Cause of rising and falling overheat in 2002 Olds Alero?

[brassplyer]

Friend of mine has a 2002 Olds Alero, they say they're having
intermittent issues with temperature, tends to overheat at idle. I've
never worked on a car of that vintage so thought I'd inquire.

They aren't losing coolant. Electric fans so a fan clutch per se isn't
the cause. Some issue with whatever directs the electric fans to turn
on? Thermostat? They say the radiator is in good shape, how would you
verify this?

Thanks

[m6onz5a]

2002is vintage? Lol

does the cooling fan come on at idle or when the engine temp gets too
hot? Could also be a bad coolant temp. Sensor. When the a/c is turned
on does one of the radiator fans come on?

[gregz]

That should test at least one fan. Probably two relays for two fans. I was
just looking at my cavalier. I don't remember temp going up on idle, but
not too high, but does now.

I checked everything on my 2001 . The temp gauge seems ok, and that is what
the computer is looking at to turn on cooling fan through a relay. Fuses
too.

Greg

[Bill]

In article <31ba293d-c4b8-4ba7-b443-
3a225b...@f37g2000yqc.googlegroups.com>, brass...@yahoo.com says...

There are possible mechanical and electrical problems.

Mechanical...
Clogged radiator (replace radiator)
Blocked front of radiator (clean)
Thermostat (replace)

Electrical...
For this you will probably need to consult the factory service manual
set of books for this vehicle to see how these systems work - should
work. And have the FULL electrical diagrams manual for troubleshooting.

The sensor which activates the electric fan. (there are probably two
different sensors, factory manual would say which is for what.)
The electric fan.
Power and wiring to fan, relay(s), temp sensor(s), fuses.

Electrical A/C...
If the problem only happens with the A/C on...

Then is engine computer getting A/C "on" signal?
A/C pressure sensor may be used as signal to activate 2nd fan.
2nd fan itself.
Relay(s), wiring to sensors/fan, fuses to fan/relay circuits.

Also the engine computer perhaps "should" increase the idle speed a bit
when A/C on. Consult factory service manual set of books for this.
(Order books from dealer or helminc.com)

[m6onz5a]

On Apr 3, 12:03 pm, Bill <Nomailors...@yahoo.com> wrote:
> In article <31ba293d-c4b8-4ba7-b443-
> 3a225b51a...@f37g2000yqc.googlegroups.com>, brasspl...@yahoo.com says...

that's the coolane temp sensor.. usually located by the water outlet,
or on the radiator.

Chas

[Steve W.]

m6onz5a wrote:
> On Apr 3, 12:03 pm, Bill <Nomailors...@yahoo.com> wrote:
>> In article <31ba293d-c4b8-4ba7-b443-
>> 3a225b51a...@f37g2000yqc.googlegroups.com>, brasspl...@yahoo.com says...
>>
>>
>>
>>> Friend of mine has a 2002 Olds Alero, they say they're having
>>> intermittent issues with temperature, tends to overheat at idle. I've
>>> never worked on a car of that vintage so thought I'd inquire.
>>> They aren't losing coolant. Electric fans so a fan clutch per se isn't
>>> the cause. Some issue with whatever directs the electric fans to turn
>>> on? Thermostat? They say the radiator is in good shape, how would you
>>> verify this?
>>> Thanks
>

Start the engine and let it warm up. Turn on the A/C and one fan should
start running.

Shut the A/C off and that fan should stop shortly after.

Now with the engine warm the fans should start running when the coolant
temp hit's about 210-215 degrees or so.
The fans are controlled by the ECM through a pair of relays under the hood.
Should also be two fuses on the power side and one for the ground.
Fan 1 (left side) takes a 30 amp, fan two (right side) takes a 15 amp.
The ground fuse (30 amp) is number 55.
There is also a fan mode relay, it controls which fans run based on
temperatures and A/C mode.

If the car has a temp gauge that works the coolant temp sensor is OK. If
it only has an idiot light the easy solution would be to rent/buy a scan
tool that reads live data and watch the coolant temperature. If the
sensor is OK you will see it in the data (temp will go up smoothly as
the engine warms up)


--
Steve W.