Lotus Elan

Heat problem

PostPost by: types26/36 » Tue May 23, 2023 2:27 pm

Just a thought, when the car is hot have you felt the top and bottom of the radiator to see if they are about the same temperature, it the radiator is silted up the bottom can stay cool compared with the top.
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PostPost by: mbell » Tue May 23, 2023 6:06 pm

elanner wrote:"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."


I'd agree with this. Sounds like to have a water flow issue. So likely causes are:
- Thermostat issue
- blockages in system
- Water pump issue
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PostPost by: StephenT » Tue May 23, 2023 7:17 pm

The fans are running correctly, blowing air through the radiator.

Per the Hagerty article mine is a water flow issue. It’s fine at idle and over heats when driving. Since the car is just now drivable I have not yet registered it so I am sticking close to home on my drives. I have not had it on the freeway.

The timing is an interesting issue. I have not been able to set the timing with a timing light. The radiator is so close to the the pulleys that I can’t see the timing marks with my light, even using a mirror. I probably need a better light. If the timing were retarded would it still idle for 20 minutes and the temp sit at 160*?

I will measure the temperature at the upper and lower hoses to see if there is any difference.
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PostPost by: 2cams70 » Wed May 24, 2023 3:22 am

Ianashdown wrote: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.


You are in unknown territory when you start removing thermostats. The restriction from the thermostat contributes to the back pressure at the waterpump which helps to stop it from cavitating.

Also cold engine contributes to cylinder bore wash of lubricating oil.

It may be stating the obvious but was the cooling system properly bled of air pockets when it was refilled?
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PostPost by: StephenT » Wed May 24, 2023 3:37 am

What is the process for bleeding the air out of the system?
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PostPost by: 2cams70 » Wed May 24, 2023 6:49 am

StephenT wrote:What is the process for bleeding the air out of the system?


Perhaps someone else can chime in here as the Lotus engine in Fords has no issue with bleeding air out of the system unlike what I read on here about Lotus engines installed in Lotuses!

A couple of points though:

1. Check that the thermostat in the closed position has provision for a very slight air bleed past the valve. In the past some poor quality aftermarket thermostats have lacked this feature. The bleed will be either a very small notch at the edge of the valve plate or a spring loaded poppet valve in the plate it itself (usually the former in new design thermostats). If the thermostat doesn't have this you'll have no end of trouble getting the system to bleed.
2. The aim of bleeding is to allow air to exit the system whilst it is being filled. This can be difficult if the fill point is lower than the maximum height of coolant in the system or if there is no air bleed opening provision at a high point in the system.

If filling cars with which I am unfamiliar I usually fill the system, let it run for a while until the thermostat opens, check to see if the level has dropped and so on and repeat until the coolant level stabilises. I run the engine with the radiator cap off so I can see when it drops and top up accordingly. I don't drive it on road until this is sorted.

Keep an eye on the temperature guage though during this process.
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PostPost by: smo17003 » Wed May 24, 2023 8:25 am

And in addition to the above, on the Elan open the heater valve so that you get flow through the heater core.

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PostPost by: Phil.C60 » Sun May 28, 2023 9:17 am

I know this has been discussed many times but am also struggling with this issue. My 1971 S4 has a big valve head, phase 2 cams (.365" lift, 280* duration) and a pair of 151's so it's not that highly modified. The engine has been refreshed, and when doing this the core plugs were removed and the block cleaned out by hand rather than being acid dipped but it was pretty good. It has a brand new TTR front cover and water pump kit assembled by me with the correct impeller clearance. Ignition timing is 12* at idle, 123 ignition with a curve set to 29* at 3000rpm, approx. 24* at 2500rpm. The car performs and drives well. It now has a 74* thermostat, a revised thermostat housing with rad cap so it can be filled from the highest point, a Coolex Fat Boy radiator with electric fan, the lower blanking panel is present as is the recuperator bottle (connected to the thermostat housing). It runs at 85*-90* most of the time with the heater on and hot air coming from the heater vents (fortunately it's a convertible....) but creeps up to over 95* in traffic or when driven "enthusiastically" or at dual carriageway speeds even with the fan running. Once the temperature creeps up, driving at around 3000 rpm/55 mph will slowly bring the temperature back down to around 85*. I currently have a 13lb cap fitted to the thermostat housing and a 20lb cap on the radiator to push the boiling point up a little It has never actually overheated, but I would like to see the coolant temp. stabilised lower - maybe 10* lower with the heater off! I am considering fitting a full width alloy radiator with twin fans or an oil cooler or both!.....any thoughts, experiences or answers on a postcard.....
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PostPost by: mbell » Sun May 28, 2023 10:53 pm

How are you measuring the temp? Standard gauge?

I'd start with confirming the temp readings you are getting. Do you have a ir thermometer?

