I find myself wanting to upgrade the cooling system in my XKR. It recently came to my attention that autocross events are now being held nearby and I would like to participate in the Jag just for fun. However, my experience tells me that the cooling system is not cut out for that sort of abuse. Now to preface, my cooling system is in excellent condition. All hoses, o-rings, radiator, thermostat and water pump are less than a couple years old. About the only thing that has not been replaced is the auxiliary supercharger circuit water pump, which I want to replace for the Bosch 010 unit. Having established that my cooling system is in good condition, in daily driving, the temperatures reported by the RealGauge are always in the normal range between 185ºF and 215ºF on hot days when idling in traffic, usually at an intersection. During highway driving the temperatures usually hover closer to 195ºF and 200ºF unless going downhill at night where I have seen temperatures plummet to 185ºF. However, spirited driving in (empty) mountainous, hilly backroads that have lots of curves, keeping the transmission between 1st and 4th gear as I accelerate and corner aggressively to try and imitate the type of driving done on autocross, I have seen temperatures creep closer to 220ºF and near the red zone. In fact, even when driving normally in those roads, the temperature is usually above 215ºF. This leads me to the conclusion that the cooling system in these Jags is not efficient in high load and spirited or sporty driving conditions, but perfectly adequate for normal city and highway driving. I think the hot and humid tropical climate of Puerto Rico only serves to exacerbate the issue, especially in the summer.

Because I would like to autocross the car without blowing a head gasket or having a burst hose, I think it's necessary to upgrade and improve the cooling system. Short of the Bosch 010 pump, which really mostly improves inlet air temperatures, I don't know of many other improvements that can be made. I know Radtec in the UK make an all aluminum (including the end tanks) radiator for our XKRs, but I do not know if the capacity and efficiency of that radiator is improved over stock or the Nissens currently fitted. I also know that both Eurotoys and DCR sell an aluminum upgraded supercharger intercooler radiator with a larger capacity (the one anterior to the air condenser). Would upgrading to both those radiators, and the Bosch 010 pump improve the cooling system's efficiency or would that be a waste of money? If anyone knows of a better way of improving the cooling system efficiency, please let me know.

These are the parts I am considering:

• Radtec All Aluminum Radiator for XKR
• All Aluminum Supercharger Intercooler
• Bosch 010 Pump

 

your nissens radiator is a piece of ****

you need a real xkr/db7v radiator…that sticker that says supercharged models only wasn’t for show

 

Honestly, this wouldn't surprise me. Might as well upgrade to the Radtec radiator, and that way I can say goodbye to worrying about the plastic end-tanks failing. I will give them a call to see what they can tell me about their radiator.

 

Put a 84 deg C thermostat in and run the fans at half speed all the time.. easy mod one wire to earth on the wire loom to the ECU ..written it up on here. Move the number plate out of the inlet area. Search my posts

 

Cool, I will look up the fan mod. Re. the number plate, PR is fortunate enough to not require an ugly front plate spoiling the beauty of the car.

Is the cooler t-stat going to cause problems down the line or lower fuel economy?

 

Mine did 33 mpg on a recent trip to france ..thats a UK gallon 4.54 litres Thats 27.5 to the US gallon.
Runs at 88c unless you boot it when it goes to 92 .. The lower temp gives you a heads start in traffic congestion .
If it gets real hot turn the air con off .

 

Normally, a thermostat sets the _minimum_ temp of the system, and should not have much to do with max temp.

From my long gone track days, I remember folks drilling extra holes in the thermostat plate for better flow to the radiator at high rpm/flow. The idea was that a thermostat even fully open was creating enough of a restriction on flow that not enough coolant made it to the radiator and let the engine temp rise. Of course we have to remember that our cars somehow overheat with the thermostat plate removed altogether, so be aware of that.

You already know this, but the cooling fans on our later cars are driven by PWM, not simpler off/low/hi relays. It probably complicates turning it on full with a simple wire hack.

The other hot item back then was a product called water wetter. It enhanced the "wetness" of the coolant and promoted better heat exchange. I believe in the warmer climates, some folks run distilled water and water wetter in high concentration as coolant altogether. To my knowledge this stuff really works.

Also from personal experience, a nice chemical clean of the cooling system can do wonders to the heat exchange. In my case, it was restoring the function of the heater core, but it definitely applies to the rest of the system as well. I am talking about a simple flush and clean of the cooling system with parts-store radiator cleaner, nothing fancy/expensive.

Best of luck, keep us posted.

