Lotus Elan

Engine running hot at idle

PostPost by: RichardHawkins » Mon May 28, 2018 8:04 pm

I have been intrigued for years by the reason some cars over heat and some don't. When I overhauled the engine I found cleaning the block very difficult, the water jacket was half full of rust debris that was very difficult to remove. What do other people think about debris in the engine waterways as a possible explanation?

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PostPost by: mbell » Mon May 28, 2018 9:00 pm

I removed a large amount of rust and sand from my block while it was out and I was removing the water jacket plugs.

I never had any over heating issues even in the Texas heat and car kept steady ish temp with dual fan bring it back down before that.

However since cleaning the block out the gauge reads much lower 75/80 c rather than 90c. I think I have a 87c thermostat fitted. Only changes where I drilled a couple of breather holes through thermostat and disconnected the sender wire and reconnected.

My assumption is it is a gauge issue rather than change in running temp but haven't proven that yet.

In my view there three main causes of temp issues:
1) inaccurate gauge (so no real issue)
2) insufficient fluid flow
3) inlet temperature to high

If I was hitting a over heatting issue is be trying to understand which of these was likely the cause. Probably by checking radiator outlet temp.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: nigelrbfurness » Tue May 29, 2018 8:53 am

This is a perennial problem with S4 Elans with the tiny Triumph Spitfire radiator and has been discussed on here many times over the years and equally often at Lotus shows around the country. The solution is always a bigger radiator, assuming you haven't a leaky head gasket, loose fan belt or a loose impeller on the water pump. You should also check that the fan motor shaft isn't stiff in its bearings, I find they need lubricating every couple of years or so - this can cause the fan to run slow. Silione lube spray fixes that.

However, I think you will still have the basic problem caused by the small rad. There are many expensive aftermarket solutions including fitting the earlier wider Triumph radiator that was fitted to late S2s, all S3s and early S4s. There are some reproduction ones available with big fans mounted on them. However, the cheapest solution is a ?75 aluminium radiator for a VW Golf, easy to fit to the existing mountings with a couple of spacers and all that is required is a little ingenuity with the pipe work, fan sensor and a remote filler neck. Even the original fan frame can be easily adapted to mount on the lugs on the forward side of the radiator. All available on fleabay very cheaply. My 1760cc Elan runs at 77C all day long, even on the hottest days and the fan never comes on. It will sit and idle at 70C all day long too. Best mod I've ever made and all for under a pound you know (sic). And it looks posh under the bonnet, which may or may not be a virtue.

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PostPost by: 7skypilot » Tue May 29, 2018 10:38 am

TT radiator & header tank with a Cliveyboy Revotec fan (mounted behind the rad) has solved all overheating problems traditional with the S4.

Crawling over the Stelvio pass in traffic and in summer heat I was overheating, but the car was not!

I would also check the 'stat (74 degrees) and that the fan is connected correctly. Some years ago I'd installed a BDA and couldn't understand why the car (a Seven) was running hot. Sure enough I'd connected the fan to pull hot air from the engine compartment through the radiator, not to push cold air from outside!

Any fool can make a mistake - and this one did!
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PostPost by: William2 » Tue May 29, 2018 1:17 pm

As I said in my original post I have fitted a full width alloy rad specifically made for elans. No doubt it helps but it hasn't stopped the engine temp from rising. I have as yet not drilled a hole in the thermostat but I wouldn't have thought that would make any difference to my scenario. As suggested, I might try sticking a couple of thermal strips on the rad and cylinder head to see what they record.
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PostPost by: pauljones » Tue May 29, 2018 1:29 pm

Not an expert in cooling properties but sounds like a blockage or air in the system.
Perhaps a flush out with a pressure washer is needed.
To my knowledge the drilling of a small hole in stat ring is to allow flow when warming up. When stat is open this provides an easy route so said hole is voided so to speak.
I know you said in OP its been done but id try it again.
Or drive it without top on, see if it changes things.
Kick the tyres and light them fires...!!!!!!!
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PostPost by: 69S4 » Sun Jun 03, 2018 4:26 pm

I've just been out in my S4 for a 20 mile drive with the temperature gauge hovering around the high 80's on the open road (24C air temp day) and low 90's with the fan running in town. This time though I took an infra red thermometer with me and as soon as I returned I pulled the bonnet and started measuring spot temperatures. With the gauge reading 90C the sensor area of the head read... 90C. So at least the gauge seems honest. It was the hottest part of the system though. The entry area at the top of the rad was 80C and the bottom exit area, 65C. The block was between 75C and 80C depending on where you measured.

