Temperature Sensor Location?

[Space54]

My local garageman and self admit to being at least a tad embarrassed that we have only just noticed that the fairly large brass Temperature Sensor as in the photo below is not fixed in any way, rather it dangles thro the large hole in the radiator mounting bracket and presumably makes intermittent contact with the side of the radiator!?



Does this appear to be the correct sensor and if so how should it locate? This is also no doubt responsible for at least some small portion of the knocking/rattling so disliked my the good Lady Wife!

Thanks
Keith

[Jack]

Hi Keith,

The sensor looks to be the right one, and should be tested before you bother fitting it.

Get a cup of boiling water and drop the brass end into it. The gauge on the dashboard should read 100 deg (or close to it) and is a good test before going any further.

The fitting goes into the top centre of the radiator. There should be a threaded fitting on the "back" of it, visible by climing up via the wheel arch and looking forwards, though my question now is what is in there at the moment preventing you from losing all the water from the engine.

It is possible that another sensor is in there, the oil temp sensor can be made to fit, or there may be some kind of blanking plug. Failing that, your radiator may not have the fitting. If that proves to be the case, you may need to either modify or replace the radiator, or use a different type of temperature sensor.

It certainly shouldn't be dangling loose like that, and certainly will rattle. You are very lucky if it hasn't been damaged or caught up in the spinning fan blades not far from there.

Jack.

[Jack]

Thinking about it, it is entirely possible that is not the water temperature sensor and that it is the oil temp sensor.

If that is the case, it would explain why you've not lost all the water from the engine, I guess a quick check with the hot water and a willing volunteer watching the gauge will confirm it, if the oil temp goes up dramatically then you know which one you've got.

The oil temp I can't advise on easily, because I think on Amy's car it isn't currently connected. We have a plan to use it as a sump plug, but I don't know if that is the right place for it to go - someone will no doubt be along shortly to confirm.

The water and oil originally were slightly different fittings, one female and one male thread, so that they didn't get swapped over, the one you have appears to be the same as the water temp sensor (female), but over time it is possible that these have been swapped over if the gauges have been reconditioned.

Jack.

[Forumadmin]

That is the oil one as it has a long pipe.
The type of sensor is more complicated than that, but I am not sure on a definitive statement. Various styles of rad may have necessitated different sensor fittings. Oil temp was only fitted to Jup and went into the oil cooler (but I have seen on rear of sump).

No doubt someone will correct me.

[Srenner]

Hello all, here come's my 2 cents.

Both oil and water use a coil-wrapped copper tube. My guess is that's the oil bulb, as I think I see the coil-wrapped copper tube leading to the rad in the background of your picture. As Jack wrote, the water sending unit is at the top on the rear of the water rad.

The oil bulb originally fits in one of two styles of oil coolers. The early style finned and bent tube style mounted in front of the water rad or to the Bowman (rectangular box) oil cooler mounted just above the fuel pump blanking plate on the side of the timing cover. What number is your Jup? That tells us which cooler you should have.

An oil sump can be modified to accept the sending unit, but this is fairly involved and requires removal of the sump. On an Arnolt-Bristol, I modified a brass fitting meant for marine applications such that it replaced the oil sump drain plug and the sending unit passed through it. One has to remove the sending unit to drain the oil.

Hope this helps!

[Space54]

Well, congrats guys-there most definitely is a working sensor connected to the centre top at the back of the radiator-and if Scott managed to see that in the posted photo then all I can say is that his local optician ain't going to be getting any business from Mr Renner any time soon!

However, with regard to where the un allocated sensor should go I don't think we're any further along! I certainly don't see any "finned type" cooler to the front of the rad-nor have I found a rectangular box (Bowman) type, but I may have been looking in the wrong place! My chassis # is E3SA871R-but the total rebuild of 3 years ago might not be to the original spec. Photo(S) of the relevant oil coolers in or out of situ would be most welcome!

Jack-does Amy's car have an oil cooler, but with no temp probe fitted?

Thanks for all replies
Keith
PS whilst looking for oil cooler my mechanic friend somewhat perturbed that fan blade found to be turning quite freely on it's shaft, but will do a quick separate post so not to blurr topics.

[Forumadmin]

You probably do not have an oil cooler fitted. Amy's car does not have an oil cooler as it never registers above 40c, since it is fitted with an aluminium radiator.

Oil temperature is usually close to water temperature at the cylinder heads except when doing high speed prolonged driving when it might reach 100C. My SA has an oil rad fitted in the protected space above the gearbox in the strong air flow. There is an in-line thermo switch to recirculate oil until it is hot. I have an electronic oil temp sensor on inlet to oil filter housing.

[Srenner]

Okay, your late Jup would have had a Bowman. They are not found over here, so you would have to pry one from the hands of someone hiding one on a shelf. There are also two copper tubes with fittings to make it all come together. The sensor bulb fits into the Bowman cooler at the top where the tubes also connect.

Currently fitted to your car, there has to be an oil line from the top of the filter base to the side of the base in order to complete the oil circulation. That has allowed bypassing a cooler. You could mount a modern cooler in exactly the same place as the Bowman unit, but still need to find a spot for the bulb.

I will take a look at the fitting I made for the Arnolt-Bristol and see if it might work for the Jup. This reads the hot oil dropping into the pan rather than at the cooler, but that's not a problem.

