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MG MGA - Radiator overflowing when hot

I just bought a 1957 MGA in good condition.
When I run it for a while on a warm day and then stop the car and the engine, the temp goes up to 190F on the thermometer on the dash and antifreeze starts to pour out of the overflow hose next to the radiator cap.
Do you think this is normal or is the cap defective?
It seems quite loose when I screw on the radiator cap. The printing on the cap says "4 pounds".
Is the car really over heating?
Thanks,
Bill from Ann Arbor, MI
W Chandler

Bill

Sounds normal to me. Worth reading through Barney Gaylord's many useful articles on the topic, which include fluid recovery systems: http://mgaguru.com/mgtech/cooling/cool_1.htm

Steve
Steve Gyles

Do you have the correct filler cap for an MGA, most "standard" ones are too short and don't seal. Get a new cap from a MGA parts place.

Don't be worried otherwise, just don't top it up after it has left it's calling card, and then all should be fine. As Steve says, it's normal
dominic clancy

Yes - mine does it too -so an overflow catch tank is on the cards. By thw way, I have a 7lbs cap (long reach) fitted as was standard on the 1600 and I think it was an advisory retro fit on the 1500 .
Cam Cunningham

There must be room in the radiator when the coolant is cold to allow for coolant expansion when hot.
Check the coolant level when cold and do this after several runs.
Does the level always return to the same point?
If so, all is normal.

Mick
M F Anderson

I had a similar issue which resolved when I replaced my cap. I purchased a new cap from Scarborough Faire which has resolved the problem.

M.D.
'57 Coupe
M. D.

Am I the only MGA owner who just cant resist topping up the radiator to the brim even though I know it will overflow whenever I stop the car?

I know it is kind of stupid but I think it stems from my being more comfortable with seeing the radiator full.

Also I suppose that if the rad overflows each time I stop the engine, then its a good indication that there is enough coolant in there!

Colyn
Colyn Firth

Fit a coolant recovery system Colyn, then it will always be full without your topping it up!
Lindsay Sampford

Colyn,

When you continuously top up your radiator do you use coolant (anti-freeze mixture) or water?
If you top it up with water you are diluting your coolant. In the coming Winter your engine will not be protected.
If you top up with coolant each time you are diluting your wallet.

Mick
M F Anderson

I always use an anti-freeze mix Mick, in fact it is almost time for its pre-winter coolant and oil change.

Maybe if I start looking it as $ notes on the floor and not just water then I will stop filling it up!

The coolant recovery system will probably be the best answer Lindsay, if I get a transparent one then I will be able to see that there is plenty of coolant there and stop worrying.

Thanks

Colyn
Colyn Firth

The radiator cap should certainly be a 7psi one.
MGA radiators always overflowed when full, even when they were new. They have to find their own level.
Try this. You fill it right up. Take it for a run, switch off - it pours out the overflow as usual. When cool, remove cap and suck out all the coolant you can in the radiator neck. Measure this amount or mark the level in a bottle. Pour it back. This is your max coolant level.
When you next want to check the level, suck it out as before and compare it with your previous measurement, if its the same put it back in. If its lost some add your normal mix to make up the difference before putting it back in.
Works for me and saves distilled water (that's what I use) and antifreeze + there's peace of mind for the next outing.
Pete
P N Tipping

Another slightly different point here,is "when is a MGA radiator full"? As you know, with the horizontal extended neck, which tends to slope slightly downwards towards the motor, it is hard to see if the rad is full...there is always a small residue of water lying in the neck below the cap due to the "slope" of the neck, giving an impression that the rad is full.... many a time I have added a couple of litres of water until the rad is "full" i.e. flowing over the outlet.
Gary Lock

Well thats done it now Gary! Just when I thought I was well on the road to recovery!

How will I ever be able to cure myself of my "MGA Radiator Topping-Up Syndrome" now?

Will I now have to attend regular meetings of MGARTUS Anonymous where I sit amongst a circular group of similarly afflicted people and say " My name is Colyn Firth and I am an MGA radiator top-up- aholic?"

I never thought I would end up like this!!

