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Thermostat needle



 
 
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  #1  
Old November 13th 05, 01:29 AM
2forgetmenot
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Default Thermostat needle

Let me state my problem again with this.
Everyday I warm my car up for 5-15 minutes before driving. After
approximately 2-5 minutes of driving the thermostat needle starts to
slowly drop down to cold, the car down shifts by itself and the engine
roars loudly becaue the RPM's are so high when the transmission down
shifts. I took my 94 Mazda Miata to a Mazda dealer. They first said the
thermostat was getting stuck. They checked that and that was not the
problem. Then they did some type of engine cleaning (so they said)which
cost me $74. The final analysis was I probably had a bent valve, which
would have cost me $750 to repair. I elected not to repair, becaue this
was an educated guess, but I wasn't interested in taking a stab in the
dark for $750. Any ideas?

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  #2  
Old November 13th 05, 01:46 AM
Chuck
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Default Thermostat needle

Replace the thermostat. Even new ones may not work properly.
"2forgetmenot" > wrote in message
lkaboutautos.com...
> Let me state my problem again with this.
> Everyday I warm my car up for 5-15 minutes before driving. After
> approximately 2-5 minutes of driving the thermostat needle starts to
> slowly drop down to cold, the car down shifts by itself and the engine
> roars loudly becaue the RPM's are so high when the transmission down
> shifts. I took my 94 Mazda Miata to a Mazda dealer. They first said the
> thermostat was getting stuck. They checked that and that was not the
> problem. Then they did some type of engine cleaning (so they said)which
> cost me $74. The final analysis was I probably had a bent valve, which
> would have cost me $750 to repair. I elected not to repair, becaue this
> was an educated guess, but I wasn't interested in taking a stab in the
> dark for $750. Any ideas?
>



  #3  
Old November 13th 05, 02:00 AM
Don Bruder
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Posts: n/a
Default Thermostat needle

In article
outautos.com>,
"2forgetmenot" > wrote:

> Let me state my problem again with this.
> Everyday I warm my car up for 5-15 minutes before driving. After
> approximately 2-5 minutes of driving the thermostat needle starts to
> slowly drop down to cold, the car down shifts by itself and the engine
> roars loudly becaue the RPM's are so high when the transmission down
> shifts. I took my 94 Mazda Miata to a Mazda dealer. They first said the
> thermostat was getting stuck. They checked that and that was not the
> problem. Then they did some type of engine cleaning (so they said)which
> cost me $74. The final analysis was I probably had a bent valve, which
> would have cost me $750 to repair. I elected not to repair, becaue this
> was an educated guess, but I wasn't interested in taking a stab in the
> dark for $750. Any ideas?
>


Automatic transmission with an in-radiator cooler, presumably...

Temp drop MIGHT have to do with the cold tranny-juice hitting the
(already hot) radiator once you've put it in gear and the fluid starts
circulating.

Downshifts... Possibly the cold tranny fluid picking up heat from the
radiator changes behavior - perhaps gets "thinner" suddenly - and alters
the pressure it's putting on things enough to cause the downshift? High
RPMs in the lower gear are to be expected, so the key is figuring out
why the tranny is downshifting, I'd say. I'd strongly suspect that the
temperature difference between the warmed-up engine and the cold tranny
"mixing juices" in the radiator is responsible for the temp change, but
I'm trying (and failing) to come up with some way that warming the
tranny fluid could cause a downshift.

What happens if you continue driving it? Does it "come back to normal"
over the course of - oh, say 10-15 minutes (as the tranny comes up to
full temperature)? or does the misbehavior continue indefinitely?

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info
  #4  
Old November 13th 05, 03:07 AM
Lanny Chambers
external usenet poster
 
Posts: n/a
Default Thermostat needle

In article
outautos.com>,
"2forgetmenot" > wrote:

> Everyday I warm my car up for 5-15 minutes before driving. After
> approximately 2-5 minutes of driving the thermostat needle starts to
> slowly drop down to cold


What happens if you don't warm up the engine first? Letting it idle for
longer than a few seconds is not necessary, and letting it idle for 15
minutes may actually be bad for the engine by promoting carbon deposits
(hence the dealer's engine cleaning).

Try starting the engine, waiting for the oil pressure gauge to level
off--which takes less time than fastening your seatbelt--and then just
driving off at a moderate pace. The engine should be warm enough for the
heater to become useful within a mile or two, even in winter. Just try
to keep it under 4000 rpm and avoid full throttle until the oil pressure
drops and stabilizes around 55-60 psi at highway speeds. That's when you
know everything is up to full operating temperature, and ready to accept
a full load.

That's how I treat my '94, and at 136k miles it runs better than new and
uses zero oil between changes.