Cheers,
Scott

[chapman]

If you look in carbuilder solutions catalogue you will see various fittings which fit onto the the port where the oil pressure pipe fits. The fitting on the radiator is BSP so you should be able to find some way of using the oil pipe port and some bits from a plumbers merchant to get the oil temperature if you have no oil cooler, they also sell a fitting which allows you to use an electric temperature gauge which fits into the same port
Tom Chapman

[Brian Cole]

The item on temperature gauges is interesting. When I first bought my car the oil gauge capilliary was coiled up against the bulkhead, so I assume it must have been fitted at some time to an oil cooler no longer on the car. I fitted the capilliary tube and bulb to the sump, at the rear off side, with a standard off the shelf brass tank connector sweated to the sump. This seems to work quite well.
The water gauge is a different story. As we all know the radiator dumps a lot of water via the expansion pipe during warm-up. This means that the bulb spends most of it's life above water level in the radiator and can not be relied upon to give an accurate reading. I have removed the toggle in the thermostat and this has improved matters a bit, but the bulb still ends up above water level eventually. The only solution I can see is to fit an expansion vessel as all modern cars use, or refit the bulb fitting in the rad where it will always be wet. Richard Gane I understand is going to race his Jupiter and in this situation I would have thought an expansion tank was essential. Views?

[Forumadmin]

The amount of dump of water on warm up should not be enough to uncover the temperature bulb. But anyway I have had a simple expansion vessel fitted for years which although not elegant does many jobs, namely
1. catches a gallon of any boil off in event of a problem such as head gasket, thus meaning you are not stuck trying to find a stream,
2. provides some top up fluid when doing my daily check,
3. acts as a source of back siphon fluid for any expansion.

What is it? An empty plastic gallon bottle with a plastic tube drooping into it from the overflow pipe which has been cut off.


Also I have head temp sensors that tell me exactly what is happening. If the bulb sensor is more than 10 degC different from either head sensor there is something wrong.
1. No water in radiator
2. head gasket
3. exhaust valve wear
4 blocked radiator or head
5 failed water pump
6 fan belt
7 fan pitch needs adjusting or electric fan not kicking in at correct temp

Otherwise, if I am not looking at the gauges, I smell the cooling fluid or see it on the windscreen when it overflows the gallon can!

[Brian Cole]

Does it matter if the gallon container is above or below the sawn-off expansion tube? Where have you located yours?

[Forumadmin]

I have mine wedged on top of the steering box. The pressure cap will allow any excess pressure to blow off, but when cooling will not allow the return of fluid easily unless there is a return valve in it. The return of fluid might be improved by fitting a rubber washer to the top of the pressure cap, so sealing the system to outside air except via tube to expansion tank.

You might see this negative relative pressure as the hoses starting to collapse inwards or as a slow hissing sound from water pump or other poorly sealed point. The tube should go to the bottom of the container so that all fluid can be sucked back up (assuming you have a vacuum tight water system).

The top of the container should be about the same height as the temp sensor as that way, if system is not vacuum tight, the system might balance itself with whatever siphon exists. No doubt you could come up with a better design as an expansion tank and I have seen them fitted to Jowetts. But, with leaks in various places common on Jowetts, my main aim is to catch any overflowing water and to provide some storage for spare fluid. A failing fan belt , water pump, electric fan and incorrect pitch on fan blade can cause boiling if I am otherwise engaged enjoying the car, so this back up helps a minor problem becoming a disaster.

Quite frankly fit a new rad and clean out the heads and you should never get warm. I run without mechanical fan on the Jav, only occasionally needing the electric fan to boost cooling. In fact the previous owner Ben Shaw modified the fan assembly by truncating the fan shaft at the water pump. The SC never gets warm except when there is no mechanical fan. The SC really needs a variable pitch fan or electric one fitted. The SA has a variable pitch fan, normally set almost flat and, except for hot weather and hard long motorway driving, could run without a mechanical fan, leaving the electric one to do its job in traffic.

[chapman]

All of these solutions explain fully the fundamental design failure of the Javelin Jupiter cooling system which is that the water pump is fitted in the wrong place , it is miles too high in the system and to work efficiently should be much lower down .
If the water level is low in the radiator because it has been kicked out through the radiator overflow then several things happen .
Firstly as stated the bulb of the water temperature gauge is no longer in the water so the temperature reading is false so the temperature can increase leading to cooking of the oil and subsequent break down of the oil polymers leading to failure and bearing wear.
Unless an oil cooler is fitted and the oil temperature gauge is installed into the cooler or somewhere else in the system an incorrect reading for oil temperature also results which leads to the same result as the water temperature gauge
A further result of the low level of water is that the water pump eventually gets cooked and fails.
I have had an electric water pump fitted in the same place as the mechanical one but still encountered all the problems I have described so I have now decided that I will stick with the electric pump but try to re site it at the bottom of the radiator feeding the engine as it has a 90 litre a minute capacity instead of the 10 litres of the mechanical one , this is complicated by two feeds in and two feeds out but I will fabricate some sort of manifold for it and I will definitely use an overflow tank .Photographs will follow
Tom Chapman

[Jack]

Tom, this sounds very sensible, and given the costs and time involved in fixing the existing water pump, it strikes me that having an electric alternative is not the worst idea in the world - after all in an emergency it may be that having the bits in the garage saves the day in an emergency. I know there are at least a couple of other people who have had problems with their water pumps which have slowed restorations and affected cooling.

From memory wasn't there something about the system being originally designed to work the other way around? Have I imagined this? I know the water pump was a bit of an afterthought, hence the precarious pump held by a bit of rubber hose arrangement, but couldn't remember the other details.

Jack.