I've spent at least 3 years and untold thousands of USD trying to get Her Highness' temp gauge needle to run in the middle of the "N" and not two or three thicknesses above the "N" when in traffic during the evening commute home from work.

 

Trust me, been a lonnnngggg way down that road, every chemical flush, every filter. You need a new rad core no other word for it. Car will run 20% faster to.

Old Jag racecar mechanic did it for me...without permission. Best decision i never made. No half ***. measure will fix a shitclogged rad.

 

Do you have the correct thermostats in it? There has been a fair bit of discussion here about it, they need to extend far enough to block off the bypass ports, and most thermostats spec'd for the V12 don't move far enough. It's amazing what $10 worth of thermostats can do for the cooling system.

 

Did you do that?

 

You're not alone.

Somehow, somewhere along the line, the Old Jaguar community became obsessed with keeping that needle locked onto the "middle of the N" at all times. Personally I believe it's a fool's errand....and I don't mean that as an insult to you personally. But you may have spent thousands of dollars needlessly.

An increase in temp gauge reading does not necessarily spell doom. And a consistently 'normal' reading on the temp gauge does not necessarily ensure that all is well with the cooling system.

Jaguar itself eventually 'solved' this problem by throwing in the towel and joining the ranks of other manufacturers who use temp gauges that are heavily dampened and/or are designed to give a fixed "Normal" reading over a rather broad range of coolant temps.

The cooling system is no place for nonchalance, especially with a V12. But this whole "Middle of the N Bit Has Done Got Out of Hand" (apologies to Waylon Jennings)


Just my two cents

Cheers
DD

 

Doug
This point you make about the N on the gauge is 100% true, and I am so pleased someone of your standing has said it. Some examples:

• The Lutz mod will improve cooling but make the gauge run higher, as cool water is no longer short-circuiting through the front water manifolds
• The gauge is not a precision instrument; because of its design and the odd pathway the electricity has to take to get to and through the gauge, where any slight tiny corrosion will affect its reading by affecting resistance, no two 30 year old cars will read the same on the gauge for the same temperature
• I have electric fans, and I have an "on at 90 off at 85" OEM-style main fan thermostatic switch in the water pump inlet. This is because the fan was cycling on and off too much in traffic, as a surge of cooled or hot water kept it going on and off. So a gap between on and off was required. When the switch cuts in the water inlet temp is 90, and the gauge is halfway to the H. scary at first, but in fact the water temp is only 5 degrees higher than when the fan is off!
• I know my system is in top shape; anyone who believes their system is good solely because the gauge says so, is asking for trouble.

The moral is, know your car; know exactly what temp the inlet water is at for a given gauge position, by measuring it with a reliable and dirt cheap instrument available on ebay etc etc for a few dollars/pounds/euros etc etc.

 

Going thru the wiring, replacing connectors were needed, repairing wires and replacing when needed. Replacing ALL fuel, coolant and vacuum lines, nd stripping off some parts and cleaning up the engine bay. all total, 3 years

 

Right !

The gauges are notoriously flakey. A million years ago I compared 'middle of the N" readings with some other owners using infra-red thermometers. We found as much as 20ºF difference from car-to-car.

But, beyond that, I personally think there's too much fixation on coolant temp to begin with. It's coolant flow, more than coolant temperature, that should be the main concern....up to a point, of course. If the coolant temp increases a bit under certain conditions, there's no reason to panic....if you're confident that coolant is flowing thru all areas of the engine.

Thinking back over the years there have been owners who have insisted that the temp should never be higher than thermostat rating and, if it is, the engine is 'overheating' and there is a problem that needs correcting. They'll spend tons of money on this. Often needlessly, IMO.

The V12 cooling system is no place for nonchalance, for sure. But paranoia, I think, has emptied a lot of wallets and caused a lot of undue stress that detracts from the fun.

Cheers
DD

 

How about the longest for me that would be a weekend for someone who knew what they were doing?

Just check out my a/c threads that started over 3 years ago. Nothing like posting both your ignorance and your dumb stubbornness for everyone to see on a worldwide forum.

Plus I'm not finish yet!

 

We've all been there.

And I don't see anything in the A/C thread to be ashamed of anyhow.

I recently did something really, really dumb. So dumb it'll take me years to put together the courage to confess. Worsened by the fact that I should have known better.

Cheers
DD