We get lots of people asking if we can recommend an engineer in various parts of the country (or indeed the world) who is good with tractor engines.
If you use a good engineer (or mechanic) and you have been pleased with their work, then please click over to the website and leave details of the company in the comments box.
It would be a really useful resource to have recommended engineers from all areas.
We regularly get emails coming in from people saying the’ve overhauled their engine but it still doesn’t start or run very well.
When we dig a little deeper we begin to find out why.
It always amazes us how many people go to all the time and effort of of dismantling an engine and then only do half a job of refurbishing it.
Just Buying An Engine Kit Won’t Cut The Mustard
All too often people buy an engine kit and fit it, but fail to do a decent job of the valves or the head. Or worse still they replace the piston rings, think that the pistons themselves are OK, maybe just use a honing tool on the cylinder liners because, well, they don’t look all so bad do they?
I know we don’t like to spend our hard earned cash unneccesarily and replace parts that are serviceable. However, if the rings are worn, so usually are the pistons they run on and the liners they run in.
Every so often engines develop a broken piston ring for no apparent reason, when everything else is in good condition, so that may be an exception. But wait, are you really sure that broken ring was a one off or did something else cause it. Occasionally things do break for no apparent reason, but more often there is a cause.
We Didn’t Bother To Re-Gring The Crankshaft
“It didn’t seem all that bad. There were a few rough spots on it but I didn’t have a micrometer to measure it, thought it would be OK.”
Vintage Tractor Engineer’s blood is now reaching boiling point.
Valve Seats. I Used Some Paste And Sand Paper
Is rubbing the valve seats with a bit of paper really going to create a sufficiently good sealing surface? OK, so yes, it will improve them. Re-cutting will be a much better job with new valves and guides. Sometimes a new valve seat needs to be pressed in and then cut if the old seat is too worn.
The Head Gasket Failed And The Engine Boiled
“I replaced the head gasket. It went OK for a while, then it started to leak again. I’ve got to replace the gasket again now.”
Maybe you should have realised the head may have warped or cracked. As a minimum it needs pressure testing, probably skimming.
“It was cheaper to buy a new cylinder head than have the old one serviced”.
That should tell you something about the quality of this new head. If it’s cheap then it’s probably rubbish. VTE would recommend having your old one skimmed in preference to one of these cheap heads. If your existing head is beyond repair consider getting a second hand head and having it serviced.
- Was the camshaft OK?
- Timing gears or chain condition
- Injector pump
- Cleanliness is king
There’s obviously a lot more to it than this, but the point of this article is that you need attention to detail. Stripping and rebuilding an engine can take 2-3 days, so a few extra pounds spent on the job will often be well worth it.
Your link arms will not lower. It’s a frustrating problem.
We commonly associate hydraulic problems with poor pump performance and reduced or slow lift capacity. However, we get quite a number of people reporting that their link arms won’t lower.
We’ve had an email from the owner of a Massey Ferguson 35 who has this problem, so we’re going to take a look at what could be the problem and what needs to be done to get the system working again.
Lift Arm Shaft
The rate of drop of the arms should be set so that the lower links will just fall under their own weight when lifted by hand. This is altered by adjusting the cap screws in the ends of the lift arms shaft.
If the screws are tightened too much, not only will it prevent the arms from lowering but it can also cause erratic action of the hydraulic system.
However, if a heavy implement is attached to the linkage and the arms will still not drop then it is likely to be related to the pump control valve. We first need to uderstand how the position of the control valve raises and lowers the arms.
The Pump And Control Valve
The lower part of the pump is immersed in hydraulic fluid. When the control valve is open it allows fluid to be sucked up into the pump and then on into the discharge passage (to pressurise the lift cylinder and lift the linkage arms).
The contol valve slides to regulate the supply of fluid to and from the lift cylinder, the degree of which depends upon the relative settings of the manual control levers (and also by any control exerted automatically by the hydrauilc control mechanism).
The sliding control valve is essentially seperated into two compartments, one facilitating fluid inlet to the pump and the other compartment allowing an outlet from the high pressure chamber.
NOTE, the control valve is always held towards the drop position by a compression spring.
- When the valve slides forward, its inlet slot passes within the suction chamber, hence the pump can draw fluid and pressurise the fluid into the lift cylinder.
- When the valve is positioned centrally, both the inlet and outlet slots are positioned outisde of their chambers and hence the oil is locked in the system and the linkage arms remain stationary.
- When the valve slides rearwards (by the force of the compression spring) the outlet slots are brought within the discharge chamber, thereby permitting oil to drain from the system (lift cylinder) back into the sump.
The rate at which oil drains from the system depends on how much of the outlet slot is moved into the discharge chamber. In fact there are two pairs of slots in the discharge end of the control valve. The second pair of slots are positioned further along the control valve, so if the control valve is moved further rearwards then all four slots discharge oil and thus the rate of drop of the lift arms increases. The second pair of slots are also larger.
