Oliver11 Posted June 28, 2020 Report Share Posted June 28, 2020 I have a TR 3 1956 after a good run and leave motor runIng for a few minutes some times It pushes coolant out of the overflow about 250mls of Coolant wasted I have a 4lb cap on the radiator new thermostat new hoses no leaks anywhere can anyone give any ideas how to stop this happening paul Quote Link to post Share on other sites
RogerH Posted June 28, 2020 Report Share Posted June 28, 2020 Hi Paul, do you have too much coolant in the system. There should be just enough to cover the bottom of the neck from the rad. - about 1" from the top. If that is OK then have you got an air bubble in the system - have you recently taken the system apart. Roger Quote Link to post Share on other sites
Hamish Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Perhaps it’s a little overfilled especially if it’s a regular occurrence? the coolant just needs to be couple cm covering the bottom of the rad neck extension. you can fit an expansion tank. I did this mod. A blanking cap on the rad a suitable hose off the rad overflow to the expansion tank And the 4lbcap on the tank Something like this Looks period-ish https://www.ebay.co.uk/itm/362989569116 Edited June 28, 2020 by Hamish Web link Quote Link to post Share on other sites
mikej Posted June 28, 2020 Report Share Posted June 28, 2020 Cooling water heats up for a few seconds after turning off the ignition and it may boil if already on the hot side of normal, watch the gauge as you turn off the ignition. As Hamish, too much water will not help. Quote Link to post Share on other sites
Z320 Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Hi Paul, my profession is being a civil engineer for house heating systems I try to explain. The pressure in any heating system is caused of two different issues: 1. The pressure by expanding water. Take any sealed water system (heating / cooling, no matter) with NO air in it and no expansion container. The water expands with raising temperature and the pressure raises fast and extremely. To avoid this you need air in the system to be compressed (in houses a container with a diaphragm), so the pressure raises more slowly the more air you have in the system. On our TRs (and other engines) this is about 1 liter of air. So do not overfill the system, always keep enough air in the system. Air in there is no problem! 2. The pressure by vapor pressure. Take any sealed water system (heating / cooling, no matter) with A LOT OF air and only some water in it. The water vapors with raising temperature and the pressure raises due to the temperature. edit: for details about the temparatur when this starts to rule please see later post This is where you want to go to with a car cooling system: let only the vapor pressure rule. The vapor pressure in the air over of a coolant / water mix 50/50 is: 4 PSI (0,279 bar) at about 78°C 7 PSI (0,483 bar) at about 90°C 13 PSI (0,896 bar) at about 105°C So that's simple: the coolant can be hotter (the safety valve / rad cap will not open) with a rad cap with higher pressure. To tell you the truth: I have no explanation at all how a car cooling system of ab car can work with a 4 PSI cap. I would risk to switch over to a 13 PSI cap and add an emergency overflow bottle - but this is up to you. This is the set up on my TR4A: - I always let enough air in there to let the vapor pressure rule! edit: this is the one and only urgend thing on the temperatures (mainly below 100°C) we drive our cars - she comes with a 13 PSI rad cap, highest temperature I ever had was 110°C (electronic gauge) without any problems - I added the TR4A emergency overflow bottle again (was missing when I bought her), but this is always try like a bone in the desert - I have never any overflow in there or any loss of coolant in any case Hope this helps, Marco Edited June 28, 2020 by Z320 Quote Link to post Share on other sites
Ian Vincent Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) 1 hour ago, Hamish said: Perhaps it’s a little overfilled especially if it’s a regular occurrence? the coolant just needs to be couple cm covering the bottom of the rad neck extension. you can fit an expansion tank. I did this mod. A blanking cap on the rad a suitable hose off the rad overflow to the expansion tank And the 4lbcap on the tank Something like this Looks period-ish https://www.ebay.co.uk/itm/362989569116 I have always thought that the extended neck on a sidescreen radiator is the expansion tank. Rgds Ian PS if I overfill mine it dumps the excess until the coolant is just covering the bottom of the neck when it’s cold. (Just like Roger said) Edited June 28, 2020 by Ian Vincent Quote Link to post Share on other sites
stuart Posted June 28, 2020 Report Share Posted June 28, 2020 1 minute ago, Ian Vincent said: I have always thought that the extended neck on a sidescreen radiator is the expansion tank. Rgds Ian It is thats why you should only fill it so you can just see water lapping as you look down into the neck that leaves plenty of room for expansion. Stuart. Quote Link to post Share on other sites
DavidBee Posted June 28, 2020 Report Share Posted June 28, 2020 32 minutes ago, Z320 said: Hope this helps, Marco Marco, I just want to thank you for your generosity. This explanation is painstakingly clear and accurate. Quote Link to post Share on other sites
Lebro Posted June 28, 2020 Report Share Posted June 28, 2020 Agree with not filling the rad to the top, but if you want more coolant in there you can fit a pressurised header tank as described above, or (as I have done) fit an expansion bottle connected to the overflow stub on the rad, pipe must go to the bottom of the bottle, & you need a rad cap which seals perfectly around the top rim. I don't know if these are available for the TR3,(which has a deeper 2nd seal) I made my own seal for the top. You can then fill the rad right to the top, & water simply expands into the bottle, & then gets sucked back into the rad when cooling down. Bob. Quote Link to post Share on other sites
