Cooling System Upgrades

The mantra for Jaguar V12 owners is to avoid the engine running lean or overheating. Here is the journey I have been on to continue improving the cars cooling capability. Jaguar V12 expert, Roger Bywater indicates that the pre-HE V12 has a tendency to overheat even when operating as designed. Upgrades are in order……

The previous owner had upgraded the stock, clutch driven fan with a high flow flex fan. This fan moved a lot of air.

A couple of years back I had two instances where the water pump started to leak at the gasket. I replaced the gasket both times and noted that the bolts on the fan mounting were loose. This fan must have become unbalanced and was vibrating the water pump. I took this as an opportunity to make an upgrade I had been considering for a while.

The bolts on the fan mount were coming loose

I repurposed the check “Catalyst – EGR” indicator to be a “fan on” indicator.

Used a piece of window tint over the white lens

I have read that simply wiring an indicator light to the fan input can cause a false reading if the fan starts to rotate when the car is moving and generates voltage…..

……so I added another relay to be triggered by 12V to the fan for the dash indicator

In 2006 the radiator sprung a leak. This was another good time for an upgrade 🙂 I had the radiator shop re-core the radiator with the largest possible core. In 2010, the coolant header tank sprung a leak and another upgrade was in order….so I ordered a neat stainless steel version from Cathouse Spares. I was concerned that rust from the original steel header tank may be in the system so I also installed a couple of Tefba filters at the same time.

Radiator ready to be removed and re-cored. Its important to fill the gaps around the radiator with foam to stop that being an easy air path

New stainless header tank next to the original. I repainted the new tank with POR15

Installed these filters in 2010. Have recently taken them out as they never collected any particles (replacing the coolant often must be working) and they are an un needed restriction.

Unlike a normal car….the Jaguar V12 has two thermostats. In theory, one thermostat could fail and cause that bank to overheat while the temp gauge monitoring the other side indicates that all is well. Sounds like another upgrade opportunity…..I decided to monitor temperature in both banks.

Here is the stock series 2 console (with the wood trim I had added)

I picked up a center console from a series 3 junkyard car. The tray is higher and has another area for mounting the trip computer

Modified the trip computer area to mount three gauges and used the hole on the left for the cabin temp sensor which is mounted under the tray in the series 2 console. Covered the console with leather

Did some searching and found these 52mm gauges that didn’t look too modern and fit the feel of the interior. Needed to install resistors inline with the back lighting so they are as dim as the stock gauges at night.

Both thermostat housings have unused bosses that can be drilled and tapped for 1/8″-27 NPT temp sensors

FYI….as this is a rare model car, I realize that the stock items are important so any interior or mechanical changes are reversible and I am keeping all of the original parts wrapped up and stored safely.

In stock form, the car comes with one engine mounted cooling fan and a second smaller electric fan controlled by the otter switch in the water pump inlet. The large, all aluminum V12 gets very hot and takes up most of the space in the engine bay so heat soak after shutdown can cause problems with vapor lock and reduce the life of under hood electronics and wiring. An upgrade to address this was needed.

Using this adjustable air temp switch to turn on the fan and it is wired to stay on after shutdown until the engine bay cools down. This is also a failsafe in case the circuit controlling the main fan fails for any reason.

I don’t have any issues with overheating, but I am always on the lookout for ideas to continue improving the cooling system. Will update this post when I find them…….

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