Calling on my tractor mechanic friends… I have a very specific issue related to a 3 cylinder Perkins diesel tractor. It has been running real rough and down on power, smoking etc. I was about to tear it all down and replace the head gasket. Instead, I found this:
#4 rocker arm (intake) is broken. That sure enough explains it. But what happened?
What causes a rocker arm to break? Both valve and pushrod move freely. Did it just fail?
Also, notice the arms are stamped steel. All of the replacement parts I’m seeing online are forged / solid metal. Are they interchangeable? Was that an improvement made later on? Sure seems stronger.
Hi Chris, it is’nt unusual that those stamped rocker arms cracks and fail, i’ve seen it before, it seems Perkins only used them periodically, on some engine types.
I just welded them, and it works still today, but probably nothing i should recomend? (I even welded the forged ones at both Perkins an Volvo BM, and it holds up)
The reason they break is probably just metal fatigue.
Thanks Goran! That’s exactly what I needed to know. I could weld it up, but I think I’ll make the investment and order forged replacements for all valves. Perkins parts are cheap here.
Cody, the valve lash was my first thought, since I had rebuilt this engine myself and it’s easy to doubt your own ability… But I know the lash was set correctly, and the adjuster was still tight, so the setting was preserved.
I’ll get parts ordered and post an update when it’s all put back together.
Chis ironically i just replaced 2 rocker arms in my D15 because one of the adjusters got loose and fell out. My advice would be to just inspect all the other rocker arms and replace the damaged one. Also check the push rod closely to see if it is seated properly and not bent. I suspect the issue is just metal fatigue as was mentioned but i think if the others look fine i wouldn’t replace them. It seem more likely to be a bad part. Also double check that you have good oil flow at the head. When you put it back together. My D15 the first time it was rebuild someone didn’t line up a bushing for the cam correctly and i had to drill it out to get oil flow to the head.
It probably has to do with cost more then anything else. I would be in the replace them all camp, not because it is strictly necessary, but if one is stresed another might be close, and I already have it apart. There is probably a reason why you are seeing only cast ones available on the market.
They definately have the same mileage / running hours so either replacing all or welding the broken one depending on the cost of the parts and one’s economic situation, that would be my standpoint. But preferrably the first option.
It is probably the biggest factor. While they aren’t hard to get to, the only time equipment breaks is when you need to use it. I would consider welding them back together a quick fix to get the other work done. Then come back and redo it more properly as the solution. If there is time to wait for parts, then I would just wait.
While I agree with the advice and often do something temporary while ordering the correct parts it had been my experience in life that temporary fixes are left in place until the next breakdown. I told people when i was an off shift technician they could have the correct fix or the temporarily permanent fix because no one would bother to do the correct fix at the weekly maintenance downtime. My boss would get mad till i pointed out things he had me temporarily fix months earlier.
Before someone asks why i didn’t do the correct fix during downtime it was first shift that made the schedule for what got done.
Chris,
If you do a “temporary” fix, say welding that one rocker arm, you can put the engine back together, see how it runs, and get some work done while you are awaiting parts. Long term, yes, get the cast rocker arms. Benefit might be better running and less tendency for the adjusters to loosen on their own.
Just my two cents.
My principle is to try to repair defects at home, so you gain experience and skills to eliminate various errors. Knowledge and skills are priceless values, especially if there are no spare parts and the machine stops working. Order spare parts, but try your hand at repair, it’s a very useful experience.
Hi, I have a Fordson Dexta which is the predecessor to the Massey Ferguson/Perkins version. I have a MF 2135 with a loader and gasoline version of the 3cyl that I’m using daily for the plant cleanup. I also have one of the MF diesel units that will be scrapped soon. Internal components of some versions are interchangeable as Ford had Perkins assemble the Dexta engines with Perkins internal components. All was good until MF bought Perkins. Then Mr Ford refused to do business with his competitor. MF realized that the 3 cylinder was an excellent small tractor engine so made their version.
Gummed up valves from using veggie oil for fuel or feeding woodgas to the engine can stick the valves.Ether can cause a backfire that possibly caused an issue. Aside from sticking valve, hydro lock from a cylinder filled with fluid is about all I can think of that could cause a failure other than the rocker arm simply failing due to some issue with the rocker arm it’s self.
This engine doesn’t have pushrods that can pop out of engagement with the rocker arm or tappet so it is not possible for a disengaged pushrod to push the valve/rocker further open than normal and result in the valve being struck by the piston.
Thanks again to everyone for their feedback. I did order a new rocker arm, but as Mike and other suggested, figured there was no harm in getting some work done while I wait. Parts are coming on the slow-boat from India.
Sure enough, the arm welded up just fine, and I managed to get a 7 acre field bush-hogged. Here’s the tractor running, before and after the repair.
Before:
After:
I managed to break the bushhog axle mount while mowing, and I was able to weld it back using a PTO generator I got recently. First real test of that. I didn’t get video of actual welding but you can see the results below. Not my prettiest weld, but strong enough for the job.
Then, after I finished up that field, the rough running came back. I thought to myself, well that weld didn’t last long. Here’s what I found after I opened it back up:
Nothing at all wrong with my weld! A totally different rocker arm failed (#1, front of engine). I welded that one back together too, did yet another valve adjustment, and the tractor is once again usable. Still waiting on the replacement parts… but I’m not at a complete standstill. Thanks everyone for the feedback and encouragement to just weld it.
There is my next tractor project. The Allis Chalmer D17 has has the same tires for as long as i can remember. I did have to replace one front tire last year as it was worn through and running on the actual tube. Turns out those are not designed for too many miles… well the funny story on the tires is I desided to order tires last weekend and one of them when flat 2 days before delivery of the new tires today after somewhere between 40 and 50 years of life. My uncle doesn’t remember when his father changed one tire but he is pretty sure the other was on it in the 60s when they drop off the tractor. I know th miss matched set was on it as long as i can remember and i am 50. So i thought it was funny it went flat while the replacement was on order.
I borrowed a tractor to bale the 900 bales i had ready yesterday and am working on hauling those today once that is done i will probably tackle the tires.
