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MG MGA - Hybrid coolant recovery system
| The coolant recovery system on my coupe is a hybrid - it seems to work fine - the radiator ends up full after the car has cooled down! The radiator has a blanking plate rather than a pressure cap. Expansion of the coolant in the radiator/engine is handled by a hose connected to a pipe stub connected to the radiator just below the blanking cap. This hose is then connected to an MGB expansion tank. The inlet into this tank is a pipe that goes almost to the bottom of the expansion tank making it a sealed system. The expansion tank is fitted with a recovery type radiator cap (CPC 13 psi http://www.cpcauto.com.au/radiator_caps.aspx ) to handle the coolant expansion. The overflow from this cap is piped to ground by a flexible hose. On contraction of the fluid in the system, air is drawn in the recovery valve on the cap. The expansion tank is of such a capacity that on the system reaching ambient temperature there is still coolant in the bottom of the expansion tank (coolant covers the inlet pipe but I don't believe this is essential). See photos of the system and caps attached. The pink colour of the coolant is Redline Water Wetter. This seems like a good option for people wanting to put a recovery system on their MGA - does anyone see any problems with the setup. It doesn't give me any problems. Mike  |
| Mike Ellsmore |
| Mike, Your system sounds OK, but a couple of comments. When the engine cools the water in the expansion tank should cover the end of the internal return pipe. If it does not you may draw air back into the radiator. On the first heating cycle you may get some overflow from the expansion tank. This should not be replaced as space is needed for subsequent heating cycles. Replacing overflow with plain water will dilute your water wetter and anti freeze concentration. Replacing the overflow with water containing additives will send you bankrupt in the long term. A pressure cap of 13 PSI seems too high if you are using a standard MGA water pump with standard seals. Why not 7 PSI? I prefer the alternative arrangement where the pressure cap is on the radiator and the expansion tank is open to the atmosphere. Then you can use a transparent plastic overflow tank and observe the situation at any time. That said, your system will work OK. Mick |
| M F Anderson |
| Mike I have been running that system for the past 14 years. Works just fine. I only use a 7lb cap in the expansion tank. 14lb sounds like an overkill and don't forget that will be the pressure throughout the system, not just the tank. http://www.mgaroadster.co.uk/radiator_expansion_tank.htm Steve |
| Steve Gyles |
| Mick, if it draws air back into the radiator on cooling does it matter as it would be expelled next time the coolant heats up? Not sure why it ended up with a 13 psi cap. The engine is an 18GB with the stamped water pump impeller rather than a cast one. The temperature runs all day at 75C/165F with normal touring but gets up to 90C/195F when worked hard in competition. It does have an oversized radiator - 65 mm core thickness (my roadster's radiator core thickness is 40 mm) , no belt driven fan, only a single 12" Davies Craig unguarded 12v thermostat controlled fan in front of the radiator. Mike |
| Mike Ellsmore |
| Mike I would be a bit concerned about 13psi in the MGB expansion tank. I understand they are a bit prone to splitting along the brazed seam. Not sure why anyone should have any concerns about the system. It is what is fitted in just about every car in the world since and including the MGB. Steve |
| Steve Gyles |
| Mike, What you say is correct about any air drawn back in being expelled the next time it heats up. However, unless you have water throughout the system at all times you never really know if only some of the air is pushed out on heating and some remains in the radiator. If at least some water is expelled into the expansion tank everything is OK but you need to check that water is entering the tank during heating. It is simpler to monitor if the internal return pipe is below the water level when cold because you can check for correct operation even when cold. If water covers the return pipe when cold you are 100% sure that there is no air in the system. If your car runs at no more than 75C/165F then any pressure cap serves no purpose at all. I think you should go back to 7 PSI and reduce any tendency to leak at the pump. With regard to Steve's comment I always liked the system on Triumphs ( pressure cap on radiator and the expansion tank in clear plastic and vented to the atmosphere). You could always see what was happening without removing any caps. Have you ever considered using the high pressure plastic expansion tanks (with pressure cap) as used on many modern cars, including mine. Never remove a cap again, just lift the bonnet to check. Mick |
| M F Anderson |
| Mike, I will one day get around to fitting a coolant recovery system, if only to prevent every well- meaning passer by from pointing out my cars water leak! The only reason I haven't done this yet is that the little puddle of coolant at least shows me that the radiator is almost full ;-) Speaking of well meaning passer bys, have you noticed that your carbs appear to have disappeared! :-) Colyn Ps. is that the HRG head or the modern version? and how does it go? |
