Shrouded thermostat

[guduell]

Somewhere here and in the workshop manual i read about the importance of shrouded thermostats. Are these anywhere to buy? Or are the normal one you buy good enough? As I understand the shroud blocks the bypass direct into the head and the water have to pass through the cooler when the engine is hot.

[guduell]

Noone has any idea?

[oehrick]

Its not something I've come across, perhaps thats why there hasn't been any response ?

Do you have an overheating problem with the standard thermostat ? or is it more of a theory question ??

[guduell]

For what i know i have no problems with heating.

I got curious as it is stated as needed in the motor supplemen p33 point 62: previous type of termostat must not be fitted to mk2,3 engines. I think Brian wrote something similar in a post.

I guess that the shroud stops water bypass the engine and that it might get hot without noticing as the temperature sensor is in the termostat housing. (In this case it would have been better to have it at the rear of the engine.)

So i wonder i the thermostats you buy now are ok.

[Brian]

The design of the shroud was to restrict water circulating via the by-pass and force it all to go to the radiator.

Shrouded thermostats have not been available since the mid to late 1970's and the new design is not really suitable for these engines. IMHO.

I live in a fairly temperate area and my solution is to take the thermostat out altogether. I know people will say the engine will not reach and run at its correct operating temperature but, having used the new style thermostats and suffered from overheating, I prefer to use the radiator blinds to control the engine temperature and a piece of card in front of the radiator on the tractors I have without blinds, if needed.

Most of the time I use my tractors it is to work them and the temperature rises quite quickly anyway.

There was also a different design of water pump used on the earlier engines which will not fit the later engines and the later version will not fit the early engines.

[guduell]

Ok thank you. The overheating, is it noticeable on the temp gauge or just locally at the rear of the engine (where the water might not circulate)?

[Pavel]

Here in Australia, where minimum winter temps. are much warmer than yours, it is tempting to not replace a thermostat when it has become unserviceable -- even though we occasionally get ground frosts and snow on the top of a 1000 metre high mountain some 15 Ks from where I farm. However, for reasons that you, Guduell, have touched on, I would not run a diesel engined tractor without one -- or at least part[?] of one.
You will be familiar with the effect caused by placing a finger partly over a stream of water coming out of a pipe [solid or hose] -- it jets much further. [The same effect is used in a carburettor -- the venturi]. By removing the WHOLE thermostat you lessen the extent/reach of the flow rate to the rear of the block and cylinder head.
The trick, if not replacing with a new one, is to remove the bellows, or wax capsule, and the centre movable disc and refit the wide base plate. This, mostly, maintains the flow rate to the rear of the engine.
As Brian has explained; the shroud was to ensure most of the coolant flow was directed to the radiator. Modern stats. now employ what is called a 'giggly pin' in the base plate which just about serves the same purpose. If a new, complete, one does not have this 'giggly pin'; then drill a 3.5mm hole in the base to achieve the same effect.

Pavel

[shepp]

The non shrouded thermostat was fitted up to engine number 1425096
and the shrouded type was fitted for engines after that number. The workshop manual contains a warning that the shrouded type may be fitted to the earlier engines but the non shrouded type should not be fitted to the later engines. The operation of the shroud is such that as the thermostat opens the shroud gradually seals of the by-pass tube at the front of the cylinder head, so that a restricted flow of coolant is then circulated through the radiator until the thermostat is fully open when an unrestricted flow is obtained. It is important to note that both these earlier thermostats were bellows thermostats. In practice the bellows thermostat is unobtainable whether shrouded or not, unless you can find original new old stock on Ebay. The replacements are all the wax capsule types and unshrouded, they will suffice for all the engines - BUT - Pavel has referred to the "giggly pin" . In fact it is a "giggle pin". Many of the replacement wax capsule thermostats marketed today for these tractors (and other makes!) do not have the giggle pin. The purpose of the giggle pin is not as Pavel says, it is to enable the bleeding of air from the cylinder block up through the top hose when the coolant is either drained and replaced or topped up. In either case and particularly after a complete drain and replacement you might think the system is full as the radiator neck is overflowing - BUT a large amount of air is trapped in the cylinder block and head. You start the tractor up and run it and as there is no coolant under the thermostat around the capsule to heat up and open the stat it stays closed, the air cannot escape and the engine continues to heat up as there is little coolant in the block and head. Then DISASTER strikes if you do not realise what is going on! BE WARNED! If you are fitting a new thermostat without a giggle pin, drill a small hole in the plate and fit a small brass split pin loose in the hole to act as a giggle pin. If you are doing a complete coolant change on a tractor and you do not know the type of thermostat fitted, take it out and check it has a giggle pin, if not drill as above, and also test it in hot water whilst it is out. Then refit and refill.

With regard to the water pump, a particular design was fitted again up to engine number 1425096 and after that number a different pump with different ports in the water pump body were fitted and the two should not be mixed up - fit the correct pump for the engine number!! Also fit the correct gasket as they were different for the two pumps and an incorrect gasket will block off vital port holes to the block!

