Diagnosing Cooling problems

Tips
When in doubt - Change the thermostat, they are cheap and responsible for 40% of cooling problems. 40% is due to corrosion and buildup and the rest is mechanical failure, gaskets etc.
Always keep the radiator water green (glycol) - prevents rust (read MUD), icing and shows your system is clean.It also raises the boiling point of the water, ie it will not boil at 100 deg/C.
Remove all hoses, thermostat etc and blow out all hoses, radiator, head, heater at least once a year from all directions.
On cars fitted with factory oil coolers, remove & clean it out as well (a pain), you cannot blow it clean in the system and it is a collecting point for mud.
NEVER put water into a steaming radiator! - It will crack/warp your head and/or radiator.Let it cool down first!
Never open a hot radiator! - leave it for 15min or ground the fan for a few minutes first. You will burn yourself and those around you. If it has boiled, it could vomit hot water at any time!
Put a small amount of grease on all fittings before re-fitting the hoses - prevents rusting and will make removing hoses easier (No it won't leak).
NEVER throw glycol (antifreeze) on the ground (kills the grass) or leave it lying around, animals (esp kids, dogs, cats, birds) will try to drink it (smells nice) and it's lethal!
Do not mix diffent types of antifreeze, always empty into a pan and flush the system first.
Always check new thermostats in boiling water first!
Fill the system slowly, squeeze the hoses to check no air is in the system.
Before upgrading your motor, seriously consider fitting a thicker, aftermarket radiator as well!
Periodically check your fans are working.
In sub zero temperatures and your car is not heating up properly - tape a piece of board or thick plastic over part of your radiator, experiment with different sizes.


Mysterious loss of water and eventual overheating.
Let car idle for 10 min and then check for water under the car, around the radiator (the top tank is suspectable to small cracks which leak under pressure)
and the bottom of the cambelt cover and inside the car around the passenger footwell.
Check exhaust for white smoke, white smoke = head gasket leak.Exhaust will be wet and sweet smelling.
Check spark plugs - Any "clean" plugs will show where gasket is leaking.
Check engine oil - white/milky oil indicates water in the oil.
Check fan operation
Check around engine block, welsh plugs will usually rust through and start seeping from the centre of the plug. They are bastards to find as the water will boil away on the hot block. Look for stains under the plugs. Same goes for small leaks around the water pump

Gauge moves up and then comes down
Thermostat is sticking and not opening fast enough, in that time the pressure has risen and dumped water into the overflow bottle. If the fan is faulty it could blow a hose or head gasket.

Dumping water into overflow bottle
Radiator cap faulty, replace
Thermostat faulty, replace
Fans not working - sender, fuse, relay, motor faulty
Radiator blocked - clean entire system.
Head gasket leaking gas into water - bubbles in radiator, steam. Perform pressure test.

Burst Hose
Thermostat stuck closed - remove it and immerse it in boiling water, if it does not open - chuck it.
Major water leak - fill system and check for leaks
Perform steps under tips to remove any potential obstructions.
Check fan operation.

Radiator cold in places
Radiator tubes blocked

It's overheating and I'm miles from home
If there's a leak - fix the leak! - any water you put in will be pumped out in seconds. Refer to tips section before burning yourself.
Make sure you have plenty of water and spare water in the trunk, keep the revs down (shortshift), coasting on flats, switch the motor off on downhills and WATCH THAT GAUGE!
Frequent stops to check the water and grounding the fan sensor will help.
Switch the heater to high heat and open the windows, it will help cool the motor.
Spraying the radiator with cold water will also help
DO NOT spray a hot engine block with cold water - you risk cracking it!
If you can - remove the thermostat till you get home/garage.

Fan/s not working
Sender unit on thermostat housing faulty?
Remove wire from sender and touch it to the motor, fan should switch on.If not it could be a fuse, sender, relay or fan motor.
NOTE - fans will not work when radiator is empty, sender can only work when immersed in water not steam.

Heater not working
Heater valve on firewall jammed
Heater radiator blocked - remove two hoses and blow out repeatedly with water.
Heater radiator control flaps stuck, can be a cable or electric motor fault.

Car takes ages to warm up
Either your thermostat is jammed open, or
Your motor is so worn, there's hardly any friction and it's running rich.

Car takes ages to warm up and gauge drops lower than normal at speed
Your thermostat is jammed open, not good. Refer to Thermostat section.

Thermostat
Always check new thermostats in boiling water first
Never run without a thermostat or modify the thermostat, the engine temp will not be constant and take longer to warm up. Causes accelerated engine wear & gasket problems.
Yeah I know race cars don't have them - don't do it
a) they modify (restrict) the housing
b) they are flat out all the time
c) the motor is pre-warmed
d) most use electric water pumps

Water Pump
The water pump bearing and seal will eventually go. When it does it will scream on startup and start to leak water or start/stop screaming loudly while driving - CHANGE IT IMMEDIATELY!- The water pump on these motors runs off the cambelt, if it seizes - it could destroy your motor
There is an O-ring on the rear of the pump and a gasket on the front, if either leaks it is advisable to change the pump as well.

