Cooling - best way?

[l10tus]

I have a few issues with the coolant in my car , and wondered if anyone could offer some advice as to what course of action would be best to take, to improve it?

It started when I took the car for its first decent run - 300 miles each way, but found I'd used (or lost) about a pint of coolant in the process !

I must admit my passenger and I could both smell what seemed to be boiling coolant / steam and burnt oil / petrol smells during the trip.

The oil leaks at the front of the car were causing the oil smells - (needs more gasket sealant - to be addressed later!)

But as for the water loss - upon inspection, It turned out that the radiator cap used on the thermostat extension conversion didn't fit that well, so the top seal was leaking coolant when it got upto temprature / pressure.

I pinched the little lock tab ears slightly on the rad cap and this seemed to seal a little better, but endeavouring to ensure a full seal, I also applied a smear of non-setting Hylomar Blue gasket sealant to the mating surfaces of the upper rubber seal of the rad cap and the thermostat extension housing rim.

At the same time, I removed the rubber sealing grommet from around the rubber overflow tube in the Tudor overflow bottle top, (still positioned the nose of the car) - I was advised that atmospheric pressure was required to refill, when cooling had taken place - was not being helped by a vacuum in the Tudor bottle, when the radiator cooled down and sucked coolant back into to top up the system - this seemed logical ? (although the Lotus Workshop manual says it should be an air tight seal ?)

On the return journey the oil / petrol smells were still there slightly, but hardly any water was lost - about an egg cup full needed to fill the system, (I noted there was still a small air gap when I removed the rad cap and looked into the thermostat extension housing).

Not too bad it seemed - but still not completely full !

So, I have had some thoughts about trying to make it completely air tight / full of coolant, I list them out for your thoughts and comments please :-

1) Modern cars always, always, have header / expansion tanks - fact?

2) They are generally positioned above the highest point of the cooling system and usually nearly always incorporate a 'gravity assisted' refill when cooling down to refill.

3) my plan is to mount an expansion vessel against the bulkhead, as high as possible, with hopefully a gravity feed back to the system? - I'll still use a 'Twin Seal' 10lb pressure cap - but on the expansion vessel only - not the stat extension ( another 'blank cap' ?

4) My S3 wide rad conversion still has a filler cap, but it is fitted with a 'blank' rad cap.

2) Reduce the length of the overflow pipe - making it as close as possible to the return fill point - (there must be a meter and half at present, going from extension housing to nose of car) - is there a recommended sensible length / internal bore size required, as this seems an awfully long way, for any coolant to be sucked back ?

3) My thoughts are that it must make a hell of a vacuum to lift the 'refill' coolant out of the bottle in the nose, along a meter or so long pipe and back into the thermostat housing, whilst attempting to refill the system completely - I'm thinking it's almost impossible for the temprature generated cooling down vacuum / suction, to pull it that far - is nearer better?

So, Summarising: Fit Gravity expansion tank, short overflow hose using specified / suitable / small bore pipe, twin seal rad cap on expansion vessel, blank cap on extended stat housing ?

FYI: Engine presently fitted with a 74 degree stat. When coolant is 'full'' the engine temp ranges from 74 - 80 degrees.

Fitted with S3 Wide rad, twin electric cooling fans controlled by a stat in the extension housing.

[rgh0]

Do you have the correct cap that has two seals and are both the seals areworking. The outer seal seals the cap to the rim and the inner seal seals the coolant from the vent hose. This inner section relieves pressure and also incorporates a return valve arrangement that opens under vacuum to suck the fluid from the recovery bottle back into the system.

you need to have the coolant liquid level above the hose bottom in the recovery tank when the car is cold. The coolant in the engine expand when hot and flows to the recovery tank and is sucked back in when cold. I may take a little while for this process to purge any air in the system and you may need to fully fill the system to the top a couple of times to achieve that.

The recovery tank is fine where it is, there is plenty of vacuum to lift the fluid back into the engine as it cools provided there are no leaks in the hose to the recovery tank and the tank has coolant in it..

cheers
Rohan

[l10tus]

Rohan,

Thanks for the reply.

Did you see the questions at the end of my epistle - any thoughts?

Rubber grimmet - to seal or not to seal?

Length and I.D. of overflow pipe?

Ta,
Phil.

[rgh0]

See my comments against your specific questions below

cheers
Rohan

I have a few issues with the coolant in my car , and wondered if anyone could offer some advice as to what course of action would be best to take, to improve it?

It started when I took the car for its first decent run - 300 miles each way, but found I'd used (or lost) about a pint of coolant in the process !

I must admit my passenger and I could both smell what seemed to be boiling coolant / steam and burnt oil / petrol smells during the trip.

