G'day all,
I've noticed I am quite often having to top up the radiator fluid after any kind of decent drive. What could be causing the car to lose so much coolant? I can't see any obvious leaks.

Has anyone added an expansion tank to their S?

cheers

Brent

 

What level are you topping up to ? There is no expansion tank on these cars, so room has to be left at the top of the radiator to allow for coolant expansion. The original handbooks told you what the level was. Certainly if you top it up right to the top, you'll lose some of that coolant. For cars with an expansion tank, one normally fills the radiator full, (like with my 1977 MG Midget 1500), and the expansion tank is where the coolant expands into.

 

I'm having to add a couple of litres, this after a 50 mile round trip

 

I fitted one to my ‘66 years ago from memory it might have been from a austin/Morris 1100.
I’ll post a picture later.

 

expansion tank versus recovery tank.

That is the question.

you are probably thinking recovery tank, where the coolant flows to when the pressure cap's valve opens and coolant flows out of the radiator, so it doesn't end up in the ground.

an expansion tank requires a sealed radiator, and any filling is done at the expansion tank, such is the system in the Series 3 XJ-6. In other words, the "Radiator Cap" at the expansion tank does not have a pressure spring valve which opens when the pressure inside the radiator exceeds the pressure capacity of the radiator CAP.

What CAP do you have? 7 lb., 12 lb. or higher? You should have a 7 lb. with a recovery tank. Any tank, plastic, metal, it does not matter as long as it fits somewhere near the radiator and the bottom nipple or "hose port" of the tank is lower than the hose at the neck of the radiator.

The theory is to create a vacuum by always having one third of the recovery tank full of coolant, so that when the temperature of the coolant goes down, the coolant that was expelled from the radiator will be sucked back into the radiator. That is the THEORY.

Whether it works in practice, I'm not sure.

 

Actually I think it might be indicative of a larger problem It is chewing through coolant now, I drove it yesterday and it was running rather badly and began to overheat very quickly. I cannot see any oil in the coolant and (although Ive not been able to check since yesterday) I have not found any coolant in the oil. But there is something clearly not right, one of the core plugs (I think that's what they are called here) looks a bit doubtful.

There was a fair bit of smoke coming out the back, although it doesn't appear to be oil smoke. Could coolant be getting into a cylinder??

 

You should do a pressure test. If you see no leaks (and at that rate you would) and it is not in the oil it is being introduced into the combustion chambers (read blown head gasket). Give it some attention as you do not want to have a hydro lock!

 

I think George is right, sounds like head gasket, smoke will be white with water vapor and more than when just cold, also the pressure from the cylinder can over pressurize the radiator and blow the water out of the overflow, this can happen before the engine warms up.

Oil smoke is blue/grey rather than white which is water vapor, quite normal to get some white smoke when the exhaust is cold as water is a by product of the combustion, but it should go quite quickly any longer and water is getting into the cylinders.

Try to diagnose it as quickly as possible so you don't do any further damage, a pressure test can show the leak, if the pressure rises when you start the car, you definitely have a head gasket problem.

 

Does this smoke happen when you use the Heater?

take a very close look at your Heater Valve (Heater Servo), with engine warmed up and running;

If your Heater Valve is the ORIGINAL, or ORIGINAL TYPE, look to see if coolant is coming out of the "weep hole" on the left side of the valve. This means the inner diaphragm of the valve is torn and this could account for the loss of coolant, it comes out in droplets.

In my S type, a huge cloud of white smoke would come out the exhaust pipes and this happened whenever I used the Heater. As soon as I turned the heater OFF, no more smoke. I was also having the coolant loss issue. I can only guess that coolant was getting into the intake and being burned in the combustion WHENEVER the Heater Valve was in the OPEN position. (i.e., the Heater was being used).

Unfortunately the original Heater Tap / Valve / Servo is no longer available, but you can use any aftermarket Heater Valve that is NORMALLY CLOSED and Opens With Vacuum.

also any replacement Heater Valve must have 5/8" ports and 3/16" vacuum nipple.

I got a replacement Heater Valve for a 1965 Ford Galaxie which works perfectly if not better. The Made in China variety. It is NORMALLY CLOSED, with 5/8" ports and 1/8" vacuum nipple, so I had to get a stepped adaptor for the vacuum hose. No big deal.

 

Good point Jose, I forgot the s type vacuum heater valve.

 

Hey buddy You should know that I haven't got any heater controls after our marathon effort to identify the missing vacuum tank I'm looking for

 

TilleyJon,
the S type's Heater "Tap" (as the Service Manual calls it), is or was a wonderful and beautifully made part. But they wear out inside and kaput!

I have purchased 6 of them (used), and they all were dead on arrival. I even separated one of them into its two halves to study it, and there is a large Bell-shaped rubber diaphragm inside which I assume shrinks and expands upon applying vacuum and this diaphragm ruptures after 30 years. Enter the weep hole to let you know it's dead.

But the symptoms of a ruptured diaphragm are exactly as he describes, which understandably can be interpreted as a blown head gasket. But no, in my car it was the Heater Tap causing the cloud of white smoke as I described.

And he says there is no oil mixed with coolant, so it must be the Heater Valve / Tap / Servo causing the coolant loss and cloud of smoke.

How does a ruptured Heater Tap diaphragm cause coolanmt to enter the intake? That's a question for George, not me.

 

Aye, I was wondering if that was the case but hoping there would be some esoteric bit of Jag knowledge that could have meant something else.

I'm not sure where to find a pressure tester, to be honest though since the car is fairly new to me I had been planning on reconditioning the engine, I'd hoped to be able to drive it around a bit a little more first but I think it might be time to pull the head off and have a look.

Any recommendations as to where to send it to be reconditioned? I'm in London.

 

here's the original S type Heater Valve part number C19704 dismantled to see what's inside.

 

here's the original Heater Valve C19704 (only used in the S type and some Daimler Limos of the same period use a somewhat similar valve but it is different).

 

here's the replacement Heater Valve I use in my S type

 

Take it to Tilley Farm in Somerset. They'll fix you up.

 

If you want to trailer it up here I will happily help, I have a fantastic machine shop just up the road, if you want someone in London, a friend of mine had a garage in Wembley, he may have some good contacts up there, PM me and I will see what I can do.

 

If there was quite a bit of water on the vac side it will get sucked down the vac lines into the inlet manifold and then out the back end in steam !

 

I'm quite near wembley actually, but I will send you a PM, I'd be quite keen to be able to do some of the work myself although it's got to be about 30 years since I have changed a head gasket!!!! The lower timing chain is very noisy so it has to come off soonish in any case.

cheers