Following the welding and subframe replacement (See thread 'XK8 Rescue'), I've started on the engine work. Was just going to change the tensioners, but its a bit late, the right cam chain has been slightly chewed by a duff tensioner, and broken plastic bits have gone down the engine.

But to the point... the coolant came out a very cloudy yellow, which didn't look right. Now, as I take it further apart, I find a waxy white substance in the header tank, on the thermostat and in the top hose. It was sort of quite solid wax in the top hose, but is soft on the thermostat and a bit like a warm candle when scraped out of the header tank.

Is this some sort of radiator sealer? Is it just very ancient coolant precipitation? It doesn't appear to be water soluble.

Whilst I'm replacing the cam chains and pulling the sump off to clear it out, I might as well replace the head gaskets. The worry is what this wax has blocked up and where...

Any ideas?

 

It could be some kind of leak repair gunk or a reaction between incompatible antifreeze formulations.

It might be wise to flush the radiator and heater core. But even then it's hard to say how much has been removed. Try heating some in a commercial radiator flush and see if it dissolves.

 

Agreed. Flush your entire cooling system until it is squeaky-clean again before buttoning it up and refilling with the properly-designated coolant. Regardless of how your coolant gelling formed, it can be an engine-killer if it is not completely eliminated....

 

The IPO may have added green coolant to the orange coolant (or visa versa). I've read that could cause gelling, but I've never read of anyone's experiences after knowingly mixing the two colors. If this was the case with your engine, a good flush should do the trick.

 

I think I have come to the conclusion it's some form of leak treatment, but I could still be wrong. Somehow I doubt the previous owner would have known to use such a treatment, but he might just have grabbed any-old-cooling-additive to top it up, so it could be that...

Anyway, whilst it was quiet in the house (ie. all the important people were out), I took several waxy coated parts into the kitchen and experimented on them with hot water and soap. It turns out that with water above 90c, the gooey stuff melts and mostly washes out. It helps to agitate it a bit, or direct a hot water jet at it. I also think it helps to make coffee and eat chocolate hobnobs, it seems to take about the right time to let the water soften the stuff up.

Therefore a plan is hatching.... turn the heating system hot water tank to very hot, connect a hose pipe to a hot tap and flush out what remains of the cooling system. I figure that several sessions of fill-wait-coffee-hobnobs-flush should help get it out of the places I can't reach. Bearing in mind that the heads/cam chains are coming off, there shouldn't be too many places I can't check.

Can't wait for the next unexpected revelation... haven't got the heads off yet...

Best,
Nervous of Surbiton.

 

I think it's stop leak odd. That's the conclusion I came to with mine and it was much worse than your pictures. I used a commercial radiator flush (Prestone I think). Flushed and drained several times. The reason I think it was stop leak was when I was done flushing the second time the cooling system held coolant almost as well as a colander.

I ended up replacing the thermostat tower, the water pump, expansion tank, and many hoses. The good news was the head gasket didn't leak and the Jag has been running like a top for 3 years now.

However the experience left me with a heightened sense of smell. And I get a bit of a twitch when I get a whiff of hot coolant.

 

If you get your "whiffs" down to just an occasional dribble from the reservoir, I'd probably leave it at that. Many of them have micro cracks, even when new (as was mine).