Overheating

RD5T3R · Post by **RD5T3R** » Tue Oct 11, 2005 5:55 pm

Hi Guys
As brand newbie owners of a 1991 BRG V spec MX5 we too loved the chance to be
involved at the World Record attempt and we were probably the only one there
with no wing mirrors - coming soon we hope!! However, we only just made it as
the car started overheating - again!

Since we bought it about 3 weeks ago we have had the rad flushed, thermostat
changed, new water pump fitted, cam belt replaced, timing done and full
plugs/oil/filters serviced. But she still overheats after doing 100kms for
about half an hour and then we put the heater on full bore, open the windows,
slow down to 75/80, etc, or she's gonna go past that 3/4 point and get
seriously HOT. We noticed a number of people had moved the front number plate
off the intake area - is this why? Are we in for a head removal job? Any
wise ideas out there?

Thanks

Stu & Viv
RD5T3R

Ken McNoe · Post by **Ken McNoe** » Tue Oct 11, 2005 9:50 pm

Hi Stu and Viv

Congrats on the purchase. Try moving the licence plate, it may be the
issue. Some people have said that having the licence plate obstructing
the intake area can cause overheating

Hope this helps

Ken McNoe

Phone: 09 483 8237
Mobile: 021 536 911

poison · Post by **poison** » Tue Oct 11, 2005 9:54 pm

Hi Stuart

Any blockage of the air intake area will have a bad effect, but not to this
extent. Anyway before you race off and get a head job

take it to a
mechanic and have them do a head gasket leak test, this will test for exhaust
gasses in the water and will tell you if the Head Gasket is OK. The more
likely problem will be a dirty radiator, and flushing will not cure this, the
top tank needs to be pulled off and all the cores cleaned, or worst case is a
new radiator core. Only get this done at a specialist radiator shop.

Gazza
"PO1SON"

Michael & Kate Cooper · Post by **Michael & Kate Cooper** » Tue Oct 11, 2005 9:59 pm

Congratulations on a wonderful choice of car!

If your number plate is blocking the front intake hole, this will reduce the
cooling of the engine, however it shouldn't be enough to make the car overheat
as dramatically as you say. Ours is attached to the bumper above the hole -
you can buy or make a bracket that holds it to the side of the hole (I think
it attaches to one of the tie-down hooks).

Sorry, no tips on fixing your problem, but I'm sure the more knowledgeable
folk on the list will have you sorted out by tomorrow afternoon! Fire away
guys...

Ciao

Kate

Ken McNoe · Post by **Ken McNoe** » Tue Oct 11, 2005 10:06 pm

Okay, I have just proven I don't know a great deal about car
stuff...oops!

Ken McNoe

Phone: 09 483 8237
Mobile: 021 536 911

Wayne Sinclair · Post by **Wayne Sinclair** » Tue Oct 11, 2005 10:13 pm

As suggested get a head gasket leak test done, maybe put a radiator flush
through then drain system. If the water is a brown colour and not the colour
of the anti freeze the radiator most likely needs taken apart and cleaned
professionally. Discolouration will come from the block if the system has been
neglected, but the radiator core acts a little like a sive and collects most
of the rust particles and looses it ability to cool. A look into the cap
position will give some indication. BUT is it overheating or is the gauge
telling you its overheating senders do fail, but not often. Not sure on the
cost of a sender but may be cheep to eliminate.

Good luck
Wayne

Okibi · Post by **Okibi** » Tue Oct 11, 2005 10:15 pm

What everyone else said . and make sure you move that license plate out of
the "mouth" of your MX-5 although I doubt it will cure your problem.

While you might get some of the cardigan crew complain "I've had mine for
years like that and it never overheated", the truth is it really can affect
the water temps, especially on a race track.

- Dave.

peter · Post by **peter** » Tue Oct 11, 2005 10:26 pm

just a quick question or two -
when you start the motor do one or both of your fans turn on?
and, does your aircon work?
Last time my car had your symptoms the aircon pump was dead...

and welcome to the list - have you joined the club yet?

Peter

DRGN 1

EricW · Post by **EricW** » Tue Oct 11, 2005 10:40 pm

Yes, definitely get a head gasket leak check done, although you can check this
quickly by taking the radiator cap off (while the engine is cold) and seeing
if there are bubbles in the coolant as the engine warms up , but if the engine
is not losing coolant I would suggest that a more likely cause is a blocked
radiator core, particularly if turning the heater and fan on makes a radical
difference. As someone else said, get the radiator re-cored rather than
flushed as flushing is unlikely to fix the problem if the thing is that
blocked.

A word of caution that you probably do not need, but, for the sake of safety,
I will say it anyway,

DON'T take the radiator cap off, or work on the system, while the engine is
hot!