Colyn




Colyn Firth

Colyn and Gary,

You can only retain your sanity by fitting a coolant recovery system.
The simple type, open to the atmosphere, is your best bet.
The pressurised MGB system is a bit more complicated and does not really have any additional benefits.
The coolant bottles and fittings used on Triumph cars are available from Moss.

http://www.moss-europe.co.uk

Search part number 137632.
It only takes a few minutes to fit.

There is only one complication. You have to find the correct radiator cap.
It needs to be a long neck MGA type but also have the three seals.
One seal is for the top of the neck, one seal is for the bottom of the neck, and one seal is for the coolant return.

Mick
M F Anderson

Colyn, you think you've got all the problems!..how about us "down-under"... trying to keep the water IN the radiator!...it's not a very big filler hole on the bottom.
Would love to start up a MGARTUS Group down here. Is there a cure at all?
Gary Lock

Contrary to some opinions, the recovery/expansion tank does not need to be sited below the top water level of the radiator. Barney shows his system on the firewall shelf. I have mounted my MGB expansion tank on the front face of the firewall, immediately behind the rear carburettor. The only problem with my siting is that it inhibits easy access to the carb for adjustment or removal of the filter box. I have to unbolt the tank first. Whilst I am happy with my expansion tank system (same as modern cars), it is not quite so easy to check water levels compared to the clear plastic bottle recovery bottles. It's quite dark inside the MGB tank and the filler neck is at an angle. It always requires a torch or dipstick to check.

Gary. You must have the same problem down under when it comes to oil changes. That sump plug hole is quite small for filling up.

Steve
Steve Gyles

I fitted the plastic bottle just to the side of the radiator..see attached pic.. The mounting cradle for the bottle was bent to fit behind one of the bolts holding the radiator to the body. The inlet hose is very short and the overflow/vent hose runs down the same location as the original.. Had it in place a long time now and it blocks nothing ( I have the carb air hose in place as well) and never have to refill. Cheap and cheerful....keeps the radiator filled even when upside down in Oz.

Neil Ferguson

Neil I do not understand how your system works? How does water ejected from the radiator find it's way back into the rad?
Bob Turbo Midget England

Gary,

There is a simple answer to your problem--a rotisserie.
David Werblow

Bob..the cap has two seals and a small vacuum poppet valve. These caps are standard items..not specials and you just have to look for the ones with two seals and make sure you have the right one for the top to shoulder distance on your radiator..They should all have the small vacuum valve. The top seal sits on the top neck and the lower seal sits on the lower shoulder in the radiator filler. The poppet is there to ensure you cannot pull a vacuum when the water cools down and should be present on all caps..usually just pullingin air. (otherwise ,,smaller radiator!). When the water heats up and expands the water overflows in the normal manner but is caught in the plastic bottle and not spat on the floor. When the radiator cools down the water is drawn back via the poppet valve and refills the radiator. There are two hoses into the top of the bottle and the transparent hose seals without any help from seals etc. The overflow hose must go low down in the bottle and should be under the loest water level. The other hose is a vent/overflow line which after system is set up should not flow water ..just vent air when water arrives and vice versa. Works very well ! The bottle is a Tudor type( a rip off pricewise) but can be any sturdy preferably transparent bottle.... bought a cheapy on Ebay for my jeep. The amount of coolant recycled is about half/two thirds the bottle capacity ( 1 pint). Funny about that last unit of vol. measure..I hardy ever use it these days for arbitary liquids and it made me thirsty.
Neil Ferguson

Niel, -- Your bottle gets in the way of reaching under the carbs to adjust things. How easy is it to remove the bottle bracket?

Bob, -- The radiator cap must have a seal at the top edge of the filler neck. The tube from rad overflow to bottle goes to bottom of bottle, and the bottle cap must be vented. Thermal expansion pushes fluid from rad to bottle. With thermal contraction in the radiator, atmospheric pressure pushes the fluid back into the radiator. This would work with the bottle sitting on the ground or held six feet above the radiator. Gravity is not an issue (except to assure fluid stays at the bottom of the bottle).

