elie boone Posted September 26, 2002 Share Posted September 26, 2002 On a closed cooling system with an ali. header tank ( tested at 2 bar ) can i use a solid cap or do i need a cap with a pressure relief valve. Link to comment Share on other sites More sharing options...
Simos Posted September 27, 2002 Share Posted September 27, 2002 Hi Elie, I know it's not exactly the same as I have a plastic header tank but I use a solid cap on my BD with a standard rad. Link to comment Share on other sites More sharing options...
Elmo Putney Posted September 27, 2002 Share Posted September 27, 2002 I might be missing the point here but aren't all cooling systems closed? Whats the advantaqge of using a solid cap over a valved one, surley it just means when things go wrong, they go very wrong, rather than a clout of steam? I work for Ford and I still wouldnt buy one! Link to comment Share on other sites More sharing options...
Casbar Posted September 27, 2002 Share Posted September 27, 2002 I use a solid cap, with a plastic header tank on my xflow. No, not all systems are sealed, before I converted my xflow's system, there was a pipe that came off of the filler cap, that released coolant into a catch tank, when pressure built up. Result, having to top up the system frequently to keep coolant above the thermostat. Fit a header tank, no need for a catch tank, system sealed, no need to top up unless something breaks Link to comment Share on other sites More sharing options...
Simos Posted September 27, 2002 Share Posted September 27, 2002 AFAIK most coolant systems have an overflow into an overflow bottle (unsurprisingly) that has a pressure cap on it. The closed system just has a header tank (above the highest point in the system). This has advantages for trackdays and hard blatting as it means failure to suck coolant back from the overflow tank (when cooling down at lunchtime say) doesn't result in air pockets. Link to comment Share on other sites More sharing options...
elie boone Posted September 27, 2002 Author Share Posted September 27, 2002 Thanks for the info. I did ask because my tintop has a sort of pressure valve in the cap ( closed syst. ) Simos, if its fine for your BD it should be fine for mine Link to comment Share on other sites More sharing options...
Bob Corb Posted September 27, 2002 Share Posted September 27, 2002 Elie The only thing to beware of is that you will reach very high pressures as the system hasn't got anywhere to expand into. If you have a pressure cap with a catch tank then there is no air/vapour in the main circuit to squash and something will blow no matter how strong the header tank is. If you have a system with a header tank which has a small amount of air in the top (typically 3% if the system volume then you may get away with it. Anyway, you should make sure that the radiator is upto the job, get that pressure tested too and then make sure that you have some trick hose clamps to prevent things blowing off. Good luck Bob Link to comment Share on other sites More sharing options...
Nigel Riches Posted September 28, 2002 Share Posted September 28, 2002 My 1982 car had the sort of cooling system where the filler cap was fitted in the top hose, with a piece of plastic pipe running down the side of the radiator, out to the street, when the coolant expanded the excess fluid was expelled via this pipe, net result, lower coolant level as none was drawn back of course, it did stabilise at this lower level and didn't seem to suffer any ill effects, and ran like this for about ten years, how ever I have now got a "sealed" system, where excess coolant is overflowed to an expansion tank, ( must be partially filled with coolant, and overflow pipe immersed in this) excess coolant flows to the expansion tank, and upon the cooling system temperature becoming lower the necessary fluid is drawn back into the system via the water filler cap, the filler cap must be able to allow excess coolant out when hot ie running at normal working temp, and also to be able to admit coolant from the expansion tank when the system pressure drops as the coolant temp decreases, this results in a system which is full of coolant at all times, hopefully, and more stable engine temperature, never run a fully closed system as something will burst big time, it's all to do with heat and pressure and expansion, and there is a limit, often in one of the hoses, regards Nigel. Link to comment Share on other sites More sharing options...
elie boone Posted October 9, 2002 Author Share Posted October 9, 2002 The answer from Bailey motorsport manufactor of some very nice header tanks : you do need a valve in the cap for security reasons so i have one of those on order but it is +/- 17£+vat+p&p so i will bin ( +/- 20£ )the ali one ☹️ Link to comment Share on other sites More sharing options...
Simos Posted October 9, 2002 Share Posted October 9, 2002 I can see the logic of a pressure cap if set high enough for emergencies. Wouldn't want it going off in normal operation and then inducing a partial vacuum when it cooled down (crushing hoses not deigned for vacuum) I don't have a pressure cap although there is a substantial airspace in the header tank above the level of the cylinder head which will compress nicely. It has never given the least indication of exploding with pretty boggo hoses and jubilee clips. It did blow at Cadwell when an alternator failure took off the water pump drive and overheated the engine. This was not necessarily a bad thing as boiling water on my lap drew my attention to the overheat way faster than a light on the dash. I put the hose on, filled with water and drove 300km home. The key is that the header tank or at least normal water level must be above the highest point anywhere else in the system. IMHO, Simon. Link to comment Share on other sites More sharing options...
KayTee Posted October 9, 2002 Share Posted October 9, 2002 I intend using the VW Golf ball-shaped header tank on my car (1600cc BDA). It has nice markings, and about 50% of it remains filled with air, which should compress nicely when things heat-up. All this mounted suitably high against the scuttle/bulkhead should be ok, shouldn't it ? Roger K. ? Need to make a nice bracket for that one, though ... ah, well, if that was the last of my problems ... Cheers ! - Karsten Link to comment Share on other sites More sharing options...
elie boone Posted October 9, 2002 Author Share Posted October 9, 2002 Simos, I do not agree that the header tank must be in the highest position in the system, that is on a closed system. It has to be if you fill the system to avoid airlocks but once it is operational it can sit lower. Link to comment Share on other sites More sharing options...
Simos Posted October 10, 2002 Share Posted October 10, 2002 Hi Elie, if the header tank is not the highest point, would the airspace not migrate during operation to the highest point, which might in fact be your cylinder head ? Cheers, Simon. Link to comment Share on other sites More sharing options...
edmandsd Posted October 10, 2002 Share Posted October 10, 2002 I run a closed system using the alloy Caterham rad although I replaced the useless plastic bungs with metal ones. I have a small header tank with pressure cap. The tank is at the highest point. Home of BDR700 Link to comment Share on other sites More sharing options...
elie boone Posted October 10, 2002 Author Share Posted October 10, 2002 Simos, if you fill or refill the system then the header tank must be in the highest position. The pick up point for the header tank on my engine is the highest point ( modified Escort MK2 thermostat cap ) If the system is full and you close the header tank there is no way for the air to go in to the engine, also the tube witch goes to the engine is at the bottom of the header tank. Even if there is a litlle air in the engine " most unlikley " then the hot air will be pressed in to the header tank replacing the cooling liquid. Link to comment Share on other sites More sharing options...
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