Not only will the system be highly pressurised, especially if the head gasket
is leaking, and you run the risk of serious injury from superheated liquid,
but the sudden drop in pressure and subsequent vaporisation of the coolant can
also severely damage an aluminium engine.

I doubt that the airflow restriction caused by the number plate is really
significant at normal road speeds, unless it is right in the "Mouth"

Eric

KSCRIM · Post by **KSCRIM** » Tue Oct 11, 2005 11:01 pm

Another item which can cause the overheating is a radiator hose which has
delaminated inside, particularly in the return hose from the rad to the
block. Easy enough to detect as the hose feels soft to compress. The
delaminated section can suck in and obstruct the water flow. Or a section of
the inside may have come free at one end and swung around causing an
obstruction.
The radiator could have external blockages in the fins causing insufficent
air flow, or the fins could be corroded to the extent that the cooling
efficiency is seriously reduced. I have seen the fins loose on the cores.
Yes, get the number plate out of the mouth, the cooling system does not have
very much surplus capacity. The NB's have a larger mouth for that reason.
There must be something seriously wrong as the air temps have not been high
enough recently to cause problems.
The main fan may not be working, The second one only comes on when the A/C
is on, and then you get some relief

Kevin 98NB6C

[...]

Stuart & Chaanah Oliver · Post by **Stuart & Chaanah Oliver** » Wed Oct 12, 2005 9:08 pm

Stu ,

Replacing the radiator cap may also help, if faulty it will not hold
pressure which will cause the coolant to boil. This should be noticeable buy
loss of coolant in the radaitor and the catch tank over flowing on coolant
dripping from the radaitor once you have stopped.

Good luck Stu

[...]

Mikkels · Post by **Mikkels** » Wed Oct 12, 2005 9:18 pm

I had this problem. Had the radiator rodded out with some
success. Now only overheats going up big hills. Used to
overheat around town on a hot day.

I have an 1800 in my 1600 car. I think I need to have the
radiator re-cored. Any suggestions for a radiator or better
core that handles the heat load a little better? I foresee
a Turbo in my future so will need a bit more capacity than
what I currently have.

Don

[...]

Ian · Post by **Ian** » Wed Oct 12, 2005 9:38 pm

Don..

My books suggests two cheapish mods...a 16lb radiator cap (NBs had a 16lb
cap) apparantly helps...
A NA rad from an auto, has considerably more capacity than the manual rad!
Cheers

Ian · Post by **Ian** » Wed Oct 12, 2005 9:41 pm

PS...the MX5 Performance Projects book states the auto rad has almost TWICE
the capacity of a manual radiator, and is a straight bolt in!

Ian · Post by **Ian** » Wed Oct 12, 2005 9:46 pm

Depending on where you live, 30% antifreeze (as opposed to 50%) will also
improve the cooling efficiency...

Mikkels · Post by **Mikkels** » Sun Oct 16, 2005 5:53 pm

Ian

Thanks for the tips. Will keep an eye out for an auto
radiator.

Cheers

Don

[...]

Euen · Post by **Euen** » Sun Oct 16, 2005 9:44 pm

Don

Ross Campbell may still have one. All my mechanicals came out of a 96 1800
auto but I didn't need the radiator.

Cheers
Euen

Mikael Bjornstjerna · Post by **Mikael Bjornstjerna** » Sun Oct 16, 2005 10:28 pm

Hi,

Overheating is sometimes related to a malfunctioning thermostat that
doesn't open when the engine hots up. Removing the thermostat will
permanently leave open
the circulation between the radiator and the engine and cool it, but
since fuelconsumption increases without thermostat it's recommended to
install a new one, although
driving without thermostat is ok. This is the easiest (and cheapest)
first step, next is the waterpump, etc.
Otherwise, removing front numberplates and put the heater on will help
in a crisis situation.

Mike

Le 16 oct. 05, ` 06:53, mikkels@ihug.co.nz a icrit :

[...]

Okibi · Post by **Okibi** » Sun Oct 16, 2005 10:43 pm

"although driving without thermostat is ok"

I disagree, it's better for your engine life if the water and the oil gets
up to temp as soon as possible.

It's also safer if your car heater can defrost windows sooner rather than
later.

My 2 cents.

- Dave.

joanie · Post by **joanie** » Sun Oct 16, 2005 10:51 pm

Overheating is sometimes related to a malfunctioning thermostat that
doesn't open when the engine hots up...

