1997 cobra with cooling problem

The 4V DOHC motors have special procedures to remove the air from the cross over. The SOHC motor will self purge after a few heat/cool cycles. The DOHC will generally not self purge. If the procedures are not followed, over heating is the usual result.

Note, if the problem were air in the cross over, this usually makes the dash temperature gauge read low because the sensor is in contact with air instead of coolant.

Note2, it is NORMAL for the engine temperature to vary. This should be intuitively obvious if one just thinks about how the fan control works. IE, it turns on a set temperature. Turns off once the temperature drops below a certain point. However, most ppl do not see the dash temperature gauge move because of the anti-slosh circuit in the dash.

Note3, switching to a lower temp t-stat only changes when the t-stat is fully open. Once fully open, both t-stats will pass the same amount of coolant. Once the t-stat is FULLY open, the engine temperature is controlled by the PCM cycling the fan on/off.

SO....I recommend that you search and find the correct procedures to burp the air from a DOHC.

Confirm that the car's cooling system is in good repair. Holds pressure. Correct coolant percentage. Correct coolant level. The radiator is clean inside and out. Air diverters in place. Low and High speed fan runs.

Consider renting a coolant pressure tester from your local autoparts store. This will answer if the system is holding pressure once and for all.

Monitor the engine temperature as reported by the PCM. An ODB2 scanner is the easiest way. If the temperatures are normal, IMO it is safe to assume that everything is OK and the temperature swings are the result of a bad anti-slosh circuit in the dash.

If the motor is actually overheating, then it will be necessary to trouble shoot the cause.

i have the same exact problem .. i installed new t-stat and drained and refilled the radiator ,, same problem .. I dont know what it is ..

last time I tried to burp it, I noticed that the coolant resevour tank was alittle low so I attached a funnel to the cross over and attempted to fill, but I couldnt because coolant came out of the crossover into the funnel and it never went back in .. not sure what that was about

Radiator Filling procedures 4.6L (4V) DOHC

89notchboy said:

last time I tried to burp it, I noticed that the coolant resevour tank was alittle low so I attached a funnel to the cross over and attempted to fill, but I couldnt because coolant came out of the crossover into the funnel and it never went back in .. not sure what that was about

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Did you allow the motor to cool completely?

For chronic overheating problems, consider performing a coolant system pressure test. The tool can be rented from most any local autoparts store.

There are also kits to test for hydro-carbons in the anti-freeze.

The fill procedures for the DOHC are CRITICAL. It will over heat if not followed. The SOHC motor will self purge after a few hot/cold cycles. The DHOC will not self purge.

>>From Ford service CD
Check all hose clamps for correct tightness. Make sure the radiator draincock is closed.

Place the heater temperature selector in maximum heat position.

Remove the pressure cap from the cooling system reservoir and the fill plug from the engine crossover tube.

CAUTION: Do not fill the cooling system through the reservoir only. Coolant will not enter the engine. Only the reservoir and the radiator will be filled and engine overheating will occur.

Add coolant into the fill neck on the engine crossover tube until coolant reaches the top of the fill neck on the cooling system reservoir.

Install the cooling system pressure cap on the reservoir.

Continue to fill the cooling system at the engine crossover fill neck until full.

Install the engine crossover tube fill plug.

WARNING: To avoid the possibility of personal injury or damage to the vehicle, do not operate the engine with the hood open until the fan has been first examined for possible cracks and separation.

CAUTION: If the engine temperature gauge does not move, coolant level is low in the engine and must be filled. Stop the engine, allow to cool, and fill the cooling system as outlined.

Run the engine until the thermostat opens (coolant flowing through the radiator lower hose becomes hot).

Stop the engine and allow to cool.

Add coolant to the engine crossover tube fill neck until the cooling system is full.

Install the fill plug.

Repeat the fill procedure if necessary.

im going to try again to burp it . .

should I try filling it with the car running?

89notchboy said:

should I try filling it with the car running?

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The step by step instructions tell you when to run the motor.

Notice the step "Install the engine crossover tube fill plug." is before the step "Run the engine until the thermostat opens (coolant flowing through the radiator lower hose becomes hot)."

If the motor is run with the engine crossover fill plug removed, the water pump suck air into the system completely defeating the purpose of the entire procedure.

After the coolant system is free of air, add coolant via the expansion tank.

Take your time. Don't cut corners. Remember there is no elevator to success. You have to take the steps.

Best thing is to have the stealership remove the air its worth the money.

Kilgore Trout said:

Best thing is to have the stealership remove the air its worth the money.

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Just wondering what does the dealer do differently? Do they pull a vaccum and use the vacuum to fill the voids?

The procedure looks very labor intensive with all of the heat/cool cycles called out. One would guess that would make it expensive.

I could certainly see the case that if the dealer used vacuum equipment, the job could be done in a lot less time without all of the heat/cool cycles.

They use a vacuum device yes.