what damage can be expected from broken valve spring?

derwen1959 · Jul 15, 2018

I know of a JCB where the valve spring broke and damaged the head and piston ? the owner has got new head and piston. the damaged piston has not been removed and he has not tried to turn engine over by hand... but could more damage be caused like bent con rod or even worse.... he has removed head himself but is reluctant to do any more and he cannot find anyone to take on job of fixing it, the engine is Perkins Phaser

M-MAN · Jul 15, 2018

It very unlikely there is any damage below.

derwen1959 · Jul 15, 2018

thanks for reply... assuming there is no other damage would the engine run ok with one new piston and three worn pistons or would it run uneven... I need to do research first.. because if I do job I need to make sure it is correct first time , in the past I have always renewed all pistons and things are good

Destroked 450 · Jul 15, 2018

What kind of damage did it do to the piston?
I've seen a dropped valve cause all kinds of damage to the piston and head.
We had a broken valve spring on a 1650 Oliver years ago, there was a mark on the piston where it was hitting the valve but it wasn't hurt to a point it needed replaced, the valve was warped so we replaced it and the spring then put the engine back together.
It was still running some years later when my brother sold it.
If the piston has a small dent in it where it's hit the valve I wouldn't bother replacing it, if it's a big dent and has swelled or hammered the top of the piston down near the ouster edge then yes it needs replaced.
The head needs checked to see if the valve is bent and if there's any possible seat or guide damage from the piston smacking to valve back up in the head.

derwen1959 · Jul 15, 2018

I have not actually seen machine but I have been informed that piston and head are badly damaged as the owner lifted jacks and loader and moved machine when he heard noise!!! perhaps damage would be minimal if he stopped engine immediately

Destroked 450 · Jul 15, 2018

If it damaged the head enough to need replacement it ether dropped the valve into the cylinder, bent the valve, or broke the valve, any of these would have done a lot of damage to the piston and possibly cracked the cylinder wall or even bent a rod or crankshaft.
He got ahead of himself buying parts before finding out the full extent of the damage.
You need to look it over close before committing to the repair job.

buickanddeere · Jul 15, 2018

(quoted from post at 09:51:12 07/15/18) I know of a JCB where the valve spring broke and damaged the head and piston ? the owner has got new head and piston. the damaged piston has not been removed and he has not tried to turn engine over by hand... but could more damage be caused like bent con rod or even worse.... he has removed head himself but is reluctant to do any more and he cannot find anyone to take on job of fixing it, the engine is Perkins Phaser

Valve Guide bore could now be oval instead of round

Robert Major · Jul 16, 2018

Hi I'd say you are well into doing the job right with the head off and having to remove the sump, for the one busted piston. See what the bore wear is like and what the bearings are like /crank condition , then check the rod to see if it's straight. If It's a perkins phaser you are working on a 3cx that probably still has a fair amount of value to replace it. if it was some dog rough old 3c mark 2 or 3 i'd say chuck it together and run it till she pukes and buy another one.
I have a 4wd Belarus 1507 (1770 in Canada ) here broke a valve and made a mess with the last owner, He put a used piston and rings in a honed out cylinder, shoved it together with a used head and new head gasket and it runs fine. But the catch is I gave him $2000 for it and I'd get my money back throwing it in the scrap if prices are high, and it blew up again later. Regards Robert

thepumpguysc · Jul 16, 2018

All sorts of damage "coulda" happened.. you wont know until its torn down..
IF you wanna take it on, tell the guy you'll get it running but theres no guaranties UNLESS you TEAR IT DOWN..
Whats gonna happen if you do what he tells you to do & it shakes & smokes??
YOU gonna tear it all the way down & DO IT RIGHT on YOUR DIME??
I run into that scenario all the time..Throttle shaft leak..
Customer wants the leak fixed.. I inform him that its probably gonna leak somewhere else & a full reseal is in order $$.. NOPE, just fix the leak.. OK but NO warranty.. I fix the top cover leak & a week later its leaking from the bottom of the pump..
Am I supposed to eat that?? NO.. I warned the guy & HE elected not to do it right..

David G · Jul 16, 2018

I think you are getting into a mess unless you are comfortable working on that engine.

Moonlite37 · Jul 16, 2018

with having a new head, the condition of the valve guide would be on issue

derwen1959 · Jul 17, 2018

I am going to suggest to the JCB owner to find someone else to do job.... thanks for all replies

David G · Jul 17, 2018

That is really a good idea, remember, no good deed goes unpunished.

tractorguy2 · Jul 17, 2018

I have replaced several broken valve springs in old tractor engines. None of them had any damage other than the broken spring.

dr sportster · Jul 20, 2018

That is not a broken spring .that is a dropped valve and very likely the con rod is bent. Keepers came loose.

what damage can be expected from broken valve spring?

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