94 SL2 Overheating

Hi,

I have a 94 saturn SL2 that's overheating. So far I've done the following:

1. The coolant doesn't leak
2. The radiator is new
3. Connected the radiator fan to the battery and the fan spins
4. Had a mechanic look at all the fuses and relays, all are fine.
5. Had three mechanics told me that it's the temperature sensor (one of
them)

So my question is as follows:

My Hanes manual says that I should replace the thermostat. Is the
thermostat the same as the temperature sensor? If not are there
instructions on replacing it?

Where would I get the part numbers for what I need?


Thanks,
Andrew

To clarify a bit,

the car overheats when it is sitting idling. If I'm driving over 30 or
40 mph the temperature comes back down.

Thanks,
Andrew

Andrew E. wrote:
> Hi,
>
> I have a 94 saturn SL2 that's overheating. So far I've done the following:
>
> 1. The coolant doesn't leak
> 2. The radiator is new
> 3. Connected the radiator fan to the battery and the fan spins
> 4. Had a mechanic look at all the fuses and relays, all are fine.
> 5. Had three mechanics told me that it's the temperature sensor (one of
> them)
>
> So my question is as follows:
>
> My Hanes manual says that I should replace the thermostat. Is the
> thermostat the same as the temperature sensor? If not are there
> instructions on replacing it?
>
> Where would I get the part numbers for what I need?
>
>
> Thanks,
> Andrew

On Fri, 22 Sep 2006 17:29:30 -0400, "Andrew E."
> wrote:

>To clarify a bit,
>
>the car overheats when it is sitting idling. If I'm driving over 30 or
>40 mph the temperature comes back down.
>
>Thanks,
>Andrew

Sounds like the radiator fan isn't turning on. There is enough
airflow over the radiator when driving and the fan isn't needed. Stop
moving and it eventually has to come on to prevent overheating.

I always thought there should be some indicator that the fan is on.
It's a handy thing to know.

Does your car have A/C? Turn that on and see if the fan starts. Then
you know the wiring to the fan is OK.

>Andrew E. wrote:
>> Hi,
>>
>> I have a 94 saturn SL2 that's overheating. So far I've done the following:
>>
>> 1. The coolant doesn't leak
>> 2. The radiator is new
>> 3. Connected the radiator fan to the battery and the fan spins
>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>> 5. Had three mechanics told me that it's the temperature sensor (one of
>> them)
>>
>> So my question is as follows:
>>
>> My Hanes manual says that I should replace the thermostat. Is the
>> thermostat the same as the temperature sensor? If not are there
>> instructions on replacing it?
>>
>> Where would I get the part numbers for what I need?
>>
>>
>> Thanks,
>> Andrew

In article >, "Andrew E." > wrote:
>Hi,
>
>I have a 94 saturn SL2 that's overheating. So far I've done the following:
>
>1. The coolant doesn't leak

How did you determine that? Just checking for drips underneath the car isn't
enough -- for example, a leaking head gasket could leak coolant into the
combustion chambers where it will be evaporated and blown out the tailpipe,
and you'll never see any drips. Have you verified that the cooling system
actually is, and remains, full?

>2. The radiator is new

Why?

>3. Connected the radiator fan to the battery and the fan spins
>4. Had a mechanic look at all the fuses and relays, all are fine.
>5. Had three mechanics told me that it's the temperature sensor (one of
>them)

I doubt it.

It's possible that a failed temperature sensor is causing overheating by
preventing the electrically operated fan from coming on -- but as long as the
vehicle is moving at any appreciable speed, there's enough air being forced
through the radiator that the fan isn't really needed for cooling, so this is
unlikely IMO unless you're doing a lot of driving in very heavy stop-and-go
slow speed traffic. The more likely symptom of a failed sensor is a gauge
that's *falsely* reporting the engine to be too hot, when the temperature is
actually normal.

IS the engine actually overheating? (Noticeably hotter than normal when you
lift the hood, smell of hot coolant, wisps of steam drifting out from under
the hood, clouds of steam pouring out, etc.)