The oil leaks at the front of the car were causing the oil smells - (needs more gasket sealant - to be addressed later!)

But as for the water loss - upon inspection, It turned out that the radiator cap used on the thermostat extension conversion didn't fit that well, so the top seal was leaking coolant when it got upto temprature / pressure.

I pinched the little lock tab ears slightly on the rad cap and this seemed to seal a little better, but endeavouring to ensure a full seal, I also applied a smear of non-setting Hylomar Blue gasket sealant to the mating surfaces of the upper rubber seal of the rad cap and the thermostat extension housing rim.

At the same time, I removed the rubber sealing grommet from around the rubber overflow tube in the Tudor overflow bottle top, (still positioned the nose of the car) - I was advised that atmospheric pressure was required to refill, when cooling had taken place - was not being helped by a vacuum in the Tudor bottle, when the radiator cooled down and sucked coolant back into to top up the system - this seemed logical ? (although the Lotus Workshop manual says it should be an air tight seal ?)

On the return journey the oil / petrol smells were still there slightly, but hardly any water was lost - about an egg cup full needed to fill the system, (I noted there was still a small air gap when I removed the rad cap and looked into the thermostat extension housing).

Not too bad it seemed - but still not completely full !

So, I have had some thoughts about trying to make it completely air tight / full of coolant, I list them out for your thoughts and comments please :-

1) Modern cars always, always, have header / expansion tanks - fact?

rh - Modern cars have two types of systems typically - a pressurised expansion tank or a non presurised overflow recovery tank. Older cars without either of these systems essentially used the top tank of the radiator as a pressurised expansion tank.

2) They are generally positioned above the highest point of the cooling system and usually nearly always incorporate a 'gravity assisted' refill when cooling down to refill.

rh - The vent line and cap to external overflow recovery tanks of are usually at a high point so that air is removed and the system can be filled you fill through this cap.. Most external overflow tanks dont have "gravity assist" as they suck from the top of the tank via a dip tube. The external pressurised expansion tanks typically fill and empty liquid from the bottom into the rest of cooling system. They often also have a vent line from a high point in the circulatiing system to the top of the pressurised expansion tank to remove air from the circulating system ( this is how my S1 Esprit systme is designed)

3) my plan is to mount an expansion vessel against the bulkhead, as high as possible, with hopefully a gravity feed back to the system? - I'll still use a 'Twin Seal' 10lb pressure cap - but on the expansion vessel only - not the stat extension ( another 'blank cap' ?

rh - You are describing installing a pressurised expansion system which you can do but it is not really needed.

4) My S3 wide rad conversion still has a filler cap, but it is fitted with a 'blank' rad cap.

rh - not a problem if you have the extended filler on the thermostat housing and the proper recovery cap fitted and working to an overflow recovery bottle

2) Reduce the length of the overflow pipe - making it as close as possible to the return fill point - (there must be a meter and half at present, going from extension housing to nose of car) - is there a recommended sensible length / internal bore size required, as this seems an awfully long way, for any coolant to be sucked back ?

rh - A 6 mm tube is plenty big enough the flow rates are very small. The length of tube is not a problem once it is filled with liquid and a liquid seal is present in the overflow bottle and the cap on the extended filler neck is correctly sealing

3) My thoughts are that it must make a hell of a vacuum to lift the 'refill' coolant out of the bottle in the nose, along a meter or so long pipe and back into the thermostat housing, whilst attempting to refill the system completely - I'm thinking it's almost impossible for the temprature generated cooling down vacuum / suction, to pull it that far - is nearer better?

rh - as the engine cools it would actually create sufficient vacuum to lift water up close to 10 metres vertically so a height difference of a few hundred mm is not a problem

So, Summarising: Fit Gravity expansion tank, short overflow hose using specified / suitable / small bore pipe, twin seal rad cap on expansion vessel, blank cap on extended stat housing ?

rh - summarising - understand the difference in how a non pressurised overflow recovery tank system works versus a pressurised expansion tank system works. You can install either. Alternatively you can run with the radiator header tank as the expansion space with just a drain pipe, fill it to the level that it does not overflow when hot i.e. the coolant expansion just fills but does not overflow the radiator header tank and eliminate all the added weight of either expansion system

FYI: Engine presently fitted with a 74 degree stat. When coolant is 'full'' the engine temp ranges from 74 - 80 degrees.

Fitted with S3 Wide rad, twin electric cooling fans controlled by a stat in the extension housing.

