I have a late 1998 XKR with 65,000 miles on the clock. It runs like a train and has been well looked after. About 6 months ago 2 things started to happen each time I took it out. The main thing was poor heat from the heater and by October, when you start to need it most, no heat at all. The other thing was occasionally low coolant light would flash on, normally going up hill or under acceleration. It would go off again when breaking or going down hill. As the level sensor is at the back of the expansion tank this made perfect sense, and the level was only down a small amount. Top it up and it would be fine for another 50 miles then same again, but still no heat. I asked around and the consensus was an air block around the heater and if I kept filling the coolant up, eventually it would clear. Wrong. We refilled the coolant and followed the the fill procedure from the XK8/R workshop manual, high revs etc, and the heater started to work. Brilliant! Next week took it for a run, no heat and coolant low again. Manually change into lower gears to keep the revs up and heat started to come through. AUX HEATER PUMP! I hear you shout. That's what I though too. Almost reached home and noticed the engine temp light on and the needle at the top of the gauge. Must have got there instantly because it has never moved from the centre of the gauge before. Stopped the car immediately, opened the bonnet,(hood for our friends across the pond), fans were running, engine smelled hot. Let it settle, started it up and an enormous cloud of steam poured out the exhaust. To cut a long story short, right hand head gasket failed at cylinder 3 (full of coolant, but very clean piston). Now trying to get head off but 3 head bolts are jammed solid. Broke 5 13mm Snap-on socket heads and now rounded a couple of bolts. Any ideas greatly appreciated.

Once the engine was stripped down we though at least we can now get the aux heater pump out. Still not easy, but managed it. Even with hose clips off the pipes were seized on to the heater matrix. Gentle twisting with grips started it moving, once it started moving it came off fairly easily. Did the same with the heater valve and the first connector broke. Valve scrapped. Hoses actually come off the plastic much easier than the metal connector on the matrix, so don't use grips. A screwdriver on the end on the hose then lever it back works well enough. Got the pump out, connected it up to a battery and it worked fine. B*****ks! Heater matrix jammed solid. Managed to clear the matrix to the extent that we can pour water through it and it flows out the other side. Lots of white calcium or limescale in the stuff coming out. Flow looks at little slow to me so think it's still partially clogged. Anyone know the best way to clear the crud?

 

Block one pipe then fill the matrix with de scaler and leave to stand. Then back flush the matrix until you get clear water.

Jim

 

Welcome to the forum gander,

The limescale etc sounds like the PO has been using hard water instead of 50% Coolant/50% Distilled Water mixture and possibly the dreaded Bar's Leaks if there's been a persistent leak.

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

 

De-scaler worked. Back flushed and lots of white flakes came out. Running free now, hope the problem is cured. Just need to rebuild the engine.

 

Man, I feel for you. My XK8 was packed with Bar's leaks when I bought it. Luckily for me a hose blew before the head gasket and I discovered it. I had to flush with de-scaler 3-4 times to clear it up completely. Good luck with the rebuild.

on a side note, I was in line behind a guy at the auto parts store not long ago. He was purchasing 2 cans of Bars Leaks. It was difficult to resist smacking him in the head with the breaker bar I was buying.

or we could talk about my wife's new car. A 2 year old Honda. They fixed a couple of paint chips with white out. Looked perfect until we washed it.

 

Engine rebuilt with 4.2 MLS head gaskets and purring like a little kitten. Importantly for this thread we have heat, lots of it. Blocked heater matrix was the problem. Lesson learned, don't mix coolants, use distiller water not tap water in the cooling system.

 

Here in Hampshire (southern England) the ground is solid chalk about 5 miles deep. The water is so hard it sometimes comes out of the tap looking like watery milk! But I have a water softener - and the normal installation is for the 'mains' tap to be direct off the supply, and the branch up to the storage tank has the softener fitted in it.

This means that the hot water circuit, and any other downstairs taps (downstairs loo etc), has a soft water supply. So fill your rad up with water from either a hot water tap, or a downstairs loo tap.

 

The problem with softened water is that you are replacing calcium with salt water. It is much better to use distilled or deionized water.

 

Not quite RJ - the salt is only used to drive out the Sodium and Calcium ions from the resin bed when it is saturated during the regeneration cycle. The softener does not add salt to the water as regeneration takes place either in the dead of night (no water usage), or offline in fancy units.

After regeneration there might be a trace of salt left on the resin but the first water usage washes it off.

 

Sorry, did not state that clearly. The calcium is replaced by the sodium in the exchange media, not sodium chloride. But it still means that the cooling system has a higher conductivity than distilled water.

 

Guys, 5l of distilled water is £2.50 at halfords. Doesn't make sense to risk using anything else.