If so, I'm betting the problem is a failed thermostat. *Especially* if the
thermostat wasn't replaced at the same time the radiator was. (It should have
been. They're cheap, and they fail fairly regularly in older vehicles. As long
as the cooling system is drained anyway, it's just silly not to replace it.)

>
>So my question is as follows:
>
>My Hanes manual says that I should replace the thermostat.

I agree. :-)

>Is the
>thermostat the same as the temperature sensor?

It is not. The temperature sensor does just that: senses the temperature, and
sends a signal to the temperature gauge. The thermostat controls how hot the
engine gets; specifically, the thermostat is a valve that sits between the
engine and the radiator. It stays closed until the coolant reaches the correct
temperature (190F, I believe), and then opens. This prevents water from
circulating through the radiator until the engine is warmed up.

If the thermostat is stuck open, the engine takes a very long time to warm up
(which is bad in a variety of ways) -- and if it's stuck *closed* (or doesn't
open fully), the engine overheats. Of course, that's also bad. :-)

>If not are there
>instructions on replacing it?

If you have the same Haynes manual that I do, it's on pages 3-2 and 3-3.
Or you could look in the index under "Thermostat, check and replacement".

The instructions for checking and replacing the temperature sensor are a few
pages later, listed under "Coolant temperature sending unit - check and
replacement".
>
>Where would I get the part numbers for what I need?

You should be able to find a thermostat for your car at just about any auto
parts store, or maybe even in the automotive department at Wal-Mart.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

From what you state, it sounds like either a failed coolant temperature
sensor or the fan relay.

Bob

"Andrew E." > wrote in message
...
> To clarify a bit,
>
> the car overheats when it is sitting idling. If I'm driving over 30 or 40
> mph the temperature comes back down.
>
> Thanks,
> Andrew
>
> Andrew E. wrote:
>> Hi,
>>
>> I have a 94 saturn SL2 that's overheating. So far I've done the
>> following:
>>
>> 1. The coolant doesn't leak
>> 2. The radiator is new
>> 3. Connected the radiator fan to the battery and the fan spins
>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>> 5. Had three mechanics told me that it's the temperature sensor (one of
>> them)
>>
>> So my question is as follows:
>>
>> My Hanes manual says that I should replace the thermostat. Is the
>> thermostat the same as the temperature sensor? If not are there
>> instructions on replacing it?
>>
>> Where would I get the part numbers for what I need?
>>
>>
>> Thanks,
>> Andrew

Hi

>> I have a 94 saturn SL2 that's overheating. So far I've done the following:
>>
>> 1. The coolant doesn't leak

> How did you determine that? Just checking for drips underneath the car isn't
> enough -- for example, a leaking head gasket could leak coolant into the
> combustion chambers where it will be evaporated and blown out the tailpipe,
> and you'll never see any drips. Have you verified that the cooling system
> actually is, and remains, full?

Yes it remains full over several months.

>
>> 2. The radiator is new
>
> Why?
>

Because my other radiator cracked and I had to replace it.

>> 3. Connected the radiator fan to the battery and the fan spins
>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>> 5. Had three mechanics told me that it's the temperature sensor (one of
>> them)
>
> I doubt it.
>
> It's possible that a failed temperature sensor is causing overheating by
> preventing the electrically operated fan from coming on

This is exactly what is happening. The fan doesn't come on even when the
temperature indicator on the dashboard is way over half. As I said, the
fan is fine and the relays and fuses have all been tested (by a
mechanic) and are fine. If the relay is shorted the fan turns on.

-- but as long as the
> vehicle is moving at any appreciable speed, there's enough air being forced
> through the radiator that the fan isn't really needed for cooling, so this is
> unlikely IMO unless you're doing a lot of driving in very heavy stop-and-go
> slow speed traffic.

This is exactly when the overheating happens: during stop and go
traffic. If I'm driving at an appreciable speed the engine stays at the
1/4 mark.

The more likely symptom of a failed sensor is a gauge
> that's *falsely* reporting the engine to be too hot, when the temperature is
> actually normal.
>
> IS the engine actually overheating? (Noticeably hotter than normal when you
> lift the hood, smell of hot coolant, wisps of steam drifting out from under
> the hood, clouds of steam pouring out, etc.)
>

Yes I've had it steam up before and it is *very* hot otherwise.

