Javelin on A38 Near Exeter 1964

[isleofthanet]

Hi,

If you scroll down the photo is near the bottom of the page, I wonder if the car has survived to the present day?

http://holidaywest.weebly.com/

Best Wishes

Alan

[paul wilks]

Overheating is nothing new for Javelins then after all!
I always have to keep a close eye on my temp gauge!!

[Forumadmin]

I am convinced the vast majority of overheating problems are due to blocked radiators or blocked heads or both after having travelled with Scott through the desert up very long hills in temperatures well into the 30s C or 90s F in a Jav well loaded and having looked at many, many heads and rads that have come out of service.

[paul wilks]

I have a reconditioned radiator and a rebuilt engine! I always blamed the radiator when the new engine was fitted so resolved to get a new radiator. Now I'm at a loss.

Paul

[Forumadmin]

Try using a spot temperature gun to see where the engine is hot and cold. This might give an indication where there may be a blockage. Head gasket leak can be checked with gas sensor in rad. I would then check out the advance curve on the distributor.

[David Morris]

Hi Paul,

I didn't know you had problems with overheating? I was visited by Malcolm Wragg this week and we were discussing the correct gap between the radiator core and the fan. Malcolm has found that the air flow through the radiator is vastly affected by the gap. Fortunately, he has the type of fan that has a screwed thread with lock-nut, rather than the taper fitting, so he can make adjustments.

He has solved his overheating by moving the fan AWAY from the radiator core. It might be worth giving him a call and seeing what he recommends as the ideal spacing?

All the best,

David

[Forumadmin]

I would be most interested to learn how the air flow was measured and where. There may be a difference from centre to outside of rad. I would also like the fluid dynamists amongst us to explain what the optimum distance is. Certainly a cowl around (or partially around) the fan would help immensely and this would need to be as close to the tips of the fan as is safe. The Rolls Royce jet engines have fans 18ft across and they fly within .1 mm of the cowl at 10000rpm plus! If the statement is correct, the spin induced in the air flow may need some time to balance out with the rearward push induced by the blade. Not only is the result contrary to my engineering brain's intuition but it also seems to disagree with the test referenced below. But I am always open to being surprised. Strange things happen with fluids and Jowetts.

But here is the math. http://www.mathworks.co.uk/company/news ... iques.html

These results and the mathematical modelling suggest that moving away from the rad decreases air flow but they never went closer than 1 inch. Also there may be a difference between pulling and pushing the air.

Low fin density radiators may not benefit from a shroud. Higher fin density radiators will, because there is more chance the air will try to go around the outside due to the resistance of the core. This may also explain why open cored rads are better on the Jowett.

It actually makes sense for push to be better. The airflow of the intake of a fan is laminar, while the exhaust is turbulent. For heat transfer, you want highly turbulent air flow. Thus putting the fan in front of the rad is better. Perhaps Gerald did get it right!

Please tell me if this agrees with your results

[robert lintott]

There are several other factors which affect cooling performance on a Javelin

1 If a leaking oil cooler has been removed it will have blocked up the radiator fins with oil and collected dust /dirt . My current javelin had signs of this and overheated . I removed the radiator, soaked it externally with engine cleaner --GUNK-- and pressure washed it from the rear . Masses of dirt were removed and fortunately no leaks when put back in service .

2. The blanking plates between the inner wings and the rad. were missing . Bill Locke supplied replacements which I fitted

Cooling is now much improved . I am not sure whether the water pump is working well and there could be blockages in the water transfer castings between the heads and the blocks .

Positioning the fan is interesting but surely account must be taken of the forward speed of the car , air comes in through the grill at say 50 mph and will affect static measurements

A cowl around the fan would seem a good bet to concentrate the flow --and keep fingers away from the fan ! Many current production cars have the fan behind the radiator with a very close cowl to avoid leakage

Has anyone fitted an electric fan behind a Javelin radiator ? Bob

[Forumadmin]

Many have fitted electric fans behind both Jav and Jup rads, some without retaining the mechanical one.

For 30 years my Jav had an electric fan in front of the rad with the fan spindle cut off at the water pump. After problems with overheating a new standard fan assembly was fitted, eventually the problem was solved by fitting a new rad a second time, the first seemed to have been reconditioned with a blocked core!

My SA has a variable pitch fan that can be tuned to the air temperature thus reducing power loss when not required. It can easily be removed (thus giving an extra 5% of power at the wheels) and then the thermostatic electric fan behind the rad can cool when stopped in traffic on a hot day.

The SC seems never seems to get hot except when the fan fell off, the aly rad and clean heads do the trick.

[paul wilks]

The blanking plates between inner wings and rad have never been fitted (I wish I had rescued them when we scrapped my dad's Javelin in 1967!) and HJU has always ran hot but a lot worse in the past necessitating a stop to cool down. Things are NOT that bad now.

Does anyone know where I could get blanking plates from?
How are they fitted?

Thanks everyone for your input.

Paul

[Jack]

Does anyone know where I could get blanking plates from?
How are they fitted?

Thanks everyone for your input.

Paul

Hi Paul,

They are very simple pieces of metal, with the edge bent over so that they can be screwed into place on the inner wings. I would have thought that you could easily experiment with the cooling by trying out a piece of plastic/metal in the same location, but the cowlings should be in many Javelin owners pile of spares they will almost certainly never find a use for - JCS apparently has a large number of used Javelin spares and bits, I would try them first, also in the Jowetteer the Southern Section mentioned a store of used parts they are shifting so perhaps worth a call there too.

If you could borrow one as a template you could very easily knock one up that would do the same job, but there must be a fair number of these stored away somewhere in all these piles of used spares around the club we hear so much about.

Jack.

[robert lintott]

Dear Paul, I got mine from Bill Lock, they were newly made and fitted well . There are cutouts for the heater hoses and throttle cables and they fix to the innerwing with self tappers. They rest against the vertical casing of the radiator . Maybe there are secondhand ones around or JCS ? I thought they made a difference but no guarantees!

Good luck with the NCS , Bob

[robert lintott]

Paul,, unless you have all the bending kit making these plates would be quite difficult they are quite complex items. Advantages of the original or new build are that the screw holes line up with those in the inner wings, which would be difficult to drill, the cutouts have rolled edges to prevent cutting into the hoses and they fit first time ! Good luck Bob

[paul wilks]

Thanks again everybody!

[Keith Clements]

Peter Holden just phoned with overheating problem on his Jav. Suggested he weigh the rad which should by about 16lbs. As has been said previously, a heavier radiator probably indicates it is full of debris and scale.

Peter also inquired about the core type which I said needed to have wide spaced fins. The ones on the JCS reconditioned ones are 3 mm spacing.