Overflow bottle - Radiator

[AarhusTr6]

hi

 

Would someone explain the concept of the overflow bottle to this rookie please?

 

I understand that on a modern car it has an overflow that fluid expands into, ie with an in and return pipe but on my beloved TR it only has a one way in pipe.

 

Appreciate the education!!!

 

Rich

 

 

 

[harrytr5]

It is called a no loss system.Water expands when it gets hot and it relieves its self by expanding hot water into the bottle.When cooling down it gets sucked back.That is my understanding of it,

rightly or wrongly.Someone will come up with a more technical reason.

Regards Harry

[RogerH]

Hi Rich,

I'm sure it is the same as the TR4A.

The rad cap has a two seal arrangement. The top seal keeps the rad closed at all times.

The lower seal that has a spring can be lifted by excess pressure. This allows coolant to flow into the bottle.

This bottle should always have 1" of fluid in it and the pipe running to the bottom.

 

In the very short time the seal has lifted it will get rid of fluid and instantly draw back fluid if it needs it.

 

So you need the correct rad cap and a partially filled over f;ow bottle.

 

Roger

[Fireman049]

Hi Rich ~

 

Both my 3A and 'E'-type are fitted with closed circuit cooling systems.

The radiator should be fitted with a plain (unpressurised) cap and the expansion tank fitted with the pressurised cap.

This set-up allows the cooling water to be drawn back into the radiator when the engines cool down.

I connected the rad. and expansion tank with rubber hose capable of withstanding the operating pressure.

 

Tom.

[Mike C]

There are a lot of TR's running around without overflow bottles. If these have the radiator completely filled with coolant , the coolant drips out of the overflow pipe when it heats up and expands. The loss part is the coolant dripping on to the ground.

 

When the radiator subsequently cools the coolant contracts and air is sucked in to the top of the radiator-leading to a small reduction in cooling efficiency. Eventually the air pocket in the top of the radiator matches the coolant expansion and the loss from the overflow stops.

 

With a good cooling fan loss in radiator efficiency is not critical unless you operate in stop/start traffic conditions at high ambient temperatures.

 

My expansion tank and brackets came from an old Volvo sedan, it is bigger and more robust than the original.

[AarhusTr6]

Hi

 

Interesting. My local Triumph guy said keep bottle half full (just a comment).

 

The picture in the link

http://www.revingtontr.com/tr4a/triumph-catalogue/ag

 

shows it quite well. So from my understanding, the cooling of the engine creates a vacuum and this then draws the fluid back it . . simple I guess. So from a service and check perspective I will check level from Rad cap and bottle.

 

So for fluid, what do people put in theirs and whilst on the subject - any other tips? Maybe of interest, I read on another forum (on the subject of rad's) that the cheap alloy ones on eBay should be avoided and if you have heating issues that its best to renovate your original OEM rad.

 

Thanks all,

 

Rich

[RogerH]

Hi Rich,

when the system cools down it tries to create a vacuum but the centre of the rad cap has a one way valve in it - and so it sucks fluid back in.

Not necessarily as much as it spewed out.

 

Don't go near Ali rads unless you really need the weight saving.

The original copper rad coos more efficiency than an Ali rad.

 

Just use the normal 'blue ' anti freeze (Halfords, Bluecol etc) Do NOT use OAT antifreeze (normally orange)

I run with the winter mixture all through the Summer.

 

Roger

[SteveB21]

Rich

 

Here's a picture to help you - I have my bottle filled to the halfway mark when cold, with the hose just off the bottom of the bottle. Use "blue" ethylene glycol antifreeze (don't mix anti-freeze types) and change every 2 years to keep corrosion at bay. The high point of the system is the off-take on top of the engine, so it can help to re-fill the system with the front of the car on ramps / stands, make sure the heater valve is open when re-filling (sorry if that is obvious...). It can take a couple of runs to get all the air out of the system after a full flush and re-fill, so don't panic if the level in bottle goes down after your first run post-refill - just top it up - do check for leaks if it doesn't stabilise after a couple of runs though...

 

Cheers

 

Steve

[Alfrom]

There is one other little thing to note and that concerns the overflow pipe. Do not use just any old rubber pipe for this job, as it needs to not only withstand the hot water but also a little movement and possible damage resulting from abrasion against the radiator or something else in the area. The pipe could get worn away to the extent that extremely small holes appear, resulting in the loss of the coolant push/suck back process described above.

The initial symptoms are that with successive runs, the bottle gradually fills up and the radiator level falls. This is because water gets pushed out of the engine into the bottle but air gets into the pipe as the engine cools so preventing the suck back from the overflow bottle. Topping up the radiator (either at the cap or at the thermostat housing) just means you fill the overflow bottle even more!

Over time, the holes get bigger and eventually, you will see the water coming out of the pipe as the engine warms up and much of the water won't reach the bottle.

Sorry about the long-winded description but I write from experience. Just make sure you get the right material for the pipe and route it in a way that prevents abrasion against anything.

[barkerwilliams]

As a self-bleeding system it ensures the radiator is always full of liquid and there is no dead-air-space at the top of the radiator which leads to less than maximum cooling by the rad.

