Over-cooling issue

[FerneyO]

I have a 2013 Caterham 7 (Roadsport 170) and have noticed that on cold mornings (~ 35F to 40F), it can take up to 60 miles to get the temp guage up to 95 degrees C. On typical warm days, this usually only takes 7 or 8 miles.

On occasions when it is cold, and I need to turn the heater on, the temperature guage will drop from ~95C down to ~60C within a few minutes.

I also note that the electric fans almost never come on.

So, I'm thinking that the engine is being over-cooled. I would like to try blocking off part of the radiator to reduce airflow.

Do other people have this problem? Has anyone tried reducing air-flow through the radiator?

......Dave.

[Doug Liedblad]

What temperature thermostat does it have?

[FerneyO]

What temperature thermostat does it have?

I don't know - it was the standard one that came with the kit.

[magnusfeuer]

The obvious cause would be a thermostat that is stuck open.

Check if the radiator is warm when the car hits 60C, at which point the thermostat should not yet have opened to the radiator.

/Magnus F.

[Doug Liedblad]

Remove thermostat. If open when cold, replace it.

If closed you can test it by heating it in a pan of water on the stove.

Note temperature that it opens at.

[FerneyO]

The obvious cause would be a thermostat that is stuck open.

Check if the radiator is warm when the car hits 60C, at which point the thermostat should not yet have opened to the radiator.

/Magnus F.

OK, I just did a static test in the garage. Started the engine and set to 2400 rpm.
Indicated 60 C Radiator cold
Indicated 70 C Radiator cold
Indicated 75 C Radiator cold
Indicated 80 C Radiator cold
Indicated 88 C Radiator starting to get warm at radiator top - this was about 5 minutes
Indicated 90C & holding
After another ~ 5 mins bottom radiator getting hot
Indicated 98C Fan on for ~ 1 minute
Indicated 98C Fan off
Indicated 98C Fan cycling on for ~ 1 minute each time
End of run.

Conclusion: the thermostat is working and openingat 88C.

[FerneyO]

Remove thermostat. If open when cold, replace it.

If closed you can test it by heating it in a pan of water on the stove.

Note temperature that it opens at.

Did not try this as my previous test indicates that its opening at 88C.

[FerneyO]

Now, most of you guys are CA flatlanders and run your cars with ambient temps in the 90F's.
Up here in the mountains, we already have below freezing overnight. My problem onlly seems to be at the low ambient temperatures (ie: <40F). When you really need the heater to work.
When the day gets warm (ie: >70F). The heater seems to work fine....But, thats when its not needed.

.....Dave.

[FerneyO]

So, what I'm thinking of doing is to create an aluminum shield that partially covers the radiator input side. Probably the best shape would be to cover the complete radiator with a circular hole matching the electric fan outline and another cut out mapping to the oil cooler.

This should reduce the cooling effct, but still be fully functional. Has anyone else tried similar arrangements?

.....Dave.

[FerneyO]

Thinking about this some more. In cold weather, with the heater off, the engine is maintaining ~90C (need to confirm exact temp). Turning the heater valve on circulates hot water into the heater and that extra cooling effect from the heater is enough to drop the indicated temp to 60C. In fact the regular radiator circuit may not even be connected in through the thermostat. The heater in fact, is being too efficient at cooling the engine.

I'm thinking that putting a shield over the radiator should have no effect, as the radiator in closed off.

Anyway, I made a temp shield out of cardboard to try out. I'll do an experiment to try it out.

[magnusfeuer]

If your thermostat and fan works as expected, you are probably looking at over cooling. An oil cooler (without a thermostat) will make the problem worse.

The plumbing of my 2002 Cateram led hot water from the block directly to the heater, regardless if the thermostat was open or not. So heater on during warm-up will increase the time it takes for the engine to reach operating temperature.

A piece of cardboard over the radiator will work quite well. This used to be a common trick during my childhood's Swedish winters. Blocking a larger area will also stop cold air from entering the engine bay, thus removing another cooling factor. You will have to experiment.

/Magnus F.

[Doug Liedblad]

Now, most of you guys are CA flatlanders and run your cars with ambient temps in the 90F's.

.....Dave.

I take exception to the above.

I don't have a heater as it's only extra weight.

I've driven the car in below freezing temperatures and the engine warms up just fine.

[Doug Liedblad]

Even with a static test the car should be warming up faster than 10 minutes to get the entire radiator hot.

[FerneyO]

Doug,

sorry to call you a flatlander.

on last Saturday night going home from the picnic, the car was driving fine at ~95C indicated temp for most of the 250 miles. Then it started snowing on old hwy 40. I drove through a big puddle of slush & snow & it spashed inside the 'door', soaking me. I turned on the heater and within 5 minutes the engine temp had dropped to ~60C. So turned the heater off. I was shivering and my hands were shaking, I was so cold.

I'm assuming that when the temp dropped to 60C, that the thermostat would have closed. See attached picture of my duratec plumbing. The red flow arrows would have stopped but the yellow flow arrows would still be flowing.

plumbing.jpg
So how is it possible to get the engine so cold with only the heater cooling it?

I wonder what elso could be going on.

......Dave.

[FerneyO]

An oil cooler (without a thermostat) will make the problem worse.

/Magnus F.

Magnus, there is no thermostat on the oil cooler, so I probably should try partially blocking the oil cooler as well - with the cardboard trick.