My 1999 Jaguar XKR has started overheating when it is driven hard. It will run all day if I stick to 70 MPH and pull away gradually, but if I start accelerating hard etc. it overheats very quickly. Is this likely to be a radiator problem? the car runs very well and there is no oil in the water or vice versa. I have removed the thermostat, what is the next step? I am also struggling to acquire a radiator, does rad flush help?

 

A new thermostat is a good idea, but do you know if your fans are running?

Obtain a 100 ohm resistor with wire leads (any wattage). Unplug the coolant temperature sensor (gray two pin connector, front and center on the top of the engine). With the ignition fully on, and engine off, 'plug' the resistor into the contacts on the harness side of the connector. If the fans start, all is well with the fan circuit and controls.

If you have an OBDII reader, also read the coolant temperature cold and warm and see if cold is ambient and warm is about 85-100C. This will check the temperature sensor. Also the fans should turn on at about 101C.

 

hi, yes the high speed fans are coming on, I have removed the thermostat so that can't be causing the overheating.

 

Do not run with the thermostat removed....replace it with new. The thermostat must be in place for proper coolant channeling in this vehicle. Running without a thermostat is not a valid test on this engine.

 

Your statement that you are looking for a radiator and have removed the thermostat, makes me wonder if you have recently removed/replaced the coolant.
Could you have air trapped in the system due to an improper purge?

 

If you overheat a Jaguar V8, you could be struggling to find a replacement engine and not just a radiator. Overheating the V8 is an engine killer and the forum is littered with reports of disasters.

S N G Barratt (UK) list the 1999 XJR radiator (P/N MJB4190BC) as a 'special order only' item but it is available.

SNG Barratt - The Ultimate Jaguar Parts Specialist

Removing the thermostat is alright as an emergency fix for a sticking thermostat to get you home but not for normal running. The XK8/XKR cooling system is a low volume/high flow rate system and a properly functioning thermostat is essential for correct circulation.

Graham

 

+! to air. Did you remove the plug from the top of the intercooler to bleed?

 

Hello all and thank you for your ideas.
The car has suddenly started overheating, it has not boiled over (it has got very close) and yes I have purged the system correctly. My thoughts are that the radiator may be not giving the full cooling capabilities as the car runs very well and I have not let it boil so I am doubting head gaskets and engine damage at this stage (also trying to avoid any chance of it).
Do you need to empty the air con system to remove the rad? I do have a rad dealer that will attempt to re-core the rad if I take it into them.
Any help or thoughts are appreciated,
Gerard.

 

Is the radiators clean and clear of obstructions, over time dirt ,dead bugs, leaves, can get caught in the fins and restrict air flow. Try a good degreaser, cleaner spray and garden hose and flush them out. Try to do it were you can see what comes out, a lot gets trapped between condenser and radiator. No you don't need to remove condenser to pull radiator, can be a little tricky but can be done. Pull panel on top of radiator it will give you good access top.

 

I will give it a go at the weekend, thanks dieseldoc!!

 

It is possible that the cap on the coolant overflow tank has a bad seal. It is essential that this system be able to hold pressure or it will overheat. Consider replacing the cap...it is an inexpensive item.

 

could the radiator be plugged up some???? He says at hwy speed, holding 70 it is fine, it is when he gets on it that the car heats up. At those speeds do the fans working or not even make a diff in colling???

 

If this problem has only started during the current warmer weather in the U.K. my guess is silicate drop out and you're on the right track with a recore.
As others have said check the simple stuff first but I used to see this regularly in the UK whenever the weather warmed up - during the winter months the same vehicle would run fine.

 

HI i have a 99 xkr and recently noticed water from the over flow after i have turned the engine off and left the car a few minutes i can also hear gurgling noises the temperature gauge it on half way and i believe i have purged the system correctly, i have ordered a new expansion tank cap ,does anyone have any other thoughts on this they would be appreiated.steve

 

Welcome to the forum. The temp. gauge will read halfway until the engine is on the verge of failing, then it will jump into the red zone. Replacing the cap is a good idea, but did you remove the plug on the top of the intercooler to bleed the system?
If you require assistance with a problem it's more efficient to open a new thread, especially if you start with 'new owner needs help with.....'

When you have time please visit the new member area and introduce yourself and your car:
New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

 

Thanks for the reply,I bled through the large allen key on the supercharger(hope this is the correct way) i have noticed that the hoses are not rock hard as it would be if it was overheating .steve

 

Read your actual operating temperature with an OBDII scanner. If you are over about 210 F (99 C) while cruising something is wrong (usually thermostat or water pump failure). The gauge will not indicate red until you approach 235 F (113 C).

 

Remove the water pump and check the fins that spins the water,do this now, before the engine fails. Clean the old gasket off if necessary slowly using a copper penny or razor, apply a light coat of black rtv to prevent leaks.

 

many thanks for the advice members ,the problem was the expansion tank cap best £13 ive
spent in a while

 

Just parked the 2006 XKR (owned since new, 57K miles) in my driveway when the A/C started blowing warm air, the red overheating warning light came on and the water temp gauge pegged. I shut the engine off immediately and checked the oil dip stick -- no water in the oil and the oil topped up. After the engine cooled, I checked the coolant level in the overflow tank and it was topped up. For the previous three days, both engine cooling fans ran for two minutes after I shut the engine off which is unusual. No hard driving. Usually the fans shut off when the engine ignition is switched off.

I have absorbed the three recommendations in this thread about bad coolant cap, bad water pump and bad thermostat. Does anyone have any diagnostics to suggest short of replacing the lot or dis-assembly.....Thanks