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Although I own a XJ12 (Double Six, really) I was advised to write in this forum for V12 troubleshooting. Moderator, I do apologise if I am mistaken and, in this case, please move my post and thread to the appropriate forum.
Is it not preferable to buy a modern, high efficiency, radiator instead of the original spare part, for my series III 1992 V12 cooling system? I am overhauling the whole system (pipes, pump, thermostat) and I am in two minds if I should stick with the original or adapt something that fits but has a greater efficiency. Given how delicate our aluminium engine is I am inclined for the latter.
Please comment freely and please do link me to high efficiency radiators that will fit our engine. Also, please, link me to spare parts dealers and vendors. Thank you to everyone who will invest his time/expertise to help me.
Upgraded radiators have been getting mixed reviews from V12 owners for as long as I can remember.
In some cases the quality isn't very good. In some cases the fit isn't very good. In some cases the desired improvement never materialized.....possibly because actual repairable faults elsewhere in the system were not repaired.
In yet other cases very positive results are reported.
These mixed reviews have prevented me from buying the upgraded radiators. I consider them an expensive experiment. What's more, I've been happy with the original design radiators....although it's virtually certain nowadays that any original radiator will need a new core.
Aluminium radiators are excellent if well made. In Europe, Alicool or Radtec are the best and are of very high quality, both UK makers with motorsport quality standards. Alicool (and for all I know Radtec) will make a rad complete with integral shroud and mountings for electric fans (SPAL only I would advise) which is a great package. You lose a belt, gain another MPG, and a quieter engine. Controlling the fans is best done, in my experience using Grant Francis' system, which if you go this route he will gladly explain.
Aftermarket electronic controllers tend to have a very short life expectancy under a Jaguar V12 bonnet.
Given how delicate our aluminium engine is I am inclined for the latter.
The Jag V12 isn't particularly delicate at all. Fundamentally it is very robust; almost indestructible. The only proviso is that the cooling system be 100% maintained so that proper coolant flow throughout the engine is ensured.
Much ado is made over coolant temperature. Personally I think this focus on temperature is, to some extent, misplaced. What hurts a V12 isn't so much high coolant temperature but, instead, poor coolant flow.
Aluminium radiators are excellent if well made. In Europe, Alicool or Radtec are the best and are of very high quality, both UK makers with motorsport quality standards. Alicool (and for all I know Radtec) will make a rad complete with integral shroud and mountings for electric fans (SPAL only I would advise) which is a great package. You lose a belt, gain another MPG, and a quieter engine. Controlling the fans is best done, in my experience using Grant Francis' system, which if you go this route he will gladly explain.
Aftermarket electronic controllers tend to have a very short life expectancy under a Jaguar V12 bonnet.
I would like to hear other forum members' comments too. But I very much like this solution, a kit with shrouds and supports. Given that I am still uncertain as to who will do the installation, and fearing incompetence (as Doug mentioned, incompetence may cause a failure of the experiment), the simpler the kit, the better. In fact, Doug's comment being well taken and understood, I ask Doug and you, is it a difficult upgrade?
This forum is enticing ... it generates an itch to try it myself. Would you both discourage a DIY? I can buy the tools although not a 2.5 ton car lifter. I can drive the car up on semi-ramps or I could jack it up ... As Doug suggested, some failed experiments may have been due to poor installation...
I will google SPAL, Alicool and Radtec. Thank you Greg,
The Jag V12 isn't particularly delicate at all. Fundamentally it is very robust; almost indestructible. The only proviso is that the cooling system be 100% maintained so that proper coolant flow throughout the engine is ensured. Much ado is made over coolant temperature. Personally I think this focus on temperature is, to some extent, misplaced. What hurts a V12 isn't so much high coolant temperature but, instead, poor coolant flow. Cheers DD
Again thank you for your time and expertise! This includes the shroud and the fans. Would you recommend not installing these fans and using SPAL? Perhaps they may sell the kit without the fans but I am unsure if the SPAL would fit in this shroud.
Regards, Tommaso
PS: I was unaware that there was a manual gearbox V12
A clue to poor flow is a fluctuating temperature needle or high coolant temperature. But, a steady needle and low coolant temperature is not proof of good flow. There's an element bit of hope-and-pray to all of this
The only thing you can do is keep everything in the cooling system very clean and in perfect condition.