Think we've been here before, but my experience has been that rarely do
thermostats fail in the closed position - more often they fail in the open
position, which means the car that never really gets up to temp. It is easy
enough to pop out the thermostat and test in a pot of boiling water that it
opens and shuts ... In saying this I have not removed a thermostat form the
MX5 it may be more difficult than some other cars...
Cheers Joan H

Mikael Bjornstjerna · Post by **Mikael Bjornstjerna** » Sun Oct 16, 2005 11:44 pm

The thermostat is the first thing to check out and it takes 20 minutes
to fix. Take away the air filter / thick black plastic tube in front of
the upper engine part and the the connection tube between radiator and
engine is visible further down. Remove the tube where it's connected to
the engine and be aware of cooling liquid pouring out. The thermostat
sits in the engine opening and should cost around 25$. You're right,
without thermostat it takes longer time for the engine to heat up which
might be a problem during winter.

Another problem, RUST. Is there a way to stop it?

Cheers

Mike

Le 16 oct. 05, ` 11:51, Graham&Joan Hilder a icrit :

[...]

KSCRIM · Post by **KSCRIM** » Mon Oct 17, 2005 8:00 am

Thermostats can and do fail shut. I had one fail shut in my Sigma GSR turbo.
The overheat cooked all the valve stem seals and the camshaft seal. Idle
smoke and oil leaking out of the front of the head!!. Not to much later the
head cracked also. It is a lesser problem to run without a thermostat than
to try to struggle home with just the heater doing the cooling.

Kevin 98NB6C

[...]

Michael & Kate Cooper · Post by **Michael & Kate Cooper** » Mon Oct 17, 2005 8:07 am

Ours failed in closed position and blew the cap off the radiator during laps
at Ruapuna.

kate

From chris.tankard@aderant.com Fri Apr 27 17:28:05 2007
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Subject: Some changes and what they are like ....
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As part of my project I needed to make room for the intercooler. Thus
the Air conditioning had to come out, and it made sense to complete the
conversion from power steering to manual (keeping the faster power rack)
at the same time.

For those who are interested ...

The air conditioning removal was fairly straight forward. After having
the unit degassed by and auto air conditioners, it was pretty much
matter of removing the nose ducting and splash shield then following the
air con parts and removing in sequence. I opened the condenser unit and
removed the internals and popped it back in to allow the blower to
connect to the rest of the system.

Have I noticed any difference - a little - the car does seem to rev a
little easier. There were a ton of parts in there - I will weigh them
this evening - I am sure I took a few kg's out of the front. On the
slight negative - with the internals removed from the condenser the
heater 'blowing' does make a little more noise than before, but nothing
that I would call annoying.

With the power steering - this took longer. The objective here was to
make room, add lightness and give myself better feeling steering than
what PS was giving me. Additionally I always found the PS 'twitchy' at
high speeds (I do the occasional track day).

To do this you have to cut the power steering pipes at the back of the
unit and loop the 2 coming from the housing unit and the 2 going to the
rack (this allows air to move keeping the steering lighter). The pipes
to the pump and the fluid tank get capped to keep out dirt etc. PLEASE
DO YOUR OWN RESEARCH ON THIS BEFORE ATTEMPTING - after all it is your
steering you are taking a hacksaw too and you don't want this to go
wrong

My feedback on this - great once you are moving, but it is a lot heavier
than standard (although I am yet to have the wheels realigned for this).
If you only use the car around town etc - I would not recommend this
change - ever. But you DO get a lot more feel out on the open road and
in the twisties. The car does feel a lot more planted and solid and
most defiantly less twitchy as you go faster. Anyone thinking of this
change - if you are in Auckland you are more than welcome to play in my
car before trying it with your own.

C

Mikkels · Post by **Mikkels** » Mon Oct 17, 2005 9:25 pm

Hi Euen

Thanks for the tip. I will give Ross a call.

Don

[...]

WiM · Post by **WiM** » Tue Oct 18, 2005 10:33 pm

removing a theromstat is fairly easy, it requires new coolant fluid
afterwards tho'. Maybe another question: has the Coolant Temp Sensor
on top of the thermostat housing been checked? I had that one failing
on me and my radiator was boiling over too...
Check the thermostat first with the boiling water trick, if that
fails you might have to go for a new Coolant Temp Sensor...
Hope this helps,
WiM

Quoting Graham&Joan Hilder <graham.joan@paradise.net.nz>:

Overheating is sometimes related to a malfunctioning
thermostat that
doesn't open when the engine hots up...

Think we've been here before, but my experience has
been that rarely do >thermostats fail in the closed position - more often
they fail in the >open position, which means the car that never really
gets up to temp. It >is easy enough to pop out the thermostat and test in
a pot of boiling >water that it opens and shuts ... In saying this I
have not

removed a >thermostat form the MX5 it may be more difficult

than some other cars...
Cheers Joan H

WiM
'91 1.6 MX-5 GT

www.mx5ireland.com
www.cardomain.com/memberpage/312875

* not a newer version of GT4, nooooo GReddy Turbo 5

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