bending pushrods

[welshblue52]

Hi All,
a new member with a problem - any thoughts, please

My problem is bending, and in some cases, shearing pushrods.

Background history
I brought the tractor in November 2008, and set about tidying it up and putting it back into original condition. For some unknown reason, it was a poor starter. The eventual outcome was an engine rebuild in June 2009, which included a head skim. Since then, I’ve had the problem. It’s got through about five pushrods. There would appear to be no logic with when and which rod.

In attempting to sort the problem, I have checked the torque on the cylinder head bolts ( all correct ) and reset the tappet gaps after a settling-in period ( set correctly, possibly tending to the loose side ).

The latest incident happened after I’d spent three hours rolling a field. Not during the labouring period, but under low load on the way back home.

Firstly – does anyone have any thoughts on why this is happening ?
Secondly – does anyone know where I can acquire a new set of pushrods ? By my research, part no 6488 – rod ( valve rocker push ).

[Brian]

We would need some details of the engine like the serial number and some date codes to date the tractor. Push rods are not the same through the Major range, they vary in length and I wonder if you have the right ones for your engine.

[welshblue52]

Thanks for the input, Brian.
Will sort out the relevant information and get back to you.

[BearCreek Majors]

Be sure the rockershaft assembly was reassembled corectly, if not the rocker arms will not get proper lubrication and bind. Does the compression release work properly?

Pat

[Roadless63]

We had this problem on our power major, the engine had not been apart in our ownership (15yrs) and we believe the 5000hrs to be genuine on the clock, this bent a pushrod near on number 4 cylinder one day. It was replaced with a good second hand unit and this has served fine carrying out baling and other lighter duties ever since. The only comment I can make on our engine was that we found the thermostat had been removed. This is not good news for cooling the back of the block since too much water bypasses the block, it needs some restriction to allow water to circulate properly. The original type thermostats have a sleeve which closes off a bypass port when it opens, not sure you can get this type nowadays. We wondered whether the head got warm that end leading to sticking valve or change in rocker clearance etc.
Probably not the same failure mode as yours but thought I'd share it none the less!

[Roadless63]

Just reading your post again, you mention head skim, any chance the pistons could be contacting the valves on full lift? Is there a difference in head gasket thickness, some engines were available with shims to replace machine material from the head. Are the pistons correct, fitted correctly, made to drawing ie not too tall. Just thinking of situations where the valves could strike the piston. How about rockers, are there more than one ratio, are valves/springs going coil bound on full lift and loading the pushrods that way. Are the right valve springs fitted, have new ones been fitted, again not to spec. The list goes on I'm afraid but it sounds like you may have to borrow some correct spec parts and compare like for like.

[BearCreek Majors]

Also check to make sure the oil is not deluted with fuel, if the injector bleed off line is leaking it will delute the motor oil again causing valves to stick, rockers to bind, etc.

Pat