Ian Vincent Posted June 28, 2020 Report Share Posted June 28, 2020 1 minute ago, Lebro said: Agree with not filling the rad to the top, but if you want more coolant in there you can fit a pressurised header tank as described above, or (as I have done) fit an expansion bottle connected to the overflow stub on the rad, pipe must go to the bottom of the bottle, & you need a rad cap which seals perfectly around the top rim. I don't know if these are available for the TR3,(which has a deeper 2nd seal) I made my own seal for the top. You can then fill the rad right to the top, & water simply expands into the bottle, & then gets sucked back into the rad when cooling down. Bob. But do you need that extra coolant Bob? When we were doing the LBL Rally last year the temperature was in the high 20's or low 30's for most of the trip and it included going up and down both the Stelvio and the Gavia twice. At no time did the temperature gauge in my TR3a go significantly above the midway point and when it did the electric fan cut in and brought it down. I checked the coolant level every morning and it was always just covering the bottom of the neck. Rgds Ian PS I did have fuel vapourisation problems on one occasion though when I had to stop to wait for a large campervan coming the other way as we were approaching the summit of the Stelvio. PPS I also have a recored radiator with the starter handle holes removed Quote Link to post Share on other sites
BlueTR3A-5EKT Posted June 28, 2020 Report Share Posted June 28, 2020 9 minutes ago, DavidBee said: Marco, I just want to thank you for your generosity. This explanation is painstakingly clear and accurate. Thank you Marco an informative explanation of the theories. I had noticed the change in the rate of temperature rise in the TR when the cooling water system is fully filled. A sidescreen TR issue - What happens when the cabin heater is positioned highest in the cooling water circuit of a vehicle and fills with air? (think also domestic/house water heated radiators here) No or reduced cabin heat available. So you introduce a vent valve (domestic radiator) to remove or bleed the trapped air out of the heater matrix, thus allowing the heater matrix to fully fill with hot coolant and allow for heat transfer when demanded. Why do modern vehicles use a fully filled water cooling system with an expansion bottle? Cheers Peter W Quote Link to post Share on other sites
Z320 Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) 26 minutes ago, Lebro said: You can then fill the rad right to the top, & water simply expands into the bottle, & then gets sucked back into the rad when cooling down. Bob. Yes this works, but every time you supply the rust in the engine with fresh oxygen, this is why they switched over on house heating system to a expansion container with diaphragm decades ago Edited June 28, 2020 by Z320 Quote Link to post Share on other sites
RobH Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) 1 hour ago, Z320 said: Take any sealed water system (heating / cooling, no matter) with A LOT OF air and only some water in it. The water vapors with raising temperature and the pressure raises due to the temperature. This is where you want to go to with a car cooling system: let only the vapor pressure rule. The vapor pressure in the air over of a coolant / water mix 50/50 is: 4 PSI (0,279 bar) at about 78°C 7 PSI (0,483 bar) at about 90°C 13 PSI (0,896 bar) at about 105°C So that's simple: the coolant can be hotter (the safety valve / rad cap will not open) with a rad cap with higher pressure. To tell you the truth: I have now explanation at all how a car cooling system of ab car can work with a 4 PSI cap. The figures you quote are for gauge pressure Marco - you have forgotten to add on ambient pressure. With a 4psi rad cap the pressure on the coolant is 4+15 = 19psi absolute, making the equilibrium/boiling point about 107 degrees (give or take for the glycol content). Edited June 28, 2020 by RobH Quote Link to post Share on other sites
Z320 Posted June 28, 2020 Report Share Posted June 28, 2020 Yes, with the coolant 78 deg C hot inside the rad the pressure is 4+15 PSI absolute, while outside the rad, under the bonnet the pressure is 15 PSI absolute? So 4 PSI is the overpressure. If there is any interest about I post a simple everybody-experiment this evening Quote Link to post Share on other sites
BlueTR3A-5EKT Posted June 28, 2020 Report Share Posted June 28, 2020 47 minutes ago, Z320 said: Yes, with the coolant 78 deg C hot inside the rad the pressure is 4+15 PSI absolute, while outside the rad, under the bonnet the pressure is 15 PSI absolute? So 4 PSI is the overpressure. If there is any interest about I post a simple everybody-experiment this evening Yes I am interested Marco. Peter W Quote Link to post Share on other sites
RobH Posted June 28, 2020 Report Share Posted June 28, 2020 You are forgetting that the calculations of vapour pressure are for a sealed system Marco. It doesn’t start from ambient pressure, it starts from zero. At 78C the vapour pressure would be 6psi in a sealed system but in the radiator there is already 15psi of atmospheric pressure present so this excess pressure causes the vapour to condense back into the fluid. No vapour pressure can be added to the system until 100C is reached, where vapour pressure equals ambient pressure. At this point vapour ceases to condense and the pressure in the system starts to rise. The extra pressure one experiences when removing the rad cap from a hot engine is mainly due to expansion of the water and air - not to vapour pressure. Quote Link to post Share on other sites
