breaking push rods

[daveinmiss]

Ive got a D15 AC that broke a pushrod. I replaced it. Cranked the tractor again and it broke that one. Some of you mechanics tell me what you think is wrong with it. Thanks.

 

[Bob Huntress]

If it was the same pushrod, I would check the corresponding valve and rocker to ensure that they are not stuck or binding.

 

[jd b puller]

Not sure of the details of this motor, but often times if a push rod bends, it's because a valve is stuck.

 

[old]

Well lets see. A sticking valve will do that of a cam that has a problem but more then likely a valve problem. Or of course a vale that is super bad out of adjustment could also do that
Hobby farm

 

[Bob Huntress]

Old, I considered the misadjusted valve, but if he changed the pushrod since the problem originated, he must have readjusted the valve???

 

[old]

I would think so also but I prefer to give as many option as I can and hope most are wrong. Shoot it could even be a problem with the roker arms but a lot less likely

 

[VADAVE]

Had that problem with a '71 chevy, 350 engine. Turned out the rocker studs were just slightly out of true which allowed the rockers to wear a grove in the side of the stud. When the grove got deep enough the rocker started catching and breaking the pushrod.

 

[El Toro]

Did you adjust the valve after installing the new push rod? Hal

 

[jose bagge]

start isolating the problem by turning the engine "bottom dead center" on that cylinder and then try to depress the valve in question. Could be a bent valve stuck in the guide- if it won't depress it will bend/break the pushrod.
I'm going to assume as others have that since you replaced the pushrod you got a good look at the rocker, and adjusted it properly.
If the valve depresses, it could be cam timing. If this is an interference motor, and the cam timing is off, the valve could be coming in contact with the piston ad bending the pushrod that way.

 

[Anonymous-0]

Dave, some more details would help some of the guys solve this problem. Have you been running the tractor? Any recent work on engine? did you just buy the tractor? Have you had the head off? Help us out a little. Tom

 

[Mark - IN.]

Well, clearly the pushrod is moving, but what its trying to move either aint, or aint propery. Make sure the folcrum is moving properly, and if it is, go after the valve. I don"t know what the spring pressure on that valve is, but suspect that it can"t be more than you weigh, so if you take the folcrum off and put a board across it and apply pressure downward, it should move down, and when you let off, it should come back to normal heighth. Out of curiosity, when you replaced the pushrod and adjusted it, was that cylinder at bottom dead center so the cam lobe would"ve been pointed away from the pushrod?

 

[Mike M]

I have never saw any break yet ? I would think they should bend first ? I have bent some into S shapes in our 351 Ford engine. I thnik this was due to valve float.

 

[Jerry/MT]

I"ve seen bent push rods but I"ve never seen them break. I imagine if the valve is really stuck you can break the push rod. They usually bend from stuck valves on engines that have not run for a long time.

Have you changed anything that effects valve timing(cam chnge, cam gear or timing chain change, etc)? Is it possible that the valve timing is off and your piston is hitting the valve(s)?
That"s all I can think off for the moment.

 

[El Toro]

You should bring No1 piston near the radiator to TDC on the compression stroke. Then see if both valves are closed and your timing marks are aligned. If this checks out ok, your valve timing is ok. The valve may not have enough clearance in the guide could have carbon buildup. You may need to pull the head. Hal

 

[Dick L]

Are you using the term break as not being of use?? I never saw a push rod made of a material that would break rather than just bend. A stuck valve will do it every time if you can get the engine to turn over.

 

[Anonymous-0]

You broke the pushrod???? Most of the time they just bend. And you say you broke it twice. WOW!!Somethings wrong with that engine, big time.