Hello fellow Jag-sters !


My '98 Jag XK8, runs with a 4.0, Low Kw is having cooling problems. This is the best car I've ever had !
I've had the car for 4 years now (16000 miles), but not untill now has it developed any problems.

This is the biggie !
When the car is running idle, the temp will reach workingtemp arcording to normal, but when I start driving the electric fan will begin. If I turn off the heater, the fan will raise it pace to maximum, and the temp-needle will burst into redzone ! When I check the engine, the coolant hoses (Thermostat-radiator-block) is under really high pressure. If I slowly open the resoviour the pressure will drop and overflow the catchtank.


It's possible to drive the car through heavy traffic without overheating, IF I run the heater at Hi-full Blow. However as soon as I hit the highway, the needle will lie in perfect match to the middle, and the fan will stop blowing.

This is what I've done.
I completed an oilchange, into high-performance Longlife 5W-30.
I Flushed & replaced the coolantliquid.
I tried removing the thermostat and checked it in hot water. It did open.
The car will drive, but due to this problem, I parked the car for no-use.



My best idea is an airlock-problem - If so, how do I best solve the problem ?

Thank you !

 

So you say you have really high pressure ? Does this mean the hose swells ? If so stop driving the car and get the hose swapped asap. The hose feeding the thermostat housing is known for failing internally which blocks the flow of water and you over heat. Reduce the pressure/flow in some way and the pressure releases and you get flow. The temperature guage is a damped switch with three positions cold, normal and goodbye engine ! If you continue to allow this to happen you will need a new head gasket.

 

Welcome to the forum jackiracki,

The temperature gauge is not reliable - the engine will be seriously overheating before it moves towards the red. There's too many sad reports on the forum of Jaguar V8 engines destroyed by only a short period of overheating.

The first suspect has to be a sticking thermostat which you have already checked. Next, on an early model is possibly failure of the water pump impeller. The blades break off reducing coolant flow and blocking waterways.

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham