Overheating

[Neill1607]

The fans don't come on, which I assume is due to the radiator fan thermal switch failing - Is there a way I can check?

But I don't think that's the only problem; driving the car this evening with the ambient temperature at 18C, doing 30-40mph & not getting stuck in any traffic, internal heater at max with fan on 4; I wouldn't expect the temperature to just keep rising, I'd expect it to stabilise then rise when stopped at lights or in the drive. I'd have expected the airflow through the radiator to have kept it cool enough whilst driving. Instead the temp gauge just showed a steady increase to nearly "red" by the time I got home.
Any suggestions?
Thanks

[epipete]

Airflow through the radiator will cool the any fluid in the radiator but not move it around the pipes! So firstly (not being offensive) have you checked the coolant level? low levels may not trigger the fan sensors!

If the level is ok then there must be a blockage or failure somewhere as the coolant is pumped via a water pump driven off the main belt, hence the fluid is being constantly moved (& heated by the engine) even when the car is stationary, it is the forward movement that cools it via the radiator. When stationary the increasing temp triggers the fans which in sucking cool air replicates the forward motion.

I believe that there is also a secondary electric pump which operates, again, at a set temp!

Pete

[Specky]

The second pump is electric and only works if the car is switched off and also pumps the coolant in the opposite direction.

Things I'd check:-

Coolant level
Replace thermostat.. Or remove it for the short term

This in theory should point you in a set direction.

Coolant level low... You have a leak... Refill system with water... Pressurise system with test equipment.. Find the leak... Pay attention to the radiator end caps. Replace the radiator if that's your issue and the water for coolant.

Coolant level normal... Remove thermostat... Disconnect either side of the radiator.. And purge the system with water.. Reassemble... Refill with coolant.

Thermostats can fail at any time...

Failing open is not so bad... High fuel consumption, low heat etc
Failing closed is bad... Restriction, blockage, high heat etc

TTFN

[Neill1607]

Sometimes we all overlook the simple things, so always a good idea to cover them first - yes, I have checked the coolant level & it's fine.
To me the symptoms seem to indicate a failiure of more than one part of the cooling system.
Good suggestion on the thermostat, I'll try taking it out & see what difference that makes.
Do the radiator fans have a seperate fuse?
How can I check the water pump?
How can I check the secondary electric pump?
I'm used to tracking down things like this on the Esprit! but I'm new to the Elan so not sure where anything is yet.

[Specky]

And just to double check because of your location...

Were you nearly stationary when the car started to overheat, the gauge went past 3/4 ( +/- 15 % because the gauges are old and poor.) and then you drove home at low speed.. Or did you get some serious airflow through the radiator for a descent period?

Anyway... The overheating is a symptom of a failure somewhere, mainly because you're having it when there's forward motion. The fans or pump starting are also a resultant of the coolant temp switch being activated...

To test the pumps and fans, all three have sockets.. Use a battery, some wire and give it ago.. When the fans work, that's obvious.. For the pump... put your hand on it, you will feel it very slightly vibrating. It's the silver cylinder near the L/H light pod.

Just to reiterate the electric pump is only utilised when the car is stationary, ignition off etc...

Testing as you really don't want to start the car if you have a main water pump failure etc..

The electric pump has it's connecting plug just above the gearbox.. IMHO a lame ass White plastic conector which is prone to internal corrosion and the wires snapping. There's a bolt in the middle, undo that.. Gives you access to the pins.


The electric fans can be made to work by shorting the wire a the sensor, ignition on, engine not running etc

This could be a sensor failure, but it doesn't explain why it's that hot in the first place..

Voltage check at the sensor.. That'll check out, the fuses, relays, wiring

Mechanical water pump testing...

I guess taking it off is not an option... OK I know it's not an option at this stage

It can only be a bearing seizure, or an impeller failure... Both would have your temperature through the roof, infact... Blown pipes, engine etc

So in a wacky logic you could start her up and feel if the pipes pressurise. Just for a couple of seconds, even crack the coolant tank lid after the 2-3 second run (warning, not to be done on a hot engine, running engine etc)

Have you got Elan scan?

Do the radiator fans have a seperate fuse?

Check the wiki at the top...

How can I check the water pump?

Done that

How can I check the secondary electric pump?

Normally start the car, leave her 20 mins till she overheats, the moment the fans cut in, switch her off, run round to the front, put your hand on the housing, feel slight vibration, run back round, start car, fans cut in.. Take for a drive to cool her back down to normal operating limits.

I'll amend this post as I go..Think I can stop amending now..

TTFN

[hodge]

Hi, the thermostat holds coolant in the engine till it gets up to temperature, the fan switch is on the thermostat housing but positioned 'after' the thermostat ie on the cold side if the thermostat is closed.
The fans won't come on if the thermostat is closed, no matter what the temp gauge (which is on the engine side) is showing.
I'd check out your thermostat, it's straightforward to remove, (they're cheap and easily available, halfords stock one, check wikiLEC for ref number).
Thermostat should open and coolant be flowing around radiator by time the temp gauge reads approx 1/4 (82c iirc). Fans should switch in at around 3/4 ( if hot coolant reachs the switch).
You can test your old (removed) thermostat by putting it in a pan of water and heating it up to see if it opens.
Good luck.

[Neill1607]

Ok thermostat is out & Fans are now kicking in at the right point & bringing the temperature back down again.
The secondary electric pump is also working fine.
So looks like all I need to do is get a replacement thermostat. The wiki says a 1000cc mini one will do the job, but what about the gasket. Mine split in two when the thermostat housing came off - Is the gasket the same as a mini or something different?
Thanks for all the help guys.

[Specky]

Normally there are several gaskets in a thermostat box, and they have multiple holes for different engines... So my top tip is open the box before you purchase said item...

Halfrauds are a classic example of having thermostats without gaskets as potential customers remove them.

TTFN

[Brit-Car-Nut]

Of course, the Isuzu Impulse gasket is correct. Readily available in the US, don't know about the UK.