Z320 Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Hi Rob, thank you very much for your veto. That let me have a closer look on the facts apart from that what I believed as the fact. And this is a absolutely wonderful and humblene example how something that someone has been convinced about is wrong. Because you are absolutely right, the vapor pressure is below 1 bar / 15 PSI atmospheric pressure as long water is only 100°C hot, coolant mix 50/50% is below 105 - 110°C hot. This meens for me: - the only importend thing is always to have enough air in the system to be compressed by the expanding water - it is possible to use a 4 PSI rad cap up to about 115°C coolant (50/50 mix) temperatur (vapor pressure is then about 15+4 PSI) - a 13 PSI rad cap allows about 125°C Allow me to stroke everything on my post what is not correct, so others can see what is right / wrong. Experiment comes later, I have to make photos. Ciao, Marco Edited June 28, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Here are the photos. As you can see by the pencil I do not overfill the rad. The diameter which gives pressure (and force) on the rad cap is some less than 29 mm wide, that is about 1 1/8", the expanse of the diameter is pretty exact 1 square inch. Possibly this is not only by accident? Next you see two rad caps, a 7 LBS (PSI) one, not in use, and the 13 PSI one from my TR4A. When I press the seal down I can feel the different load of the springs, on a scale, for example our bathwoom scale, I can play with it and see the load when it opens. You have to try several times to got the feeling for it. The 7 LBS cap opens at 4,5 kg, that's about 10 LBS, so this is about 50% stronger as stamped on it. The 13 LBS cap opens at 6 kg, that's exacly 13 LBS! Well done, the 7 PSI cap with 10 PSI is no problem in my opinion. Is the other way around also possible, a 4 LBS opens at 2 LBS? What do you think about? Edited June 28, 2020 by Z320 Quote Link to post Share on other sites
ianc Posted June 28, 2020 Report Share Posted June 28, 2020 Why not convert to a modern system with remote header tank? See my article in TR Action 112, or section B18 in the Technicalities CD. I think that exceeding a setting of 7 psi is not a good idea as it over-stresses the hoses. With a remote header tank, a 7 psi cap on the remote tank is quite sufficient, and 4 psi would not be a problem. Ian Cornish Quote Link to post Share on other sites
Z320 Posted June 28, 2020 Report Share Posted June 28, 2020 (edited) Indeed this 7 LBS cap is very special, it reaches not deep enought down in the radiator nack, so it never seals it. A 100% product of "we don't know what we are producing- but we do it anyway" Edited June 28, 2020 by Z320 Quote Link to post Share on other sites
james christie Posted June 28, 2020 Report Share Posted June 28, 2020 I made an opportunist purchase if a 7lbs rad cap locally last year to replace my 60 year old 4lbs cap and the composite head gasket blew in a minor fashion three weeks later. Are these two events related? james Quote Link to post Share on other sites
Z320 Posted June 29, 2020 Report Share Posted June 29, 2020 (edited) I never had this, so just 3 thoughts. Isn't the damage on a blew head gasket the heat and pressure from the cylinders, this is much more than 7 PSI? My TR4A had that 13 PSI already when I bought it 11 years age, and probably also the 17 years before with the previous owner. This works without problems. 13 PSI is only the max pressure, you don't have that automaticly / always with the cap but with the missing air in the system (to be compressed by the expanding coolant). What a lovely idea: I will fit a coolant pressure gauge on the car to see what the pressure does! Edited June 29, 2020 by Z320 Quote Link to post Share on other sites
mikej Posted June 29, 2020 Report Share Posted June 29, 2020 I'd still be interested to know what the top-hose water temperature is, after a run and during subsequent idle on a day when it blows water. I had the same issue until the the radiator was re-cored* several years ago. I use a 4lb cap with no separate expansion tank or other modifications. *without the start handle hole. Quote Link to post Share on other sites
Richardtr3a Posted June 29, 2020 Report Share Posted June 29, 2020 I had overheating at over 60 mph because the engine rebuilder ,at the Seven Dials in Brighton, failed to set the liner heights correctly in spite of having the copied page from the manual delivered with the engine. I then uprated the radiator with extra tubes and fins. I tried a 7lb cap and water leaked from the water pump, the heater hoses and the lower radiator hose. 4lb cap was OK. I then fitted an expansion tank with the input at the bottom and a 4 lb cap and the radiator has a blanking cap only. There are two different lengths of cap and it is ,of course, important to get the right one for your tank. So I fill the radiator to the top and have about 1 1/2" in the bottom of the expansion tank. It all works really well even though the expansion tank is lower than the rad filler. Quote Link to post Share on other sites
Z320 Posted June 29, 2020 Report Share Posted June 29, 2020 49 minutes ago, mikej said: I'd still be interested to know what the top-hose water temperature is, after a run and during subsequent idle on a day when it blows water. I had the same issue until the the radiator was re-cored* several years ago. I use a 4lb cap with no separate expansion tank or other modifications. *without the start handle hole. You could add a sensor in the thermostat housing for a low price LCD gauge in the car Quote Link to post Share on other sites
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