> If so, I'm betting the problem is a failed thermostat. *Especially* if the
> thermostat wasn't replaced at the same time the radiator was. (It should have
> been. They're cheap, and they fail fairly regularly in older vehicles. As long
> as the cooling system is drained anyway, it's just silly not to replace it.)
>
>> So my question is as follows:
>>
>> My Hanes manual says that I should replace the thermostat.
>
> I agree. :-)

So given the above do you still agree?
>
> If you have the same Haynes manual that I do, it's on pages 3-2 and 3-3.
> Or you could look in the index under "Thermostat, check and replacement".
>
> The instructions for checking and replacing the temperature sensor are a few
> pages later, listed under "Coolant temperature sending unit - check and
> replacement".

So is this what I'm looking for? Does the coolant temperature sending
unit cause the engine fan to come on?

>> Where would I get the part numbers for what I need?

>
> You should be able to find a thermostat for your car at just about any auto
> parts store, or maybe even in the automotive department at Wal-Mart.
>

Does this apply to the coolant temperature sending unit?

Thanks,
Andrew

Hi

I had the relay tested and it is fine (according to the mechanic). Does
the coolant temperature sensor control when the fan comes on?

thanks,
Andrew

Bob Shuman wrote:
> From what you state, it sounds like either a failed coolant temperature
> sensor or the fan relay.
>
> Bob
>
> "Andrew E." > wrote in message
> ...
>> To clarify a bit,
>>
>> the car overheats when it is sitting idling. If I'm driving over 30 or 40
>> mph the temperature comes back down.
>>
>> Thanks,
>> Andrew
>>
>> Andrew E. wrote:
>>> Hi,
>>>
>>> I have a 94 saturn SL2 that's overheating. So far I've done the
>>> following:
>>>
>>> 1. The coolant doesn't leak
>>> 2. The radiator is new
>>> 3. Connected the radiator fan to the battery and the fan spins
>>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>>> 5. Had three mechanics told me that it's the temperature sensor (one of
>>> them)
>>>
>>> So my question is as follows:
>>>
>>> My Hanes manual says that I should replace the thermostat. Is the
>>> thermostat the same as the temperature sensor? If not are there
>>> instructions on replacing it?
>>>
>>> Where would I get the part numbers for what I need?
>>>
>>>
>>> Thanks,
>>> Andrew
>
>

Hi,

I tried turning on the A/C and the fan does not start.

Thanks,
Andrew

Jim, N2VX wrote:
> On Fri, 22 Sep 2006 17:29:30 -0400, "Andrew E."
> > wrote:
>
>> To clarify a bit,
>>
>> the car overheats when it is sitting idling. If I'm driving over 30 or
>> 40 mph the temperature comes back down.
>>
>> Thanks,
>> Andrew
>
> Sounds like the radiator fan isn't turning on. There is enough
> airflow over the radiator when driving and the fan isn't needed. Stop
> moving and it eventually has to come on to prevent overheating.
>
> I always thought there should be some indicator that the fan is on.
> It's a handy thing to know.
>
> Does your car have A/C? Turn that on and see if the fan starts. Then
> you know the wiring to the fan is OK.
>
>> Andrew E. wrote:
>>> Hi,
>>>
>>> I have a 94 saturn SL2 that's overheating. So far I've done the following:
>>>
>>> 1. The coolant doesn't leak
>>> 2. The radiator is new
>>> 3. Connected the radiator fan to the battery and the fan spins
>>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>>> 5. Had three mechanics told me that it's the temperature sensor (one of
>>> them)
>>>
>>> So my question is as follows:
>>>
>>> My Hanes manual says that I should replace the thermostat. Is the
>>> thermostat the same as the temperature sensor? If not are there
>>> instructions on replacing it?
>>>
>>> Where would I get the part numbers for what I need?
>>>
>>>
>>> Thanks,
>>> Andrew

Andrew,

It's time to get a schematic diagram for the car. The official Saturn
manual has one, don't know about other sources.

Figure out which relay pins are the coil.
Pop the relay and check for voltage to the coil. Have someone turn on
the A/C or something like that.

