Iain T Posted May 15 Author Report Share Posted May 15 (edited) 1 hour ago, johny said: According to my calculations our system coolant expands by about 0.25L on warm up and with a tank that'll be slightly more so the air space in the tank needs to be double that volume to give a pressurisation of approximately 15psi... I think Boyles Law applies. If I fill half way I'll have plenty of safety P1V1=P2V2 Edited May 15 by Iain T Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 Well done, sounds as tho` you are well on your way. Bit confused you saying 6mm return to the rad, do you mean from the rad as a bleed for any air. If that`s the case, bear in mind about putting a 3mm throttle in the line, you don`t want your tank becoming a second radiator. Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 One of these, dimension for inlet and outlets differ. The overflow I'll possibly vent to air. https://www.merlinmotorsport.co.uk/p/vertical-aluminium-water-header-tank-obphe002 Link to comment Share on other sites More sharing options...
johny Posted May 15 Report Share Posted May 15 19 minutes ago, Iain T said: I think Boyles Law applies. P1V1=P2V2 Yes that was what I was going by so as the coolant volume increases if it compresses the air space in the tank to half the pressure will double. Starting at an absolute pressure of 15psi (atmospheric) youll get 30psi absolute = 15psi atm. Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 7 minutes ago, johny said: Yes that was what I was going by so as the coolant volume increases if it compresses the air space in the tank to half the pressure will double. Starting at an absolute pressure of 15psi (atmospheric) youll get 30psi absolute = 15psi atm. Calculation agreed😃 Link to comment Share on other sites More sharing options...
johny Posted May 15 Report Share Posted May 15 Woohoo so the level is quite critical as too much and it'll lift the cap, too little and you could get localised coolant boiling around the cylinder head? Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 Yes top one is just an overflow, if if your calcs are out and you over fill it, where do you intend connecting the top tank out let too? Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 Sorry Johny must disagree with you there. That is the beauty of this system, so long as you take the bleed back to the tank from the highest part of the system, in this case the thermostat housing, its better if you have a positive head in the tank, but if you haven`t once the engine starts it self bleeds. Hope that makes sense??🤔 Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 According to the various diagrams I've researched the top 10mm inlet can go to the top of the radiator via a new pipe brazed into the radiator and the original radiator filler removed and blanked off. Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 (edited) 7 minutes ago, Firefly said: Sorry Johny must disagree with you there. That is the beauty of this system, so long as you take the bleed back to the tank from the highest part of the system, in this case the thermostat housing, its better if you have a positive head in the tank, but if you haven`t once the engine starts it self bleeds. Hope that makes sense??🤔 So what you are saying is the spout overflow goes back (with a restriction/non return) to the thermostat housing and the top 10mm spout is redundant? The bottom 18mm outlet Tees into the lower rad hose Edited May 15 by Iain T Link to comment Share on other sites More sharing options...
Steve P Posted May 15 Report Share Posted May 15 24 minutes ago, johny said: Woohoo so the level is quite critical as too much and it'll lift the cap, too little and you could get localised coolant boiling around the cylinder head? This is true as I found out recently after re-fitting the heater and matrix after a clean out, I overfilled it and ended up with water and blue anti freeze coming from the rad cap. I will try and get some pics but the car is in my lockup. S 1 Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 NO, the overflow is just that, it dumps any over fill to the ground. The connection in the top of the tank is the one that should be connected to the highest point in the system, i.e thermostat housing so that any air will always rise to the highest point, and then it will be drawn back into the tank, because the bottom tank connection should be connected to inlet side of the water pump, where there will be a slight depression. Then you get a constant circulation pulling any air into the header tank, thats why its important to have a restriction. Link to comment Share on other sites More sharing options...