[fatboyoz]

Hi Phillip,
Perhaps you are over thinking what you are trying to achieve.
I have an early S4 with the wide radiator, 74 degree thermostat (in original thermostat housing), twin front mount fans and 10 lb double seal radiator cap overflowing into the standard Tudor overflow bottle. When changing coolant, it only takes a couple of drives to purge all of the air out of the system, and then the system does not need topping up for the two years between coolant changes.
I was always under the impression, that people fitted the extended thermostat housing, fitted with a radiator cap, to aid in filling the system. Not sure why you would then require the overflow to be at this point, and not at it's original position, on the radiator?.
For simplicity sake, why not put a plain radiator cap on the extended thermostat housing and close off the overflow at this point. Put your 10lb, double seal radiator cap back onto the radiator, where it belongs, and re-institute your overflow at the radiator directly into your overflow bottle.
As for the Tudor bottle needing to be completely sealed, this is not a requirement. My bottle cap has a air hole in it to allow the pressure in the bottle to equalise as the quantity of coolant, in the bottle, changes. The tube into the bottle does need to be held just off the bottom of the bottle so that the coolant can come an go. This is achieved by having the overflow tube an interference fit in the bottle cap. Perhaps, this is what the manual is referring to when stating the the bottle needs to be sealed?
Cheers,
Colin.

[l10tus]

Rohan, Colin,

Thanks for the in depth replies, much appreciated.

I'm thinking to try both suggestions, firstly the option of re-instating the pressure cap on the radiator and re-fitting the overflow pipe from there, into the nose mounted bottle.
(Colin, I like your description of the seal on the overflow pipe- I'll go with that)

Secondly, (because I just bought an overflow brass tank) to install the gravity

The attachment 20161029_132141.jpg is no longer available

fill tank as option 2.

To be fair, the car had only one chance on the return trip /run, to try to remove the last bit of air from the system, before I removed the cap to check. (And found a small amount of top-up water was necessary) - as Rohan says, it takes a couple of cycles to completely fill the system, does this mean that eventually there is always water held right upto the top of the filler neck when inspected - and does inspecting the water level ( by removing the cap to check) tamper with the operation, mid cycle??

I just can't get my head round the fact that hot / expansion water flows into the bottle when pressurised, but as soon as the engine cools, the 10lb pressure relief valve in the cap shuts ( at this point all the water would symphony back into the overflow bottle ?) and then the secondary release valve open's to suck water all that way from the bottle ?

Or am I getting my cycles mixed up?

[rgh0]

The tube from the cap to the recovery bottle remains full of liquid as it is sealed at the bottom by the liquid in the recovery bottle and coolant pushed from the engine as it expands remains in the tube and in the bottle. When the engine cools it draws coolant from the bottle and tube as needed to prevent a vacuum in engine.

cheers
Rohan

[Chancer]

Being pedantic the coolant isn't sucked up by a vacuum but pushed back by atmospheric pressure against a slightly lower coolant pressure when the engine has cooled.

I say the above to reinforce the point that the overflow bottle must not be sealed or the coolant will not be pushed back to the radiator by the atmospheric pressure, where the pipe enters through the lid there should be a gap, the pipe should go to the bottom of te container and be Under the fluid level as has been said.

[john.p.clegg]

Just found this in the service notes...

John

[Grizzly]

Being pedantic the coolant isn't sucked up by a vacuum but pushed back by atmospheric pressure against a slightly lower coolant pressure when the engine has cooled.

Just to clarify. your saying it's not the fact the water expands causing pressure, so if that pressure causes the cap to vent and loose Coolant volume inside the system, so as the water cools and contracts it isn't that Vacuum caused that opens the top up valve in the cap and draw Coolant from the overflow bottle back into the engine?

Thats the way i understood it? i found the stock set up with the overflow bottle almost a waste of time as when you open the Rad cap the fluid in the Rad - Overflow bottle would vanish into the overflow bottle as it was lower than the rad level. So what you would get is Air in the Rad - Overflow pipe and if the Rad needed to top up it would have to draw that air in first before getting any coolant (yep i know i fitted a clear pipe so i could watch how it worked, clear water in the Overflow and Blue antifreeze in the engine)

The only way i could imagine it would draw Coolant not air was to raise the overflow bottle so the Coolant was backing up and overflowing out of the Rad filler then replace the cap (so there was no air in the pipe or the filler neck) it makes it a pain to check the level of the Rad if you are Paranoid like me as the Coolant would always drop into the Overflow bottle.

Am i doing some thing wrong?

