Temperature reading low when driving

[Lotus54]

My temp gauge would read at the bottom of the scale when just crusing in the hiway. When parked, it goes up and the fans come on at about the 3/4 mark-- so it appeared it was working ok.
I figured maybe the thermostat was just bad.
So I got. New 180 stat, it is still exactly the same.
Voltmeter reads about 14 (I haven't put a real voltmeter on it and read it while driving yet).

When I stop and idle or slow traffic, the gauge will slowly go up a bit.

Is this common?

My Elanscan cable should be here this week sometime, so I can monitor temps...but any thoughts?

Mark

[tweetdriver63]

With the stock thermostat, the temp will normally be around the 1/4 mark or even below, then when stopped it will climb up to the 3/4 mark, where the fans will come on and start brining it back down. I thought something was wrong at first when I got my Elan, but soon found out on here that that's the normal behavior.

I got the 210-200 fan switch from rodneydickman.com so that the fans come on at about the 1/2 mark. That's much more comforting.

[rip]

Elanscan will help a lot.
The dash temp gauge uses a different sensor from the ECU.

If the idle mixture is 14:1(ish) when 'warm' & the temp looks normal, then I supect the CTS for your gauge is faulty. It maybe as simple as a dirty connection to the sender.

[Rice crispy]

Mines exactly the same and has been since I got the car. Go upto just below 1/4 normally then upto 3/4 in traffic and fans kick in.
David

[tigerdog]

Mine was like that when I bought Smaug - barely up from bottom of the scale under normal operation. Turned out to be a bad thermostat, never fully closing. New thermostat fixed the problem and made the car run better. As mentioned above, Elanscan check will tell you if the temp is right and thus if the gauge or sender is faulty.

[Lotus54]

Thanks,all.

I'll let it ride until I get the ElanScan goi g and see what is really going on.

I havnt put my exhaust analyzer on it yet.

Mark

[HJ2]

I'm a little confused now...
I want to install a fan switch like Tweetdriver. But do i need to install another thermostat then as well?
I want to exchange the thermostat and coolant anyway as a precaution measure, so if another type of thermostat is needed anyway, now would be the time!

[HJ2]

Anyone?

[racerstev]

No new thermostat is needed to add a on off switch for the fan. Just ground the fan
switch wire to have it come on. Be aware, if grounded with the car off the electric
water pump will kick on not the fans.

Steve

[HJ2]

Thanks steve,
But i ment to install a low(er) temperature switch, and if i need to place another thermostat then!
Cheers,
Henk-Jan

[Brit-Car-Nut]

HJ:

Going to a lower temperature thermostat is not a good idea. The ECU watches the temperature and doesn't lean things out until it reaches 190 degrees as it thinks it is still in need of some "choke".

A proper working "stat" allows proper saturation of the coolant both in the block and radiator. If it passes through too quickly (no thermostat), the coolant never picks up the heat so the engine is overheating all the time but the gauge / sensor thinks it is staying very cool. When racing, nobody uses a thermostat but they all use blanking sleeves that slow the coolant flow just for this reason.

If you are going to flush the cooling system, I would replace the stat with a decent brand unit rated at the proper temperature: 92 degrees C or 195 degrees F. Remember to absolutely DRY and clean both gasket surfaces as well as the notch for the stat and use a proper sealer on the gasket and a little to hold the stat in the notch while reassembly is going on. I have always used Permatex Hi-Tack or Permatex Aviation for sealers but the biggest problem with a vertical thermostat is that it sometimes falls out of the notch during reassembly. Be patient, take your time and everything works out.

Oh, yeah... the jiggle pin (has to have that) goes at the top.

Cheers

[mmatthej1]

Sort of related to this subject, can anyone say whether the cooling fan is supposed to turn off, when the ignition is switched off?

In other words (and slightly turning it around), if I arrive home with a hot engine, with fan on, should it stay 'on' (to continue cooling), after I turn off ignition and exit the car?

[Brit-Car-Nut]

I have read a lot of entries about overheating and would like to add my two cents:

The stock cooling system appears to be adequate for basically normal climates.

The very first thing you need to check is that you have the proper mixture of coolant and water as all water boils at a lower temp than a mixture and all coolant boils at an even lower temp. The pressure cap is also very critical as coolant boils a a higher temperature when under pressure. If you have doubts, you can still get a pressure cap from LMF Vauxhall in the UK.

You also must check that your coolant level is FULL as air bubbles don't hold heat very well.

If you are having overheating issues, you should first verify that you have the correct thermostat and that it is working correctly. You can always remove it and place it in a small pot of water with a thermostat and heat it on the stove watching the thermostat to see when the inner flap opens and how far it opens.

IF that is good, then when first starting, watch the temp gauge and you should see the temp go up rather quickly at first (thermostat is closed), then it will go down as the stat opens up. This should happen several times as the coolant stabilizes at the opening temperature and then the gauge should remain constant.

