Kenneth Nelson <citbuff@sbcglobal.net> wrote:
Hello all - I talked recently with Phil Dingle, a longtime Jupiter owner in Rochester, Michigan, who has had his since the 60's, and told me he'd experienced overheating problems with subsequent headgasket leaks due to the fact that the Jup engine has the waterpump on the HOT side of the engine, when standard practice is to locate the pump on the cold side. Since any boiling of the coolant would naturally lead to steam in the pump and upper hose, the pump can't push vapor, so this seems like a bad aspect of the design. Phil also said due to the setup of the headbolts from the alum. crankcase to the iron heads, and the design of the sleeves and their sealing, that the different thermal expansion rates of the alum vs iron lead to low clamp loads on the headgasket and maybe the sleeve seals. As I'm new to this breed, I'd appreciate hearing of the experiences of others in the group regarding Phil's experience and any suggestions as to fixes, gasket
sources, new waterpump designs, better fans, radiator capacity expansions - ie., anything I should or can do to avoid overheating beyond making sure the rad is clean and the thermostat is working and I don't have hose leaks. I'd rather not blow a gasket when I first try to start up my first engine!
Thanks,
Ken Nelson
Palo Alto, Ca/Michigan
Overheating.
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Mike Allfrey
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Dear Ken,
Having owned a Jupiter for forty-six years, may I give a few tips?
There are a few points to bear in mind with respect to Jowetts:
One
If you suspect a leaking head gasket, before starting the engine, insert the starting handle and turn the crankshafy a couple of revolutions. Should you feel a hydraulic lock, lean on the handle to squeeze the coolant past the piston rings.
In my experience, the only time a Javelin or Jupiter engine starts up instantly is when one cylinder contains leaked coolant and, having instantly fired up, proceeds to split the crankcase. The laws of physics are completely correct, you can't compress a liquid!
I am fairly worried now, because since installing electronic ignition, the engine has developed a habit of starting instantly.
Two
I have always borne in mind the words that introduce the cooling system, in the Jowett Cars Linited specifications released to the press at the time of the Javelin's announcement:
"Cooling System -- Thermo-syphon assisted by a water pump". Note the word 'assisted'.
Three
Our club here in Australia, has been using solid copper shims (no gasket) under the cylinder liners since 1957 and, for us, head gasket leakage is a thing of the past. Our cylinder liner protrusion is 0.006" to 0.008". We also re-tighten the so-called 'Monotorque' head gaskets after the engine has reached normal operating temperature.
Four
It would take a fair amount of latent heat to cause the water pump to be affected by steam and vapour locks.
It is most important that the radiator cap is properly seated on a rubber washer at the bottom of the filler neck. I have seen instances of old fibre washers being used to seal a filler cap -- not good practice.
My engine runs happily in 34 to 38 degrees Centigrade ambient in shade, at 90 to 95 debrees Centigrade showing in the temperature gauge. I try not to take the car out in higher ambient temperatures simply because it is uncomfortable to drive in such conditions.
It has to be remembered that, if the anbient is high, then the coolant's temperature will be correspondingly higher than normal.
Give me your postal address and I will send you a CD with my Technical Notes Series that have been developed over many years. The Notes are Microsoft Word documents and the disc can be freely copied, provided due acknowledgement is made. Such information can be very helpful to someone who is new to the Jowett scene.
Kind regards,
Mike Allfrey.
Having owned a Jupiter for forty-six years, may I give a few tips?
There are a few points to bear in mind with respect to Jowetts:
One
If you suspect a leaking head gasket, before starting the engine, insert the starting handle and turn the crankshafy a couple of revolutions. Should you feel a hydraulic lock, lean on the handle to squeeze the coolant past the piston rings.
In my experience, the only time a Javelin or Jupiter engine starts up instantly is when one cylinder contains leaked coolant and, having instantly fired up, proceeds to split the crankcase. The laws of physics are completely correct, you can't compress a liquid!
I am fairly worried now, because since installing electronic ignition, the engine has developed a habit of starting instantly.
Two
I have always borne in mind the words that introduce the cooling system, in the Jowett Cars Linited specifications released to the press at the time of the Javelin's announcement:
"Cooling System -- Thermo-syphon assisted by a water pump". Note the word 'assisted'.
Three
Our club here in Australia, has been using solid copper shims (no gasket) under the cylinder liners since 1957 and, for us, head gasket leakage is a thing of the past. Our cylinder liner protrusion is 0.006" to 0.008". We also re-tighten the so-called 'Monotorque' head gaskets after the engine has reached normal operating temperature.
Four
It would take a fair amount of latent heat to cause the water pump to be affected by steam and vapour locks.
It is most important that the radiator cap is properly seated on a rubber washer at the bottom of the filler neck. I have seen instances of old fibre washers being used to seal a filler cap -- not good practice.
My engine runs happily in 34 to 38 degrees Centigrade ambient in shade, at 90 to 95 debrees Centigrade showing in the temperature gauge. I try not to take the car out in higher ambient temperatures simply because it is uncomfortable to drive in such conditions.
It has to be remembered that, if the anbient is high, then the coolant's temperature will be correspondingly higher than normal.
Give me your postal address and I will send you a CD with my Technical Notes Series that have been developed over many years. The Notes are Microsoft Word documents and the disc can be freely copied, provided due acknowledgement is made. Such information can be very helpful to someone who is new to the Jowett scene.
Kind regards,
Mike Allfrey.
E0 SA 42R; Rover 75