Tazio Posted January 28, 2019 Share Posted January 28, 2019 I am just finishing the rebuild of a BDR, the existing cooling system has an overflow pipe from the thermostat housing which flows into an unpressurised expansion tank, I understand that when the engine cools any water expelled into this tank is drawn by back into the cooling system by syphon action. Frankly I find this weird, and would much rather have a closed cooling system, with a true pressurised expansion tank .Question is has anyone done it, and am I right in thinking this is a better solution? Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted January 28, 2019 Area Representative Share Posted January 28, 2019 Alan, original spec would have been unpressurised, surely? Link to comment Share on other sites More sharing options...
Drumster Posted January 28, 2019 Share Posted January 28, 2019 Alan,My x/flow was originally unpressurised and it was changed to a pressurised system when Roger King rebuilt the engine. So I guess it's a better system?However my Zetec is unpressurised in similar fashion to the x/flow and I've never had any problems or given any thought to changing it.If it works , why not stick with originality as GJT suggests Link to comment Share on other sites More sharing options...
Tazio Posted January 28, 2019 Author Share Posted January 28, 2019 I just don't like the idea of relying on the water expanded out of the cooling system into the expansion tank relying on syphoning back where it should be.......And Chris, I don't know whether it actually does work yet, haven't run the engine long enough yet lol, and this is a verbatim quote from RK...'A proper, sealed, header tank installation is practically compulsory with this installation. When we insisted that our race customers fitted one, we reduced overheating and head gasket problems by more than 95%'. Link to comment Share on other sites More sharing options...
Wrightpayne Posted January 28, 2019 Share Posted January 28, 2019 I think running with a proper header tank you need a plain cap on the engine Tstat housing i.e. it seals at the very top but no spring loaded seal. the tube between the housing and the new header tank becomes pressurised.Perhaps others could clarify.Ian Link to comment Share on other sites More sharing options...
Tazio Posted January 29, 2019 Author Share Posted January 29, 2019 Ian, I have seen another installation on a BDR in Norway, using the flat VX expansion tank located on the scuttle, it used the standard thermostat housing and cap,, last year he did over 3000ks over all the Alpine passes, so it seems to work. Link to comment Share on other sites More sharing options...
elie boone Posted January 29, 2019 Share Posted January 29, 2019 The cap you need if you go for a closed system is QH FC61. Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted January 29, 2019 Area Representative Share Posted January 29, 2019 AlanHow "original spec" do you wish to be? Like Chris, my Crossflow now has a pressurised system but I had no problems with the traditional approach. Link to comment Share on other sites More sharing options...
john g Posted January 29, 2019 Share Posted January 29, 2019 I have the 'open' system on my xflow and in hot weather, in traffic, the temperature does rise considerably. I have fitted a fan overide switch to switch the fan on before the fan kicks in but on the odd occasion I have needed to 'pull over' and let things cool down. Would a sealed system have any effect on an old engine? Is there a simple numpty guide to installing a sealed system? Interesting thread this. Link to comment Share on other sites More sharing options...
Tazio Posted January 29, 2019 Author Share Posted January 29, 2019 I have the bits to create a pressurised system, a K series tank and associated bracket, to connect to the crossmember ( Bruce was good enough to fabricate a bracket to hold this), the plumbing will connect to the heater take off on the water pump, and the existing overflow pipe. Simple really. And Stephen its very easy to revert to standard, I just want to ensure the engine isn't compromised. Fan control is via a the fan switch on the rad, with a manual fan overide. I'll see how it works in action. Link to comment Share on other sites More sharing options...
Wrightpayne Posted January 29, 2019 Share Posted January 29, 2019 Is the fan override another hole to drill in the dash? Ian Link to comment Share on other sites More sharing options...
Drumster Posted January 29, 2019 Share Posted January 29, 2019 Alan,Your set up sounds similar to my x/flow, although back in the day I had a heater. It worked well until the piggy back connector I used for the manual override broke and this happened Link to comment Share on other sites More sharing options...
Nick T Posted January 29, 2019 Share Posted January 29, 2019 Just to add to the conversation, my xflow had an un pressurised system. I ran it for 15 years with no issues, including track days and a couple of very hot CLM trips. Link to comment Share on other sites More sharing options...
Tazio Posted January 29, 2019 Author Share Posted January 29, 2019 Ian, No more holes as I am 'hard', I ditched the heater, so no T piece connections to fail, and allows the use of the heater fan switch as a fan override. My main concerns with all of this is engine longevity , and just don't like the idea of cooling fluid being expelled into the expansion tank, and maybe or maybe not syphoning back when cool it cools down, I'd be checking the level all the time, or with my memory, forgetting to check the levels....Thanks for all the input guys. Link to comment Share on other sites More sharing options...
randybugger Posted January 29, 2019 Share Posted January 29, 2019 Pressurised system on my Xflow Link to comment Share on other sites More sharing options...