 

Everyone on the road needs a thermostat!

It's job is to speed up warm-up time before you go revving the crap out of it
Also it keeps the temp constant while running, without it your temp will
range up/down depending on your speed and revs - even in hot areas, worse in cold areas.

Your engine parts expand and contract according to the temperature, not good in terms of
wear and reliability. They are designed & measured to work together at around 85 deg C

The exhaust isn't affecting the radiator - the car moves forward, not backward
Heat wrap is designed to speed up exhaust gas flow by keeping the gas hot, not to cool
radiators

The "S" motor is a 30yr old design, the heat issue is because water flows from cyl #1 to cyl #4,
getting hotter and hotter instead of across each cylinder evenly and out the back of the block.
At that time engines that used this design had wet liners, not dry like the "S".
The cylinder bores are also hopelessly too close to each other, the water can only cool the
front and back of the bores and can't get between them

Your car is supposed to have a "ramp" below the front bumper, it's probably been ripped off
like on many cars.

 

Restriction???

Even in race engines which run at redline all the time we remove the plunger but
still run with the restrictor plate (Mafix had this problem a while back - refer to his thread)
and block the circulator pipe

Why?

Because the water has to pass through the radiator at a certain speed in order to cool -
too fast (ie without the plate) and it doesn't have time to cool in the radiator.
You'll find that race engines also run with a bigger pump pulley to slow the water down
to normal (ie street speed) and save some ponies for the wheels.
Too fast and the water cavitates in the pump and flow is lost

Things are not as simple as you think

I bet your fans are working overtime trying to keep things cool and suggest you look
elsewhere for your problem (clogged radiator/head maybe?, running lean? faulty fan/sensor etc)

Another thing to bear in mind is that when you mod the thermostat, you MUST block the circulator
pipe behind your exhaust with a plug or else it just pumps boiling water straight back into the motor!

Nice to see someone thinking outside the box for a change and asking questions

 

1) Thats a mistake - you only need to unplug the wire and the fans come on if the ignition is switched on
It's the one on the water hose below your alternator, GT4's, 182's etc have the
switch at the bottom of the radiator
(a much safer place for it)

2) After changing, it's to eliminate air and check for leaks. Water won't circulate unless the motor is turning

3)No, its under the alternator as well, inside the bulge. The pump is on the cambelt side

 

Running too cold?

The temp gauge is one of my least liked items on the car.
11pm is normal, 12pm is "I'm going into meltdown now!" mode


The gauge should be redlined from the 12 oclock mark

In bad winter conditions (below zero) it's possible the engine takes too long to warm up and runs cold
when moving, esp with a larger rad fitted - The solution is to tape a piece of plastic card or cardboard
in front of the radiator, provided you never cover more than 1/2 the radiator

 

wash it out with acetone, kerosene, thinners or similar and make sure it's clean inside

Handy Cooling Tip
For those suffering from cooling problems there is a cheap & easy solution

The manual ST162 has a single core radiator and a low power fan
The auto versions have a 2 core radiator with an inbuilt oil cooler and high power fan.
The Diesel Corona auto ST160/ST191 has a 3 core radiator with inbuilt oil cooler and high power fan.
Bolts straight in using your exsisting brackets & top hoses from a 202 will work

These radiators can sometimes be bought cheaply and are a worthwile investment.
The 182, 202 radiator will not fit in your car without moving the bottom & top brackets.

 

The auto version is easy to find and works with Gen2/3 headers as well
The Corona version is hard to find and clearance probs with the hose/fans and
later headers

I've switched the Deisel ver to my FE motor with stock exhaust and it's a good fit.
My GE is now much happier with the 2 core auto rad and gen2 exhaust - I was getting an error 42
so filled the oil cooler with oil, closed the pipes and it helps to stop the temp swinging wildly when the fans kick in.

 

No, but it will make things more stable, prevent blown hoses & H/G and keep engine wear down
Optimum temp for these motors is 85-90deg C

Handy Tip
Tried 2 new thermostats this week and the car kept overheating! :twisted:

Before fitting a thermostat - take both thermostats and place them in a coffee cup,
pot etc and cover them both with boiling water.
They should open at the same time, if not - the one that opens 1st is the one to use

 

You don't need anything fancy to clean the heater radiator, some pliers and a hosepipe is all.
Disconnect the 2 firewall hoses and blow out the radiator from both sides till all mud is gone

Here's the heater/ventilation problems I found & fixed on mine, leaking dash fix is on another page
http://st162.net/forums/viewtopic.php?f=57&t=3828&start=520
My problem (as shown) was a combination of dirty radiator, leaves and a stuck heater valve