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Piston Rings Explained

The different rings on a piston perform different functions and it is important to fit the rings in the correct order on the piston and also the correct way up. We have found this video from Youtube which gives some simplified explanation of the function of the different piston rings and how they work.

Tractor engines of different sizes and from different manufacturers have differing arrangements of rings. This video gives a brief explanation and is worth taking a few minutes to watch.


TEF20 Hydraulics Oscillating Drive Strip

Having problems with oscillating valve cir clip. How do you get cir clip in position inside valve. Does the valve slide? My old girl is in the 400,000 series. Acquired her last year, finally getting around to
refurbishing her. She still goes, but how so got me beat – more sludge than the black lagoon in back end of her. Any help greatly recieved.


[ad#486-x-60-banner]Hi Jed,

Yes the valve slides.

There ws an alteration to the design of this component at serial number

It would appear that the control valve and keyrod (or oscillating drive
strip – depending on version) can be assembled together whilst being out of the pump. This should make it some what easier to work on the retaining circlip. It is of the upmost importance for the circlip to be located correctly in its groove.

As long as the pump is not fitted to the tractor, the valve and oscillator keyrod/drive strip should simply slide back into its bore after lining up the square/slot.

Hope you have some luck.



Ferguson FE35 Compression Test

Hi all,

I have a mf 35 4 cylinder engine rebuilt pistons liners rings little ends
valve seats recut new valves head skimed it used to start up on 3 cylinders then the 4th cylinder come in we have had the injectors and injector pump serviced now it takes up to 4 atemps to start even in hot weather, if it was cold don’ go there because it won’t start. Heater plug is working only got 1.

I suppose it must be something to do with the injection timing. Did you have a look at the timing chain and tensioner and also the backlash on the injection pump drive gear?

Hi steve
No we didn’t look at the timing chain or the tensioner or the backlash of the injection pump, one thing we did do is to check the compression 120 psi when dry and 190 psi when wet,do you know what the compression should be please. Many thanks, Phil butler

I’ve been searching for the compression test data which I knew I had somewhere but just couldn’t find. Anyway I’ve found it now.

The data I have is that the dry test should be 380PSI and then the wet test no more than about 10% above this. I would think that anything above 350PSI would be acceptable.

The dry figure I have is considerably higher than yours, but you have had new pistons, liners and rings. Did you fit the rings yourself? Were rings 2 and 3 fitted with the tapered periphery of these rings towards the crown of the piston?

The good news is that there is a difference between your two tests so that eliminates the cause of your problems been with the head gasket or valves.

However, the difference between your dry and wet tests is quite a lot, which all points towards a problem with either the liners or the pistons/rings.

Did you do the compression test on all 4 cylinders? and observe similar results.

I believe your compression test is very low, so I would think this is probably the cause of your starting problems.

Just a thought. Have you connected your tester through the injector fitting with a clear passage from the cylinder to the guague? Did you turn the engine over so the test gauge gave 5-6 readings before taking the reading?

I haven’t tested lots of the 23C engines myself, so I haven’t got any data of my own to compare with your test results. The 380PSI I quoted was a ‘text book figure’ I once wrote down, but I think it is about right.

120PSI is certainly low.




Painting A Vintage Tractor

I would always say that there is no point preparing and painting a tractor
if you need to go back at a later date and perform some mechanical repairs;
basically because all the good paintwork is often scratched and damaged when doing the repair work.

When a job such as an engine rebuild is been undertaken this is a good
opportunity to prepare and paint the engine as you go along.  When all the
engine ancillaries are removed from the block it makes it much easier to
clean and paint in all those hard to reach areas.

Also whilst a major component of the tractor is dismantled it makes sense to replace all the gaskets (usually contained in the parts kit) and hence stop
all the oil leaks that are part and parcel of an old tractor.  Oil leaks that soon show up on a new paint job.  If you do nothing else mechanically to a tractor before painting it, then stopping the oil leaks is a must – there’s just little point painting the tractor if oil is going to leak all over it.

We are not experts at painting here at Vintage Tractor Engineer, but I think the advice above is sensible.  Customers usually prepare and paint their tractors at the same time as we are doing the mechanical repairs.  We often just do a few hours work on an engine and then wait for the owner to catch up with the paint work.


Fitting Fordson Dexta Cylinder Liners

I’m rebuilding my Fordson Dexta engine (diesel) and need some info on the cylinder liners. I’ve just removed 3 seized pistons and pressed out the cylinder liners. The question is should I use high temp loctite 620 on the new liners when pressing them in. The older liners presumably didnt use it and are a simple press fit. There liner are not flanged.

Hi Peter,

To be honest we have never fitted Dexta liners ourselves. Last time we had one done the engine shop pressed in unfinnished liners and then bored and honed them to size (as they distort slightly during the pressing process).
This makes me think that the pre-finnished ones will not be quite as tight-a-fit, so as to minimise distortion. If this is the case then some loctite may be advantageous, particulary if they are not flanged. I cannot see any harm in using the loctite.

PS. If you keep the liners cool it will help minimise distortion when fitting. Also if you have any means of keeping the block warm such as filling the water jacket, or our engine shop put the block in the steam cleaning cabinet to warm it up.

Hi Steve,
Thanks for the advice. I managed to get the new liners in today. I stuck them in the freezer for several hours and let the block sit in the sun for the same. I used the loctite as the liners are unflanged but I can tell you they were a very tight fit in the block. The top end of the liner was so tight it took some extra effort to press them all the way home. This resulted in about 5thou distortion over half an inch from the top so that the pistons wouldn’t fit. I then honed each cylinder liner back until the new piston slid in. Next job is to refit the crank shaft.

I mistakenly took the gear off the camshaft so now I’m worried that I have lost the timing positions. Would you have any advice on how to re-establish the timing positon for the camshaft?


Hi Peter,

The Dexta workshop manual is available to download from a website….


Hopefully all the info should be in there.
Sounds like you had some fun with those liners!



Hi Steve,
Thanks for the link to the manual I’ve downloaded it. Those liners did prove difficult. We actually cracked one about 1/4″ from the top on closer inspection. It runs aroung the circumference for about 1.5″. These liners have a grove milled around the outside, I don’t know what purpose that serves as the old liners don’t have this. This is where the crack emminates.
Looks like I’m going to have to press that one out and try again. I’ll lap out the top of the bore to make things easier on the second try.


Fordson dexta ford dexter engine cylinder liners replacing

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