--
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html
  #5  
Old November 13th 05, 03:42 AM
Kenneth S.
external usenet poster
 
Posts: n/a
Default Thermostat needle

This sounds to me like a vaccum leak somewhere. Have you, or anyone
else, checked the engine for such a leak? Perhaps what's happening is that,
despite the warmup period, the engine is still running below operational
temperature when you start driving. Then, as it reaches operational
temperature, the leak opens up enough to cause the problems you describe.
If it's a vacuum leak, it shouldn't cost much to fix.


"2forgetmenot" > wrote in message
lkaboutautos.com...
> Let me state my problem again with this.
> Everyday I warm my car up for 5-15 minutes before driving. After
> approximately 2-5 minutes of driving the thermostat needle starts to
> slowly drop down to cold, the car down shifts by itself and the engine
> roars loudly becaue the RPM's are so high when the transmission down
> shifts. I took my 94 Mazda Miata to a Mazda dealer. They first said the
> thermostat was getting stuck. They checked that and that was not the
> problem. Then they did some type of engine cleaning (so they said)which
> cost me $74. The final analysis was I probably had a bent valve, which
> would have cost me $750 to repair. I elected not to repair, becaue this
> was an educated guess, but I wasn't interested in taking a stab in the
> dark for $750. Any ideas?
>



  #6  
Old November 13th 05, 04:21 AM
Chris D'Agnolo
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Posts: n/a
Default Thermostat needle

Oh, everyone forgot to mention, don't go back to that dealer! Well, at least
that's my humble opinion. Bent valve? Am I missing something or is the
dealer blowing smoke up his _ _ _?

I don't think you mentioned how many miles were on the car or when your last
tranny service / fluid change was. Seems this could be a possibility before
you start pouring $ down the dealers black hole.

Good luck,
Chris
99BBB
92BB&T for sale

"Kenneth S." > wrote in message
...
> This sounds to me like a vaccum leak somewhere. Have you, or anyone
> else, checked the engine for such a leak? Perhaps what's happening is
> that, despite the warmup period, the engine is still running below
> operational temperature when you start driving. Then, as it reaches
> operational temperature, the leak opens up enough to cause the problems
> you describe. If it's a vacuum leak, it shouldn't cost much to fix.
>
>
> "2forgetmenot" > wrote in message
> lkaboutautos.com...
>> Let me state my problem again with this.
>> Everyday I warm my car up for 5-15 minutes before driving. After
>> approximately 2-5 minutes of driving the thermostat needle starts to
>> slowly drop down to cold, the car down shifts by itself and the engine
>> roars loudly becaue the RPM's are so high when the transmission down
>> shifts. I took my 94 Mazda Miata to a Mazda dealer. They first said the
>> thermostat was getting stuck. They checked that and that was not the
>> problem. Then they did some type of engine cleaning (so they said)which
>> cost me $74. The final analysis was I probably had a bent valve, which
>> would have cost me $750 to repair. I elected not to repair, becaue this
>> was an educated guess, but I wasn't interested in taking a stab in the
>> dark for $750. Any ideas?
>>

>
>



  #7  
Old November 15th 05, 11:10 PM posted to rec.autos.makers.mazda.miata
external usenet poster
 
Posts: n/a
Default Thermostat needle


"Don Bruder" > wrote in message
...
> In article
>>

>
> Automatic transmission with an in-radiator cooler, presumably...
>
> Temp drop MIGHT have to do with the cold tranny-juice hitting the
> (already hot) radiator once you've put it in gear and the fluid starts
> circulating.


"Tranny-juice" is moved aeound by a pump, connected directly to the engine.
As such, it flows as soon as the crank rotates, not once a gear is selected.


  #8  
Old November 16th 05, 02:15 AM posted to rec.autos.makers.mazda.miata
external usenet poster
 
Posts: n/a
Default Thermostat needle

In article >,
"Mal Osborne" > wrote:

> "Don Bruder" > wrote in message
> ...
> > In article
> >>

> >
> > Automatic transmission with an in-radiator cooler, presumably...
> >
> > Temp drop MIGHT have to do with the cold tranny-juice hitting the
> > (already hot) radiator once you've put it in gear and the fluid starts
> > circulating.

>
> "Tranny-juice" is moved aeound by a pump, connected directly to the engine.
> As such, it flows as soon as the crank rotates, not once a gear is selected.
>
>


Or maybe it's not, in this particular case?

I'm grasping at straws trying to figure out why the temp gauge would
drop suddenly after an extended warmup like the OP reported. The only
thing I can think of would be the tranny being in gear somehow chilling
the radiator, and in turn, the engine. Maybe I missed it, but I haven't
seen any responses from him - I'd like to know whether it continues once
the problem has started showing itself on a drive, or clears up, or what.

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info
 




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