Re: Is this consistent with a failing coolant temperature sensor?

Matt wrote:
>
> jim wrote:
> >
> > Matt wrote:
> >> jim wrote:
> >>> Matt wrote:
> >>>> 2) the oil level is about 2/3 qt. too high on the dipstick.
> >>>>
> >>>> I expect most of the high level is simply from overfilling, but could
> >>>> the oil pick up that much blow-by in 300 miles at 160 F? Maybe I should
> >>>> check the PCV valve too?
> >>> If the oil is overfilled and stays overfilled I don't understand how you
> >>> conclude that means there is excess blow-by?
> >> I wasn't clear. I mean maybe the full condition is all or partly due to
> >> blow-by condensing in the oil rather than being overfilled at the last
> >> oil change. Could the oil level rise 2/3 qt in 300 miles assuming 160 F
> >> t-stat and a PCV problem?
> >
> > It sounded pretty clear to me. You said "I expect most of the high level is
> > simply from overfilling". Obviously you don't know exactly where the oil level
> > was after the last oil change. Trying to reconstruct where the level might have
> > been by speculating on engine temp and pressure at this point is pure
> > foolishness.
> >
> > I don't think the oil is going to rise due to condensing blow-by. Worn rings
> > will show up as missing oil. Plugged PCV can also cause you to lose oil, but you
> > would probably be able to see where it is going. If the engine is running
> > extremely rich it could cause raw gas to get into the crankcase that would make
> > the level rise. But if that was what was happening I would think you talking
> > about other symptoms than those you have mentioned. Do you get terrible gas
> > mileage? Is there black smoke out the exhaust? Does the engine run rough?
>
> No black smoke. Runs well---no complaint there. It pings at idle when
> cold, probably using regular. I haven't fueled it or checked the gas
> mileage yet.

I doubt that it pings at idle when cold. Probably you hear a little
lifter noise.



>
> > If the only real problem you have is the oil is a little dirty then change it.
> > Do the job yourself or check the level after someone else does it.
> >
> > -jim
>
> I changed the oil and filter. The owner's manual says it takes 5.0
> quarts, so I just dumped in a whole 5 qt. jug. Now I find that the oil
> level is again about 2/3 qt. high, so it would seem the manual is wrong.
> The oil on the dipstick looks a lot cleaner now.

I'd be real concerned if it didn't look clean right after an oil
change:} Keep checking as you drive see how fast it gets dirty. I
wouldn't worry about the slight overfill if you added the right
amount.
-jim


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jim wrote:
>
> Matt wrote:
>
>>> The computer will never go closed loop running that cold...
>> I don't know which loop you mean. Explain?
>>
>
> The computer relies on the info from the coolant temperature sensor. That is
> different from the sending unit for the dash gauge.


That is surprising---not that I would know.

In the intake manifold I found two devices other than the injectors.
One is toward the rear of the car, (on the side with the even-numbered
bank of cylinders). When I unplug it, the gauge stops working. The
other is on the end of the manifold beneath the throttle body. When I
unplug that one, the gauge is unaffected. Your post seems to imply that
that one gives input to the computer. Which one controls the warning light?

I'm thinking that if one sending unit is bad, maybe the other is too.
Mileage is 160K.

Maybe I should get somebody to hook the car to a computer for general
diagnostics. Presumably a bad temperature-sending unit would be
detectable. Should I go to the GM dealer for the diagnostic---or would
a large repair shop have the right equipment?

Matt <[email protected]> wrote:
>My car has an analog temperature gauge. The reading is below 100F when
>the engine is cold, then climbs as I drive, but doesn't go much above
>160F.
>
>Bad thermostat? But I have a receipt from the previous owner for
>thermostat replacement five months ago. I just got the car.

Maybe. Maybe they used a cheap one that broke open. Maybe they used
the wrong one, that is set for too low a tempeature. The first thing I
would do is to measure the temperature at the radiator and compare it
to what the shop manual says it should be. The second thing I would do
would be to get a known-good thermostat (NOT a cheapie from a chain store)
and replace it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."