Lotus Elan

small loss of coolant

PostPost by: bob_rich » Sat Sep 02, 2017 6:30 pm

Hi All

I have a question regarding a small loss of coolant I am using in my Lotus Elan use a 50% water 50% Halford ethylene glycol solution. I seem to have a very small loss of coolant after a long run when engine has got quite warm stuck in the M25 traffic. when I got homeI stop the engine and I can here a small hiss but cannot locate it. If I release the pressure the noise stops. There are not signs of any coolant leakage and all the normal test for coolant loss in the engine ( into exhaust, into oil etc) show nothing is amiss but I can hear the hiss.
If I was leaking coolant it would be a bright pink but there is not a sign of that anywhere.

so my question is this could the high temperature when in traffic and engine gets to around 100C (but is stable as fan clicks in and holds it OK so no thermal runaway) could the water vapour alone leak out and this is my hiss without any Ethylene Glycol so I don't get the tell tail pink colour of the coolant and my hiss is just steam and as a result my coolant level falls.

Despite this coolant loss the engine feels OK but I do have to top up the coolant

So could the high temperature cause the separation of the water from the coolant solution?

My second question is that I have heard that K Seal is a very good engine cooling system leak sealer and this may
be one way to stop the problem.

has anyone any comments on the use of K Seal?

Thanks in advance for any info

cheers

Bob
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PostPost by: promotor » Sat Sep 02, 2017 10:01 pm

Most likely to be one of the seams in the radiator - check were the radiator is brazed and also check all of the fins.

My cortina does this frequently - I can hear the hiss, the water level goes down but I never see the leak even though I know where it is leaking!
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PostPost by: billwill » Mon Sep 04, 2017 12:17 pm

You don't mention the overflow system and you removed the rad cap early so perhaps you do not understand the overflow system.

There should be a pipe going down from the radiator filler 'cup' into the overflow bottle in front of the radiator and that bottle should at minimum be about a third full of coolant.

The Rad cap on an Elan is a double valve system, the main valve seals the radiator until the pressure exceeds the figure stamped on the cap. If there is no air (or other gas) in your cooling system this pressure may be achieved with expansion of the coolant, long before reaching boiling point because the fluid is not compressible. So the expanded amount comes out of the main valve and joins the coolant in the pipe down to the overflow bottle. The down pipe should always be full.

When you stop and the engine cools down, the coolant contracts again and the light-pressure reverse valve in the centre of the Rad cap opens and it 'sucks' coolant back up the pipe from the overflow bottle.

If you remove the cap early you break the partial-vaccuum and you let air into your coolabt system

~~~~
So to answer your original question, there may be nothing wrong, you may be hearing a slight sizzling sound of the return valve in the Rad Cap.
Bill Williams

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PostPost by: Grizzly » Mon Sep 04, 2017 1:01 pm

Don't put K-Seal in.... Rough fix that usually causes more issues than it repairs.

My money would be on pipe clamps, my +2 would do some thing very similar when it was very warm (use half a cup of coolant on a good run) i suspect the coolant would evaporate off almost instantly making it difficult to spot. I only noticed when i removed the Radiator for a reason that eludes me (slept since then) and noticed the water mark on the lower hose went past the indentation the pipe clip made in the rubber (in other words it leaked)

So i fitted quality Mikalor pipe clamps and it never did it again. The stock Wire pipe clips are not very good to put it mildly.

As for the stock bleeding system, not confident it works to be quite honest. Even if it did not many people prime the Overflow pipe with coolant before sealing the cap so i don't see how it would draw coolant and not air at least for the volume of the overflow pipe.I ran my +2 for many years without a overflow bottle fitted with only the Clamp issue to report, since then i have fitted an overflow bottle with a clear hose to my 2 seater and the only time i saw the clear water in the overflow bottle diluted with antifreeze was when the Fan switch died and it overheated.

Note i prime the Overflow pipe with coolant some thing not many do.
p1040141.jpg and
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PostPost by: bob_rich » Mon Sep 04, 2017 3:12 pm

Hi All

Thanks for the interesting replies. Perhaps I should outline the cooling system mods. I have used a system common in modern cars with a header tank , I used one from a Lotus Elise. The header tank main feed Is fed to a T piece in the bottom hose while the expansion and over flow is taken to a T piece in the top hose (together with temperature gauge sensor ). It works fine on my Lotus 7 so I used the same idea on the Elan +2s. I have attached a picture of the engine bay that shows the arrangement.

On the drive to/from the Lotus do at Brands Hatch this Saturday the car sat in traffic on the M25 the fan kicked in OK and held the temp steady despite the slow crawl at Dartford. When I got home I could hear the hiss which subsided when I I released the pressure. After it was fully cooI it seem to have lost about a cup of coolant.

I will try and trace down the hiss and try not resort to sealant--my suspicion is around the Otter switch for the fan which is held in a grommet in the radiator header tank.

thanks for the comments.

I had never heard of K seal until recently what problems can it throw up ?

cheers

Bob
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PostPost by: Grizzly » Mon Sep 04, 2017 4:51 pm

May be mistaken but isn't the header tank bleeder line supposed to be the highest point to remove trapped air?

See Pete's picture 5 posts down
lotus-twincam-f39/cooling-system-expansion-tank-installed-t21383.html

BTW, Nice Throttle bodies 8)
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PostPost by: bob_rich » Tue Sep 05, 2017 12:43 pm

Hi Grissly

thanks for the comment and I found the link most interesting. The camera shot does not make it clear ( I went out and checked with a level ! ) but the T piece in the top hose is around 10mm above the thermostat housing ( top of T piece to top of stat housing. Having used a Elise header tank I can pressurise it with a fitment made up with a bike tyre pump and a spare cap to get the coolant into the system -- which is what the Elise requires during the filling up of the coolant.

Thanks for all the useful comments

cheers

Bob
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