Then take it from there.

On Fri, 22 Sep 2006 20:16:25 -0400, "Andrew E."
> wrote:

>Hi,
>
>I tried turning on the A/C and the fan does not start.
>
>Thanks,
>Andrew
>
>Jim, N2VX wrote:
>> On Fri, 22 Sep 2006 17:29:30 -0400, "Andrew E."
>> > wrote:
>>
>>> To clarify a bit,
>>>
>>> the car overheats when it is sitting idling. If I'm driving over 30 or
>>> 40 mph the temperature comes back down.
>>>
>>> Thanks,
>>> Andrew
>>
>> Sounds like the radiator fan isn't turning on. There is enough
>> airflow over the radiator when driving and the fan isn't needed. Stop
>> moving and it eventually has to come on to prevent overheating.
>>
>> I always thought there should be some indicator that the fan is on.
>> It's a handy thing to know.
>>
>> Does your car have A/C? Turn that on and see if the fan starts. Then
>> you know the wiring to the fan is OK.
>>
>>> Andrew E. wrote:
>>>> Hi,
>>>>
>>>> I have a 94 saturn SL2 that's overheating. So far I've done the following:
>>>>
>>>> 1. The coolant doesn't leak
>>>> 2. The radiator is new
>>>> 3. Connected the radiator fan to the battery and the fan spins
>>>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>>>> 5. Had three mechanics told me that it's the temperature sensor (one of
>>>> them)
>>>>
>>>> So my question is as follows:
>>>>
>>>> My Hanes manual says that I should replace the thermostat. Is the
>>>> thermostat the same as the temperature sensor? If not are there
>>>> instructions on replacing it?
>>>>
>>>> Where would I get the part numbers for what I need?
>>>>
>>>>
>>>> Thanks,
>>>> Andrew

Hi,

Already done. That's what the mechanic did: he opened the relay and
shorted the coil and the fan turned on.

Andrew

Jim, N2VX wrote:
> Andrew,
>
> It's time to get a schematic diagram for the car. The official Saturn
> manual has one, don't know about other sources.
>
> Figure out which relay pins are the coil.
> Pop the relay and check for voltage to the coil. Have someone turn on
> the A/C or something like that.
>
> Then take it from there.
>
> On Fri, 22 Sep 2006 20:16:25 -0400, "Andrew E."
> > wrote:
>
>> Hi,
>>
>> I tried turning on the A/C and the fan does not start.
>>
>> Thanks,
>> Andrew
>>
>> Jim, N2VX wrote:
>>> On Fri, 22 Sep 2006 17:29:30 -0400, "Andrew E."
>>> > wrote:
>>>
>>>> To clarify a bit,
>>>>
>>>> the car overheats when it is sitting idling. If I'm driving over 30 or
>>>> 40 mph the temperature comes back down.
>>>>
>>>> Thanks,
>>>> Andrew
>>> Sounds like the radiator fan isn't turning on. There is enough
>>> airflow over the radiator when driving and the fan isn't needed. Stop
>>> moving and it eventually has to come on to prevent overheating.
>>>
>>> I always thought there should be some indicator that the fan is on.
>>> It's a handy thing to know.
>>>
>>> Does your car have A/C? Turn that on and see if the fan starts. Then
>>> you know the wiring to the fan is OK.
>>>
>>>> Andrew E. wrote:
>>>>> Hi,
>>>>>
>>>>> I have a 94 saturn SL2 that's overheating. So far I've done the following:
>>>>>
>>>>> 1. The coolant doesn't leak
>>>>> 2. The radiator is new
>>>>> 3. Connected the radiator fan to the battery and the fan spins
>>>>> 4. Had a mechanic look at all the fuses and relays, all are fine.
>>>>> 5. Had three mechanics told me that it's the temperature sensor (one of
>>>>> them)
>>>>>
>>>>> So my question is as follows:
>>>>>
>>>>> My Hanes manual says that I should replace the thermostat. Is the
>>>>> thermostat the same as the temperature sensor? If not are there
>>>>> instructions on replacing it?
>>>>>
>>>>> Where would I get the part numbers for what I need?
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Andrew