[fatboyoz]

Hi Chris,
Once you have filled the radiator, and perhaps squeezed the top radiator hose a few times, you put the radiator cap back on and leave it on for the next two years, or however long your coolant change schedule is. The expansion and contraction of the coolant with each heat cycle will eventually purge all of the air from the system. You then check your coolant level by looking at the level of coolant in your overflow bottle. I keep my bottle half full. It should only be necessary to add extra coolant, to the bottle, for perhaps two or three runs after you have changed the fluid. As I stated previously, I do not have to adjust my coolant for the two years between changes.
If you keep taking the radiator cap off to check the coolant level, you will allow coolant to flow into the overflow bottle and re-introduce air into the system. A vicious cycle to be sure.
If your system does not operate in this manner, you are either removing the radiator cap unnecessarily, or you have a faulty radiator cap.
Cheers,
Colin.

Being pedantic the coolant isn't sucked up by a vacuum but pushed back by atmospheric pressure against a slightly lower coolant pressure when the engine has cooled.

Just to clarify. your saying it's not the fact the water expands causing pressure, so if that pressure causes the cap to vent and loose Coolant volume inside the system, so as the water cools and contracts it isn't that Vacuum caused that opens the top up valve in the cap and draw Coolant from the overflow bottle back into the engine?

Thats the way i understood it? i found the stock set up with the overflow bottle almost a waste of time as when you open the Rad cap the fluid in the Rad - Overflow bottle would vanish into the overflow bottle as it was lower than the rad level. So what you would get is Air in the Rad - Overflow pipe and if the Rad needed to top up it would have to draw that air in first before getting any coolant (yep i know i fitted a clear pipe so i could watch how it worked, clear water in the Overflow and Blue antifreeze in the engine)

The only way i could imagine it would draw Coolant not air was to raise the overflow bottle so the Coolant was backing up and overflowing out of the Rad filler then replace the cap (so there was no air in the pipe or the filler neck) it makes it a pain to check the level of the Rad if you are Paranoid like me as the Coolant would always drop into the Overflow bottle.

Am i doing some thing wrong?

[l10tus]

Chris,

You've hit the nail on the head !

That's exactly what I was getting at.

Obviously, I suppose you have to do initial checks to make sure the engine is not running dry, but once you feel you've achieved the satisfactory necessary circuit sealing, there's no reason to remove the rad cap to check.

The trouble is I've got neurotic thinking the engine is going to overheat, so think I'm going to try the gravity header tank system - that way it's easier to check the level without spoiling the circuit seal, each time the cap is removed.

Lots of owners must have been lucky using rad caps that seal first time, but you can read about all the various issues in these forums. i,e.

Some owners don't realise the need for twin seal rad caps, some cars don't even have overflow bottles fitted - so I should worry !

[Grizzly]

Hi Chris,
Once you have filled the radiator, and perhaps squeezed the top radiator hose a few times, you put the radiator cap back on and leave it on for the next two years, or however long your coolant change schedule is. The expansion and contraction of the coolant with each heat cycle will eventually purge all of the air from the system. You then check your coolant level by looking at the level of coolant in your overflow bottle. I keep my bottle half full. It should only be necessary to add extra coolant, to the bottle, for perhaps two or three runs after you have changed the fluid. As I stated previously, I do not have to adjust my coolant for the two years between changes.

Hi Colin.

What you are describing does not happen on mine, as i say once my car is fully bled it doesn't loose coolant when run (i have checked this very carefully) the only time it would loose coolant is if it overheated (for example if the fan failed to come on). I know how you describe it sounds sensible but what started all this off was i ran my +2 for quite a number of years with the Overflow bottle missing (was removed by the previous owner and frankly i didn't know he had taken it off) i drove it twice to the south of France and used it every day with never having any over heat issues and the amount of air in the Rad never changed, it was pointed out on another thread that the Overflow bottle was essential but as i say i've never seen the coolant move (hot or cold).

It's why i asked if i was setting my car up correctly because i was expecting it to work as you describe (self bleeds every time the car is run)

[Grizzly]

Some owners don't realise the need for twin seal rad caps, some cars don't even have overflow bottles fitted - so I should worry !

I can tell if my rad cap is leaking because the Coolant won't stay in the overflow pipe (bottle level is lower than my Rad coolant level so as long as it's submerged and the cap's good the coolant stays in that clear hose). I agree it's a pain if i am going anywhere and want to check my levels first. Up until very recently i'd just check the level and put the cap back on and never had an issue but at the same time never saw it pull coolant up that clear pipe.

Maybe i have an air bubble some where in the coolant system? Just seems odd all my Elan's are the same.

I'd be interested how many stock Elan owners purge the Overflow pipe like that?

Ah well.

[vincereynard]

Here is a shot of my system - pretty is it not?

Unfortunately, by some slight oversight by the aforementioned professional restorers, the black overflow tube terminates at the bottle lid and does not extend to the bottom.

Therefore it is not going to work is it! Still it looks nice.