One way to see that coolant is flowing is from an inline coolant filter. Downside is that you've gotta periodically clean the filter, which is not a big deal, and they add another place that can leak. The one I installed leaked due to plastic threading keeping the caps on - talking with manufacture to see if they have suggestions or a higher quality one...
Thank you Pirk, it is incredible but I was thinking exactly of this: installing a transparent hose, as recommended by Australian Greg in his PDF on cooling system, but inserting in it a filter. But I then thought against it because a filter can reduce coolant flow speed. What is your experience? Did you install a more powerful pump?
@ Doug, would a pump with slightly greater flow rate be advisable, regardless of filter? If flow is so essential why not increase the rate?
Rather than a fancy radiator, perhaps the best thing to do it put in the proper thermostats ( much discussion here about brands that extend far enough) to ensure that all of the coolant actually goes through the radiator. The best radiator in the world in no good if the coolant never circulates through it.
@ascanio1 Original pump with a Derale Tornado 16" electric fan with a 200on/185F off temp switch and a soon to be replaced original aux fan. New stats. 2 Thermocure flushes. Temp gauge on the free NPT port A bank after aux air assembly removal.
For the 10 minutes or so that the car ran before the inline filter popped the threads and started leaking, I could see exactly when the stats opened, flow of the coolant, debris it was collecting, temp of the engine when stats opened - it was great... Until the plastic threads crapped out... Really would like to get a filter on both banks, think it would be super useful and changing the filter is pretty easy with minimal coolant loss... A shame they couldn't just make an entire metal threaded filter assembly - the whole thing was really well made except for that essential part.
One way to see that coolant is flowing is from an inline coolant filter.
True enough, it tells you have coolant flowing. But it can't tell you if coolant is flowing into all areas of the cylinder heads.
This is the most critical area. And there's no way to peek inside to see what's going on.
All you can do is keep the system very clean, make sure everything is in good operating condition, make sure the system is properly bled, and use the right thermostats.
The sticky I wrote at the top of this section goes into detail what I have done to ALL my Jags, 6 or 12.
Our PreHE 1976 XJ12, been in the fleet forever, is sitting close to 655000kms, and the engine is untouched. Cooling system, wiring, etc etc, have been kept as Doug stated. NOT hard, very simple to do.
ALL my Jags run Efans, and never had an issue.
Thermostats, as mentioned, will kill that engine in lees than a heartbeat. Make 110% sure they are long enough/
Have a read of this attachment.
Tommaso
I would find out the make of the fans, and the sizes. If the fans are not to your liking, then just ask them to source SPALs instead. They will make the shroud to fit them, no bother. The main fan wants to be at least a 25 amp one, the smaller one, which i suggest should come on with the aircon, should be about 17 amps. the air movement figures given by fan makers are largely made up as far as I can tell. Only SPAL give proper figures, but my experience has been that the amp draw of a fan is the most reliable guide to its efficacy. When my main SPAL kicks in, I can see the temp gauge drop while the car is stationary and ticking over! In fact it almost never does, the smaller of the two being enough, except after a fast run and a traffic stop.
I have found that only SPALs work reliably for the long term.
As to filters etc, i do not believe in them. Just keep the system up to snuff. I believe that filters etc are just another source of leaks and trouble! The cooling system is NOT delicate, it just needs maintenance more than once per 40 years!
Greg
Last edited by Greg in France; 07-04-2021 at 03:36 AM.
Welcome. I own a 1993 Daimler Double Six 6.0L and a 1992 XJS 5.3L. I live in Hong Kong where it often stays between 28 and 33 C from early May into late October. Driving here means lots of stop and start traffic so it is really one of the worst places to drive these V12s (in relation to cooling). I have never once had any problem with either cooling system. I am slowly working through some issues with my newly acquired XJS because of shortcuts the previous owner followed, but its a gem and a logical, methodical approach (as spelled out in Grant's sticky and Greg's comments) is what you need to follow. The radiator in the DD6 seems a lot bigger than the XJS and it runs cooler, no doubt, to the XJS. It is noticeable how much cooler this 6.0L runs. In the DD6 I have never had the the temperature needle rise beyond the midway point, ever, even in stop and start traffic with the AC on full and it 32 degrees outside.
