overheating at speed
 

I have a 97 1.8 standard mx5. Today was hot in the UK (probably about
85F). On a long motorway journey the temperature gauge was creeping up.
This was at a steady 75-80mph. Slowing to 65mph lead to the temperature
returning to normal. Coolant levels normal.

What's the most likely cause of this? My ideas so far:

Clogged system
Failing water pump
Bad thermostat

Any opinions most welcome

In article .com>,
wrote:

> Clogged system
> Failing water pump
> Bad thermostat

Probably not the water pump. Assuming you have no coolant loss, check
the fan(s) as well. My similar symptoms were caused by an intermittant
fan motor, which had a dead spot on its commutator.

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

Thanks for the ideas.

I'm surprised the fan is mentioned - should it ever turn on at 70mph?

A friend suggested I check the air flow. Though there's a good number
of dead flies and a few bent vanes, the rad is pretty see-through.

My next idea is to change the thermostatic valve - it might not be
opening fully

In article .com>,
wrote:

> I'm surprised the fan is mentioned - should it ever turn on at 70mph?

Yep, if the ambient temperature and engine load are high enough, and
especially if the A/C is on (because the condenser throws hot air at the
radiator). The Miata does not have a huge reserve cooling capacity even
when everything is working properly; if it's not, it tends to overheat.

When my fan motor went bad, I saw the needle creep upward on 95-degree
days if I went over 80, or over 75 uphill, or over 60 with the A/C on.
Around town, the A/C condenser fan, which still worked fine, was
sufficient to keep everything cool. On a 1.8, the ECU switches the
condenser fan on at 106C even if the A/C is not in use, just in case the
main coolant fan is fritzed. Handy safety feature, but it sure made
diagnosis difficult. By the time I discovered the bad fan motor, I'd
already replaced the thermostat and radiator, removed the front plate,
and sacrificed two chickens and a goat.

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

Lanny Chambers wrote:

>
> Yep, if the ambient temperature and engine load are high enough, and
> especially if the A/C is on (because the condenser throws hot air at the
> radiator). The Miata does not have a huge reserve cooling capacity even
> when everything is working properly; if it's not, it tends to overheat.
>
> When my fan motor went bad, I saw the needle creep upward on 95-degree
> days if I went over 80, or over 75 uphill, or over 60 with the A/C on.
> Around town, the A/C condenser fan, which still worked fine, was
> sufficient to keep everything cool. On a 1.8, the ECU switches the
> condenser fan on at 106C even if the A/C is not in use, just in case the
> main coolant fan is fritzed. Handy safety feature, but it sure made
> diagnosis difficult. By the time I discovered the bad fan motor, I'd
> already replaced the thermostat and radiator, removed the front plate,
> and sacrificed two chickens and a goat.
>
> ---
> Lanny Chambers
> '94C, St. Louis
> http://www.hummingbirds.net/alignment.html

No ox? No wonder it took so long. Even without reading the miata
enthusiast's manual I knew that sacrificing an ox, in addition to 2
chickens and a goat, is required for problems that can not be diagnosed
on a miata. Sheesh, everyone knows that. It sounds to me like you
cheaped out on buying the ox.

pat

In article >,
pws > wrote:

> It sounds to me like you cheaped out on buying the ox.

In my defense: after my earlier livestock purchases, the car maintenance
budget was somewhat depleted for the quarter. Still, I kept scanning
farmanimals.ebay.com for oxen, but I kept getting outbid by a cult of
fundamentalist Babylonian sodbusters from Kansas. *sigh*

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

Lanny Chambers wrote:

> In my defense: after my earlier livestock purchases, the car maintenance
> budget was somewhat depleted for the quarter. Still, I kept scanning
> farmanimals.ebay.com for oxen, but I kept getting outbid by a cult of
> fundamentalist Babylonian sodbusters from Kansas. *sigh*
>
> ---
> Lanny Chambers
> '94C, St. Louis
> http://www.hummingbirds.net/alignment.html

Damn you Lanny, now I have to clean coffee off of my keyboard!

That was rather good, I concede defeat and will continue to plod along
with my day job rather than attempt the comedy circuit. :-)

Pat

"Lanny Chambers" > wrote in message
...
> In article >,
> pws > wrote:
>
>> It sounds to me like you cheaped out on buying the ox.
>
> In my defense: after my earlier livestock purchases, the car maintenance
> budget was somewhat depleted for the quarter. Still, I kept scanning
> farmanimals.ebay.com for oxen, but I kept getting outbid by a cult of
> fundamentalist Babylonian sodbusters from Kansas. *sigh*

This reminds me of a hilarious episode that happened to me about a year ago.
I was on holiday on a small Greek island. One day a whole bunch of people in
white descended on the island, all Americans (myself and my friends with
whom I was there are from the UK). It transpired that they were members of
some cult or other who were convinced that Armageddon was to take place on
one of the days we were there, and the only place in the whole world that
would survive was this particular island. They holed themselves up in a
hotel they'd group-booked, then reappeared the night before the Big Day and
went wandering around the town. Needless to say, Armageddon didn't actually
take place. What we wanted to know was:

- How did they get back home? One would assume they got one-way tickets.
- Once they got home (if indeed they did), did they have anything left to go
back to? Or had they told their bosses to shove it, sold the house and spent
all the money on one hell of a party?
- What DID they get up to in that hotel in the few days they disappeared
from view??!!

All I can say is keep scanning farmanimals.ebay.com, Lanny, something's
bound to turn up sooner or later.

Eric

In article >,
"Eric Baber" > wrote:

> Needless to say, Armageddon didn't actually
> take place. What we wanted to know was:
>
> - How did they get back home? One would assume they got one-way tickets.
> - Once they got home (if indeed they did), did they have anything left to go
> back to? Or had they told their bosses to shove it, sold the house and spent
> all the money on one hell of a party?

Here's a website about a book I read for a college psychology course:

http://www.whenprophecyfails.org/

It's the classic study of exactly the same phenomenon. The cult in
question believed it would be rescued by an alien spaceship just before
the Earth exploded. The authors infiltrated the cult to gather data.
When the date passed and the Earth didn't go boom, the cult attributed
the planet's survival to the power of their prayers.

The book is out of print, but widely available used. It's a fairly
depressing read for anyone who imagines the ignorant can be persuaded
using reason and logic.

---
Lanny Chambers
'94C, St. Louis
http://www.hummingbirds.net/alignment.html

"Eric Baber" > wrote in message
...
> This reminds me of a hilarious episode that happened to me about a year
> ago. I was on holiday on a small Greek island. One day a whole bunch of
> people in white descended on the island, all Americans (myself and my
> friends with whom I was there are from the UK). It transpired that they
> were members of some cult or other who were convinced that Armageddon was
> to take place on one of the days we were there, and the only place in the
> whole world that would survive was this particular island. They holed
> themselves up in a hotel they'd group-booked, then reappeared the night
> before the Big Day and went wandering around the town. Needless to say,
> Armageddon didn't actually take place. What we wanted to know was:
>
> - How did they get back home? One would assume they got one-way tickets.
> - Once they got home (if indeed they did), did they have anything left to
> go back to? Or had they told their bosses to shove it, sold the house and
> spent all the money on one hell of a party?

In my limited experience, it's cheaper to buy a round-trip ticket to
someplace than a one-way. I have taken a few one-way trips by buying
round-trip tickets and not using the return tickets.

Of course, if the end was near, what difference would it make on how much to
spend on the trip? The bills would show up after the end...