Tazio Posted January 29, 2019 Author Share Posted January 29, 2019 Thanks Randy.... Link to comment Share on other sites More sharing options...
anthonym Posted August 18, 2023 Share Posted August 18, 2023 I am now engaged in this same battle with my BDR. Overflow does not siphon back home.In typical use or high speed use, no problem, it is slow speed low airflow uphill (edit I live in the Alps) when the trouble starts.I thought it isn't a siphon (height matters) but a drop in system pressure (cooling) that sucks the coolant back in like sucking on a straw - except it's not.- anthony I since found this: "So, it is the overflow atmospheric pressure that pushes the coolant back into the reservoir. The radiator does not pull coolant from the overflow tank." and "When the engine has been turned off, the coolant will start to cool down as well. As it cools down, it will contract in volume as well. This decrease in volume will result in a vacuum because of a drop in pressure. Due to this vacuum, a vacuum valve in the radiator cap opens allowing the coolant which was flown into the radiator coolant overflow tank back into the radiator." So that's both vacuum suction and atmospheric pressure in play. Something I have not checked is whether there are any markings to show how much coolant must be present when cold. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 18, 2023 Member Share Posted August 18, 2023 "So that's both vacuum suction and atmospheric pressure in play.""Vacuum suction" isn't a force. You can't *pull liquids. The effects that we describe in that way are due to the difference in gas (such as atmospheric) pressure between the two ends.Jonathan* The attractive forces between the molecules are too weak. The ones on the surface will evaporate. Link to comment Share on other sites More sharing options...
Nigel Riches Posted August 19, 2023 Share Posted August 19, 2023 Something else to check is the air tightness of all the places where hoses are clamped between the expansion tank and the thermostat housing, including the pipe inside the expansion tank, the end of which should at all times be below water level, if any of these are not fully secure an air leak can prevent the return fluid getting back to the engine. I struggled for quite some time my old tin top with this, replaced all hoses and clamps and problem solved. Link to comment Share on other sites More sharing options...
Nigel Blandin Posted August 19, 2023 Share Posted August 19, 2023 I fitted a pressurised system to my BDR when we were getting high temps in traffic. Just took the overflow up to an alloy expansion tank on the bulkhead. I use one of those lever caps on it, 25psi iirc. Return to the pump. Just don't get the caps mixed up...trouble ensues. Works perfectly. Link to comment Share on other sites More sharing options...
GordonW Posted August 19, 2023 Share Posted August 19, 2023 For the Roger King cooling schematic and description featured in a previous thread search -"Sealed Cooling Upgrade Instructions? Ford Kent X-flow"I followed this on a Ford build and it worked faultlessly on a race engine. If you can't find it PM me your email and I'll send it to you. Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted August 19, 2023 Area Representative Share Posted August 19, 2023 https://www.caterhamlotus7.club/forum/techtalk/sealed-cooling-upgrade-instructions-ford-kent-x-flow Link to comment Share on other sites More sharing options...
anthonym Posted August 19, 2023 Share Posted August 19, 2023 Thanks everyone all seems in order.. how to test the vacuum relief valve beats me . Breather in cap is clear.edit: "You probably have some sort of air leak on the coolant overflow hose" I have tested this hose (seen in the images above), but with a syringe for flow out being pushed and return being sucked, but.. I suspect that suction is a lot more than the vacuum derived pressure change. I will check it again now.Guess what? Damage found to the overflow hose, at the hose clamp end to the rad cap and more where the hose transits the overflow cap ("40" years of chafe and age); I tried holding one end and blowing, but no apparent leak, however, when it is hot, indeed very hot who knows? So replaced it with a length of brand new fuel hose, same size spec. Testing required, when it's not quite so warm here.anthony - still trying to think how to describe a vacuum that I know isn't a vacuum to explain aircraft lift and how a straw is used to .. drink coca cola.. and return fluid to my cooling system. New hose fitted as here: Link to comment Share on other sites More sharing options...
OldAndrewE Posted August 19, 2023 Share Posted August 19, 2023 still trying to think how to describe a vacuum that I know isn't a vacuum to explain aircraft lift and how a straw is used to .. drink coca cola.. and return fluid to my cooling system.All these situations create a pressure difference. It is the high pressure that pushes, not the low pressure pulling (sucking) Link to comment Share on other sites More sharing options...
OldAndrewE Posted August 19, 2023 Share Posted August 19, 2023 It is important that the overflow/catch bottle always has liquid in it and the pipe is always below the liquid level Link to comment Share on other sites More sharing options...
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