 

I'm not a fan of thicker inter-cooler radiator since whilst it has more coolant/thermal capacity and can delay heat soak, it also ends up making the air hotter and slower before it gets to the engine cooling radiator, which I think is a bad tradeoff. I'd rather heat soak the supercharger than overheat the engine. I had a thick aftermarket inter-cooler that came with the XKR, and I started to overheat the engine in sprint and stop traffic. After that I removed it and put in a much thinner one, and problem did not reoccur.
Upgraded inter-cooler pump is good, and could consider drilling out/re-plumbing the inter-coolers so water goes straight through in one end and out the other, and does not have to do the tight 180 degree turn at the far end to come back out the same end it went in. Larger radius curves would speed up the flow. Of course same tradeoff as above, more efficient removal of heat from inter-cooling circuit sends hotter air into the engine cooling radiator.
You could add a misting system to lower the cooling air temp before it hits the radiators, but likely only a good solution for short races since you can get through a lot of water quite quickly, so need big tank, add weight, etc. Similarly bunging ice cubes into the cooling systems is not much good as tanks are small - likely only viable for 1/4 mile stuff.
Of course since we know the Eaton is partly responsible for global warming, you could consider spinning it more slowly, which would reduce boost/power but likely also reduce heat. Water/Meth might help a bit as well (Nitrous is very cold...but who wants a scuba tank in the trunk)
And then for the really brave you could try and figure out how to run on methanol....
Assuming you still want a daily driver, I would keep all the radiators clean inside and out, lose the plastic radiator ends, switch to Bosch pump, and worst case spin Eaton more slowly if still overheats. And the aircon remains off....you can always drop the top and turn on the heater as well :-)

 

I think a methanol injection would be a good way to go forward although a little complicated? I know a guy in Texas on the forums has done it to his.

 

The only time mine got really hot was when cuing for the Britania tunnel under the thames.
When I sat at idle , I am sure the air con was on so fans at full blast the temperature crept up BUT When I moved forwards even 10ft the temperature dropped immediately from 102 down to 95.
I put this down to the water pump turning too slow at idle.
I have a spare pump but no pulley so I cannot check the clearance between inside of pulley and pump with a view to getting one of a smaller diameter.
Have lathe and tig welder anything is possible . . For now I think I will slip it in neutral and raise the revs a little.
Addendum.
Measured existing pulley and its 115mm Dia. So you would need to go down to 100mm for any improvement ( and a shorter belt)

 

I just heard back from Radtec regarding their radiator for the XKR. This is what they said:

So, given that xalty states that the Nissens radiator I have is insufficient for the XKR, I am going to venture into trying out the Radtec aluminum radiator. I will report back once I have tested it out. I'm going to go at this piecemeal. I will first try the radiator and report back. If that's enough of an improvement I will leave it there. If not, then I will try the 180° T-stat and then the Bosch pump.

 

Just having a higher cfm fan would help, or a pusher fan in addition to the stock fans.

the body opening is not large enough, at least on the 4.0 cars. When I’m driving 75 mph or less the coolant temperature is higher than when I’m driving 80 mph or higher. More air flow makes all the difference.

it would be cheaper and less complicated to just add more air flow vs. a radiator change.
IMHO.

Z

 

The OP has the wrong radiator in his car period full stop. Until you fix that nothing matters

 

true. First things first.

in my case, the car has never overheated, at least it hasn’t since I’ve owned it. As far I can tell, and the detailed service records confirm, the car still has the original radiator in place. Which appears to be in an “as new” In appearance.

That said, the bumper to bumper traffic in the Texas and Oklahoma summers does give me anxiety. Which is likely unwarranted.

I have experimented with running all distilled water plus WaterWetter for the pump lubrication. That did lower the usual coolant temp by about 10 degrees F.

Not much, considering the aggravation of dealing with the barely used antifreeze.

Z

 

Genuine question, what is it about the nissens that makes it so?
My original factory XKR (2000MY) radiator (has the supercharged only sticker) sprung a leak and l also went with a nissens replacement. From memory specified for XKR, there is a different listing for N/A cars. Whether the two are in fact different or simply a marketing ploy l don't know.
Core sizes are the same other than thickness with nissens actually thicker at 34mm verses OEM at 26mm. There is however a mismatch with the nissens side tanks to fan shroud fit which needs to be addressed in order to maintain fan efficiency.
Change over was several nice hot summers ago with no problems since

 

Gian...just curious if you ended up installing the Radtec radiator? If so, can you comment on the install & performance?

 

Not yet. I had to prioritize other things and my cooling system is running good enough after I discovered a tiny leak that ended up becoming a burst octopus hose. After replacing that hose, my cooling system has been a little more efficient, but not where I'd like it to be for future track driving.

 

The priorities are ..

remove any number plate obstructions from the air intake.
fit an 82 deg C thermostat.
wire the fan to run continuously at full speed
find a pulley to run the water pump about 10% faster as its too slow at idle ( if you find one let me know ! )
If in heavy traffic put in neutral and raise the rpm slightly/turn off the air con

 

Hi Guys. This is what we did on mine.
We fitted a custom inter-cooler radiator with larger frontal surface area and a thinner cross section of 1”. We fitted a lightweight, aluminum, paragon bumper beam, to increase air flow across all the radiators then drilled it out to the max. we lowered the front registration plate for better airflow through to the radiators and fitted the upgraded Bosh high flow circulation pump. The system gets flushed out about every two years and the radiator checked and cleaned for bugs and dirt nearly every Sunday. (The cross beam has now been painted black to hide the lost teeth look). I've looked at the other cooling options but each has its downsides. The car is running great, it works, it doesn't overheat but I'm always looking for something more.
The big toothy grin!!

 

We don't use front number plates in PR, and that's how it should be everywhere else tbh. But the priorities were the transmission leak, tuition, and other education related expenses.