| c firth |
| Mick, agree with the modern system...just add a shortened neck with a recovery cap, and position one of those long alloy tanks adjacent to the radiator. |
| Gary Lock |
| Probably worth noting that Barney also has the modification fully covered: http://mgaguru.com/mgtech/cooling/cool_204a.htm He also addresses the higher rated pressure cap: http://mgaguru.com/mgtech/cooling/cool_200d.htm Steve |
| Steve Gyles |
| These modern systems are perfect and the best way for a sealed system. But if you can't be bothered with fitting this extra stuff under the bonnet, here's what I do. Its quicker to do than to read this: 1. Initially, top the standard radiator right up. 2. Run it up to temperature once or twice to ensure the system is fully 'overflowed' - so rad now at its optimum level. 3. Leave to cool down. 4. Get a squeezy bottle (with a tube added if necessary) and suck out all the water you can see in the MGA's rad neck. 5. Measure the quantity / mark the bottle and keep it! 6. Put it all back in and refit cap. To check level any time after this (when cold) suck out all you can see as before. Compare this quantity with the original measurement. If less top up with your A/F mixture to that original measurement and pour it back into radiator - cap on. You are now back to that illusive optimum level again. You have to check the oil and brake fluid levels anyway, so checking the rad is all part of our special little ritual before a run in an MGA... Pete |
| P N Tipping |
| All very complicated solutions guys! Why not just leave all systems as standard, top up the radiator when cool, go and enjoy a run out in your car, getting it right up to normal temperature. Park it, allowing the excess coolant to overflow onto the floor. Job done! Leave it as it is and enjoy the car - if you have no leaks the level will remain optimum for the foreseeable future and the slight reduction in coolant level will not be noticed in terms of cooling efficiency. Too simple? Have I missed something? Bruce. |
| Bruce Mayo |
| Yep that's me leave it as it is; my little check described is very quick and checks for any leakage. When you look in the top you can't really tell with the radiator's curved neck. Pete |
| P N Tipping |
| Bruce Same with me with the expansion tank. I just leave it. I peak inside the expansion tank at the annual service and that's it. I have the bonus of no drips whatsoever. Can't remember the last time I had to top up. Steve |
| Steve Gyles |
| I am 100% in the Mayo school! Can't remember the last time I topped up and I don't think there is anything to see in my filler neck anyway. |
| Neil McG |
| And then you run the car in 42c temperatures (in Aus. at least!) and in heavy stop-start traffic, and all that goes out the window! (And coolant on the ground!) Keeping our cars 'cool' over here is not so easy. I have driven my daily-driver for 42 years now and have not managed to solve the problem yet. Barry. |
| BM Gannon |
| Colyn, don't worry, no one nicked my carbies, they are on the other side! Yes, it's an original HRG head and it goes okay. I am with Barry - while the standard MGA cooling system is fine for normal days and touring it does get a bit stressed in the Australian summers and city traffic (we had 5 days over 40C/104F this summer). As Melbournites we know to avoid Elliott Ave on a hot Sunday afternoon - cross town route, uphill and regularly grid locked on weekends. Mike  |
| Mike Ellsmore |
| Oops...I meant 5 days in row over 40C/104F this summer! |
| Mike Ellsmore |
| Here's the link to a previous discussion on this. Mine is still working well. No spillage on the garage floor, radiator always full, looks neat, works well. http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=6&subjectar=6&thread=2012110801173229071 IBM |
| I B Morris |
| mmmm looks like that didn't work. Its in the Archives as "Coolant overflow tank" IBM |
| I B Morris |
| I tend to be in the "top it up just in case" camp with my standard set up. I find it hard not to top up the rad before a long journey even though I know most of what I have put in will end up on the ground. If the temperature gauge starts to climb up into the higher 190s and starts me wondering about the coolant level, I can put my mind at rest by opening the heater control. Once I feel the hot air blowing through the heater I stop worrying. If the heater works, I then know that there is enough coolant in the rad to keep the engine cool. I suspect that if MG had originally supplied a small dummy illuminated sign on the dash that said "Radiator Full" instead of the temperature gauge, most of us would have been much happier. "Ignorance is bliss" Colyn |
| c firth |
