I did some work on my car a few weeks ago and the cooling system was emptied to allow disconnecting the coolant reservoir. It staid like this for about 2 weeks.
Everything back together, coolant to the level, checking, no leaks, good job!

A few days later I did a drive test for about 80 miles, and 30 miles after the start, coolant level low on the screen. I drove the car slower and the light goes, I was out of any water source in a Nevada like landscape. 10 miles later, I reached the destination and filled with some water (I was surprised to see that no pressure escapes when the cap was removed).

Now, coming to the problem... yesterday I drove the regular 10-12 miles to my home,the car runs like a rocket, with S pressed and it kicks like a sport car.

Today, I was gone to check the water temperature with an OBD tester and it was right ( from 92 C to 86 C in a few minutes standing with the engine running, only P1111 code). Then, going the 10 miles back, I just seen that the kick-down was not present anymore, even with S pressed.
The car was lazy maximum speed seen was only 80 mph and a few miles later, the Restricted performance , Traction control and other deadly messages stroke on my screen (I was so stressed that I can't remember any other message).
I putted it on N , stopped the engine and a quarter mile later I stopped the car. Dad, bring the Land Rover and the rope...

But 1 minute later, I cranked it, it started and no more messages for the next 2 miles.

Both fans were on, and a hissing noise from the throttle body was very obvious with the engine off but the ignition on.

Any idea?

Ah, and I just fitted a new harness to the gearbox, but what is the link with the soft water hoses and no usual hissing when the cap is removed?

 

It's not unusual to have a air lock when the system is refilled. Keep watching it and avoid long drives without carrying extra coolant. You are using anti freeze, aren't you?
The noise from the throttle body is probably motor, which is usually more of a whine than hissing sound.

While the car was sitting the battery may have run down. Make sure it's fully charged. A lot of strange events and codes can occur if the voltage is low.

 

Did you reconnet the two small hoses at the front of the resevouir correctly? They appear to cross each other if connected correctly.
I suspect the RP is not heat related, but something else, like did you wet any of the electrical connectors in this process? (like the knock sensors at the front of the engine)

 

Thank you for the answers, yes I have antifreeze, the winters here are very cold, it's only now when I topped with pure water, about one quart.
Voltage may be right, I am familiar with the message Traction control related when the engine starts sometimes (after long periods without starting it), but not this time.
The tank was off only from the bottom hose and the top overflow thin one, the other two were connected all the time,they are numbered anyway.
The coolant flows in the tank when the engine is running(pump is working...), the level is one inch bellow the top of the tank when cold and it grows up in the neck of it after a few minutes running.
I don't know why the hoses are not firm and the noise of pressure relief is not as before when I am removing the cap. I can hear a little noise only , to the overflow tank when the engine is hot, but I expect the coolant to pop over it when the engine is at normal temperature and cap removed.

Is my low performance(only 80 mph when it supposed to be 110) related to this or something else?

A drum may be out of discussion as the car worked well after.

 

Yesterday, I did some more research, I cleaned the cap with some lime removal solution, and seems that the hoses are firm and the cooling is normal.
I cleaned the pins of the gearbox harness, checked other connectors in the engine bay, and test drove it for 1-2 miles. It seems OK, but still no kick-down effect.
Then I remembered that last week I did also some work on the center console,removing the gear lever cable (the two 24 mm nuts ) from it's location to recover a lost nut.
This reminds me that it may be misaligned, 1-2 mm causing the gearbox lever not being fully engaged in the proper gear.
I will search for the right adjustment procedure and I will try again next days.
Question, if the cable is misaligned, it will throw an error code (scroll of death) right from the beginning or it can happened only when the oil is hot?

 

The cooling can be out of discussions, I just bought an ELM327 (piece of crap, just a demo software was provided, but good for the temperature and rpm), and the temperature is between 90 C and 98C when driving , with fans kick in at 96C when parked and off at 91C. The hoses are pressurized, the heater,works, maybe it's OK with the cooling.
The kick-down effect, even if my car have a blank pedal stopper, without wires, is still missing, maybe it works a little with S pressed, but not like before when the sound of a bad *** motorcycle was present at a blink of an eye.
Any thoughts, except "did you checked your gearbox fluid level?"

No codes stored.

 

Does anyone have a sketch or picture of the correct hose hookup as I am having a similar problem of losing enough water to trigger a low coolant alarm once a week.

 

This is how they look from the top on my 2001 XJR, don't know about yours since it was originally RHD.
Vector

 

You could also have a bad thermostat. Fill it up with coolant and let it run with the cap off so the air can escape to get rid if the air in the system.

 

Guys you are awesome, after I rebuilt my cylinder heads (see the thread Restore oil treatment blows cylinder head) I must have got the lines switched.
1 photo has solved my problem,VECTOR thank you, thank you, thank you.

 

This has happened twice this week.

 

So, my ELM327 works now with my Nokia mobile phone, using a Symbian software,more complex.

The temperature is right, so no problems with the cooling anymore, it was just an airlock probably.

 

After a few miles more, monitoring the engine temperature (88-92 C degrees during high speed driving) I am sure that the cooling is right now on my car! Just to be sure that this kind of problems are out of your cars, bleed your cooling carefully, using the heating in the same time and topping up the expansion tank. I am pretty sure that engine temperature is one of the most important data on our aluminum engine cars and a simple system like an electronic gauge can save a lot of money.
After the last hard reset and 100 miles more, the motorcycle sound is back when S is pressed, but still not P1111 on the tester, just P1000.

 

Or a RealGauge upgrade: RealGauge - TheJagWrangler

 

Not for me, I like figures, and other prices. A dual gauge with volts and degrees is perfect for me.

Today, while driving my Land Rover Discovery 2 , (td5 for the experts, aluminum engine too ), suddenly I heard a belt noise. This was never happened for the last 5 years, so I plugged in the tester while driving,( Hawkeye), and searched the live data; temperature was 108 C and going up... I stopped in a quite place near the shop where I am doing the hard repairs usually (closed of course , it was Sunday) , and pulled the bonnet... the top hose was punctured and the coolant was everywhere. I was lucky to have a spare one at home and one hour later it was fitted, but with my eyes and mouth full of coolant taste.

Lesson... use a temperature gauge,with the sensor fixed to the engine's head to watch those old cars engines, you never know... Loosing the coolant can influence the standard sensor data too.


On the Jag, I adjusted the throttle cable as seen on the XK8 sub-forum, and my rocket-motorcycle combination is back again!

 

Well, my problems were not solved, I can see the P0121 code most of the time, I suspect a faulty throttle body, a new thread was opened more updated to the actual symptoms.
https://www.jaguarforums.com/forum/x...ailable-95605/