I would let the engine idle and wait until the fans switch on. From other posts, this should be somewhere between 1/2 and 3/4 scale on the temp gauge. as the fans go on, the temp should drop and the fans should go off, cycling as needed to keep the car at the proper temperature for the engine management system to work properly.

When driving, if the temp goes up, you can turn ON the heater fan to high (which basically increases the cooling capacity) and the temp should go down. If it does, then I would suggest that you first consider that the waterpump might not be circulating the coolant adequately. If you are convinced that the pump is working correctly, then the radiator is suspect. Are the fins clear and free of debris and grime? If you have A/C, the condenser is in front of the radiator and it blocks some airflow already. Make sure the condenser is clear and free of debris and grime as well.

If everything physically looks to be near perfection, then the radiator should be checked by a qualified shop as the tubes could be clogged or damaged which will cause overheating. Take the radiator shop's advice on how to solve any problems you find. They are the experts - if you don't trust them, why did you go there in the first place?

If you really feel that you want your cooling fans to come on sooner, you can replace the switch with one that activates at a lower temperature but honestly, that won't "fix" an overheating system. I know that some use the Fiero switch and others use a BMW switch, but they will try to keep the system temperature below the correct temperature for the engine management system which would most likely increase fuel comsumption as the ECU "thinks" the engine is running cold.

Hopefully, with a little diagnostics, you will be able to identify where you are having problems and then make corrections to bring it back to proper operation.

Those of you in very HOT climates: All of the above still applies except that the radiator itself might not be adequate for the amount of ambiant heat that will reduce the ability to "cool" the coolant as it passes through the radiator. You then have to look at an improved. larger capacity radiator or some similar way to increase the cooling capacity.

[Brit-Car-Nut]

Sort of related to this subject, can anyone say whether the cooling fan is supposed to turn off, when the ignition is switched off?

In other words (and slightly turning it around), if I arrive home with a hot engine, with fan on, should it stay 'on' (to continue cooling), after I turn off ignition and exit the car?

If you are above the temperature for the fans to be running, YES, the fans will remain on AND the supplemental coolant pump will run to keep the coolant circulating until the temp goes down to a safe point.

[mmatthej1]

Thanks for that Brit Car Nut (great soubriquet btw!) - will keep an ear out, next time!

[HJ2]

Thanks John!

For my car everything works nominal, no overheating problems. Normal driving: just a tad over the 1/4 mark. this used to be a tad under the 1/4 mark, but I had a re-core for my radiator, Cu based.... The fans come on at the 3/4 mark, and cycle flawless

After I got the car it overheated once due to a ripped coolant hose (brittled because of age) I remember how little time there was from the 3/4 mark till actual overheating and no place to go safe! After this incident I flushed the engine multiple times with engine cleaner and it was dirty I replaced all water hoses (Samco kit) and had my radiator re-cored. I also changed the (belt driven) water pump. I refurbished the electric pump as the seal had cooked out past the shaft The system is filled with green coolant, pre mixed. I also replaced the rad cap with a new one. I don't believe it gets any better than his for my little engine

Now I want to increase the time window between visual indication of overheating on the dial and the actual overheating (white smoke!) , hence the lower temp switch.

As I understood so far the fan's operate stand alone (no ECU communication) so a lower temperature fan switch is no problem. No need to change thermostat then, indeed
However the bandwidth of the temperature of the coolant decreases from 1/4 ... 3/4 to 1/4 ... 1/2. As I understand this is well within nominal operating bandwidth and gives no trouble to the other sensors that DO provide feedback to the ECU, but the trade off is that the fan's wear more as they come on more often and run longer.

The benefit is relaxed driving in traffic jam, and we have that a LOT here in the Netherlands
Any other thoughts on this?

[RayD]

Good write up John,

I’m not sure the fans continue to run when the ignition is turned off … or at least not on a 1992 UK version of the SE.

I have a manual override switch for the fans and it requires "ignition on" to activate.

I realise a lot of cars fans do continue to run in an over-heat situation after ignition off but I thought Lotus had opted to have the electric pump stay on instead.

Ray

[HJ2]

Indeed.
My fans go off when ignition off. Pump keeps running in case fans where running prior to ignition off!

[Brit-Car-Nut]

Sorry, I thought when I looked at the wiring diagram the key off supplied both circuits.

I still don't drive my car much and the fans are always off when I turn it off, so I never noticed they don't continue.

I thought there was a time delay relay involved. If not, I will probably add one because if it is hot enough to require the fans, it will put stress on the hoses if cool-down isn't accelerated.

They use them on water cooled turbos, but I guess Lotus was worried the battery would go flat before the engine cooled down.

[GeoffSmith]

Water pump only at switch off:

http://wikilec.9600.org/images/e/e0/MJ2 ... g_Fans.gif