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'[TECH] Mazda Miata overheats'
2011\06\15@224648 by Lyle Hazelwood

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On Wed, Jun 15, 2011 at 10:36 PM, YES NOPE9 <spam_OUTyesTakeThisOuTspamnope9.com> wrote:
> gradually overheats on long drive
> no coolant is missing
> fan belt is quiet ... does not appear to be slipping
> turning on interior heater with fan brings temp down
> ( i have only seen water pumps fail by leaking and screeching )
>
> What might it be ?   How can I test ?
> 99guspuppet

Two things come to mind...

Deposits in radiator are clogging it, reducing flow rate.

Impeller vanes on water pump are corroded away, reducing
pressure/force of circulation.

How hard is it to reach the pump and remove it for inspection?

Lyle

2011\06\15@225956 by YES NOPE9

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{Quote hidden}

The pump is reasonably easy to reach as I cut away the front 5% of the engine 5 years ago.
The timing belt is easy to reach and easy to inspect.
99gp

2011\06\15@233038 by John Gardner

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Restricted radiator flow/bad thermostat are likely suspects.

Pull off the main hoses and check the flow with a water hose
and change the thermostat. If the radiator flow is'nt unrestricted
or you're not sure take it to a radiator shop ASAP.

You did'nt say what year, but if it's more than a few years old
the radiator shop might be the 1st thing to do - Overheating
engines have a way of turning into brand new engines, with a
wave of your wallet..

2011\06\15@234143 by John Gardner

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I've also seen electric fans hooked up reverse polarity.

No kidding - It was done by a pro too... I got involved because
I'd built the engine (TVR chassis/TR6 engine) for a restoration
specialist.

So, been doing any wiring lately?   :

2011\06\15@234425 by RussellMc

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Do what John suggests NOW.
Whatever it is, when it comes to engines :-).

Along the way you could try a poor-man's reverse flush .
One hose off - you work out which and where.
Thermostat out. .
Radiator cap off.
Air source. Lowis prom compressor easiest. See warnings at end.

Water fill radiator.
Apply air source to open hose / stand clear / ... fountain ...

Repeat until tender.

Fun even when  not effective.
Sometimes very effective.
Sometimes not.

Collecting effusant may provide some nice samples of stuff flushed from system.

Do not:  destroy system with air pressure, destroy self with air
pressure, get perishable things wet, move rapidly and damage yourself
when fountain fountains (or slowly), spindle bend fold mutilate
staple,

YMMV.

Do what John says

2011\06\16@001923 by John Gardner

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Real-world cooling problems can get pretty esoteric - Sometimes
seen in large wet-sleeve diesels is cylinder overheating caused by
cavitation on sleeve exteriors, restricting heat transfer.

Interfering with existing mechanical resonances sometimes alleviates
the problem -  Usually accompanied by the Mechanic's Chant..

2011\06\16@050056 by alan.b.pearce

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> Deposits in radiator are clogging it, reducing flow rate.

That would be my bet. New radiator, or find a radiator specialist who would unsolder the top and bottom tanks and rod out the tubes. Had the latter done one on a car I had, and it made a world of difference.
-- Scanned by iCritical.

2011\06\16@083227 by Carl Denk

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Concur, plus, likely causes are not changing the coolant at specified time and if added water, it was not pure enough. Also, possible are defective thermostat, a hose that the liner has come loose and collapsed. Did you verify the sensor is accurate.

Fan belt can be quiet and slipping either due to tension or worn pulley.

A rich mixture burns cooler, a lean mixture burns hotter. What are sparkplug colors? Are they light gray/brown, no burnt electrodes, all similar colors? If there is a fan clutch ,not likely unless overheating when slower speeds

On 06/16/2011 05:00 AM, alan.b.pearcespamKILLspamstfc.ac.uk wrote:
>> Deposits in radiator are clogging it, reducing flow rate.
> That would be my bet. New radiator, or find a radiator specialist who would unsolder the top and bottom tanks and rod out the tubes. Had the latter done one on a car I had, and it made a world of difference

2011\06\16@093137 by Sean Breheny

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On Wed, Jun 15, 2011 at 10:59 PM, YES NOPE9 <.....yesKILLspamspam.....nope9.com> wrote:
>
> The pump is reasonably easy to reach as I cut away the front 5% of the engine 5 years ago.

??? !!!

2011\06\16@100702 by John Gardner

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....I cut away the front 5% of the engine 5 years ago...

If you're referring to the fan cowling, that might make
the suspect lineup, too...

A radiator full of bugs, or airflow otherwise obstructed,
perhaps by a newspaper account of victorious Canucks?

Anyway, Omens not good - There's a million things that
COULD be wrong, & at 21 years vintage, likely are..

2011\06\16@191156 by RussellMc

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I note that various people have commented on the possibiity of a clogged
system but nobody commented on my "reverse flush" suggestion.

This can be a very effective short to medium term cure where appropriate. My
DIY version approximates the real thing and is easy enough to do to be worth
trying.

I've personally used the system with success on several cars. Long ago in
Australia we used service station free-air to occasionally assist with
reverse flushing an old Ford Falcon that otherwise wouldn't have made it
through a typically baking hot Australian-summer longish distance road trip..

Back then the Oz speed limit was mostly 100 kph. Probably still is. North of
Sydney the Princess highway allowed 100 kph and a good clear run. At the far
end all the service stations sport "Radiators Reverse Flushed" signs.


     Russel

2011\06\16@195709 by John Gardner

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Lots of good suggestions...

