engine overheat and cold air: thermostat?

Yesterday coming home from work in -10 C, a 26 km drive,

I was getting just cold air threw the heater. I was watching the temp
guage all the way home and as I got near my home about 20 minutes in,
the temp guage on my 88 toyota pickup was at the red line.

Once parked in driveway, I noticed the rad pushing fluid into the
overflow and could smell hot antifreeze.

I have noticed the past few weeks that the temp guage has been rising
and but then would suddenly start to go down seemed unusual at the time
so I have been watching it. --yesterday was the first time, it did not
go down. I went for a little drive later that evening and this time,
the temp rose even faster -7 minute drive to move temp guage to red and
still no heat from heater.

I assumed/read that you would have one or the other,
that is, engine overheats so thermostat is stuck in closed position
No heat in car so thermostat is stuck in open position.

I seem to have both scenerio's going on.

Any thoughts -is it even the thermostat?
if so, I know the thermostat is relatively inexpensive? should I buy
3rd party or from dealer
and finally, how long/shop time to replace one (I am assuming one hour
or so) and is it worth trying to do it myself?

"gp" <gpagmail-news@yahoo.com> wrote in message
news:1142913068.633611.55170@j33g2000cwa.googlegroups.com...[color=blue]
> Yesterday coming home from work in -10 C, a 26 km drive,
>
> I was getting just cold air threw the heater. I was watching the temp
> guage all the way home and as I got near my home about 20 minutes in,
> the temp guage on my 88 toyota pickup was at the red line.
>
> Once parked in driveway, I noticed the rad pushing fluid into the
> overflow and could smell hot antifreeze.
>
> I have noticed the past few weeks that the temp guage has been rising
> and but then would suddenly start to go down seemed unusual at the time
> so I have been watching it. --yesterday was the first time, it did not
> go down. I went for a little drive later that evening and this time,
> the temp rose even faster -7 minute drive to move temp guage to red and
> still no heat from heater.
>
> I assumed/read that you would have one or the other,
> that is, engine overheats so thermostat is stuck in closed position
> No heat in car so thermostat is stuck in open position.
>
> I seem to have both scenerio's going on.
>
> Any thoughts -is it even the thermostat?
> if so, I know the thermostat is relatively inexpensive? should I buy
> 3rd party or from dealer
> and finally, how long/shop time to replace one (I am assuming one hour
> or so) and is it worth trying to do it myself?[/color]


I would check the cooling system to see if it was low on coolant first.
This would cause both the overheat and no heat condition. If low, fill
cooloing system to proper level and check for proper operation and heat. If
that solves your problem find and repair the leak in your cooling system. If
it still overheats and you have no heat replace the thermostat and flush the
cooling system and refill with the proper antifreeze ratio.

The thermostat replacement is an easy do it yourself repair. You should
be able to replace the thermostat and flush the cooling system in about one
hour or so.

If you still have problems after that I would suspect a blocked radiator or
bad head gasket for the overheating. For the no heat problem I would suspect
a plugged heater core or failed valve in the water hose going into the
heater core. I would recommend that when you flush the cooling systen you
also flush the heater core. To flush the heater core remove the hoses going
to the heater core and run water through the heater core with a garden hose.
Make sure you run the water through both pipes on the heater core, you will
be able to see any crud that comes out, flush until water comes out clean.

All was fine in that same morning, over the past few days, I have been
noticing varying lengths of time for the heat to kick in, sometimes
works well, other times, not so good. The temp guage has been also been
rising to just below the red and then it drops dramatically to well
below the normal mark. Have not paid attn to where it leveled off.

I assumed that it was the thermostat that was sticking and that was my
explanation.

head gasket sounds expensive. I will start with the thermostat and rad
flush. Any other advice to rule out the head gasket would be greatly
appreciated. Some say to run the engine and tab on the thermostat
housing.

gp wrote:[color=blue]
> All was fine in that same morning, over the past few days, I have been
> noticing varying lengths of time for the heat to kick in, sometimes
> works well, other times, not so good. The temp guage has been also
> been rising to just below the red and then it drops dramatically to
> well below the normal mark. Have not paid attn to where it leveled
> off.
>
> I assumed that it was the thermostat that was sticking and that was my
> explanation.
>
> head gasket sounds expensive. I will start with the thermostat and rad
> flush. Any other advice to rule out the head gasket would be greatly
> appreciated. Some say to run the engine and tab on the thermostat
> housing.[/color]

When you change the thermostat as Mike suggested, also change the radiator
cap. It's a two way valve and it can wear to the point it will stick, the
springs will get weak, gaskets get cracked and etc. It's a cheap item that
gets overlooked a lot when having cooling problems. Be careful and don't
drive it if the temp goes to red, if the head or head gasket isn't bad it
will be if you drive it hot.
When you change the thermostat make sure the hose where connected to
radiator is higher than the connection at the engine, fill rad and overflow
tank to cold mark, run engine with cap off until it gets hot enough to start
flowing coolant. Shut off, install rad cap and let it cool down, this should
make sure you don't get any air pockets in rad.
HTH, Dave