Yorkkie Posted May 24, 2010 Report Share Posted May 24, 2010 Hello All, recently I have had a problem sealing the bottom hose onto the radiator. The union of hose to radiator continued to leak, as I tightened the hose clip the leak got worse. My thought was that the radiator union had become deformed..... out comes the radiator. I cleaned up around the union and could not find anything visible wrong.. so I put it back.. behold it leaks. So out comes the radiator again. (those bottom hoses are a real bu&&er to get off. I decided to wrap a couple of turns of self amalgamating hose repair bandage around the union on the radiator . A new hose and new clips and it seems to have stopped..... bizzare. Anyway this got me thinking... there are 2 radiator caps for sale 7PSI and 13 PSI. I wonder what is the difference is (not 6PSI) or what application difference is probably the right question.. so should my 73 TR6 PI have a 13 or 7 cap? Regards Andy Quote Link to post Share on other sites
ianhoward Posted May 24, 2010 Report Share Posted May 24, 2010 (edited) Hi Andy My lads Spitfire needed a replacement Rad Cap - I had a 'spare' amongst all my bits and bobs - It was fine on short runs but then he started to overheat losing water. It turned out to be a 7psi (?) cap and checking the Haynes Manual a 13psi rad cap was specified - changed to that and no more problems... Stupid is as Stupid does i didn't check the rating!! Brgds PS - Still looking forward to the 'blast' you mentioned!!! Edited May 24, 2010 by ianhoward Quote Link to post Share on other sites
RobinTR6 Posted May 24, 2010 Report Share Posted May 24, 2010 I'm interested in this one as I have the same question. I thought the TR5/6 standard cap was a 7lbs. Woukld a higher pressure cap by containing more pressure reduce the tendency to run hot (especially in this weather) or in fact the reverse..... Robin Quote Link to post Share on other sites
silvertop_john Posted May 24, 2010 Report Share Posted May 24, 2010 The brown manual quotes pressure of 13 lbf/sq in, but the Haynes manual quotes 3.25 - 4.25 ib/sq in as the pressure cap release pressure. Confused I am. John Quote Link to post Share on other sites
Alec Pringle Posted May 24, 2010 Report Share Posted May 24, 2010 As far as I recall, 5 and 250 started off with 4lb caps and 82C stats, whereas 4/4A had 4lb caps and 70C 'stats originally. 5/250 caps were quickly upped to 7lbs, and the same recommendation applied retrospectively to the later wet-liner engines, although thermostat recommendations were unchanged. The very first 6 engines usually had 7lb caps, rapidly replaced by 13lbs at service, 82C stats remained normal fitment although 88C specified for cold climate winters - but 88C stats only ever with 13lb caps, never use with 7lb caps. Cheers, Alec Quote Link to post Share on other sites
ianhoward Posted May 24, 2010 Report Share Posted May 24, 2010 (edited) Interesting Alec The cap on my 5 certainly appears to be original (i.e. 'old'!), and that is 13psi... Brgds Edited May 24, 2010 by ianhoward Quote Link to post Share on other sites
Alec Pringle Posted May 24, 2010 Report Share Posted May 24, 2010 Hi Ian, I've just checked my recollections against contemporary factory manuals - which agree. A lot changes over 40 or 50 years, many an inaccurate figure has been published by later authors, and repeated, and eventually accepted as 'fact' . . . . I prefer to verify against original factory data, which is rarely incorrect - although there are of course exceptions to prove the rule ! Today's listings from specialist suppliers are not always reliable - on occasion they reflect current parts availability rather than original specification. Dare I suggest that if we'd all stuck to 70C thermostats instead of switching to 82C items on wet liner engines that there might have been fewer cylinder heads succumbed to cracking ? I'd reckon most TR5s were switched to 13lb caps in the 1970s - it seemed appropriate as 6s used the same cooling system but with the higher pressure cap. At which point 6s changed from 7 to 13lb caps however depends on which factory publication you believe. Cheers, Alec Quote Link to post Share on other sites