Using a transparent bottle allows visual confirmation of fluid in the system without need to remove a cap.
Barney Gaylord

Barney..I'd pull off the hoses and lift the bottle up out of the cradle if I ever needed to but so far (even after a few tunes etc on carbs) no need.... I may have long prehensile fingers!! I would keep the bottle a short distance down as lowering puts more of a vacuum demand on the radiator when sucking back.

Bob..I read about this simple approach on this site ( or from Barney,s ) and was amazed to see how well it worked....I attach a sketch of the refill phase and the cap seals /vac valve locations.

Neil Ferguson

I'm slightly puzzled by all the discussion around coolant leakage over the long term and the scale of the issue. If the radiator is over filled to the level of the neck and then run hot the expanded water overflows.

However, over a few cycles the amount of water in the system reaches an equilibrium level where the maximum expansion doesn't make it overflow past the cap. Beyond that time there may be a tiny amount of leakage but only from the air which gets cycled in and out of the system. The coolant will evaporate into the air in the top of the radiator making it moist. The air is then cycled in and out of the system as the rad gets hot and cold; with moist air expelled and drier air sucked back in.

So agreed there will be a tiny bit of moisture expelled each cycle and eventually it needs topping up. This will be similar for an un-pressurised coolant recovery system. The moist air is cycled in and out of the bottle just the same as in the standard system, so the coolant will be lost slowly. There may be a small benefit in that the water in the recovery bottle won't get so hot and therefore the moisture content in the air in the tank will be less.

The biggest issue for us all is that the filler neck slopes towards the engine as Gary says, and there is always a tiny bit of coolant there so you can never tell if the radiator has enough water in it or not. The separate bottle, if transparent, has that benefit. We love our cars and I don't mind checking the rad level regularly but we can overdo it! I never fill it up above the very bottom of the filler neck.

Pete's solution is wonderful, I just love it, but maybe a bent dipstick would be easier!


John Francis

I used a very similar bottle method as Neil. Mine is a little lower down. I used a bicycle water bottle cradle and a Rubbermaid bottle with the oz. markings on it. To fill it you slip the bottle outof the cradle so you can unscrew the cap. I was pretty proud of it and it functioned great. But...., there was a problem. On a hot day this summer idling and crawling for a long period entering a street cruise in I got a bad case of boiling fuel in the carbs, and barely made it to the parking area. This car had never done that before despite idling on even hotter days. Maybe ethanol in the gas has something to do with it, I don't know. My car has a standard fan, and one of those plastic radiator shrouds. It seems that while the shroud is pulling air through the corners of the rad helping to cool the engine in idling and slow moving traffic, there is less air circulating around the carbs. The bottle was mostly blocking a path from the center fan hole of the shroud that could flow around the carbs. I removed the bottle and it has been fine since. You can put the recovery bottle on the heater shelf, but I have tried to keep my car as original as possible, and a Rubbermaid bottle by the heater doesn't cut it. I have thought about using one of the Tudor windscreen bottles, but for now I am back to the rad checking setup, which isn't that bad I guess. I liked the idea of being able to glance at the bottle and know immediately how your coolant level is, hot or cold. I also don't like spilling coolant on the ground if I have happened to overfill it.

Ralph
L Poupard

Ralph..Interesting problem. I have never had such a carb. problem and I do not have a mechanical fan or shroud. I put in twin electric on a thermo at same time as the recovery bottle...see pic. and not sure of the beneficial interplay of these re air to carbs in a traffic crawl...it would depend on how long and whether the temp built up. I use a 1 pint Tudor bottle and it only very slightly shrouds the top corner ( see previous pic and is inboard of the air duct..is yours a biggy?) As mentioned I do have the airduct from front of radiator plenum to near carbs fitted ...do you? The other major difference is the vast majority of my driving is on open roads as I keep the car on Southern coast NSW and no trafiic jams longer than 10 cars long for 10 mins. good luck....
Neil Ferguson

I see how that system works now Neil not sure where you would buy a special cap.

