Guy Vinall Posted November 23, 2020 Report Share Posted November 23, 2020 Hi. Not too impressed by the standard Triumph TR6 water expansion tank, which is plastic & probably inefficient. I have fitted alloy expansion tanks to other cars, where the rad cap is fitted with a blanked off cap & the expansion tank is fitted with a pressurised cap & is kept 20-40% full and has its own overflow pipe. Water expands in the main rad when hot, runs into the expansion tank & when the main rad water cools, it contracts & by a vacuum effect, sucks the water back into the main radiator. Wondering if anyone has fitted similar & if they can point me in the direction of a supplier. Thanks Guy. Quote Link to post Share on other sites
RogerH Posted November 23, 2020 Report Share Posted November 23, 2020 Hi Guy, I don;t know of a standard kit but many folk have used a TR7 expansion tank and re-piped what is there. However although the TR4A/5/6 system looks overly simple it does actually work - not perfect but functional. You need the expansion bottle 30% full or so all the time The expansion pipe (to the bottle) needs a good seal at the rad cap end The pipe in the expansion bottle need to go to the bottom of the bottle AND the pipe needs to have its end cut at an angle so that it doesn't get sucked to the bottom of the bottle. Also ensure that the rad is not over full - apprx 1/4" over the core is enough. Make sure you have the correct rad cap. Roger Quote Link to post Share on other sites
Hamish Posted November 23, 2020 Report Share Posted November 23, 2020 Agree with Roger. but if you want an expansion tank as you describe try this. I have the system on my 3a and very happy with it. Expansion Tank Brass Original https://www.ebay.co.uk/itm/133550061997 Quote Link to post Share on other sites
Andy Moltu Posted November 23, 2020 Report Share Posted November 23, 2020 Changing the overflow tank on the 6 is a case of looking for a problem that doesn’t exist. A TR6 shouldn’t need topping up between coolant changes. The radiator and the cooling system overall has ample capacity to cool the car. If it runs hot there is a problem somewhere. Quote Link to post Share on other sites
Guy Vinall Posted November 24, 2020 Author Report Share Posted November 24, 2020 Thank you Roger, Hamish and Andy for your kind replies. I'm sure the system does work even though plastic & metal expand with heat at different ratios. I think I will order new standard Triumph Bottle, Top & Hose and see how things go. Quote Link to post Share on other sites
CP26309 Posted November 24, 2020 Report Share Posted November 24, 2020 I've never experienced any problem with the original expansion bottle, only changed it once in 48 years just for cosmetic reasons. My standard Pi car has never ever overheated. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 24, 2020 Report Share Posted November 24, 2020 2 hours ago, Guy Vinall said: Thank you Roger, Hamish and Andy for your kind replies. I'm sure the system does work even though plastic & metal expand with heat at different ratios. I think I will order new standard Triumph Bottle, Top & Hose and see how things go. You have not mentioned radiator cap which is an important link in the system Peter W Quote Link to post Share on other sites
Z320 Posted November 24, 2020 Report Share Posted November 24, 2020 (edited) On 11/23/2020 at 8:31 PM, Andy Moltu said: Changing the overflow tank on the 6 is a case of looking for a problem that doesn’t exist. A TR6 shouldn’t need topping up between coolant changes. The radiator and the cooling system overall has ample capacity to cool the car. If it runs hot there is a problem somewhere. I'm with Andy, all about the overflow bottle is wishfull thinking of not existing problems. Don't overfill the rad, keep enough air in there to be compressed by the expanding coolant and you can drive without any overflow bottle. I've fitted a self bleeding system and can drive any time I want bleeded or with all the air in. Result: it makes no difference at all on the coolant temperatures to drive with less air in the cooling system. Ciao, Marco Edited November 25, 2020 by Z320 my bad english Quote Link to post Share on other sites
