The 'E' Type Forum

I have the coolant boiling when the motor idles after +- 15 min in the garage. The coolant overflows by the headertank cap hose . The temp is +- 100 c? ! . I have checked the coolant movement in the header tank which is quite significant when the motor turns quickly and slightly running when it idles. It is the same whithout the thermostat.( I have a new aluminium radiator) Looking at the waterpump, I saw a misalignment with the alternator pulley +- 3 mm . I have checked the waterpump and I Wonder if the impeller is at the right place //housing:





On the schema it seems that the spindle bearing has a "hole" in the middle , may be for the allen lockscrew, but I don't see any hole on my bearing ! but I can adjust the spindle just against the pump housing, so there is +-1/4 mm , and the spindle can turn without touching . My question is : is it the right position for the impeller ? By the way , if I fix the impellerspindle in that position Y have quite a good alignment beetween all the pulleys ( alternator, waterpump and motor). May be my cooling problem comes from the wrong or bad adjustment position of the impeller in its housing?

Yves

I am an Engineer and design HVAC hydraulic systems (amongst other things) and I can tell you that NO pump impeller would work correctly with such a large gap, it would cause cavitation and not generate much flow or pressure at all, even without a thermostat. The gap should be virtually nothing, I would even make it touch and carefully flatten any high spots until its a very close fit.

Thats your problem. Lack of flow and pressure so the water isnt circulating around your radiator much at all. The other thing to check is that the impeller is really tight on the drive shaft.

I believe the hole is just a vent, it doesnt seem to have any other function I can see.

Thanks Ian , that's exactly what I thought without your Professional expertise .... I can now fit the pump on the motor and test it again..... I'll give you some news in a few days....

I have fitted the water pump on the motor and started ..... but the motor had a lot of explosion noises and then a fuel leak by the overflow pipe of one of the carbs.... I have stopped immediatly the motor, and had a look inside the fuel chamber of the carb and saw the float under the surface I took it out with a suction pipe , it was full of fuel !
a leak in a weld edge ? so I have to wait a new float before a new motor start. I checked the 2 others floats which seem ok !

Common problem, happened to me too. You can buy an alternative solid float from Burlen Fuel systems that is a lot better than the brass ones.

Be careful Yves, so far you have overheated your engine and nearly blown it up

Hello Yves , the hole in the bearing is for the location screw and nut as you can see - if it dosn't line up something has been made wrong-(or the shaft is fitted the wrong way round ?). The impellor should be a close fit on the tapered surface of the water pump casting - I bet you will not find many pumps that are really close here - the manufacturing tolerance is quite wide nowadays (read not as good as it used to be) . The hole in the casting is to drain off any water that has got past the mechanical seal (which works through spring tension) the rubber 'flinger'that slides on the shaft facilitates this - if a lot of water - not just a few drips- comes out of this hole then your water pump seal is unservicable . If the hole were not there your bearing would get water in it and soon fail.
Another thing , both the tanks of the radiator should be warm when the car is up to running temperature , if not then the thermostat is not opening . Finally do not use the modern type of thermostat ,use the old type with the bypass shield which blocks off the small bypass hose under the manifold when the 'stat opens.

hope this helps Barrie

Thanks Barry, I'll try the motor soon when I'll receive the new carb float..... ! and test the old thermostat .....

Mine sank. With care they can be re-floated. You will need a 1mm approx drill and some solder and soldering iron, some fine sand paper or an emery board or a fine file and a short piece of rubber tube.
First drill a small (1mm) hole somewhere on the bottom surface. Now you have at least two holes, one of which you know the location off. The hole you have drilled will allow air in as fuel drains from the unknown hole(s). You can put the rubber tube over your hole and blow gently to expel the fuel. No smoking!!!!
Use a finger to feel where air leaks out as you blow into your known hole with the tube and mark with a pencil each unknown hole you find. There may be several. The soldered seams are the favourite spots. Now use sand paper or a file or emery board to gently clean the surface around the hole till it is bright and shiney. Solder up the hole. Repeat for every hole. When you are sure you have repaied every hole you have found, finally seal the one you drilled with a solder blob. Wash in petrol to remove any residues from the sand paper and hey presto. Float fixed.
I fixed two on my car and three years on they are fine...although I do now carry a spare under the drivers seat!!!

lataud wrote:Thanks Barry, I'll try the motor soon when I'll receive the new carb float..... ! and test the old thermostat .....

Yves buy the nitrile floats that XKs sell. Unsinkable.

Personally I'd buy a new waterpump as well rather than using the original one.

I have put the new float in the carb, the motor turns very well until the coolant boil again !!! . The radiator is not hot, cold at its bottom, the header tank has some steam and coolant over flowing. I have taken out again the water pump after checked the free coolant circulating in the radiator, in the pipes over the carbs by blowing in the hoses and feel the air coming out at the pump entry at the front of the motor. Doing hat , there is no obstacle in the coolant circuit, So my conclusion is that the pump does'nt work .
When I inspect the pump , my common sense says that it must turn like the green arrows on the picture, to push the liquid to the radiator hose. But in fact the pump turns in the other way (red arrows ) So my question is : am Y right with the right rotation with the green arrows , and then my motor turns in the wrong way ??? !!! Y remember that the mechanic who fired the motor for the first time had inverted some plugs on the 123 electronic ignition at the opposite of the maintenance manual..... but my common sense (again) can't believe that a motor can turn in the wrong way !!!! does a starter can start in the two "sides" ?
My motor turns in the clockwise when I am at the front of the car and looking the front side of the motor , is it the right sens ?