[oehrick]

I've always known these as jiggle (rather than giggle) pins or valves - which may be a pronounciation thing - our friend Google seems to agree and comes up with a somewhat different usage for giggle pin.

Discussed these on S1 Landrover engines many years back and the consensus then was that a plain hole worked as well or better than the one with a pin for both cooling and air lock releasing BUT once the air was out, water flow would tend to close the valve to give best warm up from cold time, however, someone who had worked for one of the older engine makers said that in the days before tap water being widely available these also helped keep sludge or scale from sealing the hole and leading to a boil up if airlocked - discuss !

Always amazes me how quick they open when you test them, the power of wax

No thermostat in my Allen Scythes, two days running I've made a start on the orchard and been hailed off - nearly May !!!

[Pavel]

With respect, Shepp; I beg to differ.
On sealed circuit cooling systems, which, with a closed thermostat it is [however temporarily], there is the build up of pressure. All fluids and gasses when subjected to heat expand; and, unless a relief system is incorporated, will cause uncoupling of hoses, bursts or blown cylinder head gaskets -- hence the need for a bye-pass hose. Thus with this system in place pressure is relieved via the engine block, radiator and rad. cap valve. I would agree that a giggle [god knows where I got giggly from] pin aids air expulsion but it's main purpose was to protect against hose and gasket problems in case of thermostat failure in the closed position. I should add that just about all handbooks state that, after replacing the coolant, one should start the engine with the rad. cap off and top up as the level drops whilst it is still running. With a giggle pin, or 1/8" hole in the base plate, you can actually see slight coolant movement, even with the thermostat closed, which indicates that there is no trapped air. I would agree, though, that that is a little difficult to observe with the gooseneck fillers on the Major.

Pavel

[oehrick]

I've often wondered about the range of sizes of valve diameter against cross sectional area of thermostats Pavel and I guess the resulting pressure differential may be specified, related to the resistance to coolant through the passages in the block - all these things are more complex when you think

As for giggle versus giggly versus jiggle - probably down to whoever you learned about them from - my late dad (Polish) never quite mastered the English language let alone the Norfolk dialect and I often found myself relearning words I thought I knew !

One came back to me the other day as I was clearing some windblown Spruce which we had planted when I was 7 or 8, dad dug the holes, I placed the seedling in and stomped the soil around it. Pointing at something small and rustling the word I heard best translated as peacock, I knew what they were, lovely colourful birds, so feet at a blur I rushed after it bent clutched it hard and picked it up in triumph. Despite the fifty odd years which had passed I felt the pain in my fingers and palms, that was the day I learned to distinguish the difference between both his pronouncing peacock and hedgehog and what the latter do to your hands if you are stupid enough to grab one!

Here in Norfolk it used to be the case with the old horse era farmworkers that anything more complex than a hammer, hoe, pitchfork etc was known as a 'Hurdy Gurdy', (the droning handcranked violin type instrument of yore) the early traction engine differentials were known right up to the end of steam usage as the 'Jack in a Box' funny how these things get into the language and often last longer than the original meaning.

Hope you are getting that weather sorted out before Brian & Ann arrive we can't have upside down posts from them complaining about the rain...............

[shepp]

Hi Pavel, I understand what you are saying. However, in a pressurised cooling system with cold coolant and the thermostat closed the water pump is ineffective and there is no circulation of coolant or pressure build up from the pump. As the coolant heats up and expands in a static coolant situation it simply expands back through the bottom hose and into the radiator and any pressure build up is relieved by the radiator pressure cap. Usually of course in an engine that has been previously run at working temperature the coolant has fully expanded and then left a vacuum space in the radiator top tank as it cools, and so any subsequent running and expansion of coolant simply fills the vacuum space and the radiator pressure cap is not moved to release pressure.

Specifically with regard to the shrouded and non shrouded thermostats, the earlier cylinder head prior to the serial number stated did not have the bypass port in the cylinder head and hence fitting of a shrouded or non shrouded thermostat made no difference to the operation of the cooling system. With the later cylinder head with the bypass port Ford's recommendation was that only the shrouded type thermostat should be fitted to enable the cooling system to operate as designed. In practice with either cylinder head it did not make much difference which thermostat was fitted
- BUT! - the later cylinder head with the bypass port could bleed air out of the block and head on a refill into the top tank with a thermostat fitted that did not have the giggle or jiggle pin. However the early cylinder head without the bypass port could not do this and it is essential that thermostats fitted to the earlier engines prior to the serial number I have given must be fitted with the giggle or jiggle pin to enable the air to bleed out of the block and head on a coolant refill. Believe me, I have learned this by experience many moons ago!