Mike C Posted November 24, 2020 Report Share Posted November 24, 2020 3 hours ago, BlueTR3A-5EKT said: You have not mentioned radiator cap which is an important link in the system Peter W I agree. You need a radiator cap to suit an atmospheric pressure expansion tank -with two seals. When buying you may not get this type of cap unless you specifically ask for it. Quote Link to post Share on other sites
SpitFireSIX Posted November 28, 2020 Report Share Posted November 28, 2020 I run an expansion tank from an RX7? kit car. 17PSI yellow cap. Plastic AKA modern. Large enough to be highest coolant level when low and allow expansion of a larger quantity of water due to wider radiator. Thermostat housing has auto-air bleed so system gas free. Quote Link to post Share on other sites
Nigel Triumph Posted November 28, 2020 Report Share Posted November 28, 2020 On 11/23/2020 at 7:31 PM, Andy Moltu said: Changing the overflow tank on the 6 is a case of looking for a problem that doesn’t exist. A TR6 shouldn’t need topping up between coolant changes. The radiator and the cooling system overall has ample capacity to cool the car. If it runs hot there is a problem somewhere. +1. The standard TR6 cooling system including the expansion bottle works well on my 1970 car. My '77 Scimitar GTE has an expansion tank that works on the same principle. No problem with that either. Nigel Quote Link to post Share on other sites
SpitFireSIX Posted November 29, 2020 Report Share Posted November 29, 2020 Are we talking overflow or expansion tank? What does an OEM expansion tank look like? Quote Link to post Share on other sites
roy53 Posted November 29, 2020 Report Share Posted November 29, 2020 i thought that the bottle on a 5/6 was just an overflow one . It is not and expansion tank Roy Quote Link to post Share on other sites
Mike C Posted November 29, 2020 Report Share Posted November 29, 2020 10 hours ago, roy53 said: i thought that the bottle on a 5/6 was just an overflow one . It is not and expansion tank Roy In mine the coolant expands when hot and is sucked back as it cools from an atmospheric pressure tank. I'd call it an expansion tank. Quote Link to post Share on other sites
Z320 Posted November 29, 2020 Report Share Posted November 29, 2020 (edited) In my opinion it is an overflow bottle to get rid of complaints from customers about "the car looses coolant", because they never get tired of overfilling the system. My TR4A I do not overfill and the bottle is dry since years. "Suck back" is always coolant with fresh oxygen. I don't know why so much of you are so pleased with that issue? Edited November 30, 2020 by Z320 Quote Link to post Share on other sites
Mick Forey Posted November 30, 2020 Report Share Posted November 30, 2020 The standard bottle worked so well on my TR6 that I never had to top up the water for the whole season so I fitted the same one to my TR3. The same is now true for that car as well. Brilliant solution. I fill both radiators to the brim, fill the bottle to about 1/3 then then keep checking it, just in case. Much easier to see on the TR6 as the one on the TR3 is well hidden between the inner wing and the side of the radiator, secured to the inner wing. When hot both bottles are about 2/3 full and return to 1/3 when cold again. Mick Quote Link to post Share on other sites
stuart Posted November 30, 2020 Report Share Posted November 30, 2020 24 minutes ago, Mick Forey said: The standard bottle worked so well on my TR6 that I never had to top up the water for the whole season so I fitted the same one to my TR3. The same is now true for that car as well. Brilliant solution. I fill both radiators to the brim, fill the bottle to about 1/3 then then keep checking it, just in case. Much easier to see on the TR6 as the one on the TR3 is well hidden between the inner wing and the side of the radiator, secured to the inner wing. When hot both bottles are about 2/3 full and return to 1/3 when cold again. Mick Only if you use a proper "Recovery" rad cap. Stuart. Quote Link to post Share on other sites
Andy Moltu Posted November 30, 2020 Report Share Posted November 30, 2020 Surprising as it may seem the caps work reasonably well without the rubber seal found on the recovery cap. The metal to metal seal seems to be good enough to draw most of the coolant back up the overflow without. Quote Link to post Share on other sites
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