Lotus Elan and Lotus Elan Plus 2 Forums

I picked up a ‘66 Series 2 project last year. The car has not been driven since 1976… until yesterday. Now I can really begin to identify the cars needs. The first thing that has come to light now that the car is drivable is an over heating issue. The car will idle for 20 minutes and the temp gage sits steady at 160*. But when driving for just a few minutes the temp starts to climb to the point of overheating. Today I flushed the radiator and block. After refilling the system I let it idle for a long time and again it held steady at 160*. After driving for a few minutes the temp started rising again, although slower than before. I stopped driving when the temp hit about 200*, I didn’t shut off the engine but let it sit and idle for another 15 minutes and the temp dropped back down to around 190*. The radiator is the original brass unit with two 9” electric fans mounted on the front pushing air through the rad. My guess is the old radiator is fine at rest but can’t handle the extra heat of an engine under load. Am I missing something, any advice from the experts here would be appreciated.

Thanks,
Steve

I would check

1. Are the fans switching on and at what temperature ?
2. Is the thermostat fully opening and at what temperature ?
3. Is you temperature gauge accurate ?

A presurised system with antifreeze coolant will not boil until above 230 F.

cheers
Rohan

I am assuming the thermostat is opening fully but not sure how to measure that. When refilling the radiator I had the engine running. When the gage hit 160* the level in the radiator began dropping so I could add more fluid. I am pretty sure that is when the thermostat opened. So that would signify the gage and thermostat are working correctly.

I am wondering if by mounting the fans on the front of the radiator could they actually be blocking more air flow than they are creating when driving? Two 9” fans pretty much cover the radiator. I don’t think I have enough room between the radiator and the water pump pulley to mount the fans behind the radiator. I will check tomorrow.

I guess I could drop the thermostat in a pot of hot water and watch it open to verify it is opening all the way.

Just remove the thermostat to be sure it not part of the problem.

Ian
SoCal

I forgot to mention that the fans are just hooked up to 12v and run all the time. I have the parts to install a thermostat for the fans but have not installed them yet.

Have you checked that fans are actually pushing the air through the radiator and not sucking? Could the fans be turning the wrong way? Some fans are designed as pushers and some as suckers and by just reversing the rotation they are not always as efficient.
Just by flashing a radiator it does not always clean it out, sediment can build up and block the tubes and it needs to be cleaned or recored by the proffionals.

Mounting the fans infront or behind makes no difference and will not block air flow espcially if running all the time anyway. Check that the fans are actually blowing through the radiator

cheers
Rohan

Stephen

I agree with both Brian and Rohan. Check that the fans are actually blowing through the radiator by seeing if a piece of thin paper will stick to the front of the fan, it is sometimes difficult to determine airflow direction just using your hand.

If the airflow direction is correct then the radiator is probably partially blocked internally and needs recoring.

From an old Hagerty article:

https://www.hagerty.com/media/maintenan ... ing-issue/

"The answer here depends on how the car is running hot. If it’s hot even while cruising down the highway, it’s a water-flow issue. If it’s cool while in motion and only hot while idling in traffic, it’s an airflow issue."

Of course, if the fan is running backwards I guess this would be turned upside down....

Nick

Had this problem one time. After a short drive it would overheat, let it idle and it would cool down. Found out it needed new bearings.

joe7 wrote:Had this problem one time. After a short drive it would overheat, let it idle and it would cool down. Found out it needed new bearings

What needed new bearings?? I'm presuming not the engine!!

Renew the thermostat as a matter of course. They are cheap. Do not run without a thermostat. I hope you renewed all the rubber hoses, fan belt and radiator cap as a matter of course also.

Check that the ignition timing isn't retarded. Engines run hot if the timing is too far retarded.
Run it with some coolant flush in the system. Do it a couple of times. Drain and refill with correct coolant.

Provided the system isn't leaking or boiling it doesn't seem like there's much of a problem,

An easy check for the sender/gauge. - drop the sender in water, with wiring attached ( the earth is trickiest, but a crocodile clip is useful). stick it in a pyrex beaker, or an old tin can and heat to boiling (hot air gun works a treat).. what does the gauge show ?
I had a similar issue which turned out to be the (old) sender unit.

2cams70 wrote:

joe7 wrote:Do not run without a thermostat.

I was only suggesting to remove the thermostat for the purpose of testing and eliminating it as the source of the problem. However the only downside to not running a thermostat is the longer required warm-up before driving.

We always remove the thermostats from racing engines, but they are thoroughly warmed up before being driven.

Before replacing the radiator you could try having your cleaned internally with an ultrasonic cleaner.

Ian

Mine had sat for 20 years, stripped the engine without even attempting to start it. The inlet pipe to the waterpump was completely blocked / crystallised up and the block was full of sludge and hard rust deposits which a flush wouldn't have removed. Engine shop pondered sending it for an acid dip, but it got blasted out in the end.

Also a couple of freeze plugs were well past their best, I was certainly glad I didn't attempt to run it.