Yves, don't worry, your engine is turning in the right direction.
The water pump is connected to the bottom hose - it pumps cold water from the bottom of the radiator into the bottom of the engine. In turn this pushes the hot water from the top of the engine into the top of the radiator.

As an aside, I just rebuilt my pump for the second time in two weeks as I had used the procedure in the Jaguar 3.8 Service Manual and pressed the back of the impeller (same one as in your photo) flush with the end of the shaft. This was incorrect for the shorter shaft supplied in my rebuild kit.

My kit has a locating groove around the circumference of the bearing for the lockscrew. With this groove centered on the lockscrew, the spring in the seal will be fully compressed with the clearance between the impeller vanes and the housing at about .050 inches. With the lockscrew in the groove and the spring in the seal fully compressed, the rear face of the impeller is about 1/2-3/4" out from the end of the shaft (again, for my kit). Likewise, with the lockscrew in the groove, the bearing is flush with the end of the casting at the opposite end (for the pulley flange). The length of the shaft at the pulley end is correct.

When I assembled it the first time, the lockscrew was obviously not in the locating groove. Heads up....

You have the flow totally backwards, but why do you care? Just fit it if the clearances are correct.

the clearance between the impeller vanes and the housing is correct (the vanes are almost touching the pump case) . BRM says : " it pumps cold water from the bottom of the radiator into the bottom of the engine" I think it is the opposite , the hot water arrives in the pump in the big casing groove and is pushed to the hose of the bottom aperture of the radiator ( red arrows of the pic ) and to the hose which goes to
the inlet manifolds. My problem is that there is no flow toward those hoses . May be there is a lot of air in the circuit, and I don't know how to take it out? I thought that when the motor turns , the air arrives in the header tank and if I open the cap times to times, it will take it out ? there is not any air purge screw .

Hello Yves, the coolant flow as Peter says is drawn up the lower hose through the pump and through the jet hole at the back of the timing cover.
I refer you to my first post where I mentioned the thermostat as a possible cause of your problem, the type of thermostat being important , to blind the bypass hose .The 3.8 bypass hose allows a small amount of coolant to be pushed around the circuit avoiding the radiator to aid fast warming. When the thermostat has opened the bypass hose is blinded off and then all the coolant goes through the radiator
Do not overfill with coolant - the level should be at the bottom of the header tank when cold to allow room for expansion.
Another cause of high pressure would be combustion gases in the coolant - ie head gasket failure or a crack in head or block.. this can be tested for of course.

regards Barrie

Hi Barry, i tryed without the thermostat and it was quite the same , the coolant boiled in +- 20 min instead of 15 with it . i am lost with the right circulation way . The coolant circulates as the green arrows show in the pic if i am right. the thermosat open in that flow direction.

in the header tank the flow must be as the green arrows ?

Hello Yves, apart from the rotation of the water pump all your arrows are pointing the wrong way . Engine's coolant water flow is cold into the block and hot out at the top of the head. The bypass hose is the lower one of the two hoses shown in the top photo this allows coolant to cycle around without going through the radiator . You can clamp this pipe to restrict flow through it when the thermostat has opened and then all the coolant should flow through the radiator . Another thing - if the radiator was old and partly blocked flow though it would be low and more water would go through the bypass hose if it could (path of least resistance) thus avoiding the radiator. Do you have a new radiator core ? If not this could be a reason for your trouble. If a modern wax stat is fitted all these problems are worse as bypass water flow is unrestricted when hot.

Hope this helps Barrie

Hi Barrie , my radiator is a new alloy one, i agree now for the right flow "way" i was completely wrong... and i understand the by-pass hose quite well. I have tried the old thermostat and the new one and without any.... but i can't understand where is my high temperature problem ?
the motor has been fitted by a " motor specialist" he saw when he dismantled it a failure between 2 cylinders . He did what he has to resolv that failure (injection of some fluid? )
You say: Another cause of high pressure would be combustion gases in the coolant - ie head gasket failure or a crack in head or block.. this can be tested for of course.
That's a very important failure .... My mechanic "chief" has gone in Spain ... i am now "alone" with all these problems and i have to meet a new one , but the confident will not be there at the beginning.... it's a lot to take that bad news.

Hi Yves.....look again at what Barrie said do not flll your expansion tank too much and try again

Your block may be silted up and have poor flow. Was the water jacket cleaned out fully and were all the core plugs removed? Until you establish whether your engine is actually overheating instead of being over-filled (very common and NOT a sign of boiling) you may quite easily be making your own 'problem' and worrying over nothing.

Two questions:

1) When you fill the expansion tank, how far below the cap is the cold water level?

2) Please supply a picture of your thermostat.