# 98 Malibu overheating



## fjalvarez (Jun 19, 2009)

I'm working on 1998 chevy malibu 145XXX miles automatic ,A/C, 

The problem is that the car overheats this what i've notice : the fans have two speeds low and hi now the low speed kicks on at 225 degrees and by then the reservoir it's over flowing hi speed never comes on not even with the A/C on now with my scanner i can turn the low and hi speeds which leads me to belive that it's not a wiring issue 


a couple weeks ago i did the famous intake gaskets and ever since then it has that problem 


does anybody has an idea of what the problem might be or should i just change my insurance to full coverage and burn the thing 


any help would be greatly appreciated


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## manic (Aug 2, 2005)

Your best bet is to check what codes its throwing. Sensor more
that likely...Sensor or 2. Fan could be bad, thermostat could be bad..
225 is boiling...


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## fjalvarez (Jun 19, 2009)

you know i did change the t-stat change the coolant temp. sensor and fan are working (hi and low speed) no codes


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## manic (Aug 2, 2005)

Warped head, or blown head gasket. What shape is the radiator in..


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## fjalvarez (Jun 19, 2009)

You know that was my same thought i haven't done a block test but symptoms don't quite put me there for one i understand that if i have a warped head i would have milky oil or pressure in the cooling system but i don't have any of those symptoms 


now let me bounce this off of you 
the fans won't kick on until temp it's at a 225 degree mark and they come on in low speed now the pcm receives a signal from the coolant temp sensor then the pcm makes the fans come on depending on temp hi or low according to my scanner pcm it's getting the right signal but no hi fan speed and at 225 degrees so i'm thinking a new pcm or flashing it's in order 


what do you guy think?


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## mack1 (Nov 27, 2007)

Hi fjalvarez,

I'm wondering if you are giving the fan too much credit for cooling the engine. Does the temperature stays up when you are driving down the road. On older vehicles you could run without fan belt and it wouldn't overheat until you stopped at a red light. 

I'd recheck the thermostat making sure it would open up in hot water on the stove. I'd also at least use a garden hose to flush and back flush the radiator. You could also flush the engine while the thermostat was removed. 

Does anyone know what the temperature should be when the fan is told to come on. I'm wondering if 225 could be the normal setpoint. I'm also not sure that the water will boil at 225 if the radiator cap is holding it's 15 psi. Water under pressure boils at a higher temperature than 212. In my mind, I would think that the low speed would come on at a lower temperature and that the 225 would be for the high speed. You might have a wiring problem. Has anyone worked on the wiring? 

Just some thoughts and suggestions before you replace the heads and PCM.

Very best regards,
Mack1


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## fjalvarez (Jun 19, 2009)

Hey Mack1
you do bring a interesting point to the table and for that i thank you

the fans dont stay on with the car in motion and the temp stay with in spects

Now i did check the t-stat this way:
put my scanner (solus pro) and i activated the fan control on hi as i watch temp and the lowest it got was 194 degrees

Very good question about what the temp range for the fans to come on and off that would pretty much solve this case considering that if fans should come at let's say 210 on low and 220 on high 

About the radiator cap i replaced it considering there's human in the process on making i'll double check it's pressure holding capabilities 

nobody has work on the wiring as far as i know but now if the wiring was messed with would i still be able to control the fans with my scanner??


I APPRECIATE ALL YOU GUY'S INPUT IN THIS PROBLEM


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## mack1 (Nov 27, 2007)

Hi fjalvarez,

I have a haynes repair manual that covers your year. There is only one electrical print that shows the fan circuits. It is not listed as "typical", so I assume it is for all of them.

On that print, it shows two fans controled by relays and no means to provide speed control. The PCM controls both fans and I can only assume that it brings the second fan on when the AC is on or an overtemperature condition exists. It might be that only one of your fans works and it could be the one used for overtemperature. (again, I'm guessing about when the 2nd fan is switched on) The book didn't explain the sequence. 

I can post a picture of the print if you like. It might let you trouble shoot it if you don't have both fans working.



> the fans dont stay on with the car in motion and the temp stay with in spects


This says there is a problem with the fan/fans. 

What engine do you have in the car?

Best regards,
Mack1


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## fjalvarez (Jun 19, 2009)

Thank you for your offer i have access to chilton on-line and they provide a schematic of the fans circuit
on mine show three relays in play two for the fans and a third one they call a "fan mode relay"
now when the temp reaches that 225 degree mark both fans come on and stay on until i turn the engine off and turn it back on . 
Now even if i turn the a/c on both fans come on again at low speed

i do have the intake gasket problem 3.1 engine which by the way i've replaced


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## mack1 (Nov 27, 2007)

The fan mode relay is on my print also. I took a quick look and it looked like one fan had to be engaged before the other one was allowed, as controlled by the fan mode relay. That led me to think that one came on at a lower temperature than the other. If both of your fans work, it is probably working right. 

Do you think you have all the air out of the system? After draining the radiator, there is a bleed valve that you have to turn a couple of turns while the engine is running to get some of the air out. I'm wondering if you have good water flow when at idle. Does the top hose feel hot indicating that water is flowing when you have the overheating? 

All in all, you might have noticed that I shy away from the setpoint in the PCM being off that much. They don't normally reprogram their own setpoints. 

Wish I could be more help.
Best regards,
Mack1


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## fjalvarez (Jun 19, 2009)

You know i've gone thru all the checks as far as t-stat opening by top hose being hot when i refilled the cooling system i used a vacuum refiller 

at this point i'm really stuck on this car i do try to stay away from replacing the pcm cause the chances of it being bad are pretty slim 


all in all i thank you for your help and your point of view you've been a tremendous help 

i think i'll just burn the car now


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## mack1 (Nov 27, 2007)

Don't forget to get the insurance first


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