angelfj Posted May 24, 2010 Report Share Posted May 24, 2010 Hi Ian, I've just checked my recollections against contemporary factory manuals - which agree. A lot changes over 40 or 50 years, many an inaccurate figure has been published by later authors, and repeated, and eventually accepted as 'fact' . . . . I prefer to verify against original factory data, which is rarely incorrect - although there are of course exceptions to prove the rule ! Today's listings from specialist suppliers are not always reliable - on occasion they reflect current parts availability rather than original specification. Dare I suggest that if we'd all stuck to 70C thermostats instead of switching to 82C items on wet liner engines that there might have been fewer cylinder heads succumbed to cracking ? I'd reckon most TR5s were switched to 13lb caps in the 1970s - it seemed appropriate as 6s used the same cooling system but with the higher pressure cap. At which point 6s changed from 7 to 13lb caps however depends on which factory publication you believe. Cheers, Alec This may be obvious, but a caution is advised! The weakest link in the cooling system (if you utilise a heater) is the heater matrix. The use of higher than specified coolant system pressures will subject these rather delicate and often corroided, paper-thin tubes to pressures they may not survive. If the matrix bursts it just could make for a very painful burn in a most sensitive area of the anatomy! Don't ask how I know! Quote Link to post Share on other sites
RobinTR6 Posted May 24, 2010 Report Share Posted May 24, 2010 So back to my query then. I assume that the 13lb cap subjects the system to higher presssure that the 7lb one. Is that the case , and if so presumably the system can run at higher tempratures under the higher pressures. I'm still running with a 7il cap so was speculating the upggrade. Robin Quote Link to post Share on other sites
Yorkkie Posted May 24, 2010 Author Report Share Posted May 24, 2010 Higher the pressure the higher the temperature that water boils (think pressure cooker) so running a 7lb cap instead of a 13lb cap means that you will boil more easily. Andy Quote Link to post Share on other sites
88V8 Posted May 24, 2010 Report Share Posted May 24, 2010 The boiling point lowers by 3F per lb pressure. Ivor (on borrwoed compuyer) Quote Link to post Share on other sites
poolboy Posted May 25, 2010 Report Share Posted May 25, 2010 Think of the radiator cap as a "safety device" to prevent boil over and the thermostat a "regulator" for the engine's operating temperature. Both part of the cooling system, but serving different purposes. Quote Link to post Share on other sites
saffrontr Posted May 25, 2010 Report Share Posted May 25, 2010 Hi, According to the Triumph Service Instruction sheets Triumph changed over their complete range of cars between early 1968 and July 1969 from the 7lb system to the 13lb system, the last recorded being the Spitfire. There is no recorded date for the TR6 that I can find however the 2.5PI changed over before December 1968 so it would be fair to assume that the TR6 would have been changed at about the same time. There is a note to say that under no circumstance should a 13lb cap be fitted to a car originally fitted with a 7lb cap unless the water pump was changed otherwise there could be a problem with the waterpump seals. cheers Derek Quote Link to post Share on other sites
RobinTR6 Posted May 25, 2010 Report Share Posted May 25, 2010 Ok help here then. I have 68 TR5 and it has a 7lb cap, should I leave or upgarde it to 13lb so its less prone to overheating....It isnt bad but when stuck in traffic in hot weather the temperature rises to almost the gauge limit, not quite but close. It has a revotec electric fan as well. NOt sure about the thermo tho ? Robin Quote Link to post Share on other sites
ianhoward Posted May 25, 2010 Report Share Posted May 25, 2010 Ok help here then. I have 68 TR5 and it has a 7lb cap, should I leave or upgarde it to 13lb so its less prone to overheating....It isnt bad but when stuck in traffic in hot weather the temperature rises to almost the gauge limit, not quite but close. It has a revotec electric fan as well. NOt sure about the thermo tho ? Robin Hi Robin My 5 is also a 68 car (May) and as stated earlier has what I believe to be the original rad cap at 13psi... also have a Revotec fan fitted. If yours gets hot in standing traffic, have you adjusted the fan to come on at a lower temperature? Mine is set quite low and therefore comes on quite 'easily' at just to the right of the 6 o'clock position on the guage. I sometime wonder if a litle too early(?) Brgds Quote Link to post Share on other sites