[Pavel]

My apologies, Shepp, if I appear to be over pedantic.
Firstly I have no beef with your detailed description of shrouded/un-shrouded thermostats.
Secondly; the Bosch Automotive Handbook states that, whilst limited, the water pump does have an effect on coolant circulation even whilst the thermostat is closed. Coincidently this subject was part of my City & Guilds exam paper in 1970.
Thirdly; I quote the following:
"All High-Flow Thermostats are fitted with a jiggle pin that enables the system
pressure to be stabilised so that the valve opens easier. The jiggle pin also
allows air pockets to move past the Thermostat and the temperature to be
regulated more efficiently. Fitting High-Flow Thermostats will allow your
vehicle cooling system to operate more efficiently."
http://www.are.com.au/feat/techt/thermostat.htm

Pavel

[AdrianNPMajor]

Very informative discussion.
Many thanks all.
Best, Adrian.

[shepp]

Hi Pavel, the paragraph you have quoted includes exactly the point I am making, namely that the giggle or jiggle pin enables air pockets to move past the thermostat as well as producing a balancing effect. My contribution was spurred on by the fact that if you buy a thermostat today for a Fordson Major from, say Agriline , or any of the other well known parts suppliers, you will get a wax capsule thermostat that does not have a giggle or jiggle pin. In fact most of the thermostats supplied today by these suppliers for most other tractor applications do not have this pin. This simply WILL NOT be suitable as it is for Fordson engines up to and including 1425096 which have cylinder heads without the bypass tube in them. If you fit this type of thermostat as it comes to these early engines then it will not enable air trapped in the cylinder block or cylinder head to escape when you are refilling the engine coolant. The engine will heat up, there will be no hot coolant around the wax capsule to open the thermostat, the engine will continue to heat up and the next thing you know the engine will pick up on a piston. The replacement thermostat for these early engines MUST have a small hole drilled in the base and preferably a loose brass split pin inserted to act as a giggle or jiggle pin. Similarly, as I have previously said the water pump AND gasket for engines up to and including 1425096 has DIFFERENT ports to the water pumps for the later engines, although both types of pump will bolt up to both types of engine, but if you fit the wrong pump or gasket to the particular engine the circulation will be seriously compromised. Again, many parts suppliers just list ONE water pump for the Fordson Major diesel, and this is the later pump and gasket. It WILL NOT DO for the earlier engines! Check your engine serial number and track down the correct water pump and gasket!

[Pavel]

I rather think that Guduell can now pick the bones from the various posts on this subject and reach a safe conclusion. I do, though, find it surprising that new wax stats. with giggle pins, are unobtainable in the UK. Here in my part of the world they are readily available. Tridon, a large manufacturer, market one under part no. TTI-180 [http://www.ebay.com/itm/TRIDON-THERMOST ... 2222303346 = $21.80 Aus. or $16.14 U.S.]
Although why one would go to the trouble, when drilling a 3mm hole serves the same purpose, I know not.
My final fling: In the 70s Jaguar Cars were fitted with stats. that had a hole in the base plate; and that the hole should be fitted in the 12 o'clock position. The reason stated in the w/manual was so that warm/hot coolant flow would activate the opening of the wax pellet's disk sooner. No mention of air expulsion.

Pavel

[shepp]

That is interesting to know that Tridon make a thermostat with the giggle pin in it for the Fordson Major, I will search to see if there are any UK stockists or suppliers for the brand. It IS an unfortunate fact that the aftermarket thermostats supplied by the popular vintage tractor parts suppliers in the UK do not have the giggle pin. With regard to the recommendation from Jaguar, I am sure - as readers will have realised! - that there are probably several different explanations from different manufacturers as to the purpose of the giggle pin! Presumably Jaguar were referring to their XK engine, in the early 1970's I had an S2 E type roadster followed by two XJ6 S1 saloons and then an S2 saloon all fitted with the 4.2 litre XK engines, somewhere I have the workshop manual for the E type as it loved to chew clutches and I will dig it out and have a look. My point of information is simply that if you have a tractor prior to 1425096 please ensure that you fit a thermostat with a giggle pin and please ensure that you fit the correct water pump and gasket otherwise it might turn out to be an expensive education! Finis!

[Pavel]

Ah, yes -- the XJ6 -- a lovely car. My boss at the time had one [but with the smaller 3l] and I used to service it for him. Often cursed the position of the distributor and setting up the SUs. [Wished they had had 40DCOEs like my Alfa]. Then he traded it in for a BMW 2800. Silly man.

Pavel

[Pavel]

Ricky; I agree. It was very tedious having to turn the viewing screen upsidedown to read the posts. As to the possible rainy weather; wouldn't they feel comfortably at home?
As to the weather they may be receiving, or indeed what is happening now, click on the following:
http://ozforecast.com.au/cgi-bin/stormt ... =Australia
then click on the circled area they are at.
As a bonus click on the following also:
http://ozforecast.com.au/cgi-bin/satellite
which will give you a whole of Oz, plus, view of cloud and weather formations -- especially that of the Roaring Forties. If you wait a few seconds the system moves to show its direction over the last 3 hours.[Note the cat. 3 cyclone bearing down towards Brisbane in the top right hand corner.]

Pavel