| I fully accept the comments of the original system addicts etc, but that is not my preferred option. My expansion tank system could of course be reverted to originality in the time it takes to swap over the caps - 30 seconds. My expansion tank then becomes a useful receptacle for that 'necks worth' of fluid that would otherwise be dumped on the floor. Of course the logical follow-on question is why did cars sometime after the MGA era have expansion tanks as standard? One answer is covered by Barney in that it allows the radiator cap and neck to be omitted, giving a lower front end profile option to the designers. Other answers would include cleanliness, the desire to remove leaking orifices from cars - intentional or otherwise. For me it was a simple and logical improvement to get away from coolant drips in the driveway and garage. Steve |
| Steve Gyles |
| Fully accept the greater demands on the cooling system in hotter climates than we get here in UK. We have it relatively easy, no doubt. My main thought on this issue though is that, presumably, even if one tops up the coolant level right to the top before every trip, it will expand and so overflow to its "natural" level once it gets up to temperature and the rest of every journey will then be just with that level in the system. Seems to me it will be a waste of time topping up each time? Even with an expansion tank the same amount will be expelled when hot, and only returned after the journey, when cool? And, does the small volume of coolant expelled from the system really contribute in any significant amount to a reduction in cooling efficiency? I have no axe to grind on the subject, just happy to understand it better! Bruce |
| Bruce Mayo |
| Bruce The only thing I can add, but not that it makes any particular difference, is that with the expansion tank the water level in the radiator is always right up to the level of the seal of the 'dummy' cap, not just to the overflow pipe, but above it to the brim. i.e. if you remove the cap (preferably when cold) the coolant is just about spilling over the top. I guess one could claim that there is always a neck's worth of extra water in the radiator to provide cooling! Steve |
| Steve Gyles |
| The thought occurred to me after my last post that the expansion tank system does offer more than the 'neckful' of water for cooling. There is also the open line of water from the vent pipe through the rubber piping to about a pint of water or so in the expansion tank. Obviously this water does not get cooled by the pump circulation in the radiator but it does gradually get heated by conduction of heat from the mainstream water in the radiator and also by that initial amount of warmed water expansion during the engine warm up phase. I felt my expansion tank after a run yesterday and it felt quite hot. Ok, not going to make a mega amount of difference but it does take some of the heat out of the radiator. As they say in our local supermarket "every little helps". My car runs at 175 all day. Might creep up to 190 in clogged traffic. Steve |
| Steve Gyles |
| I don't think an expansion tank will make one jot of difference to the amount of cooling going on. Once the standard radiator has dumped its initial overfill and reached its "natural" level, the radiator, baring leaks, will always be totally full when hot, so there is full coverage and flow in the radiator's tubes where the cooling occurs. Using my measuring and top up method, my rad needs just 250cc returned into the emptied neck , which is very small in proportion to the top tank volume. It looks original and requires the minimum of new fluid. I don't need any convincing that the sealed system is the way to go - but that's what it came out of Abingdon with and it still works for me. Pete |
| P N Tipping |
| I agree with Pete, however what I have noticed is that my car heater seems to be more efficient after topping right up. Richard |
| R A Evans |
| I have just been reading Hilliers Fundamentals of Motor Vehicle Technology. One statement caught my eye. It said that one of the claimed advantages of a pressurised expansion tank system is that it excludes all air from the main system, considerably reducing corrosion of the cooling system components. (See page 114, available to view on-line.) Steve |
| Steve Gyles |
| Richard- surely your rad gets very empty before you top it up for the heater to work better..? Interesting about the corrosion Steve, but my anti-freeze has anti-corrosion inhibitors in it and I mix it with distilled water. I change the coolant every two years to reduce any chance of corrosion. The inside of the thermostat housing still looks like new after 15 years, whereas the one it replaced was corroded through. When drained the coolant is just a darker blue with no sign of rust either. Using this method I don't appear to be experiencing any noticeable corrosion. The distilled water year on year also flushes away any previous layers of limescale which has to help with my cooling issues too..! Pete |
| P N Tipping |
| Pete, never measured my top up before but today returned 400cc into the neck, so slightly more than yours. Richard |
| R A Evans |
| That's interesting Richard. I thought they could possibly vary which is why I didn't refer to it in my posting above. (22nd Mar) I wonder what the variations can be? Out with your squeezy bottles and measuring jugs everybody..! Pete |
| P N Tipping |
This thread was discussed between 21/03/2014 and 28/03/2014
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