I have the modern system installed on my car using the Midget expansion tank. I not sure I see any avantage in using one or the other system however. Both I think do the job very well.
Robert (Bob) Midget Turbo

John - Thanks for reading my simple solution. Its easier to do it than explain it. I use an old washing up bottle with a bit of plastic tube pushed over the plastic nozzle to suck out the coolant, then squirt it into a clear bottle marked at the appropriate level. Hope it works for you.
Pete
P N Tipping

Neil,
I have the air hose fitted. The bottle was kind of big, and it may have been blocking too much of the space between the shroud and the carbs. At least it seems that way since it didn't do it afterward or before that. The next time the rad is out I may not refit the shroud, and go with an electric fan instead.
The plastc shroud is very difficult to install, it has to go in at the same time as the rad. It is a bear.

Ralph
L Poupard

I fitted a recovery system for my MGA which functions well.
I sourced a long neck recovery cap from eBay which does the job:http://www.ebay.com.au/itm/Austin-Healey-Recovery-Radiator-Cap-Recovery-Cap-AH-/220739423055?pt=AU_Car_Parts_Accessories&hash=item3365184b4f#ht_615wt_759
I fitted an MGB sourced brass recovery tank on the near side (left side) heater shelf.
I've yet to trial the system on a really hot day though, so see if the MGB recovery tank has a large enough capacity. So far so good though.
Here's a photo of the tank and bracket in readiness for fitting.

T Aczel

I fear the black tank in a black engine bay won't show well, but here's the installed tank.
A suitable length of heater hose, secured to the bonnet release cable by cable ties joins the radiator overflow outlet to the recovery tank.

T Aczel

Tom,

Your system is a bit puzzling.
You say that you have a long neck MGA recovery type cap and a MGB recovery tank.
If you use the MGB tank with a pressure valve type cap the MGA cap should just be a single seal type, just sealing at the top of the neck.
If you use a recovery cap on the MGA radiator you just have a simple non-pressurised cap on the overflow tank.
Is the recovery tank open to atmospheric pressure as indicated by the hose not having clips to hold pressure?

Mick
M F Anderson

Mick I'm running the latter arrangement that you suggest. The radiator has a (long necked) recovery cap. The recovery reservoir (the overflow tank) has a non-pressurised cap.
Am I missing something here? It certainly seems to function well, with coolant appearing to run into the overflow tank when hot the engine is hot, especially after shutting down, and the level in the reservoir tank then falling again when the engine (and coolant) cools down.
Since setting up the system it seems to function stably and reliably.
I still wonder if my MGB tank will prove to have an adequate capacity when it gets really hot, and the coolant expands more.
T Aczel

Tom

Mick has covered my thoughts.

I have the exact same position as yours for my MGB tank. However, I use it as part of a pressurised system, not just an overflow tank that you describe. The system will work well as you have set it up, but it seems to me unnecessary to have used the MGB tank purely as an overflow when a plastic bottle would have sufficed. That said, you do have the advantage that by swapping the caps around (blank on radiator and a standard pressure cap on tank) you can switch between either system to see which you prefer. In the past, Barney has questioned the integrity of the brass MGB tank as the seam can become suspect with age. So far mine is okay.

I usually prime my tank with about 3 inches of water. I have never had an issue in the past 5 years or so - essentially fill and forget.

Steve
Steve Gyles

Tom,

I think I know what you are doing.
You are using a MGB tank as a simple overflow container, not as a pressurised tank as on the MGB.
Can you confirm that your MGB tank is open to atmospheric pressure?

Mick
M F Anderson

Just a couple of queries on the MGB overflow tank - how does it work? Does it have an inflated rubber ballon in it that collapses as the coolant in expands (there is no explanation on MGAguru/Steve's site). What is its nominal capacity - would thisd be the ideal capacity for an unpressurised system also?
Mike
Mike Ellsmore

Mike

I have an MGB tank I am about to fit. I have just measures the capacity and it is just over 1.3 litres. It does not have anything inside. The side entry pipe continues inside to the bottom of the tank, the top overflow pipe is above the sealing ring as on the radiator.

Malcolm
Malcolm Asquith

The overflow tank just becomes an extension of the radiator and operates at the same pressure as the radiator. When the water heats up and expands the water flows into the overflow tank and air is expelled via the cap seal lifting . When the system cools down the water is drawn back into the radiator and air enters the expansion tank via the poppet valve in the cap on the expansion tank....
Neil Ferguson

You can't see it in the picture, but the connection pipe on the side of the tank actually runs to the bottom of the tank inside. This will work in either pressurized or non-pressurized node. In any case you must have only one pressure cap.