Imo 74 is too low temp a thermostat. Why are you running such a low temp thermostat? Because you want the engine temp that cool or because it was reading to high?
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PostPost by: Phil.C60 » Mon May 29, 2023 7:09 am

I was under the impression that 74* was the standard thermostat, that a 74* stat is not fully open until around 78* and that TTR in particular recommend that the twin cam performs best in this range. I am also under the impression that a decent cooling system with electric fan(s) should be capable of maintaining this temperature or a couple of degrees above when driven, and a temperature that fluctuates between the set points of the fan switch in traffic. Mine won't, even with the heater on......And yes, I have checked the actual temps with an IR and allowing for heat transfer differences the brand new genuine Caerbont Smiths gauge is about right. I'm happy to spend the money going for the full width alloy rad and twin fans (maybe Coolex rad and Revotec's fan kit looks very nice) and really wanted to gauge other peoples experiences as most of the posts about this are a while ago, and knowledge changes over time plus some of the parts discussed are no longer available (Cliveyboy's kit for example). Or I'd be happy to go with the TTR header tank and radiator set up if it really works on a road car - I have a contact who runs them successfully in race cars but they use a high pressure cap and no recuperator bottle just a catch tank but of course they simply fill it before a race and worry about it later. I'd be interested to know what set up people use on the road, it seems difficult to work out simply from scanning through incomplete accounts - people rarely come back and post what actually worked for them. Some people's cars run fine with the standard set up, some peoples don't. I can shovel money and parts at it one piece at a time (and I'm sure many folks do....) but I'd like to take a slightly more refined approach if I can. I'd like to spend more time driving it, and less time trying to make it a less fraught experience when I do!
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PostPost by: 2cams70 » Mon May 29, 2023 9:23 am

Sometime I really have to bite my tongue when I read stuff on this forum. TTR recommend you run a 74 degree thermostat - REALLY!!! A lot of you blokes need to put a covering sticker over the temperature guage that says “warning - for advanced users only”.

For your reference I took a close look at the temperature guage on my almost new Ford Fiesta ST on my drive home from work today. It has a digital dash and you can get direct readouts of coolant temp, oil temp, boost pressure, etc. Ambient temperature was a cool 15 degrees Celsius. Stuck in heavy traffic for 15 minutes or so the coolant temperature reached a short peak of 98 degrees Celsius and typically bounced around between 94 to 96 degrees. On the freeway doing a steady 90km/h the temperature dropped to 87 to 90 degrees Celsius.

I suggest you don’t have a problem (sorry correction - you do have a problem if you are running a 74 degree thermostat instead of the correct 89 degree one)

In all honesty the standard cooling system in good condition is probably perfectly adequate for your application. Your money would be better spent elsewhere.
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PostPost by: Craven » Mon May 29, 2023 11:59 am

In an article Tweaking a Twink by David Vizard, he commented on rolling road tests “ after 70 deg you can just sit and watch the horsepower fall off”.
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PostPost by: nmauduit » Mon May 29, 2023 12:29 pm

Craven wrote:In an article Tweaking a Twink by David Vizard, he commented on rolling road tests “ after 70 deg you can just sit and watch the horsepower fall off”.



"on rolling road tests" : this is a different issue imho (intake temperature does have an effect on charge density, hence power), and tuning on a rolling road does not always replicate real use conditions due to the difficulty to recreate air flow...
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PostPost by: Donels » Mon May 29, 2023 2:12 pm

I had a similar problem to this albeit not on a twin cam. It turned out to be the water pump impeller was loose on the shaft and wasn’t pumping water around. As suggested by others it does sound like water is not being pumped around the system.
After the length of time it’s been standing any alloy parts could be very badly corroded causing blockage in the head, water pump etc. You really aren’t going to know until the head comes off.
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PostPost by: mbell » Mon May 29, 2023 2:17 pm

Phil.C60 wrote:And yes, I have checked the actual temps with an IR


That's good but your phrasing did come across as aggressive. Not sure if that is intentional or not.

I don't think its wrong to suggest validating what the problem is is as first step....

I can tell you my car with wide copper radiator and twin fans, 123 with similar curve is able to run a steady temp and only rises when idling stationary. The fans will keep it in range. A few weeks ago I was driving it hard (keeping up with Elise and evoras) in over 30c with no issues.

So it seems you do have a problem and you need to figure out if it's a flow rate problem or not. I'd suggest monitoring the radiator out let temp. That should tell you if the radiator is cooling enough or not.

Phil.C60 wrote:I was under the impression that 74* was the standard thermostat,


My manual lists 78 as standard.

TTR main focus is racing, so while extremely knowledge you do have to consider if there suggestions are correct for your use. By default I assume this is a road car but might be wrong.

My main concerns with low thermostat is oil temps and ensuring the oil gets hot enough. In a race car your not going to have any problems getting the oil hot enough even with a low thermostat and it's likely helpful to run cooler to help keep oil cool and maximize power.

Your unlikely to be driving a road car as hard, so less likely to get the oil temp when running a low temp thermostat.

Probably I think I am running something in the mid 80's.
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