running temperature ?

[jeffreyt]

Now I am on the forum I would like to pick some brains.
Car is a 1990 SE with 59000 on the clock and running well.
However, temperature gauge hardly gets to the first mark under normal running ( summer or winter) although as soon as I stop at lights or similar it starts to go up and will reach the first mark after a few minutes.
Heater seems to work OK after a few minutes of running.
Have I got a dodgy thermostat or a dud sender?
I would be interested to know where temp gauge should sit under normal running conditions .
Thanks

Jeff

[Giniw]

The temperature gauge should be on the first mark (1/4 mark) when the engine is warm at its nominal temperature.
The fans should start at the 3/4 mark. Some car have had a lower temperature sensor fitted by a previous owner so the fans start at around 1/2. Then the fans stop when the temperature gauge is at the 1/4 mark again.
As soon as the car is idling (traffic light, etc) the temperature rises rather fast compared to a standard car. That is normal.

If your temperature gauge doesn't reach the 1/4 mark during normal driving situation, maybe your thermostat is stuck open. Or maybe it's your temperature sensor.

[Saltire]

Hi Jeff

This is fairly normal. The gauge and the sender are not well matched, so the gauge isn't very linear. On my S2, normal hot running sees the gauge just under the first mark. If I'm crawling along in traffic, it rises gradually to the third mark or thereabouts, at which point the fans kick in. As long as yours is similar to this, I would say you're fine. But do check the fans and the separate coolant pump are working properly (the fans come on when the engine is running and hot, whereas the coolant pump works with the ignition off to circulate coolant around the engine until everything has cooled down.)

Other wiser heads than mine will give more learned opinions, but that's my experience.

Hope this helps.

[jeffreyt]

Thanks,I will check the fans are working at the 3rd mark.
I have never heard the 'coolant' pump working when the ignition is switched off.
Hope this isn't a dumb question but what's the best way of checking the coolant pump is working?

[Giniw]

The coolant pump is activated with the same sensor as the fans :
- with the key on (accessory position) and engine on or off, the fans start
- with the key off, the coolant pump starts.

If you want to start the coolant pump with a cold engine, you might try to unplug the sensor or short it, I am not sure whether it's a normally open or normally closed switch.

[dapinky]

Jeff,

As Jonathan says, nothing in your post to worry about.

The 'problem' is a result of Lotus spending as little as possible to do the job, and the sender on the engine is a poor match for the gauge (one is Isuzu, and one is Vauxhall) - whilst both from the GM parts bin, they are not designed to be perfect together.

With the needle just a tad below the 1/4 mark, the temperature is 'normal' - as it raises (it appears to do so alarmingly quickly if stuck in Summer traffic) to about 3/4 the fans should kick in, and the needle drops to 1/2 when the fans cut off. If the car is still stopped, it repeats, but as soon as you start to drive, it soon returns to 'normal'.

There is actually only a small difference in degrees celcius between 1/4 and 3/4 on the gauge (and i can't recall the exact numbers at the moment).

It can be a bit disconcerting to watch, but isn't something to worry about unless the needle doesn't come down again when the fans kick in. Obviously, should the needle ever get to the top, there is an issue of some sort - but I've never seen it happen.

[Giniw]

(A bit off topic but I don't understand why a lot of people consider the sender doen't match the gauge. To me it suits it very well since the operating temperature can be read thanks to a needle that actually moves through its available range. I can see no point in a needle that stays on the middle of the range forever? I do understand it's a bit disconcerting though, as it's quite unusual.)

[woodcock]

New M100 owner but old Elan (1966) owner. Temp is at the 1/4 mark until stuck in traffic than it climbs to 3/4 mark. Fans do not come on even with A/C turned on.
When I shut the engine off the coolant pump does not come on either. Checked the fuses all OK. Any ideas ?
Ron

[Kathryn]

Mine usually sits half way between 0 and the first mark. Fans kick in just after the half mark. I'm not worried as this is usual for my car and it has certainly never let me down in traffic jams. (Incidentally before I had my head gasket done the needle did sit a bit higher and fans cut in just below the 3/4 mark).

[Giniw]

Kathryn > It's not very good to run a cold engine either. If I were you I would check the temperatures with ElanScan just to be sure all is OK.