RobinTR6 Posted May 25, 2010 Report Share Posted May 25, 2010 Ah, Ian, clarity at last. BTW by 6 o' clock on the gauge presumably you mean the temp gauge on the dash. Mine does as well but in the hot weather the temp increases till its almost in the red which I assume is too hot. BTW what thermostat do you have and 'how do you set ' the Revotec. My temp sensor is in the styainless bottom hose join pipe, ie from the bottom hose on rad to the water pump. Quote Link to post Share on other sites
ianhoward Posted May 25, 2010 Report Share Posted May 25, 2010 (edited) Ah, Ian, clarity at last. BTW by 6 o' clock on the gauge presumably you mean the temp gauge on the dash. Mine does as well but in the hot weather the temp increases till its almost in the red which I assume is too hot. BTW what thermostat do you have and 'how do you set ' the Revotec. My temp sensor is in the styainless bottom hose join pipe, ie from the bottom hose on rad to the water pump. Hi Robin Yep - 6 o'clock on the guage... As for the adjustement for the Revotec, and mine is more conveniently located on the return pipe from the thermostat to the top of the radiator as that is where the destructions informed me to install it; if your temp sensor/valve is the same as mine it will have a rectangular black plastic 'cap' approx 1" x 1/2" - carefully prise this off and inside will be a very small adjustment 'screw'. With the engine running and the car at the desired temperature on the guage (or perhaps a tad above?) turn this (a very small flat blade screwdriver needed) to make the fan kick in at the temp required. Once satified, replace the cap. Voila! Under normal running the fan only comes on when slow moving/stopped. As for what thermostat is fitted I haven't a clue! Been there unmolested since I got the car nearly 5 years ago! Hope this helps Brgds Edited May 25, 2010 by ianhoward Quote Link to post Share on other sites
birchy Posted August 5, 2010 Report Share Posted August 5, 2010 I was just checking up on this - in the Rimmer Bros catalogue, it has a 7 PSI cap for cars up to CP75000, and 13 PSI from CP75001 (actually, it says CR75001, but I assume that's a typo). Confusingly, my Haynes manual (very old) clearly says the cap releases pressure at 4 PSI. Just as well I couldn't find a 4 PSI cap then! David Quote Link to post Share on other sites
stuart Posted August 5, 2010 Report Share Posted August 5, 2010 I was just checking up on this - in the Rimmer Bros catalogue, it has a 7 PSI cap for cars up to CP75000, and 13 PSI from CP75001 (actually, it says CR75001, but I assume that's a typo). Confusingly, my Haynes manual (very old) clearly says the cap releases pressure at 4 PSI. Just as well I couldn't find a 4 PSI cap then! David 4psi is for the 4 cylinder cars. Stuart. Quote Link to post Share on other sites
Rhodri Posted August 5, 2010 Report Share Posted August 5, 2010 I fitted a set of kevlar reinforced hoses available from most suppliers. I dont know if they are "metric" sizes or not, but they are loose on the rad etc and the clips need to be tightened excessively. Usually a hose is a tight fit, but not these. I have yet to see what happens when I use them. Could you be using these hoses? Rod Quote Link to post Share on other sites
RobinTR6 Posted August 6, 2010 Report Share Posted August 6, 2010 Yep got the same hoses I think but they are all a 'tight' fit before the clamps are on so a bit surprised to hear yours are loose. Something is afooot....if they are Robin Quote Link to post Share on other sites
jean Posted August 7, 2010 Report Share Posted August 7, 2010 My 70 TR6 still has the original radiator cap that came from the factory and it's a 13psi, never had any problems. My TR3 has a 4psi cap, but this cap is also different in spring hight, as the radiator is fitted with a higher filler neck. Do not overlook that the TR6 cap has to work in two directions, to say let water in and out of the cooling circuit Derek mentioned very correctly, a too high pressure might produce serious waterpump leaks and failures Quote Link to post Share on other sites
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