Coolant Change Procedure

[ibnct]

Thought I'd do a nice simple Coolant change on my 2004 Reg XK8 Coupe. Using the JTIS CD Workshop Manual as a guide, I raised the car on Axle stands all round, ensuring a very slight nose down attitude to ensure good drainage. On opening the radiator drain cock I was rather disappointed to find that only 5 litres of old coolant came out. (I was expecting 10 litres)
I double checked the JTIS procedure and at no point does it mention the need to remove an engine block drain plug, although there is mention elsewhere that a drain plug exists at the rear of the cylinder block behind the starter motor. At no point does the procedure refer to removal of this plug, however unless there is some sort of syphoning action, I can't see how else the engine block would drain down
I tried to locate this drain plug, but unfortunately the limited clearance under the vehicle meant my eyes could not focus sufficiently to see clearly what I was looking at. (Oh to be a young buck again )

Can anyone confirm for me whether it is indeed necessary to open the engine drain plug, and if so, provide me with tips for locating and removing this plug easily. If plug removal is not necessary, does anyone have a clue where I might be going wrong and perhaps provide me with the correct procedure

[J44EAG]

On my V8 S, I just dropped the bottom hose off, disconnected the top hose, removed the thermostat tower cap and header tank cap and let the lot go into a couple of washing up bowls. Then I hosed out.

Mike K

[ibnct]

Would be nice if it were that simple. Both top and bottom hoses connect to the Coolant outlet duct sited high up on the engine. I can't see how this allows the block to drain down without some sort of syphoning action which I don't appear to be getting

[J44EAG]

I`ve previously removed the top thermostat tower nozzle and the thermostat. That should allow a drain down via the lowest point. Removal of the thermostat bypass hose also helps.

M

[aaj]

My recollection is that the Water Pump is the lowest easily removable object at the front of the Engine (it sits below the Thermostat Tower detailed above)

Be careful when draining the system as the Coolant makes the Drive Belt, Tensioner & Idle Pulley 'Squeak' for around 4 months after they get a soaking in Coolant. Alternatively These parts can be replaced if you want to be 'squeak' free from the off.

Regards

[ibnct]

Thanks for all discussion & advice so far, particularly regarding belt squeal.
I'd really like to understand why the procedure laid down in the JTIS CD doesn't result in a full 10litre drain down. Are there any other 4.2L XK8 owners that have followed this procedure and managed to drain down more than 5 litres
If necessary, I'll just have to investigate further to try and locate and remove the engine block drain plug.

[mike020150]

My ever so slightly cynical take on this matter is that it all about design lives. Manufacturers have design lives for major components and providing an acceptable (to the marketing department) proportion of components reach the design life whilst employing minimum servicing, that's OK by them.

An example most people will be familiar with is the servicing of auto transmissions. Once upon a time, these had drain plugs for the torque converter and the transmission sump. 'Progress' first dictated elimination of the converter drain and the subsequent partial oil changes were stretched to 30K miles. Today, admittedly with better transmssions and improved lubricants, there are no drain plugs and transmissions are 'sealed for life'. The chances are that modern car manufacturers are designing for a 200K km (125K miles) life or similar. At typical annual mileages, that translates as 10 years. Vehicle manufacturers want us to buy more cars, not keep them forever, so what is wrong with this level of design life? Well, for we enthusiasts, 10 years is nothing especially when a little extra servicing can add 100k miles to a vehicle's life!

Jaguar's current recommendation for coolant changes on the 5 litre engines is 10 years/ 150K miles - hmm. Fortunately, there is nothing to stop us changing coolant more frequently and backflushing with a hose even if the task isn't as easy as it once was or is one that is no longer recommended by Jaguar. Mike.

[ibnct]

Weather permitting, I'm going to have a more determined hunt for the engine block drain plug this weekend. It occurs to me that if Jaguar dealerships are using the JTIS procedure to drain down the coolant, could it be that they too are only changing 5 litres of fluid each time?