You can use a blanking cap on the radiator and a standard pressure cap on the remote tank. This requires a high pressure (reinforced) connecting hose. The remote tank works the same as the normal top tank and pressure cap, and you still have to remove the pressure cap (when cool) to check fluid level.

You can use a pressure cap on the radiator and a blanking cap on the remote tank. This requires a coolant recovery type cap on the radiator with a rubber seal at the top rim of the filler neck. This directs fluid through the connecting hose and also allows a slight vacuum to pull fluid back into the radiator with thermal contraction. This does not require high pressure hose, or high pressure reservoir. If you use a see-through remote reservoir you can see fluid level at a glance.

You can get the coolant recovery type pressure cap locally. See NAPA-Balkamp part number 703-1411 (7-psi), $5.60 at my local NAPA store.
https://www.napaonline.com/Catalog/Result.aspx?Ntt=703-1411&Ntk=Keyword&Nty=1&Dn=0&D=703-1411&Dk=1&Dp=3&N=0

Also Stant 10206 (7-psi), or Stant 10205 (4-psi, not recommended for MGA).
Barney Gaylord

I think it is important to get the terminology correct to save confusion.

With the normal pressure cap retained on the radiator the extra tank bottle is unpressurised and is an 'overflow' tank. Therefore any suitable bottle can be used to serve this function.

If the radiator cap is replaced by a simple blanking cap the extra tank is fitted with the 4 or 7 lb pressure cap and the tank becomes an 'expansion' tank, requiring a container such as the MGB tank that can withstand the pressure. This is the design used on modern cars.

Steve
Steve Gyles

So how do you set it up to start with? Fill both tanks to the top?
Mike
Mike Ellsmore

Barney,
If you use "pressure cap on the radiator and a blanking cap on the remote tank" are you not creating a system with no pressure relief?
Mike
Mike Ellsmore

Yes Mick, I'm presently using my MGB tank as an overflow tank (with a non-pressurising cap) and yes, in that case a simple plastic bottle would have sufficed (but not looked as neat).
I intend however to run this way first (so far so good), but if this fails to provide adequate (overflow) capacity when the weather really heats up around here, my plan was to trial using a non pressurising cap on the radiator, a (short necked) recovery cap on the MGB tank, (because that's the one that would fit the tank) and, clumsy though it sounds, adding a plastic overflow tank in a somewhat unobtrusive location below and forward of the heater shelf on the left side of the engine bay. (I must say though that I state my plans with trepidation, fearing to be (again) shot down in flames! Trouble is, to my simplistic mind anyway, my planned trial sequence seems to make sense).

PS Just saw Mike's post re the initial setting up. Yes, just fill the radiator and the overflow tank both to capacity, and let the system find its own level. Once you've had the initial overflow and dump of the first hot run, the system (or at least my system) has found its own level, which it's now retained for some three or four months since I first set it up.
T Aczel

Mike, -- When you install a blanking cap on the remote tank, the remote tank overflow pipe serves as the vent.

Tom, -- The whole purpose of either type tank on the MGA is to take the guesswork out of monitoring fluid level in the cooling system. You certainly don't need two remote reservoirs.

Aside from ease of fluid visibility, there is no other practical reason for using the coolant recovery system on the MGA, just leave some air space in the adequately large top tank for thermal expansion so the fluid does not blow out.

When the remote reservoir is used on later model cars, like the MGB for instance, it is done to enable use of a low profile radiator under a low bonnet line. The MGB that uses this remote tank (1977-1980 models only) does not have a filler cap on the radiator.

It is often the same with many modern cars especially with cross-flow radiators. My (2nd generation) Mazda RX7 has a down-flow radiator with a VERY small top tank and pressure relief cap on top. It uses a remote plastic recovery bottle to provide the necessary volume for thermal expansion.
Barney Gaylord

This thread was discussed between 19/09/2011 and 25/09/2011

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