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Discussion Starter #1
:eek: lately my temp guage has been going crazy and it will jump all the way to H and then level out. ive topped off the fluid a few times and it'll be down again a few days later. i just got done checking for leaks and i couldnt find one. there is no coolant in the oil what else could it be? i dont know if it's related or not but my heater has been acting strange lately too. it is only warm intermittently. could it be a bad heater core?
how involved would changing the sending unit? any thoughts would be helpful
 

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Man that is crazy, I was just going to post about the same exact same thing. At first i thouht it was the heater core. Could it also be the temp sensor?
 

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From the 1993 Serviec Manual:

PINPOINT TEST E: TEMPERATURE GAUGE INACCURATE


E1 TEST SENDER CIRCUIT AT LOW


Insert Rotunda Instrument Gauge, System Tester 021-00055 or equivalent. Disconnect connector at sender and connect tester to cluster side of connector. Set to 74 ohms.

Does gauge read 'C'?

Yes
GO to «E2».

No
GO to «E3».

E2 TEST SENDER CIRCUIT AT HIGH


Set Gauge System Tester to 10 ohms.

Does gauge read 'H'?

Yes
REPLACE sender.

No
GO to «E3».

E3 CHECK SENDER CIRCUIT WIRING


Check sender circuit wiring and cluster flex circuit for shorts or opens with Rotunda Digital Volt-Ohmmeter 007-00001 or equivalent.
Is wiring OK?

Yes
REPLACE gauge.

No
SERVICE wiring/flex circuit. GO to «B1» .


(B1 is additional testing for "Inoperative Temerature Gauge")


Temperature Sender


Removal and Installation

1. Disconnect the lead wire from the temperature sender.

WARNING:
NEVER REMOVE THE RADIATOR CAP UNDER ANY CIRCUMSTANCES WHILE THE ENGINE IS OPERATING. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN SERIOUS PERSONAL INJURY FROM HOT COOLANT OR STEAM BLOW OUT (AND/OR DAMAGE TO THE COOLING SYSTEM OR ENGINE). SWITCH OFF THE ENGINE AND WAIT UNTIL IT HAS COOLED. EVEN THEN, USE EXTREME CARE WHEN REMOVING THE CAP FROM A HOT RADIATOR. WRAP A THICK CLOTH AROUND THE CAP AND TURN IT SLOWLY TO THE FIRST STOP. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM. WHEN CERTAIN ALL THE PRESSURE HAS BEEN RELEASED, PRESS DOWN ON THE CAP WITH A CLOTH, TURN AND REMOVE IT.

2. Remove the radiator pressure cap to release pressure and install cap.

3. Remove the temperature sender.

4. Prepare new sender for installation by applying Pipe Sealant with Teflon®D8AZ-19554-A (ESG-M4G194-A and ESR-M18P7-A) or equivalent to the threads.

5. Install new temperature sender and connect lead wire.

6. Check the coolant level and start engine. Check the temperature system functions.

 

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Is there a smell similar to maple syrup when you run the heater? If so, that is a good sign of the heater core being bad. Also take a look at the exhaust when it heats up a little. White mist is a good sign of a blown head gasket/warped heads.
 

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if you're actually losing coolant and your carpet isnt wet then you're losing it somewhere. If there arent any external leaks on the motor then you're burning it, ie: blown headgasket :( The oil doesnt always get contaminated with a blown headgasket there are different ways the gasket can blow. I'd do a compression check on all 6 cylinders and see what you come up with.
-Thomas
 

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Discussion Starter #7
another thing i forgot to include is that at start-up the car shudders something horrible. it will sputter and shake for a minute but subsides and the car will drive fine. i dont know if its related or not.
 

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My car shakes like hell in the morning for a few seconds. I dont have any coolant issues so it may not be related. But if there is water or coolant in the cylinder it will cause the car to run hard till it is burned off.
 

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Discussion Starter #9
i spoke with a guy at work who's very knowlegable about a lot of things including cars and he mentioned the possibilty that the thermostat is bad. that would explain why the heat will blow cold until the car has been run for quite a while and then get really got and then go back to cold at idle. but it wouldnt explain the loss of coolant. im going to have the compression checked this weekend and hope for the best. if the compression is good i'll probably try changing the thermostat. sound like a plan?
 

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here is what i have noticed with my birds coolant wise. i have had a heater core go and u know when that goes. windshield frosts up coolant on the floor and a burnt foot. my goodness i never felt anyhting like it since. i broke a radiator and blew a lower radiator hose. when ever the cooland would get low the temp guage goes way up but there is no heat. empty heater core. but when the coolant is very low for some reason u have to keep the rpm's up or it will stall. let the car warm and just look for smells. i had the gasket where the thermostat went leak but then it dried up on the engine. right now my brothers 3.8 leaks in the lines that r related to heating. u can hear it drip a couple times on the exhaust manifolds just after shut down.
 

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mhays806 said:
i spoke with a guy at work who's very knowlegable about a lot of things including cars and he mentioned the possibilty that the thermostat is bad. that would explain why the heat will blow cold until the car has been run for quite a while and then get really got and then go back to cold at idle. but it wouldnt explain the loss of coolant. im going to have the compression checked this weekend and hope for the best. if the compression is good i'll probably try changing the thermostat. sound like a plan?
If the thermostat is bad it wont matter if youre moving or not, coolant isnt being circulated and it'll overheat. And, a bad thermostat won't lose coolant.
-Thomas
 

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plus motorcraft thermostats are fail-safe, when they brake, they hang open.

even though you said you didn't see any leaks, i think it's the side tank on your radiator, if you had a leak there it would be kinda hard to spot it, especially if it's on the front of the unit.

have you pressure tested the system yet?

what mixture of anitfreeze to water are you using? if there's too much antifreeze you'll run hot.
 

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Discussion Starter #14
the radiator fan runs so i dont think thats the case. hopefully tomorrow ill get to check the compression and ill try testing the pressure in the system.
 

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I am having the same exact problem and all of the above is ok, HGs are fine, thermostat is brand new, just checked this afternoon and there is no coolant leak, and the heater core is tip top shape. I figure that the temp sender is bad.
 

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Make sure that your oil level is not shooting up.Check the oil and look for signs of moisture in it if so thats the dead giveaway.You have been hit with the dreaded head gasket failure.Do this as soon as possible or if you are running with antifreeze in the oil it does not take long to wreck the engine.regards older newbie
 

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Discussion Starter #17
tonight i had to drive somewhere and i ran the heater. i noticed that it would blow cold air until the temp guage would rise. once it reached very near "H" the "check guages" light would come on and the heater would blow hot for a minute and then the guage would go back down. it did this only a few times. the rest of the time the guage was reading normal. :confused:
 

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mhays806;

Based on my experience with my 3.8 cougar (which I only owned for three days)

If you had to add coolant more than once, taking into account your other symptoms, I would suspect a head gasket leak.
 
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