98 Sable - No heat when moving

Hi have a '98 Sable, 3.0L, overhead valve engine. It's generally
around 35 degrees F outside right now. If I start up my car and let
it sit there in park, the engine heats up and the temperature gauge
goes up to the 1/3 point or so and stays there, seeming to indicate
the thermostat is doing its job, and I get heat out of the registers
in the passenger compartment. If I then go driving down the road at
40 MPH or so, the registers stop putting out heat and start putting
out cold air.
Any ideas on what would cause this? I thought that probably the
heater core was partially blocked like it was a year or two ago (and
maybe it is), but my mechanic just flushed it out last week with no
noticeable change. I then thought that maybe the water pump was only
marginally working since there were a lot of problems with the water
pump, corrosion, etc, so I replaced that. The old one didn't look
brand new, but didn't look terrible, either. No noticeable change.
(It was not a complete waste; as part of the process, I found that the
tensioner was stuck, so I replaced that).
Any insight would be much appreciated. Thanks!

> wrote in message
...
> Hi have a '98 Sable, 3.0L, overhead valve engine. It's generally
> around 35 degrees F outside right now. If I start up my car and let
> it sit there in park, the engine heats up and the temperature gauge
> goes up to the 1/3 point or so and stays there, seeming to indicate
> the thermostat is doing its job, and I get heat out of the registers
> in the passenger compartment. If I then go driving down the road at
> 40 MPH or so, the registers stop putting out heat and start putting
> out cold air.

Checked/changed your thermostat?

wrote:
>
> Hi have a '98 Sable, 3.0L, overhead valve engine. It's generally
> around 35 degrees F outside right now. If I start up my car and let
> it sit there in park, the engine heats up and the temperature gauge
> goes up to the 1/3 point or so and stays there, seeming to indicate
> the thermostat is doing its job, and I get heat out of the registers
> in the passenger compartment. If I then go driving down the road at
> 40 MPH or so, the registers stop putting out heat and start putting
> out cold air.
> Any ideas on what would cause this? I thought that probably the
> heater core was partially blocked like it was a year or two ago (and
> maybe it is), but my mechanic just flushed it out last week with no
> noticeable change. I then thought that maybe the water pump was only
> marginally working since there were a lot of problems with the water
> pump, corrosion, etc, so I replaced that. The old one didn't look
> brand new, but didn't look terrible, either. No noticeable change.
> (It was not a complete waste; as part of the process, I found that the
> tensioner was stuck, so I replaced that).
> Any insight would be much appreciated. Thanks!

Could possibly be a vacuum leak in the system that control the doors that
regulate airflow. Do the other controls work that direct the flow to
different areas (defrost, vent, floor, etc). Do they work normally or are
they slow to respond?. I assume you would have mentioned if the temp gauge
also went cold when you start to drive.

-jim

low coolant level
these cars are known for rusted cooling lines and seeping coolant
is the blower working correctly?


Jeff DeWitt wrote:

> Noozer wrote:
> > > wrote in message
> > ...
> >
> >>Hi have a '98 Sable, 3.0L, overhead valve engine. It's generally
> >>around 35 degrees F outside right now. If I start up my car and let
> >>it sit there in park, the engine heats up and the temperature gauge
> >>goes up to the 1/3 point or so and stays there, seeming to indicate
> >>the thermostat is doing its job, and I get heat out of the registers
> >>in the passenger compartment. If I then go driving down the road at
> >>40 MPH or so, the registers stop putting out heat and start putting
> >>out cold air.
> >
> >
> > Checked/changed your thermostat?
> >
> >
> The thermostat would be my first guess too.
>
> Just sitting there the only air moving past the radiator comes from the
> fan, so even if the thermostat is stuck open the engine might still get
> warm, however once you get moving down the road there is going to be a
> LOT more cold air flowing over the radiator.
>
> You say the gauge shows about 1/3 when you are sitting, does it stay
> there when driving down the road and the heater quits or does it drop?
>
> Jeff DeWitt