 

​Alan

[harlequin]

Just to add to Pierre's post, the neck of the radiator is another source of air leaks as over the years the bayonet type fixing of the cap tends to distort the top surface

 

George

[Mike C]

Make sure your radiator cap is ths double seal type suitable for use with an overflow bottle.

 

In my experience, for vehicles doing limited miles, poor quality coolant causes more high cost problems than poor quality oil-and people talk endlessly about oil changes. Change your coolant on a regular basis and test it annually- I use a kit I got from Castrol a few years ago. I use a 50% solution of long life coolant and log the change dates.

 

I won't use alloy radiators as I've had too many problems with galvanic corrosion over the years. In Australia a copper radiator recore is 3-4 times the cost of a new alloy radiator but I still consider it money well spent.

[AarhusTr6]

From the owners handbook!

[AarhusTr6]

Interesting topics all around, especially the views on ally radiators.

[Aldpilot]

Nice to hear what the correct operation of the overflow bottle is. Whenever I put extra fluid in the bottle (when cold) I find after a good run that the bottle is empty and the radiator is full. I have topped up quite a few times with the same result. So now I run with an empty bottle and whenever I check the radiator, it is always full. Clearly something is not quite right, but with the rad appearing full and no overheating issues (other than in the really hot weather), I have just accepted things. Perhaps someone knows the answer. Mike

[RobH]

Perhaps your overflow bottle is too small Mike? How full is it with the engine hot ?

[Aldpilot]

Bottle is the original factory fit. It does not seem to get any water in it when running. All very strange.

[RobH]

Very odd. Might be the radiator cap perhaps - is it the right type? No leak in the overflow pipe?

[Mike C]

Do you have the double seal radiator cap required by recovery systems?

 

If the radiator is full at the start and there's extra fluid in the bottle it has to go somewhere if it's empty when you stop. Over the years I've had most mystery problems with the cap and occasionally the interconnecting hose. Leaks from the radiator and bottle are generally self evident.

[Aldpilot]

Double seal cap. Yes. A new one in 2017. I had a top hose leak recently (small split) so changed it. Not noticed any change in operation since.

[Alfrom]

The radiator cap is not the highest point in the system, so perhaps there is sufficient air space in the pipes that as the coolant expands, the air becomes compressed but the system pressure remains below the threshold necessary to open up the pipe to the overflow bottle.

I have in the past topped up the system by adding fluid at the thermostat.

 

Question: if I take off the radiator cap, should not some of the coolant come out of the radiator?

[barkerwilliams]

Question: if I take off the radiator cap, should not some of the coolant come out of the radiator?

 

If you mean on a room-temperature radiator.

 

An infinitesimally small amount coolant will move down from the radiator reducing the pressure in the radiator and the flow will stop. If it flows there is an air leak in the system. If it didn't stop a vacuum would be created in the radiator & engine waterways.

 

Air will be at the highest point of the radiator when the engine is cold.

 

As the engine warms the air and water will expand.

 

The only place to go is down to the expansion bottle, as the air is at the top it goes first.

 

Everything equalises pressure wise.

 

As the engine cools the water in the engine & radiator contracts and draws coolant up from the expansion bottle.

 

 

Air has been expelled, radiator has self bled, coolant level in expansion bottle will drop slightly corresponding to volume of air replaced.

 

 

Hence expansion bottle needs 1/2 to 1/3rd full coolant. This will drop after renewing all coolant as air, dissolved air and air pockets are flushed out into the expansion bottle.

 

Alan

Edited January 29, 2018 by barkerwilliams

[Waldi]

It is what it is, but we can see the modern systems with an expansion tank are much more reliable.

The TR system depends on proper opening and closing of the inner pressure relieve valve, no air leaks in the tube, and this every thermal cycle.

The modern system also directs some coolant in the expansion tank during warm-up and draws it back during cool down, but there is no valve between the radiator and expansion tank.

Makes sense to me.

But there is probably an explanation for the TR system, anyone knows?

Regards,

Waldi

Edited January 29, 2018 by Waldi

[BlueTR3A-5EKT]

Air locks/trapping in the system? Racers tip....TR5/6 Try using the MG Midget/Tri Spitfire 1500 thermo housing outlet pt no CHA343 - It incorporates a screwed plug used to fill/vent the cooling system.

https://images.duckduckgo.com/iu/?u=https%3A%2F%2Fwww.moss-europe.co.uk%2Fmedia%2Fcatalog%2Fproduct%2Fcache%2F1%2Fimage%2F1900x%2F3780b08b89bf73743be85dcc5f1acf25%2Fs%2Fm%2Fsm_15_07_03.jpg&f=1

 

...or just drill and tap your own and fit a radiator butterfly drain tap as a vent valve. http://classicparts4cars.co.uk/mgb-drain-tap-wing-type---arh517-614-p.asp

 

 

 

Peter W

[SteveB21]

Peter

 

That's a neat idea - do you know if the outlet pipe on the MG outlet is the same diameter as the TR6 one, enabling a straight swap using existing top hose?

 

Thanks

 

Steve