Lotus Elan

Cooling system advice please

PostPost by: HJF » Sun Jun 07, 2020 11:33 am

Hello,
My son has left his late model Sprint with me and asked me to look at a few problems for him, one of which is cooling.

I have spent a long time in the archives but still feel a bit confused and need someone to sanity check my thoughts please.

So, late model Sprint that had been a bit neglected for a few years; he’s had it about twelve months and done about twelve hundred miles to date. Car is completely standard. Driving along, the temperature is basically okay I think but hit traffic and it rises quickly and then takes a long time to come back under control when back on the move again.

This is what I am thinking.
Fit 74deg.C thermostat (available from Matty’s), not sure what is fitted currently;
Fit new Coolex Fatboy three core radiator with their modern fan pushing air into the radiator;
New radiator mounted fan switch, but what range for on / off point to not end up over cooling and over running the fan? Standard switch is currently fitted to existing factory radiator.
Manual override switch on the dash (all this via a relay triggered by ignition switched live);
Fit (missing) blanking panel below radiator (have already fitted both bonnet foams,10 pound twIn seal radiator cap, and flushed and refilled the system when he first got the car);

Any advice gratefully received.

Harry,
(In Lancashire)
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PostPost by: rgh0 » Sun Jun 07, 2020 12:05 pm

A good modern ducted blower fan on your current arrangement should be all that needed IMHO, to solve any over heating problem at low speed like you appear to have

cheers
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PostPost by: richardcox_lotus » Sun Jun 07, 2020 1:01 pm

It’s not an unfamiliar scenario. My Sprint has always had similar behaviour - i’ve learnt to live with it and spot if I think temps are going too high. Ambient temperature plays a part too.

It depends on how much money you want to throw at the problem.

You’ve already performed some basics.

The stock electric fan is very good at gently moving hot air about, but as Rowan says, a modern ducted fan is a lot more efficient. That may give good returns for your dollar or pound, and if still concerned, make sure you get one with a manual override switch.

The temperature gauge should be checked for accuracy.

A fundamental issue is the inability of the engine bay to exhaust the hot air around it, not helped by the temperature gauge sensor being just above the exhaust. Turn the engine off after a spirited run and watch the temperature gauge continue to climb, there’s nowhere for the heat to go.

Good frequent changes of antifreeze will cut down the corrosion in the water jacket which may minimise coolant flow.

A new radiator may help, but will not be cheap.

Let us know how you get on

Regards,
Richard
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PostPost by: alan.barker » Sun Jun 07, 2020 1:58 pm

I would first remove Rad and get it tested to see if it's blocked or needs flushing.
Alan
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PostPost by: 2cams70 » Sun Jun 07, 2020 2:05 pm

To be honest if it's full of the correct coolant with no air pockets, it has a correctly rated radiator cap, it's not leaking either internally or externally and there is no excessive passing of coolant through the overflow pipe there is no problem regardless of what the temperature guage says.
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PostPost by: HJF » Sun Jun 07, 2020 2:41 pm

Thanks.
Rohan and Richard - yes, I agree that a modern fan will be better. Modern fan in my Elise really belts the air through.
Alan - I removed and back flushed the rad when he first bought the car and think is is pretty clear.

I also noticed the mesh over the holes into the wing looks a bit blocked plus someone has positioned the screen wash bag partly over them so I will need to attend to this too.

Harry
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PostPost by: 2cams70 » Sun Jun 07, 2020 3:23 pm

Where the needle sits in an engine temperature guage is as much a psychological phenomenon as a physical one. Here in Australia when Holden first sold cars into Saudi Arabia customers went nuts when the needle sat in the middle of the guage thinking there was a severe overheating problem. The engineering solution was to recalibrate the guage so the needle registered no more than a quarter. Modern cars are best. Many have no temperature guage. You get a warning light when there is a problem and that's it - problem solved.

You can run an engine too cool which is as much a problem as running it too hot.
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PostPost by: alan.barker » Sun Jun 07, 2020 3:54 pm

Is there a Recuperator Bottle connected to the Rad. Is the Rad Cap the correct type with 2 Valves.
Alan
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PostPost by: HJF » Sun Jun 07, 2020 3:59 pm

alan.barker wrote:Is there a Recuperator Bottle connected to the Rad. Is the Rad Cap the correct type with 2 Valves.
Alan


Alan - yes and yes. Correct bottle and I fitted a new double seal “suck it back in” radiator cap when he first bought the car.
Thanks
Harry
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PostPost by: Hawksfield » Sun Jun 07, 2020 4:27 pm

Harry

You don't mention the temperature you encounter in these conditions.
Mine runs at a steady temperature and then If I get in traffic it rises, the readings I get depends on the ambient on the day but could be 70-80 steady running and 90 to 100 for traffic conditions. The standard cooling fan comes in at around 90 and brings the temp down once in clear traffic

I have carried out calibration check of the gauge and it is reasonably correct
Regards

John

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PostPost by: alan.barker » Sun Jun 07, 2020 4:53 pm

An IR Thermometer could be handy and they are cheap.
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PostPost by: mwhitaker » Sun Jun 07, 2020 8:19 pm

I echo Alan and 2cams learned advice/observations. My 69 Elan S4 (early) has a full width S3 radiator with recent cooling system refurb including new water pump, radiator clean/testing, new overflow bottle with appropriate rad cap-7PSI, slightly loose fanbelt (paranoid re the water pump-no redos desired!), new hoses and hot weather thermostat-71.5C I believe. No external fan still with light plastic engine driven fan. The car runs fine with usual temp gauge readings of 80c going up to 88-90 max in traffic at stop lights with prolonged idling. I was careful to eliminate any air pockets with coolant refill ( heater on, nose elevated)making a difference of about 5 degrees with level in overflow bottle changing minimally between hot/cold temps. With an IR scanner my actual upper hose/thermostat readings never exceed 75C but scanning the temp sensor demonstrates readings up to 95C because it is a hotpoint picking up significant heat from my stainless steel headers. Probably helps to make sure your timing/mixture is where it should be as well.

Cheers, Mark
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PostPost by: 2cams70 » Mon Jun 08, 2020 3:29 am

mwhitaker wrote:new hoses and hot weather thermostat-71.5C I believe


Interesting that Ford for the Escort Twin Cam specify an 89C thermostat. Same as the ordinary crossflows. Never had a problem with it and my head when I pulled it down was perfect as far as hardness testing was concerned and had absolutely no recession under the head bolts.

Note it is the radiator cap relief pressure rating and not the thermostat that determines the ultimate maximum temperature of the engine
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PostPost by: baileyman » Mon Jun 08, 2020 10:52 am

I you have room behind the rad, a sucker fan avoids blocking free air flow the way a pusher does.

John
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PostPost by: alan.barker » Mon Jun 08, 2020 11:03 am

The problem with Fan behind Rad is when you use a Strobe to check Timing.
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