Thanks for the ideas and the feedback. Unfortunately, unless I messed
something up along the line (which is certainly possible), I think I
have already eliminated most of the ideas. I guess I forgot to
mention, but the thermostat was changed a couple weeks ago. That
seems to be working fine. The coolant level is OK. The blower motor
is OK; it is definitely moving air. The temperature gauge stays at
the 1/3 mark regardless of whether the car is sitting there or
moving.
Jim suggested perhaps there is a vacuum leak in the system that
controls the doors that regulate airflow. I have not really noticed
anything strange about the operation of the system. It does not seem
to be slow to respond, but I have not really been thinking about it,
either. I will try to do some research on this. In the meantime, if
anyone has ideas on how to definitively determine whether this system
has a problem or not, I'd be glad to hear them. Thanks much!
- Phil

wrote:
> Thanks for the ideas and the feedback. Unfortunately, unless I messed
> something up along the line (which is certainly possible), I think I
> have already eliminated most of the ideas. I guess I forgot to
> mention, but the thermostat was changed a couple weeks ago. That
> seems to be working fine. The coolant level is OK.

1. Two very recent threads detail recent experiences with new thermostats
that weren't working right.
2. Was air bled from the system properly? How?

> In the meantime, if
> anyone has ideas on how to definitively determine whether this system
> has a problem or not, I'd be glad to hear them.

I know you meant to say something else, because the way to determine whether
there's a problem would be to drive 40MPH and see whether you have heat.

--
Angry American flags attack Hillary Clinton!

I can not guarantee that air was properly bled from the system. I
squeezed the upper radiator hose a number of times and got gurgling
noises from the overflow tank, indicating that fluid was moving. I
realize that that may not totally eliminate that possibility of an air
bubble.
Actually, I did not mean to say something else. When I said "system,"
I was referring to the system that controls the airflow doors.
Obviously, there is a problem with the vehicle. I'm trying to figure
out which system has the problem.

New does not necessarily mean good:

I would let it idle, and see how high the temp gauge goes, before the
cooling fan comes on. (That is if it has an electric cooling fan?)

If so, and the gauge does not move more than one third, before the fan comes
on. You still have a bad thermostat. Or alternatively, you may have a head
gasket just starting to leak combustion into the cooling system.

Air goes in the heater core if a head gasket is starting to fail, and no way
for hot coolant to get into it.

Feel both hoses going to the heater core, it can also be a partially plugged
heater core.

I hope this helps.

RK
> wrote in message
...
> Thanks for the ideas and the feedback. Unfortunately, unless I messed
> something up along the line (which is certainly possible), I think I
> have already eliminated most of the ideas. I guess I forgot to
> mention, but the thermostat was changed a couple weeks ago. That
> seems to be working fine. The coolant level is OK. The blower motor
> is OK; it is definitely moving air. The temperature gauge stays at
> the 1/3 mark regardless of whether the car is sitting there or
> moving.
> Jim suggested perhaps there is a vacuum leak in the system that
> controls the doors that regulate airflow. I have not really noticed
> anything strange about the operation of the system. It does not seem
> to be slow to respond, but I have not really been thinking about it,
> either. I will try to do some research on this. In the meantime, if
> anyone has ideas on how to definitively determine whether this system
> has a problem or not, I'd be glad to hear them. Thanks much!
> - Phil
>
>

> wrote in message ...
> Hi have a '98 Sable, 3.0L, overhead valve engine. It's generally
> around 35 degrees F outside right now. If I start up my car and let
> it sit there in park, the engine heats up and the temperature gauge
> goes up to the 1/3 point or so and stays there, seeming to indicate
> the thermostat is doing its job, and I get heat out of the registers
> in the passenger compartment. If I then go driving down the road at
> 40 MPH or so, the registers stop putting out heat and start putting
> out cold air.

When that happens, does the temperature gauge drop down to the cold side ?

Shawn wrote:
> > wrote in message ...
>> Hi have a '98 Sable, 3.0L, overhead valve engine. It's generally
>> around 35 degrees F outside right now. If I start up my car and let
>> it sit there in park, the engine heats up and the temperature gauge
>> goes up to the 1/3 point or so and stays there, seeming to indicate
>> the thermostat is doing its job, and I get heat out of the registers
>> in the passenger compartment. If I then go driving down the road at
>> 40 MPH or so, the registers stop putting out heat and start putting
>> out cold air.
>
> When that happens, does the temperature gauge drop down to the cold side ?

> > wrote in message ...
>> the temperature gauge
>> goes up to the 1/3 point or so and stays there

--
Angry American flags attack Hillary Clinton!