When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Leave the water pump, say I. Forget about an electric one also. The OEM setup is reliable and an electric one is not. The last thing you want with an XJS is more complexity!
The rad is a horizontal flow dual pass one, just make sure they understand that, otherwise nothing special.
Leave the water pump, say I. Forget about an electric one also. The OEM setup is reliable and an electric one is not. The last thing you want with an XJS is more complexity!
The rad is a horizontal flow dual pass one, just make sure they understand that, otherwise nothing special.
Ok that's what I thought. The whole cooling system was about the only thing that worked 100% when I got it lol. Which is funny because most issues come from that system it seems.
Ok that's what I thought. The whole cooling system was about the only thing that worked 100% when I got it lol. Which is funny because most issues come from that system it seems.
No, they come from willful neglect of that system.
Leave the water pump, say I. Forget about an electric one also. The OEM setup is reliable and an electric one is not. The last thing you want with an XJS is more complexity!
The rad is a horizontal flow dual pass one, just make sure they understand that, otherwise nothing special.
Well said. Most problems with the cooling system are the result of neglect or Bodged repairs.
If you make any changes do so to provide more airflow. If legal remove air pump, use a modern much more compact alternator, replace the old A/C compressor with the modern smaller ones. You can also use a Power steering pump with a remote reservoir to further enhance airflow and clean up the engine compartment .
Doing that will get enough air flowing through the engine compartment to rid yourself of the air conditioned fuel lines. And greatly simplify the engine compartment allowing even more air to flow through.
Not to mention how nice the engine will look without hoses and wiring going every which way. Nope there isn’t a “kit” for that sort of work. However it’s really not that had if you have any fabricating skills.
Well, bless my soul, Mguar; you have posted something I agree with! Airflow though the engine bay, and out of it, is the key. This is what I have observed and done:
Radiator foams removed. I realise that this is heresy to many; but it has no bad effects (cooling efficiency is unchanged or better) and these good ones: engine bay temps lower, radiator does not get bunged up at the bottom with debris.
too old to save radiator top panel replaced with struts. Again better airflow into the engine bay, better airflow to the intake trumpets
horns and secondary coil removed from the front of the radiator - where they dirtied the incoming airstream to the radiator stack - to the sides.
air intake slot created in the front bumper, which provides about 70 square inches of extra, clean, airflow straight into the radiator stack. This means any higher coolant temps in hot stops or traffic reduce far faster once on the move and again reduce engine bay temperatures.
Foams above the gearbox removed and replaced with thin heat and sound insulation. This allows engine bay heat to exit more easily.
owing to the lack at the time of replacement header tanks, the header tank and radiator purge system simplified and made more efficient and reliable by fitting a gravity fed system.
PCV system updated to include a catch can and remove the cross V pipework
All of which adds up to a far simpler and more easily maintained cooling system. I happen to have electric fans, but these are not needed to enhance cooling, so much as to simplify the front of the engine. A few snaps attached This shows the fabricated radiator top support, and the cross strut supporting the electric fan chassis. The fans can be removed as a unit on their chassis very quickly. The temporary fix for the aircon dryer has now been replaced with giant stainless P clips, see last photo, attached to brackets on the support panel. The radiator bleed pipe to the header tank is clearly visible in this photo. Now that the header is higher than the radiator and engine, system fillig is simple and easy. Cooling system overview. The alert will notice: a) no central spout on the crosspipe (a V12 saloon crosspipe is fitted which is the only new type now avaulable), b) the radiator purge tubes have gone, c) the radiator bleed is from the LHS - see red hose going to firewall header tank. The radiator filling bleed screw is in the banjo threads. The header tank is connected to the main system by a T into the heater return, the overflow is the red tank on the wing where the factory tank was. The GiF cooling slot. Any unbelievers out there, just unbolt that bumper and go for a drive. Plus the GiF labrador, Rusty, now sadly in the great hereafter.
Last edited by Greg in France; 12-15-2021 at 10:21 AM.
Great advice. I've already done most of the removal of stuff and luckily when I did the transmission the replacement with the thin material was suggested and done.
Any more pics ofpathetic times used to delete the cross pipe as its ready to go back in?
Great advice. I've already done most of the removal of stuff and luckily when I did the transmission the replacement with the thin material was suggested and done.
Any more pics ofpathetic times used to delete the cross pipe as its ready to go back in?
Can you clarify the question, please? But if you mean how did I delete the CP spout then:
The crosspipe on the later V12 saloons did not have a spout. Otherwise it dos exactly the same job of linking the two sides of the V and the water pump when the thermostats are closed.
The spout on the crosspipe is only on the CP in order to provide a high point to fill the system from. Filling it from the wing header tank is impossible as that is lower than the rad and the engine. This fact of the header being lower than the radiator is also the reason for the radiator purge pipe system, pressurised venturi, banjo etc etc. as with out them the radiator would not be purged of air by the natural action of air rising and exiting the radiator to a higher header tank - which is what happens on most cars. The solution (much discussed with Grant Francis, The Great XJS Prophet of the Southern Cross) is to provide a header tank located at a higher place than the OEM one. On lucky pre ABS owners' cars, there is such a place, though it is occupied by the washer bottle. relocating this to the wing behind a stone baffle frees up the space.
So my system has the radiator air purge pipe going to the header, as shown in the photos on my post. It is just a tube exiting the radiator via a fitting to the higher header tank by the firewall.
