Bought the car just a week ago. When I got it home I noticed the metal core of the radiator had started to break away from the plastic end cap and was leaking. Looked like the top rad hose had been bulging for sometime.

So I ordered a new radiator and fitted it yesterday, managed to get all of the air out of the system and let the car idle for a good hour, fan came on twice, top hose was pressurising slightly but nothing more than it should. Also done a sniff test on it with block tester to check for combustion gasses in the coolant tank, all clear.

Today I took the car out for a run, temp gauge didn't move above half way and heaters were blowing warm constantly, drove it hard for about 2 miles and then stopped in the petrol station, gauge was still at half way. Had covered about 15 miles

When I opened the bonnet the top radiator hose was rock solid, paid for fuel and jumped back in the car. As soon as I put the ignition on it came up with high engine temp and temp gauge in the red, started the car and within 15 seconds of driving (accelerating lightly) it dropped back down to half way where it had been.

What are peoples thoughts, is the system pressurising when the charger is forcing air into the engine or is this likely to be a thermostat or water pump issue? The heaters don't seem to blow that warm unless the idle speed is raised to around 3k. I'm unsure what to try next...

Thanks

 

Can't see it being the charger in any way.

See what others say...

 

Anyone have any ideas, is it worth changing the thermostat first incase it's intermittently sticking?

Cheers,

 

It's going to be in the cooling system somewhere.
Be careful not to roast it, the temp gauges are not the most accurate.

 

Doesn't sound like tstat. Do engine main cooling fans run high speed? Maybe check fuses & relays.

Dash temp gauge "lies" (smooths temp in annoying manner, hides true value till too late) - either use OBD tool or possibly put dash in ETM. See below:

 

I'm not sure that you've got all the air out of the system. Try bleeding it again.

 

OK. Just changed the thermostat now. When the ignition is first turned on you can hear the charge cooler pump running and opening the nipples on each charge cooler reveals no air.

BUT, should the main aux rad pump be running too as it doesnt seem to be or does this only run after the car is turned off after a run?

Thanks

 

Taken the car out for a drive, temp didnt rise above half way at any time and didn't go above 100 degress reading via OBD. When car was left to idle, even though rad fan was running temp would increase from 100 to around 105 and heaters blowing cold.

As soon as the throttle was kept at 2500rpm for 30 seconds, the temp dropped to 94 degress and heaters were blowing red hot. I'm assume there is a restriction in the system somewhere and when the pump is run at higher speed the water pump is creating enough pressure to bypass it.

When the ignition is turned off with the temp at 105 degress I can't even hear the electronic secondary pump running and the rad fan stops as the keys are removed, so I suppose it's just going to sit there soaking in this heat

 

Heater should not be blowing cold at idle (so long as not set for cold!).

Temp should only rise a few degrees from heat soak when engine switched off.

 

Yes I know they should't be blowing cold at idle! Which is what im trying to solve, has the water pump broken down and the impeller is damaged, or is there an issue with the secondary electric coolant pump restricting flow until the engine rev's are raised

 

This looks like the Coolant Aux pump... 2004-2005-2006-2007 JAGUAR XJ8 XJ8L VANDEN PLAS ELECTRIC AUXILIARY WATER PUMP | eBay

Should this be running at all times when the car is running then for a certain time when its off, any ideas? If it's supposed to run constantly then that'll explain why the heaters are blowing cold at idle as water isn't passing through it.

 

Look at elec diagram in JTIS

 

Sorry I'm new to these forums. Where is that located on here?

 

Quick update, if the car is driven at ateady pace and under 2000rpm the engine coolant temp on OBD will sit between 98/100, the coolant fan is constantly running. If you open it up and drive it hard the engine temps drop to 90 degree's and heaters become warm. Indicating to me a faulty water pump i'm thinking?

 

At this point I would take the car to a mechanic and let them sort it out for you...

 

Can the JTIS diagram be located online, of not i'll remove the pump and test the wiring pump separately.

ediit: whoop found it... https://www.jaguarforums.com/forum/s...-guides-41364/

Cheers

 

Today I have removed the pump and put power to it directly and it doesn't run atall. Have done a sniff test when the car is warm and it still didn't turn yellow.

I've attached photos of knackered AUX pump and also the main water pump. Does anyone think that the impeller blades on the water pump look blunt and not as sharp as they should be, the impeller seems solid on the shaft...?

Cheers

 

I had a similiar problem on my 4.0 s-type 2001. Finally boiled it down to a small leak in the one of the head gaskets. The car would overheat from tim eto time, use a slight amount of antifreeze and pressured up the cooling system.

 

Have same problem with my car, temperature were not going up more than quarter,after upper radiator coolant hose replacement. But when it reach it ones, plastic part of hose just burst in the middle. Already spend $1K on mechanic and no one helped. Two hoses and thermostat were changed. Mechanic was recommended as a great professional on this forum Only thing he said was drive with AC - on, it cool down car faster.

 

I know this thread is a little old, however these Jags seem to all share the same symptoms when the AUX pump dies, or starts to wear out. Here is a brand new one for $192.10 on PartsGeek:

05 2005 Jaguar XJ8 Auxiliary Water Pump - Cooling System - Genuine - PartsGeek