[Brit-Car-Nut]

New M100 owner but old Elan (1966) owner. Temp is at the 1/4 mark until stuck in traffic than it climbs to 3/4 mark. Fans do not come on even with A/C turned on.
When I shut the engine off the coolant pump does not come on either. Checked the fuses all OK. Any ideas ?
Ron

There are multiple fuses / power sources and several ways the fans / coolant pump will turn on.

Here is the wiring diagram:

Cooling Fans.jpg

You can get the manuals at http://www.lotusm100.com/manuals/

[rip]

(A bit off topic but I don't understand why a lot of people consider the sender doen't match the gauge. To me it suits it very well since the operating temperature can be read thanks to a needle that actually moves through its available range. I can see no point in a needle that stays on the middle of the range forever? I do understand it's a bit disconcerting though, as it's quite unusual.)

The gauge gives you a detailed view of the temperature in its normal operating range. Too high or too low (except when warming obviously) is a concern.
What would be the point of worrying if the temp was below 1/4 or 3/4 if the areas outside of this range are 'worry areas' anyway?

[CalElan]

New M100 owner but old Elan (1966) owner. Temp is at the 1/4 mark until stuck in traffic than it climbs to 3/4 mark. Fans do not come on even with A/C turned on.
When I shut the engine off the coolant pump does not come on either. Checked the fuses all OK. Any ideas ?
Ron

If you search the forums you'll find some tests - from memory, find the connection to the temp sensor (not the gauge), and short this to earth.
With ignition on the fans will run - so keep your fingers out
With the ignition off the pump will run - I can hear mine ..

Others will be along to confirm / deny

[jeffreyt]

thanks to all,I now understand this a whole lot better.
Quite pleased I have not got to start pulling the thermostat out of the Elan as I have a nice hole in the floor of the 944 to be getting on with,30 years of English winters have taken their toll on the bottom of the
Porsche.

[GeoffSmith]

(A bit off topic but I don't understand why a lot of people consider the sender doen't match the gauge. To me it suits it very well since the operating temperature can be read thanks to a needle that actually moves through its available range. I can see no point in a needle that stays on the middle of the range forever? I do understand it's a bit disconcerting though, as it's quite unusual.)

The gauge gives you a detailed view of the temperature in its normal operating range. Too high or too low (except when warming obviously) is a concern.
What would be the point of worrying if the temp was below 1/4 or 3/4 if the areas outside of this range are 'worry areas' anyway?

Because the thermostat might be stuck open! I have diagnosed too many from all over the world and even ran mine for some considerable time with a stuck open thermostat that was virtually undetectable by the gauge (but was obvious with ES) which is why mine is now a lot more linear and normally sits at ½ scale.

[GeoffSmith]

New M100 owner but old Elan (1966) owner. Temp is at the 1/4 mark until stuck in traffic than it climbs to 3/4 mark. Fans do not come on even with A/C turned on.
When I shut the engine off the coolant pump does not come on either. Checked the fuses all OK. Any ideas ?
Ron

If you search the forums you'll find some tests - from memory, find the connection to the temp sensor (not the gauge), and short this to earth.
With ignition on the fans will run - so keep your fingers out
With the ignition off the pump will run - I can hear mine ..

Others will be along to confirm / deny

Close - it's the lead to the fan switch you need to short to earth.
http://wikilec.com/view/Coolant_radiator_fan_switch

[Giniw]

Well, what was the symptom? I suppose the needle stays under the first mark when the thermostat is stuck open?
It's not like if the needle didn't move at all, and that's why I think Kathryn temperature gauge is suspicious.

[Kathryn]

My needle does move. As it should it soon starts to rise if I stop and the fans work as they should. I could just have wonky gauges though, because the needle on my fuel gauge never goes up to the top even when the tank is full.

[Giniw]

Yes that's not what I meant, I did understand you needle moves but you said it's mostly under the 1/4, which seems a bit low compared to my car (and most of the cars here if I am not wrong).
So if I were you I would check the actual running temperature with elanscan just to be sure.
(In any case, nothing to worry about since a thermostat is a really cheap item.)

[Saltire]

My needle does move. As it should it soon starts to rise if I stop and the fans work as they should. I could just have wonky gauges though, because the needle on my fuel gauge never goes up to the top even when the tank is full.

And I would say my experience echoes Kathryn's, which leads me to wonder whether S2s on the whole run a little cooler.