all the tools for pulling as well as a lift, just wondering what is the easiest

 

[ttocs]

check the fuses for the fan

 

[Tillerman77]

OP - the folks that have posted are giving you a hint, i.e. that Occam's Razor probably applies here, like it does for so many things.

 

[evilcw311]

Why would you pull the heads with no other symptoms of a blown head gasket?? Your fan isn’t kicking in at high temp like it’s supposed to. This would have nothing to do with a blown gasket. You need to figure out why your fan isn’t functioning correctly.


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[96blak54]

200° isnt hightemp. Factory temp is something like 220°

Park on steep hill, nose up, run engine

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[white95]

If you can’t fix it with a hammer, it’s an electrical issue.

Trust me. I’m an electrician

Anyway, IIRC the 96-97 Cobra kicks the fan on low speed @ 208* and off @ 200*. It turns the high speed fan on at 228* and off at 224*. It should also turn the high speed on when you turn the AC on.

-It’s possible that you have a defective sensor.-

The fact it runs when you pull it tells me the system runs in a “fail closed” condition to prevent engine overheating in the event the sensor failed, which you simulated by pulling the plug.

How about some questions?

Does the fan kick into “high speed” when you turn the AC on?

Do you have an old, but functional sensor you could try?

What other factors are you forgetting that could've led to this situation? Any recent maintenance or upgrades? New tune?

200° isnt hightemp. Factory temp is something like 220°

Park on steep hill, nose up, run engine

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This will help with the burping, or you can use ramps/jack stands and chock the rear wheels.

 

[Burninriverdiver]

The three wire pigtail that plugs into the radiator fan is notorious for corroding after the rubber around them deteriorates. I had the same issue but easily fixed it by cutting out the bad section and soldering in new wires. Latemodel restoration sells the pigtail new for like $15

Edit: sorry they are $40. You could also cut a good one out of a junkyard car, I'm sure ford used them on multiple vehicles

https://lmr.com/item/WPT362/94-97-F...MItOLKpsHp4wIVDF8NCh0argkUEAQYASABEgKqZfD_BwE

 

[clubcart84]

The only reason I am thinking possible head gasket is when I burp the system I get periodic bubbles in the funnel filled with antifreeze. if I rev the engine they increase a lot almost like water boiling.

 

[96blak54]

And water will boil when the sytem has an air pocket.

Try your best to eliminate all possible scenarios before an engine tare down.

Grab a compression gauge and test hot cylinder with all the sparkplugs removed. Record each cylinders compression after 4 full cranks. Youll find the the leak.

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[delling3]

Straight water boils at 212° F at sea level. The same water in a closed radiator with 15PSI will not boil until the water reaches much higher (like 250°F). This is why cooling systems are pressurized. If you have your radiator cap off, the coolant will not do it's job as well.

 

[96blak54]

^good info

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[clubcart84]

Did a leak down test this weekend and found #5 and 7 leaking into water jackets.