Overheating

I have a 95 passat and after I had an oil change it started overheating the
next day first day it was fine.
It overheats only when driving over like 1.5 RPM at 1.5 the temperature
remains pretty much constant but driving at 2.5-3 rpm constantly makes the
temperature climb higher and higher if I drive on the highway it climbs up
to 248F and then the high fan is on. The weather here is hot but not that
much hotter then before its pretty much the same, it was hotter before and
it didn't do it so its not the weather.
Any suggestions of what it could be would help
Thanks
Andrey

On Sat, 11 Jun 2005 10:25:34 -0400, "Andrey Z" >
wrote:

>I have a 95 passat and after I had an oil change it started overheating the
>next day first day it was fine.
>It overheats only when driving over like 1.5 RPM at 1.5 the temperature
>remains pretty much constant but driving at 2.5-3 rpm constantly makes the
>temperature climb higher and higher if I drive on the highway it climbs up
>to 248F and then the high fan is on. The weather here is hot but not that
>much hotter then before its pretty much the same, it was hotter before and
>it didn't do it so its not the weather.
>Any suggestions of what it could be would help
>Thanks
>Andrey
>

Have checked the water level both in the recovery tank and the
radiator?

Steve B.

The water level is good

"Steve B." > wrote in message
...
> On Sat, 11 Jun 2005 10:25:34 -0400, "Andrey Z" >
> wrote:
>
>>I have a 95 passat and after I had an oil change it started overheating
>>the
>>next day first day it was fine.
>>It overheats only when driving over like 1.5 RPM at 1.5 the temperature
>>remains pretty much constant but driving at 2.5-3 rpm constantly makes the
>>temperature climb higher and higher if I drive on the highway it climbs up
>>to 248F and then the high fan is on. The weather here is hot but not that
>>much hotter then before its pretty much the same, it was hotter before and
>>it didn't do it so its not the weather.
>>Any suggestions of what it could be would help
>>Thanks
>>Andrey
>>
>
> Have checked the water level both in the recovery tank and the
> radiator?
>
> Steve B.

Speaking generically, if it overheats at high speed on the freeway, that
usually rules out fan problems.

Some possibilities include
-A collapsing suction side radiator hose,
-malfunctioning water pump or belt drive,
-partially frozen thermostat, or
-restriction in the coolant system, like a partially blocked radiator

I have seen radiators blocked externally by grass cuttings or hay, etc,
hoses that have shed layers of rubber into the radiator, and a few other
things.

A leak from the combustion chamber, such as would be caused by a head
gasket failure or crack in the head or block, is also possible

The oil change may have been coincidental, but if you didn't do it yourself,
you might want to
look over the entire engine compartment to see if the technician left
something there that he shouldnt have that could have migrated into an
interfering position.

Once at the auto shop I work at we had a car , I think a firebird.
And it would overheat only on highway or moving fast. We fixed it by
finding a plastic cover on bottom of engine. Apparently old one had
fallen off. The cover used to funnel air over radiator. Without it at
high rpm, High heat generation, not enough air directed over radiator.

The oil change thing might be a coincidence. If so then a
restricted radiator or bad themostat could be a problem. One test I
and my boss use is we let the car idle and sit in park and let it get
hot (look at gauge) and feel upper radiator hose, should be toasty hot
, hard to hold for long. Also when fan kicks in , gauge should be
alittle above the middle, feel air flow with hand, watch out for fan
blades and hot exhaust manifold. It should feel like hot air and lots
of it. Like a hair dryer on high. In a good system the fan shouldn't
stay on long till it drops it below preset.
Maybe the oil change people knocked off a temperature sensor wire
or loosened a connection.