When I got the DD6 ten years ago, I replaced all the hoses, thermostats, water rail and bushes etc and had the radiator flushed. The original radiator is working perfectly fine so I kept it. One thing I didn't replace at that time because it didn't even cross my mind was the heater valve and the hoses that connect the heater valve. About three years ago I started loosing coolant with no obvious leak in the obvious places. It was super frustrating. Then I found it: it was leaking around the heater valve as it had corroded (see photo). So, if you replace all the hoses check the heater valve to see if it is ok.
My advice, and it is only an opinion I draw from my own experience with my DD6, is that unless there is a real known problem with the original radiator, don't replace it. Replace all hoses, thermostats, water rails (stainless steel if you can find them) + bushes, heater valve (if needed). Follow's Grant's sticky. Maintain your car well and enjoy it. These V12s are amazing engines and as Doug stated, they are sturdy as if you maintain them.
Rather than a fancy radiator, perhaps the best thing to do it put in the proper thermostats ( much discussion here about brands that extend far enough) to ensure that all of the coolant actually goes through the radiator. The best radiator in the world in no good if the coolant never circulates through it.
Yes, thank you. I read the very interesting paper in the sticky.
I have not been able to understand which thermostats I can buy in Europe. At the end of the thread a couple of members mention some thermostats but it is unclear if those are the right ones. Perhaps you can help me by posting the exact model/serial number of a thermostat that we can order in Europe? Does SNG Barratt carry the correct one (THIS) ?
@ascanio1 Original pump with a Derale Tornado 16" electric fan with a 200on/185F off temp switch and a soon to be replaced original aux fan. New stats. 2 Thermocure flushes. Temp gauge on the free NPT port A bank after aux air assembly removal ... CUT ... A shame they couldn't just make an entire metal threaded filter assembly - the whole thing was really well made except for that essential part.
Thank you Pirk. Will you update us when you fix the problem? It is a useful modification. I also saw a thermometer somewhere in your engine. Is that too a modification?
The sticky I wrote at the top of this section goes into detail what I have done to ALL my Jags, 6 or 12. Our PreHE 1976 XJ12, been in the fleet forever, is sitting close to 655000kms, and the engine is untouched. Cooling system, wiring, etc etc, have been kept as Doug stated. NOT hard, very simple to do. ALL my Jags run Efans, and never had an issue. Thermostats, as mentioned, will kill that engine in lees than a heartbeat. Make 110% sure they are long enough/ Have a read of this attachment.
Thank you, I read and downloaded the paper and I am google translating it for my mechanic in Italy... but your very cheerful language seems to beat google translate over and over!
Again, thank you for your excellent paper and, please, can you recommend a thermostat that is available in Europe?
Tommaso
I would find out the make of the fans, and the sizes. If the fans are not to your liking, then just ask them to source SPALs instead. They will make the shroud to fit them, no bother. The main fan wants to be at least a 25 amp one, the smaller one, which i suggest should come on with the aircon, should be about 17 amps. the air movement figures given by fan makers are largely made up as far as I can tell. Only SPAL give proper figures, but my experience has been that the amp draw of a fan is the most reliable guide to its efficacy. When my main SPAL kicks in, I can see the temp gauge drop while the car is stationary and ticking over! In fact it almost never does, the smaller of the two being enough, except after a fast run and a traffic stop.
I have found that only SPALs work reliably for the long term.
As to filters etc, i do not believe in them. Just keep the system up to snuff. I believe that filters etc are just another source of leaks and trouble! The cooling system is NOT delicate, it just needs maintenance more than once per 40 years!
Greg
Thank you Greg, I have already begun following Doug and your advice. I found that Alicool makes a complete kit. Do you trust their fans? I could ask to remove their fans and install SPAL in their place but I am not sure that it would be a perfect and easy 'drop-in' or 'plug and play' fit. I am all for electric fans but I need something simple, ready made in a kit. The other brand, Radtek, does not offer a kit and so I would prefer Alicool.
As I mentioned to Pirk, I love his idea but I was concerned with what Doug recommended: new system failures are usually due to poor installation. I hope that Pirk can solve the leak and update us.
Again, thank you for your time and expertise! Regards, Tommaso
07-03-2021, 10:49 AM
High efficiency cooling system upgrade
