Lotus Elan

Thermostat Housing

PostPost by: Cadence » Thu Jun 27, 2024 7:56 pm

Hello,

I need to change the thermostat housing gasket on my Sprint.

I’ve checked the Lotus workshop manual and can’t find a recommended torque setting (ditto Haynes manual)

Drawn a blank with an internet search too.

Can anyone help me with that ?

Cheers
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PostPost by: bitsobrits » Fri Jun 28, 2024 12:15 am

It's a thermostat housing. It's not critical. Tighten until 'fully snug' with a short ratchet handle. Keeps you from over doing it. FWIW I use studs, not bolts to hold the housing in place. Avoids the wear on the cylinder head threads from bolts going in/out.
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PostPost by: 2cams70 » Fri Jun 28, 2024 3:03 am

Congratulations you are well on the way to not becoming yet another DPO by asking the right questions. Usually the correct figure for that bolt size is 12 - 15ft/lb but allow me some time and let me check the workshop manual. As original is best.
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PostPost by: alan.barker » Fri Jun 28, 2024 5:12 am

bitsobrits wrote:It's a thermostat housing. It's not critical. Tighten until 'fully snug' with a short ratchet handle. Keeps you from over doing it. FWIW I use studs, not bolts to hold the housing in place. Avoids the wear on the cylinder head threads from bolts going in/out.

I imagone you use Studs on the Exhaust Manifold then lol
Alan
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PostPost by: 512BB » Fri Jun 28, 2024 8:16 am

'I need to change the thermostat housing gasket on my Sprint'

Why does it need to be changed, and out of interest, what degree stat are you using? Sorry, I didn't catch your name. If the surfaces of the head and housing are in good condition, ie not corroded, and flat, there is generally no problem in that area.

I did this job last week, to fit a 74 degree stat. I was using a 78 degree one, but this particular engine runs just a bit to warm for my liking in summer with one of those. Dry off the surfaces, fit the new stat with a smear of grease on both sides of a new gasket and just snug it up, with bolts and anti seize of course.

One thing I noticed years ago, that after a few heat cycles, the gasket compresses and the bolts need to be retightened. Same for the cam cover gasket, but that of course is cork.

Good luck with it.

Leslie
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PostPost by: Cadence » Fri Jun 28, 2024 10:03 am

Thanks everyone - great feedback - I’m ready to give it another try.

Fingers crossed
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PostPost by: 2cams70 » Fri Jun 28, 2024 10:41 am

I've just checked the workshop manual and can confirm that the correct torque spec.is 12 to 15 ft/lb. Per the manual the correct thermostat is one with an 85C to 89C opening point. A lot of people seem to think that it's a good idea to use a lower rated thermostat however in the absence of good scientific information that the original thermostat rating is wrong I'd suggest it's best to use what the smart guys who designed the engine in the first place recommend.

You're well on the way to becoming a professional rather than an amateur by asking about tightening torque specifications. Next step is to obtain some genuine factory workshop manuals.
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PostPost by: Cadence » Fri Jun 28, 2024 10:57 am

Thank you so much for digging deeper - I’ve just refitted the housing using those settings.

I’ll run it up to check all is well then retighten when cold.
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PostPost by: Uturn » Fri Jun 28, 2024 8:02 pm

2cams70 wrote:A lot of people seem to think that it's a good idea to use a lower rated thermostat however in the absence of good scientific information that the original thermostat rating is wrong I'd suggest it's best to use what the smart guys who designed the engine in the first place recommend.


A lot of engine designers had to make compromises to meet government mandates. This is a fact.
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PostPost by: saildrive2001 » Fri Jun 28, 2024 8:32 pm

I don't believe when the Twink was designed that there were very many if any government mandates. I am relying on my 80 year old memory though.
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PostPost by: 2cams70 » Sat Jun 29, 2024 2:21 am

Uturn wrote:A lot of engine designers had to make compromises to meet government mandates. This is a fact.


Please show me the facts that this meant that they needed to use a higher thermostat rating than you guys think is right.
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PostPost by: Uturn » Sat Jun 29, 2024 4:37 am

https://www3.epa.gov/ttncatc1/dir1/fnoxdoc.pdf

TLDR
Hotter engines are more efficient. Efficient engines reduce NOx emissions.

Common sense - the twink cannot be an efficient engine and a powerful engine unless you institute modern spark controls and air/fuel metering. Not sure how much a colder thermostat will help reduce pinging vs just using higher octane fuel but every little bit helps if you're chasing numbers.

2cams70 - I'm in the same camp as you, put in what the manufacturer spec'd if it's a stock car or a customer's. However, I feel we all should be free to experiment, if it doesn't work out, we can swap back to baseline.
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PostPost by: 2cams70 » Sat Jun 29, 2024 7:09 am

Feel free to experiment but all the thermostat does is regulate the minimum temperature. It doesn’t regulate the maximum temperature. That’s why you should leave it as the manufacturer intended. The consequence of an engine running too cold is increased engine wear - not something that necessarily leaps out at you and hits you in the face. Replacing the thermostat with a lower rated one is usually down to psychological reasons and not reasons based on fact.
1970 Ford Escort Twin Cam
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PostPost by: 512BB » Sat Jun 29, 2024 9:03 am

2 cams wrote 'Per the manual the correct thermostat is one with an 85C to 89C opening point. A lot of people seem to think that it's a good idea to use a lower rated thermostat however in the absence of good scientific information that the original thermostat rating is wrong I'd suggest it's best to use what the smart guys who designed the engine in the first place recommend'

And also wrote 'The consequence of an engine running too cold is increased engine wear - not something that necessarily leaps out at you and hits you in the face. Replacing the thermostat with a lower rated one is usually down to psychological reasons and not reasons based on fact'

See picture taken from my Lotus workshop manual. I think some folk must be looking at their cookery book. Now I will give you some facts.

Every Twin Cam in every Elan runs differently and has its own likes and dislikes as far as starting, running, temperature, settings etc. There are not 2 in the world that run exactly the same.

I rebuilt an engine with 40k miles on it, that I had run for 30k of those miles with a 74 degree stat in. There was NO discernible wear on any component, inc the rings, so I just cleaned it and put it back together, and 80 miles later drove off to France in it. So much for increased wear.

There is not a single member of this Board who runs their road going Elan with an 89 degree stat in. In my experience, gained from over 40 years of running Twin Cam engines, they do not like to be run excessively hot, and start to get lumpy when they are. With a 74 degree stat fitted in my every day Elan, it runs at 80 degrees on the dial, and that is perfect. With the 78 degree stat fitted, it ran at 85 degrees, and did not leave enough margin for my liking.

Leslie
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PostPost by: 2cams70 » Sat Jun 29, 2024 9:23 am

What year was that workshop manual you are reading from Leslie published?
Mine is a 1970 Ford publication. They may have upped the temperature on later cars. The thermostat has no relationship whatsoever to whether the car overheats or not. 90C is not an engine overheating. It's an engine running efficiently. If your cooling system is blocked or inefficient and the temperature reaches 97+ it will happen with any thermostat you may put in the engine that is rated under that figure
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