johny Posted May 15 Report Share Posted May 15 23 minutes ago, Firefly said: Sorry Johny must disagree with you there. That is the beauty of this system, so long as you take the bleed back to the tank from the highest part of the system, in this case the thermostat housing, its better if you have a positive head in the tank, but if you haven`t once the engine starts it self bleeds. Hope that makes sense??🤔 yes as Steve found it doesnt matter how you connect the pipework if its a sealed system and the coolant (waterless excepted) expands on heating the pressure will go up and you want this to be to the correct level for the reasons stated... Link to comment Share on other sites More sharing options...
johny Posted May 15 Report Share Posted May 15 20 minutes ago, Steve P said: This is true as I found out recently after re-fitting the heater and matrix after a clean out, I overfilled it and ended up with water and blue anti freeze coming from the rad cap. I will try and get some pics but the car is in my lockup. S Have you got two caps then Steve, one in the tank and another on the rad, both pressure type? Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 (edited) Mac do you mean as per the swirl pot installation? I noticed on your photo the top hose goes into the thermostat housing and the lower presumably Tees into the lower hose? I like the fit and forget installation where coolant levels are not as critical. https://www.merlinmotorsport.co.uk/knowledge_base_articles/view/cooling-system-header-tanks-in-your-race-car-323 Edited May 15 by Iain T Link to comment Share on other sites More sharing options...
Steve P Posted May 15 Report Share Posted May 15 Yes Johnny but I cant remember the complete setup because it was done 13 years ago, does seem to work though. I will check when I can get to the car. S Link to comment Share on other sites More sharing options...
johny Posted May 15 Report Share Posted May 15 Think your photo shows the set up pretty clearly Mac with the two connecting pipes above and below the coolant level. All that we cant see is the overflow from the tank pressure cap which must be round the other side and probably doesnt need a pipe on it... Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 Yes Iain, your swirl pot is the same animal as the Volvo tank. What may confuse you is that the Volvo dose not have a separate overflow it just spews coolant all over the top of the tank, should you over fill it, not so sophisticated as yours! 😃 If you would like me to do a sketch/drawing would be happy to do so. 1 1 Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 Yes a sketch please as related to our Triumph engines. The action of the swirl pot and connection seems to differ from a standard header/expansion tank. Cheers Link to comment Share on other sites More sharing options...
johny Posted May 15 Report Share Posted May 15 I suppose thats quite a good way to work out the correct coolant level. If the cap lifts after being filled to a certain level in future you need to maintain the level just a bit lower to ensure that youre running with sufficient pressure in the system to avoid boiling anywhere... Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 Iain, hope this helps, would like to take out a "patent" but this is how modern cars have been plumbed in for over 30 years. Thinking about your set up, you intend sighting the swirl pot/header tank between the brake master cylinder and the heater box? Could you not tee the bottom tank connection into the 1/2" pipe that returns coolant from the inlet manifold to the water pump that runs behind the exhaust manifold? this is direct to the suction side of the pump, could save a lot of pipework. Good luck. Mac Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 Mac clear as crystal now cheers! In terms of the return from the tank as you say I could tee into the connection to the water pipe return pt no 217467 which goes straight to the pump and keeps it simple and tidy😁. All I'll need to do is play with tank levels and prove Boyles Law....... I suppose a cheat could be to slightly overfill and any excess will be expelled via the overflow? Thanks everyone for your help it's number 1 on my to do list. Iain Link to comment Share on other sites More sharing options...
Iain T Posted May 15 Author Report Share Posted May 15 Mac, last question. Can the inlet restrictor be as simple as an inline part with a 3mm internal diameter hole? Iain Link to comment Share on other sites More sharing options...
Firefly Posted May 15 Report Share Posted May 15 Yes that would be fine, ideally brass bar, but mild steel is probably more readily available. 👍 1 Link to comment Share on other sites More sharing options...
Iain T Posted May 16 Author Report Share Posted May 16 To keep the radiator as is and still plumb in the header I'll fit an uprated say 20psi cap and use my existing 13psi for the header. I still can't fathom out the physics regarding the 3mm restrictor! Iain Link to comment Share on other sites More sharing options...
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