None of this was solving the coolant leak!
The car has a history of loosing drops of coolant in the distant past – immeasurable in the grand scheme of things – never enough to cause a measurable drop in level, but enough to put an occasional drip on the garage floor after hot shutdown. This was a long time ago however; the coolant leak was sorted under warranty when the car was less than one year old. It would transpire that the dealer solved the leak by tightening the heater bypass valve (a vacuum operated valve which shuts off the water flow to the heater matrix when the A/C is switched to cool) – which attaches to the cylinder head on the left hand side, under the inlet manifold. In tightening the valve, the mechanic had turned it, partially fouling the inlet manifold from underneath – which would make its presence felt over twenty years later in the form of a nightmarish experience removing the inlet manifold!!
The drip had returned a little while before I had the bodywork done. Shining a strong torch down between the inlet manifold’s pipes, I could see evidence of dried coolant building round the upper bolt which attaches the water pipe which returns water into the side of the engine. This isn’t a common problem – but nor is it unknown. It tends to develop very slowly and does not lead to a catastrophic loss of coolant if it suddenly worsens. The rubber pipe which runs from the pipe to the water pump
can do this however: it is invisible and swelling and deterioration can go unnoticed. Consequently it can fail – generally under load, with the loss of all the coolant very rapidly indeed. The Jaguar AJ6 engine is one of the strongest of any car: it will generally shrug off a loss of coolant in this way without damage. I know of several cars which have suffered in this way. None of them blew a head gasket or suffered other damage, despite more than one loss of coolant at speed in the fast lane of a motorway!
The leak worsened considerably in the time the car was at the painter. By the time he had finished it was enough to produce a pool under the car! It didn’t seem to phase him and he didn’t bother to tell me about it, which displeased me. He didn’t bother topping it up either – and it was somewhat low (though not seriously so) when I picked the car up. Tough as ever, there has been no damage done.
With the inlet manifold and thermostat housing removed, the water pipe is visible along the side of the engine. The water rail had leaked for some time – there was a small but noticeable build up of dried coolant all around both the top and bottom bolts and I worried that the bolts would be corroded. I need not have worried though – all four of the bolts were clean, untarnished metal. The coolant has been replaced every couple of years since the car was new – the lack of corrosion is my reward for that.
At the rear of the engine you can see the heater shutoff valve. This had turned up when tightened clockwise which prevented the manifold from coming off. It was VERY difficult to remove in situ, but I had no choice!
Together with the old one: I replaced it with a genuine Jaguar item – happily, in common with nearly all the other parts for the car, it was marked ‘Made in England’. I believe some of the aftermarket ones are made in Mexico.
I took the opportunity to replace all of the hoses and the coolant. The hose behind the water pump is especially difficult to replace when the manifold is on.
Making sure the new inlet manifold gasket fits – I bought it from Jaguar, but it is not the same as the original three part gasket with a plastic spacer. The new gasket is a one piece affair with the card parts glued to a central (plywood!!) spacer. I need not have worried: it works well.
Now the thermostat housing is fitted to the front of the engine and the last two water pipes attached to it and to the engine itself. This leaves only the heated air breather and its two tiny pipes and the expansion tank to do after the inlet manifold is fitted.
Now it was time to put back the inlet manifold. I was concerned by some slight scratching on the mating surface – possibly done when I was trying in vain to get the damn thing off! Indeed, I asked whether it needed to be re-skimmed on the ‘Jag-lovers’ forum. The general consensus was that it is fine – as it proved to be. I have not suffered any air leaks.
Here it sits waiting for its moment in our (very messy) utility room.
And back on! – This was exceedingly easy now the water valve was on correctly.
The oil filler tube was refitted along with the idle air valve and heated breather and I connected the fuel rail. Some of the breather pipes were a little swelled, so I replaced all of them. All the vacuum lines were a little hard, so they were replaced too.
Connected and checked all the evaporative loss system on the inlet manifold’s underside:
And fitted the air flow meter and air filter housing:
Adjusted the throttle and transmission cable:
And it was done!
I had already cleaned the engine compartment, which had become very dusty in the painter’s workshop. I did this before I removed the inlet manifold, since I like to work in a clean environment. There is less chance of me contaminating something important if it is all clean – and I can see what I’m doing!!
I was also able to buy an NOS brake fluid warning label since the old one had become tatty. It must have had some brake fluid spilled on it many moons ago – so had dried out.
Under bonnet relays and the high pressure hydraulic accumulator and pump. Jaguar used this technology under license from Citroën.
