David Brown Tractor Forum

Soaking some WD 40 to the top may do the trick. Pulling out the valve chest is several hours work, so still I would keep on exercising the spool patiently.

Hmmm. Th spool valve is not prone to rust solid. There can be some dirt or even rust, which prevents it sliding down by the spring pressure but usually the valve starts moving again when helped by pushing by a screwdriver when the control lever is fully back. Independent if the valve chest is on a w...

If there is no grey smoke from exhaust when cranking it is obvious that the injection system needs attention. An engine does not run without fuel. After a long standstill I would not hesitate to change new filters, clean the lift pumps screen and bowl, bleed out fuel from the tank line to see if it ...

As skyrydr2 wrote, a petrol car engine does not work on tractor even satisfactory without a governor. The governor does not have to be very complicated, what you see on a mower could be sensitive enough especially if there is room for a heavy flywheel. Diesel is much better if it is made to work by ...

Where I live most tractors have telescopic stabilizers, which have rows of holes which give possibility to lock the insert with the outer tube by a pin. They are connected to the reduction side holes and to the outer quarter-point of the link arms. Broken bolts are not unknown and its known that if ...

Hmmm. Modern oils do emulgate with water. It is made in purpose to prevent liquid water collecting somewhere in the system. In the old days oils did not mix with water, so if some water was poured in, most of it could be drained out from the lowest point of the sump. A paper filter is not able to co...

Hmmm. I think the explanation origins from the decision to produce cylinder block also to 990 without wet sleeves. The block has identical casting with 1200 but in order to keep that 990 in the 50..60 hp class it was rather simple way to limit the power by using shorter stroke. 1200 has stronger tra...

Hmmm. Are you sure that the small tap on the side of the injector pump is open? If its closed it will cause retarded injection and a lot of smoke.I have seen a tractor which suffered of smoky run all its life on a farm. The next owner turned the tap open and the problem was sorted. Unburnt fuel is g...

Hmmm When the hold valve plunger is off, the oli from the lift can flow freely to the lowering speed control valve. If the lowering speed knob is turned fully open the arms lif only very light objects, especially vhen engine idling. If the knob is turned fully in, the arms will lift rather heavy obj...

Hmmm. I have discussed with a fellow who had the same symptom. In his tractor the lowering speed valve is either stuck or the previous mechanic who has dismantled the valve chest has assembled the valve plunger to the bore upside down. This upside down sound stupid but I have seen that happen. Enery...

To get better access to the diff lock, its better to remove the flange, on which the oil seals are fitted. Use right size of bolts and a strong flat bar to the job, just in order to avoid the flange damages. To put the things back together you need a rod, slightly thinner than the drive shaft, on wh...

I have an 990 which has got the engine from a 1390. That means that swapping the engine between 1390 and 996 should be more or less a bolt-on operation. 990 has dual clutch but both stages on pedal, so I suppose my tractor has original 990 clutch assembly. I cant be sure if 1390 and 996 have interch...

I have seen one 990 (very identical fuel system with 996) which suffered of a dirt particle in the tank pipe. It did run a while but then stopped. After bleeding it did run a while again and stopped. The dirt was found after loosening the connection from tank line to the fuel line to the lift pump. ...

OK. Broken/disappeared 0-ring is probably the explanation. Now, when the pump is on desk, it could be a good idea to check if it needs new gasket rings. At least Dowty has replaceable seals which can give up and weaken the pressure output. I do not know about Plessey, but I guess that it has about t...

If your tractor has double acting valves on the RHS of the seat, they are independent of rear lift.

W.B.R erkki