What Can Go Wrong?
The control valve needs to be oil-tight to the bore of its sealing washers (the washers seperate the suction and discharge chambers). The fit between the washers and the control valve is therefore extremely precision as it must seal under pressure but also facilitate the control valve to move.
To prevent the control valve from sticking there is an oscillating mechanism. The oscillator is driven from one of the pump eccentrics as the drive shaft rotates. It is not uncommon for the square end of the oscillator push rod to be rounded off. This would cause the oscillator to be inoperative and so the rod would need to be replaced.
The exteme accuracy of fit between the control valve and its sealing washers means that any small particle of dirt could cause the valve to jam. Extreme care should therefore be taken with cleanliness of the system.
- Cleanliness of the fittings should be considered when connecting to the hydraulic ports (eg. connecting a tipping trailer or front loader).
- Change transmission fluid every 750 hours (or annually). Clean the pump filter (if fitted) and remove any deposits on the magnetic transmission casing drain plug.
Compression Spring And Control Linkage
Failure of the compression spring would mean that the control valve will not be pushed rearwards into the ‘drop’ position. Failure of the compression spring is quite common.
Also, it is possible that a failure/problem/jamming of the internal control linkages would prevent the control valve to move rearwords into the ‘drop’ position.
Water Or Condesnation In System
We’ve had a few people contact us to say that they have had probelms with milky oil (condensation built up over time and mixed with the water) and this, they suspect, has been the cause of their lift arms sticking up. One owner reported the arms sticking whilst the temperature was below freezing. Another owner reported the lift cylinder and its piston rusted together after just 4 months of not using the tractor – this owner had the milky oil and had to remove the top cover to free the piston.
Isolating The Problem
It is possible to drain some of the hydraulic fluid and remove the right hand transmission casing inspection cover to take a look inside the tractor. Do not put your hands through the inspection hole if the engine is running. It should be possible to see if the levers are moving the control valve and to see if the spring is returning the control valve to the rearwards (drop) position.
Removing the stand pipe would also isolate the pump, control valve and control linkage mechanism as the problem. i.e. if the stand pipe is removed then the problem is either associated with the lift cylinder itself or the lift arms binding. Beware, even with the engine stopped, the hydraulic fluid in the stand pipe could be pressurised.
It is possible that the lift cylinder seizes in the ‘up’ position if the tractor has not been run for some time, rusting in place due to excess moisture in the oil and the transmission casing. An example of this occuring is given in the comments section of this page.
Making The Repair
Obviously the necessary repair depends on what you suspect the problem to be.
Earlier in the article we looked at what to do to set the lift arms to prevent them from binding.
Repair of the control valve and its oscillating mechanism will require removal of the hydraulic top cover to access and strip the pump components. This is an involved process and you may find the MF35 Hydraulics Troubleshooting And Repair DVD helpful to guide you through this process.
This article was based around the Massey Ferguson 35 tractor. The information will also be useful for many other models that have a similar control valve and hydraulic system.
These wiring diagrams are for the 500 series Massey Ferguson tractors.
MF550, MF565, MF575, MF590
Click the link below to download the pdf wiring diagram…
The first diagram is of the main wiring. The second diagram is for the lights and warning lights wiring.
The electrical systems of these tractors are negative earth and charged by alternator (the alternator has a integral rectifier and control box). Always disconnect the battery before carrying out any work on the electrical system.
The belt tension of the alternator should be 0.5 inches at the mid-point of its longest span. Adjust as necessary.
We’ve had a query about aligning the letter G against the circlip mark when timing the fuel injection pump on the 23C engine. Bob has followed the 23C Engine Rebuild DVD and notes that on the DVD it shows the circlip mark on the lower side of the clip gap. However, Bob’s tractor has the circlip mark on the hole above the circlip gap.
Why is this? Which one is correct?
To a diesel engineer, when aligning the timing circlip with the timing groove the orientation of the criclip isn’t important. What is important is that the pump is timed and set to the groove on the circlip.
So your pump may have been overhauled and the diesel engineer has set the pump to the groove (i.e. the circlip may have been turned). So just re-set it to how it currently is.
Further to that, some DPA pumps use circlips with no grooves, in which case the squared end of the circlip is the timing indicator. If in doubt have it checked at a diesel engineers if you have a problem.
How Is This Setting Made?
There were several different versions of the pump fitted to this engine and each version has a different test plan to set up the pump.
The diesel engineer will remove an injector and connect an injector tester to that line (which injector line it is will be specified in the test plan for that version of the pump), rotate the pump to a certain position, apply pressure to the system using the injector testing machine and testing fluid, rotate the pump in the specified direction until it goes solid, maintaining the pressure he will then move the circlip to be in line with the scribe mark.