The alternator was 45C and the carburettor bodies (Strombergs) 50C. A quick check of the temp compensators showed they were slightly cooler (45C) but still shut so I'm not quite sure how hot things have to get before they do anything.

So, is the heat build up by the sensor down to waste exhaust heat rising or is the thermostat causing a restriction - the thermostat 'dome' was just over 80C, much the same as the top hose. Years ago when I was using the car the manifold pipes were lagged and the gauge usually ran slightly cooler - 85C on the open road. These ones are not so there is a lot more waste heat in the area.

I've checked the IR thermometer against a few easy standards - boiling water, the inside of my fridge, a clinical thermometer etc and it seems about right.
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PostPost by: William2 » Mon Jun 18, 2018 3:55 pm

With the recent thread regarding soft heads I was wondering if there was any connection when using a soft head and hotter running at idle when stationary. My rebuilt engine has a head that was showing signs of softness i.e. several cylinder head bolts had caused some minor cracks on the top face of the head. The engine rebuilder repaired these areas and reckoned the head would be ok. After 2000 miles I haven't had any problems apart from the hot idle running as already discussed.
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PostPost by: chrisbeck » Wed Jun 20, 2018 6:47 am

If you?ve only done 1500 miles since the rebuild, is this the first time you?ve been stuck in traffic in the summer with the car in its current build form? I think you are worrying too much.
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PostPost by: rgh0 » Fri Jun 22, 2018 11:46 pm

William2 wrote:With the recent thread regarding soft heads I was wondering if there was any connection when using a soft head and hotter running at idle when stationary. My rebuilt engine has a head that was showing signs of softness i.e. several cylinder head bolts had caused some minor cracks on the top face of the head. The engine rebuilder repaired these areas and reckoned the head would be ok. After 2000 miles I haven't had any problems apart from the hot idle running as already discussed.



A small weep from the head gasket due to a soft head can put hot gases into the coolant that can lead to overheating. Does the coolant get blown out of the cooling system or do you see traces of oil appearing in the coolant at the top of the radiator? Does the radiator pressure up even when the coolant is still cold ? If none of these happen then your problems are probably not related to your head condition.

cheers
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PostPost by: wotsisname » Sun Jun 24, 2018 8:29 am

A question , what is the thinking around idling in traffic ? Let the engine just idle or occasionally raise the rpm ? I assume the latter would give the water pump more chance to do it's job, but does burning more fuel just make the situation worse ?
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PostPost by: richardcox_lotus » Sun Jun 24, 2018 11:20 am

I believe in the owners handbook it advises revving the engine occasionally to aid cooling. I do this for piece of mind but have no idea whether it actually helps!

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PostPost by: rdssdi » Sun Jun 24, 2018 2:36 pm

I have had a hot running +2 for years. I had a water pump leak and replaced it with a Bean cassette pump. The head was removed and had some carbon removed. We also flushed the block and adjusted the valves. This is an engine that had a total rebuild at Marcovicci and Wenz years ago when the car was restored. I had to replace the timing chain and gears as Marcovicci and Wenz clogged with excess sealant the small oil lubrication hole for the valve drive components. Wearing out them all. All have been replaced and set. I only have around 150 miles on the car since it was originally restored. Estimate 12 years!


I have a fresh foam strip on top of the rad.

I had a larger alloy radiator and replaced that with a recored original radiator. Hot running with all.

I use a lower temperature fan switch. It has become obvious that the coolant at the radiator tank is cooler than the gauge reads. I suspect that the exhaust manifold throws off significant heat and the heat soaks into the protruding casting on the head where the coolant temp sender is fit. Possibly making that localized area hotter.I am running headers finished by Jet Hot coatings.

Bob

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PostPost by: 69S4 » Sun Jun 24, 2018 4:55 pm

rdssdi wrote: It has become obvious that the coolant at the radiator tank is cooler than the gauge reads. I suspect that the exhaust manifold throws off significant heat and the heat soaks into the protruding casting on the head where the coolant temp sender is fit. Possibly making that localized area hotter.I am running headers finished by Jet Hot coatings.

Bob

Bob


I did some measurements with an infra red thermometer a week or two ago (and put them up here earlier in this thread). The sensor area was significantly hotter than the rad or the rest of the cooling system so I suspect there is some heat soak from the manifolds. I'm trying to decide at the moment whether to lag the pipes again (tends to rot the manifolds over the long term) or make up a heat shield to fit below the sensor area.
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PostPost by: rdssdi » Sun Jun 24, 2018 5:08 pm

I placed some adhesive backed heat shield onto the protruding casting where the sender is attached. It did not make a difference. A properly designed heat shield might work. If you are running headers as I am, replacing the original cast iron exhaust manifolds may make a difference with heat soak.

Bob
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