I can get a thermostat that will work in there from my local auto store, but no sleeve.
The Jag _ (and the Bentley) run better on a hotter thermostat.
I can get a proper thermostat for the Bentley, but not the Jag.

 

There is a company in the UK that's name escapes me that will make you hotter thermostats with shrouds but they require machining to fit. I will see if I can find.

 

Thanks, couldn't be anymore expensive than a Bentley thermostat to have one made up.
The suppliers want £167.95 for an aftermarket, and £323.62 for an original.

 

Peter 3442
The difference in the propensity to rust and decay in the transverse brake line should be looked at in the environment to which these cars were exposed especially when new.
In the 1950s and 1960s Australia had huge swathes of inter town highways which were basically compacted dirt and unsealed. It was not unusual for roads to be closed after a few inches of rain
There ware significant build ups of dirt and mud under cars run in these conditions. I can remember a local doctor running a Mk5 without spats because of mud build up.
I lived in Cunnamulla in western Queensland, Australia which is about 400 miles from the state capital city of Brisbane.. The first 150 miles were sealed but the rest was dirt..
These conditions were great to keep mud/occasionally/wet in contact with the underside of cars. We didn't have salted roads but still had underbody rust from old earth deposits.
Without being rude I wonder how many miles your car would have done on unsealed roads compared to the typical Australian used car of its period.
Cheers

 

Bill,
I didn't intend to.disagree with you in any way. It was more a comment on my own car's sometimes inconsistent tendency to severe corrosion. In fact, the point you raised might well be a factor. The second owner (1963-1969) was a builder and he used to drive it across his work sites. I'd have expected dirt from so many decades ago to have been removed or fallen off, but there are remarkable accumulations of what looks like building sand and clay trapped in different parts of the car. I went to look at that brake line after reading your comment. The section running along the flange on the rear side of the cross brace was buried in a semi-solidified material that I dug out in big lumps (accompanied by large pieces of rust). The brake line doesn't look great - I bought a kit of new lines years ago to replace the whole system before the car is ever used again, but compared with the steel ... well they haven't been reduced to an oxide model of the original. Certainly, I agree with you: when the radiator is out, it's an opportunity to check that brake line, which is otherwise hidden and inaccessible. It's probably a good idea also to give that area a clean and test the steel structure that might be falling to pieces like mine.

 

Jeff.

The company I was thinking of was WATJAG run by Derek Watson.

They used to machine the thermostat housing for close to perfect sealing of the shroud. Obviously coolant concentration was critical with their system.

It appears they are no more unless our UK members know otherwise or if they have changed their trading style. They mainly did Jaguar & Land Rover.

Ken Jenkins is very knowledgeable in the field.

The Racing folk block off the bypass port in the rubber pipe from the water pump & run a conventional thermostat of selected temperature.

 

Glyn
You may have actually raised a subject about which I was contemplating a post.
What is the real function of the bypass system? Can engines safely operate without the bypass system?
The water rail on the typical 3.4/3.8 manifold is subject to corrosion on the bypass hose connection.
Good water rails without corrosion on the bypass connection are becoming rare.
I think it would be reasonable to weld up a blanking system on the bypass hose connection and just use a standard thermostat as is done in most other vehicles.
Your thoughts please

 

Bill ~ you are supposed to be the specialist here.

My understanding has always been that the bypass is there to stop any hotspots/uneven heating forming in the block/head during warmup to prevent stress. Simple as that.

You are spot on with uncorroded water rails becoming rare. I searched high & low for mine. Many have been welded multiple times.

Can the car run without the bypass ~ Yes. Been done in racing for years. Is it good for the block & head ~ probably not.

Hotspots are known to build up around Cylinder 1 (rear) of the XK engine.

 

Block the bypass and put one of these in the top hose?
https://www.carbuilder.com/uk/by-pas...xoCOqsQAvD_BwE

 

Mine had no corrosion at all. I think it's because mine was a Canadian car and has used antifreeze from day 1, rather than water. I see photos in the UK magazines and I have never seen internal corrosion like that in any Canadian XK engine I've pulled apart. I think it's because of the corrosion inhibitors in antifreeze.

 

My understanding was the bypass is to achieve a fast warmup after a cold start. It does this by circulating coolant through the block, and not through the radiator. I think you need a bypass of some sort, if the thermostat is closed and can't go through the radiator, it has to go somewhere; as the water pump is still turning, You wouldn't want stagnant coolant in the head or block, so it needs a path to move that isn't drawing heat out of it.

 

Lucky man. I found my perfect one on a farm in the Karoo. The car had probably had well water in it for most of it's life as there were windmills everywhere. It had internal mineral deposits but once vapor blasted it was perfect inside & out. Most are terribly corroded where the rubber hose is clamped to them.

 

Glyn
I am not a "specialist". I just bumble along and am some times called an "expert" which we define as a "drip under pressure"

On reflection I suspect the bypass system was to get some rapid heat into the water cooled inlet manifold to prevent carburetter icing.
Carburetter icing is a well known phenomena in aviation where ice builds up in the carby and inlet manifold and can be so severe as to cause engine failure. This is treated/prevented by manually selecting a hot air source which typically comes from a cuff around the exhaust system
This ice comes from the drop in temperature and pressure across the carby venturi causing water vapour to precipitate as ice. This is compounded by evaporation of fuel which also reduces the inlet air temperature.
Carby icing can occur with ambient air temperatures as high as 25C (78F)depending on the relative humidity but is really common at 15C (60F)and lower.

In many of the "old day" engines the intake manifold was attached to the exhaust manifold to provide a source of heat to prevent carby icing.
Cheers

 

Some modern cars have coolant heated throttle bodies to prevent icing too. The 1995-97 XJ6's have that for example.

 

ICE IS A ANOTHER CONSIDERATION

Just pulling your leg Bill.

Yes ~ Icing could be a major issue. A SU kit was available for Mini's to prevent carb icing. They were chronic for icing up the carb/s. So they fitted a nice little electric warmer. (known to many as the tea cozy)

It's like people that mess around with damper oil on SU's. It should not be fiddled with. It is a 20W & ideally synthetic today due to it's high VI (consistent viscosity/thickness with temperature change). Some seem to think that carbs run at approx engine compartment temperature. They DON"T ~ they run bloody cold internally below the venturi.

Big problem on VW's built in Brazil & run on hydrous & anhydrous alcohols. They go well below freezing below the venturi.

 

As they used to say, Issigonis forgot to put a radiator behind the grille to warm incoming air. The easy solution was to cover most of the grille with aluminium foil. Our two car family in the late 60s early 70s were the Mk2 and a Mini.