99 SL SOHC 5 speed Pinging when warm

My SL is fine when it is cold, but when it is warm it pings almost
constantly, especially in higher RPMs. The previous owner changed the
thermostat to a lower setting 170, I think. I also did not have any (less
than **** warm) heat over the winter. I was wondering if these 2 problems
are related. I do not have any service engine lights on.

Thanks
Wayne

In article >, "WayneF" > wrote:
>My SL is fine when it is cold, but when it is warm it pings almost
>constantly, especially in higher RPMs. The previous owner changed the
>thermostat to a lower setting 170, I think. I also did not have any (less
>than **** warm) heat over the winter. I was wondering if these 2 problems
>are related. I do not have any service engine lights on.

You might check the coolant temperature sensor.

WayneF wrote:
> My SL is fine when it is cold, but when it is warm it pings almost
> constantly, especially in higher RPMs. The previous owner changed the
> thermostat to a lower setting 170, I think. I also did not have any (less
> than **** warm) heat over the winter. I was wondering if these 2 problems
> are related. I do not have any service engine lights on.

One cause of pinging can be too low of a combustion chamber temperature.
I believe that the SL engine had a 195 degree thermostat as standard
equipment, and if so, 170 is a huge difference. You should try the
proper thermostat. Usually people go down by 5 degrees at a time if the
engine is running too hot, to go down by 25 degrees is a really bad idea.

Was he having an overheating problem that caused him to put in such a
low temperature thermostat or was he mistakenly thinking "the cooler the
better?" Was the cooling fan temperature sensor also changed to a lower
temperature? Some owners have had a problem of overheating when at idle
because the electric cooling fan didn't come on soon enough, and changed
the cooling fan sensor (though you want to be careful that it's not set
to a level that's so low that it's on all the time).

A lower temperature thermostat would mean that lower temperature coolant
is circulating through the heater core, though it shouldn't have had
that much of an effect on heat, unless you're in an extremely cold
climate, though again, 25 degrees is a huge difference, and the heater
was designed for higher temperature coolant.

Thanks for everyone's help. The car does almost have 150,000 miles. Every
hear of seafoam and will it be a fix or make things worse. I didn't have any
problems since it was a cooler temp outside. I don't get it! BTW The
cooling fan comes on when I turn on the A/C.

Thanks,
Wayne
"marx404" > wrote in message
...
> oil viscosity and gas quality? thats my guess.
>
> --
> marx404
>
> _________________
> "WayneF" > wrote in message
> . ..
>> My SL is fine when it is cold, but when it is warm it pings almost
>> constantly, especially in higher RPMs. The previous owner changed the
>> thermostat to a lower setting 170, I think. I also did not have any
>> (less than **** warm) heat over the winter. I was wondering if these 2
>> problems are related. I do not have any service engine lights on.
>>
>> Thanks
>> Wayne
>>
>
>

WayneF wrote:
> Thanks for everyone's help. The car does almost have 150,000 miles. Every
> hear of seafoam and will it be a fix or make things worse. I didn't have any
> problems since it was a cooler temp outside. I don't get it! BTW The
> cooling fan comes on when I turn on the A/C.

You might try higher octane gasoline. That's a workaround, but it can
prevent pinging. It's very destructive to the engine to not stop the
pinging.

The cooling fan is supposed to come on when you turn on the AC. You must
have sufficient airflow over the condenser at all times, even when stopped.

WayneF wrote:
> Thanks for everyone's help. The car does almost have 150,000 miles. Every
> hear of seafoam and will it be a fix or make things worse. I didn't have any
> problems since it was a cooler temp outside. I don't get it! BTW The
> cooling fan comes on when I turn on the A/C.

One more thing, while changing the thermostat back to the proper
temperature may help the pinging problem, it could also exacerbate it.
It's possible that the previous owner switched to the lower temperature
thermostat as a bandaid solution to pinging that was even worse.

This is the type of problem where it may be worth paying a master
mechanic to diagnose the root cause of the pinging. OTOH, trying
inexpensive fixes such as using the proper thermostat, or changing
fuels, may be worth a try. You can always go back to the way it was before.

In article >,
says...
> WayneF wrote:
> > My SL is fine when it is cold, but when it is warm it pings almost
> > constantly, especially in higher RPMs. The previous owner changed the
> > thermostat to a lower setting 170, I think. I also did not have any (less
> > than **** warm) heat over the winter. I was wondering if these 2 problems
> > are related. I do not have any service engine lights on.
>
> One cause of pinging can be too low of a combustion chamber temperature.

Ummmm.... no, it can't.

Pinging occurs when the fuel/air mixture is detonated too early. You
wanna explain how low temperatures can cause premature detonation?

In article >, SMS > wrote:
>Doug Miller wrote:
>> In article >,
>> says...
>>> WayneF wrote:
>>>> My SL is fine when it is cold, but when it is warm it pings almost
>>>> constantly, especially in higher RPMs. The previous owner changed the
>>>> thermostat to a lower setting 170, I think. I also did not have any (less
>>>> than **** warm) heat over the winter. I was wondering if these 2 problems
>>>> are related. I do not have any service engine lights on.
>>> One cause of pinging can be too low of a combustion chamber temperature.
>>
>> Ummmm.... no, it can't.
>>
>> Pinging occurs when the fuel/air mixture is detonated too early. You
>> wanna explain how low temperatures can cause premature detonation?
>
>This is what I read, "knock occurs more prevalently in too high a
>combustion temp which is why engines with aluminum cylinder heads can
>run higher compression as they dissipate heat better. But too cool a
>combustion temp can also increase knock."

Like I said... you wanna explain that?
>
>Yes, it's counter-intuitive.

No, it's nonsense.

> In any case, it's best to keep the engine
>temperature at what it was designed for.

Of course. But having it too low will *not* cause predetonation.

Doug Miller wrote:
> In article >,
> says...
>> WayneF wrote:
>>> My SL is fine when it is cold, but when it is warm it pings almost
>>> constantly, especially in higher RPMs. The previous owner changed the
>>> thermostat to a lower setting 170, I think. I also did not have any (less
>>> than **** warm) heat over the winter. I was wondering if these 2 problems
>>> are related. I do not have any service engine lights on.
>> One cause of pinging can be too low of a combustion chamber temperature.
>
> Ummmm.... no, it can't.
>
> Pinging occurs when the fuel/air mixture is detonated too early. You
> wanna explain how low temperatures can cause premature detonation?

This is what I read, "knock occurs more prevalently in too high a
combustion temp which is why engines with aluminum cylinder heads can
run higher compression as they dissipate heat better. But too cool a
combustion temp can also increase knock."

Yes, it's counter-intuitive. In any case, it's best to keep the engine
temperature at what it was designed for.