Thus, no banjo, no purge system needed. Because the header is the high point, the system does not need the spout to be filled, it is filled though the header tank cap like any other car. So a V12 crosspipe, no spout, can be used and the system is essentially the same as that used in the later saloons, where the header is higher than the engine and radiator because there is room for it. A huge number of hoses and joins are eliminated, including the question mark hose and all the hoses associated with the OEM header, banjo, spout exit pipe to banjo, purge pipes etc etc. The exit from the B bank thermostat housing that powers the venturi is just blocked off.
The pipe you outline in your other post is the overflow pipe from the header tank cap which goes to the new atmospheric tank - the red one in the photos. So the entire system is easily seen, is simple, and no reservoirs are hidden. My washer bottle is where the OEM atmospheric tank is normally located.
Finally the header is connected to the main system by a pipe coming out of the bottom of it that tees into the heater return pipe. You can just see the blue pipe in the photos, but here is a better shot: The blue pipe, just visible, joins the outlet at the bottom of the tank to the heater return pipe using a T shaped hose. The heater return runs down the chassis that side and goes to the bottom of the radiator.
Also attached is a piece I wrote about it for Practical Classics.
Can you clarify the question, please? But if you mean how did I delete the CP spout then:
The crosspipe on the later V12 saloons did not have a spout. Otherwise it dos exactly the same job of linking the two sides of the V and the water pump when the thermostats are closed.
The spout on the crosspipe is only on the CP in order to provide a high point to fill the system from. Filling it from the wing header tank is impossible as that is lower than the rad and the engine. This fact of the header being lower than the radiator is also the reason for the radiator purge pipe system, pressurised venturi, banjo etc etc. as with out them the radiator would not be purged of air by the natural action of air rising and exiting the radiator to a higher header tank - which is what happens on most cars. The solution (much discussed with Grant Francis, The Great XJS Prophet of the Southern Cross) is to provide a header tank located at a higher place than the OEM one. On lucky pre ABS owners' cars, there is such a place, though it is occupied by the washer bottle. relocating this to the wing behind a stone baffle frees up the space.
So my system has the radiator air purge pipe going to the header, as shown in the photos on my post. It is just a tube exiting the radiator via a fitting to the higher header tank by the firewall.
Thus, no banjo, no purge system needed. Because the header is the high point, the system does not need the spout to be filled, it is filled though the header tank cap like any other car. So a V12 crosspipe, no spout, can be used and the system is essentially the same as that used in the later saloons, where the header is higher than the engine and radiator because there is room for it. A huge number of hoses and joins are eliminated, including the question mark hose and all the hoses associated with the OEM header, banjo, spout exit pipe to banjo, purge pipes etc etc. The exit from the B bank thermostat housing that powers the venturi is just blocked off.
The pipe you outline in your other post is the overflow pipe from the header tank cap which goes to the new atmospheric tank - the red one in the photos. So the entire system is easily seen, is simple, and no reservoirs are hidden. My washer bottle is where the OEM atmospheric tank is normally located.
Finally the header is connected to the main system by a pipe coming out of the bottom of it that tees into the heater return pipe. You can just see the blue pipe in the photos, but here is a better shot: The blue pipe, just visible, joins the outlet at the bottom of the tank to the heater return pipe using a T shaped hose. The heater return runs down the chassis that side and goes to the bottom of the radiator.
Also attached is a piece I wrote about it for Practical Classics.
As a racer I have things much simpler. First I’m flowing coolant from front to back. Both sides collect on the firewall into a common tank. Then forward into the radiator. The current system has no way to ensure coolant at the back circulates as quickly as does coolant at the front of the engine. That uneven cooling at elevated RPM has caused a great deal of heat stress.
I know I won’t have thermostats but with racing we gently warm up the engine and the size of the tube determines the rate of flow. My system also prevents air entrapment. With the radiator cap well above the engine air will naturally seek the highest point.
No fans will be used. While they are great for low speed and stop and go driving they actually block the airflow at high speed ( north of 100 mph)
Finally I will be using E85 which is a much cooler running fuel than petrol or even E10
As a result of all of that I’m going to start out with a simple aluminum cross flow radiator. ( for weight considerations) I have a clean and straight proper Jaguar double flow copper radiator if the single cross flow Aluminum radiator cannot keep the engine cool
Been busy with Xmas stuff and still working (from home) but did get the plug out and replaced today.
Also removed the water filler neck to replace the gasket.
No word on price from rad shop. But my buddy just got one back and it looks greta and he said the prices were fair. Today's my last official day at work then I can start getting the jag ready for the rad.
Also attached is a piece I wrote about it for Practical Classics.
Greg,
When did you do this mod? I looked up the Unit 7 website, and the site doesn't look like it's been updated in ages. They don't have anything there about custom fabrication. I really like your mod, and would like to duplicate it if they can duplicate what they did for you. There would have to be a slight mod for the header tank tee into the heater return line since I have a LHD car. Everything else looks straight forward.
Where did you get the right angle bleeder fitting that you had trouble finding?
Greg,
When did you do this mod? I looked up the Unit 7 website, and the site doesn't look like it's been updated in ages. They don't have anything there about custom fabrication. I really like your mod, and would like to duplicate it if they can duplicate what they did for you. There would have to be a slight mod for the header tank tee into the heater return line since I have a LHD car. Everything else looks straight forward.
Where did you get the right angle bleeder fitting that you had trouble finding?
12-14-2021, 11:29 PM