Reverse-flushing might help - If it does the block needs flushing too;
that's where the crud is coming from... When seen, one often finds
the wrong coolant has been in use, or change intervals not observed.

Bad fan clutches, stuck/balky/wrong thermostats, defective fan
switches - All frequent flyers. Some systems can air-lock, thus
deceiving you into thinking they're topped off,when they're not...

Murphy rules

2011\06\16@201347 by John Gardner

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One more time - Leaking head gaskets should be ruled out by someone
who knows how to find them. Eyeballing the coolant reservoir is not good
enough. It's a common failure in elderly engines, & the initial symptoms
are exactly what you describe

2011\06\16@212137 by Carl Denk

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Concur, reverse flushing is easy, inexpensive, and certainly can't hurt. Though radiator deposits clogging the tubes are frequently hard and won't be dislodged by  flushing. Ideally an acid would easily remove the deposits, BUT probably will cause great harm, like eating holes in the radiator. As said earlier, maybe can see the conditions inside the radiator through one of the large hose connections, or one of those snake cameras would be great.

On 06/16/2011 07:11 PM, RussellMc wrote:
> I note that various people have commented on the possibiity of a clogged
> system but nobody commented on my "reverse flush" suggestion.
>
> This can be a very effective short to medium term cure where appropriate. My
> DIY version approximates the real thing and is easy enough to do to be worth
> trying.
>
> I've personally used the system with success on several cars. Long ago in
> Australia we used service station free-air to occasionally assist with
> reverse flushing an old Ford Falcon that otherwise wouldn't have made it
> through a typically baking hot Australian-summer longish distance road trip.
>
> Back then the Oz speed limit was mostly 100 kph. Probably still is. North of
> Sydney the Princess highway allowed 100 kph and a good clear run. At the far
> end all the service stations sport "Radiators Reverse Flushed" signs.
>
>
>        Russel

2011\06\17@013254 by PICdude

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Quoting John Gardner <EraseMEgoflo3spam_OUTspamTakeThisOuTgmail.com>:

> One more time - Leaking head gaskets should be ruled out by someone
> who knows how to find them. Eyeballing the coolant reservoir is not good
> enough. It's a common failure in elderly engines, & the initial symptoms
> are exactly what you describe.

If there is a head-gasket leak, where is the fluid going?  If into the  cylinders, there should be whitish smoke, if into the oil, the oil  will be murky/milky brown, and if outside the block, it should be a  visible somewhere.  If the fluid level is dropping at such a low rate  that it's not even noticeable over some days, then something else is  causing the overheating.

Cheers,
-Neil.

2011\06\17@041805 by Forrest Christian

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I can't speak for the Miata, but I can vouch that a head gasket failure can cause overheating without enough symptoms to be recognizeable.   I had a pontiac with the L4 engine which is notorious for head gasket issues - and after months of trying to hunt down an overheat issue, one morning it finally did provide enough leakage into the exhaust that the very first turn over of the engine produced a nice cloud of white smoke...

Even then, it took the shop a bit to figure out that it was a leak - I think the problem was more that the exhaust gases were getting into the cooling system than the other way around.  It wasn't until they pressurized the coolant system, let it set for a while and then re-crank the engine and see the resulting cloud that they believed me and replaced the head gasket and make the cooling issues go away.

-forrest

On 6/16/2011 11:32 PM, PICdude wrote:
{Quote hidden}

>

2011\06\17@075129 by Herbert Graf

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On Fri, 2011-06-17 at 02:18 -0600, Forrest Christian wrote:
> I can't speak for the Miata, but I can vouch that a head gasket failure
> can cause overheating without enough symptoms to be recognizeable.   I
> had a pontiac with the L4 engine which is notorious for head gasket
> issues - and after months of trying to hunt down an overheat issue, one
> morning it finally did provide enough leakage into the exhaust that the
> very first turn over of the engine produced a nice cloud of white smoke....
>
> Even then, it took the shop a bit to figure out that it was a leak - I
> think the problem was more that the exhaust gases were getting into the
> cooling system than the other way around.  It wasn't until they
> pressurized the coolant system, let it set for a while and then re-crank
> the engine and see the resulting cloud that they believed me and
> replaced the head gasket and make the cooling issues go away.

Easy check for that sort of thing is run the engine with the radiator
cap off and look for bubbles in the coolant, would that have caught this
issue?

TTYL

2011\06\17@091611 by PICdude

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Quoting Forrest Christian <@spam@forrestcKILLspamspamimach.com>:

> I can't speak for the Miata, but I can vouch that a head gasket failure
> can cause overheating without enough symptoms to be recognizeable.   I
> had a pontiac with the L4 engine which is notorious for head gasket
> issues - and after months of trying to hunt down an overheat issue, one
> morning it finally did provide enough leakage into the exhaust that the
> very first turn over of the engine produced a nice cloud of white smoke....
> ...

But there's that white smoke cloud though, which is not the case (at  least I've not seen any post indicating this yet) with this thread's OP.


2011\06\17@095713 by John Gardner

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A gas analyzer will show high levels of HC in the exhaust before there
are any other visual indications - Of course there are other reasons HC
might be high; that's where knowing what you're doing rears its ugly
head.

There is a chemical test for exhaust in the coolant that's fairly reliable;
bubbles in the coolant is end-stage. If you're still driving the car at that
point have your Nike's in the car. And your checkbook.

Likewise with white smoke. Do a pressure test..


'[TECH] Mazda Miata overheats'
2011\08\07@143352 by John Gardner
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Under no circumstances do a pressure test - Your upcoming
contribution to the economy is much needed, & appreciated...

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