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99 overheating; no heat in interior

15K views 12 replies 6 participants last post by  DrivenDaily 
#1 ·
So my 17 year old daughter comes home last night and says "oh by the way. that gauge went all the way to 260 a couple of times and a light came on. And no heat was coming from the heater." We haven't had the car (1999 3.1, 144K) for long but here is some background:
  • I've never heard the fans come on, so I've always wondered if they work.
  • The original radiator cap never went on right so I replaced it recently with an aftermarket cap. The OE cap was designed to fill the opening and with the relief mechanism extending into the tank. The aftermarket cap just appears to seal the top of the neck with the relief at the top.
  • I wondered if I should have replaced the expansion tank too. It appeared the OE cap had been cross threaded a few times. maybe it won't allow a good seal now.

Getting ready to go look at the car now. I'm expecting it to be very low on coolant (explaining why no heat at the heater core).

Need to get more details from my daughter, but I expect she'll say the overheating occurred when idling for long periods.

So my question for now is, how do I simply test if the cooling fans function or are capable of functioning appropriately? The AC needs recharged so I don't think turning the AC on will trigger. If the exp tank is bad, would that not allow the system to get hot where the sensor is to trigger the fans?

Also is the fan temp sensor the kind where if I disconnect the wire from the sensor the fans will come on?
 
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#2 · (Edited)
Updated observations:

  • Expansion tank was empty. Added water/coolant.
  • Started car and warmed up. Temp gauge want past mid point (next major tick mark).
  • Thermostat appears to open since upper hose got hot.
  • Fans still didn't come on.
  • Removed cap while hot. Didn't seem to have any pressure at all.
  • NO INTERIOR HEAT STILL.

Starting to suspect the water pump is bad?
 
#3 ·
Updated observations:
General thoughts:

You REALLY should talk to your daughter about driving the car when warning lights are on !!! Good thing it wasn't the oil pressure. :eek:

The system probably is still low on coolant; keep adding.
You can test for pressure in the system by squeezing the fat hose when hot (with gloves on).
You can get a reference for that by squeezing it when it's cold.

Let's hope that the pressure cap (and bottle) are your only real problems.
It is entirely possible that IS the case. Let's not jump to water pump just yet.

And yes, really low coolant can prevent the fans from comming on too.
And it can damage the engine too. I recommend an oil change after you get the problem resolved.

I believe that the fans should come on with the AC regardless of the state of charge. I also believe that the fan sensor applies a ground to the wire to make them run........but I don't know either of those things for sure.
 
#4 · (Edited)
Ken, you were right about still being low on coolant. Added more, opened the bleeder valve (after breaking off the bleeder insert) and viola, now have interior heat and the temp seems more stable.

Thank you for your help!

Fans still don't come on no matter what I do, so will have someone look at that. And doesn't seem to get any pressure in expansion tank.
 
#5 ·
I don't remember the exact temp, but IIRC, the fan temp is something like 210 to 220F. On my car, that's at slightly over 3/4 of the temp gauge.

I'd check with a competent scan tool (not a code reader!) and see what temp the ECU thinks the motor is. Someone here can probably chime in with the proper temp for both low speed and high speed fan (if there's two speeds - there's two fans, at least, on my car!) so you can monitor them.

One more quick test - turn the A/C on. If the compressor is running the fans are supposed to run also. If that works, then it's a pretty safe bet that the wiring is good as are the fans - since all that's left is for the ECU to decide it's hot enough to run the fans!

RwP
 
#8 ·
IIRC, you said the threads may be stripped on the bottle.
Sounds to me like you need a new bottle and cap......that match.

Until you get that fixed, the car should NOT be driven at high speeds for long distances......as it will certainly overheat again. Keeping the AC on......to force the fans to run might help some.
 
#9 ·
didn't occur to me until this morning but the new aftermarket expansion tank cap doesn't extend in to the coolant tank past the relief tube. So with the relief tube opening exposed into the tank, it will never pressurize. The old cap seperated so that's why it wouldn't pressurize.

Time for a new tank and proper cap.

The fans did come on yesterday...
 
#10 ·
New OEM expansion tank and cap appears to have solved the problem!

Looks like the former owner was chasing the overheating problem by replacing the water pump, hoses, and removed the thermostat. When all was needed was the cap to seal correctly on expansion tank.
 
#11 ·
someone please help!! i own a 99' chevy malibu that has been overheating. it will take less than ten minutes to reach the "danger zone (red)" on my temperature gauge. i have added coolant but it has gotten hot so it bubbles over, it has also shut down completely on me. i lost brake control, steering control, and the car shut off. it does NOT blow heat, it does not blow a/c. i believe it blows whatever temp is under the hood. i don't know if i need a new cap, a temp gauge, im just lost. i know nothing about cars (im a seventeen year old girl) please help!!!
 
#13 ·
Check the t-stat. Don't drive it 'til you get it fixed or you could damage it beyond repair.
 
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