Thread: 3l needing new pistons?

Brothers 3L hilux cambelt came loose, tensionor screw broke.. was running but had alot of rattle from top end. We pulled the head today and valves have just been touching pistons and has sightly marked them, should we replace pistons or should they still be good to go? Head is currently as a Head specialist getting checked over.

You may be lucky they don’t look too bad, can I assume the valves are bent? I would recommend taking the pistons out and measuring them and check they haven’t bulged out on the side of the piston or pushed the land down onto the top ring.
If the pistons are good then do rings and bearings then you’re good for another 500,000.

Id go new pistons just to be safe for the turbo or supercharger you should put on the side of it.

Originally Posted by DLW

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Thanks for the response, guys that he dropped head into said it looked really good but are going to check everything out, we couldn't see any visible bends or damage on the head. Was wondering if we could just take rough edges out of marks and put head back on due to financial costs but think we might try take pistons out and do what you said, as he has no intentions of selling the truck. Any tips on pulling the pistons?

Originally Posted by 2post

You may be lucky they don’t look too bad, can I assume the valves are bent? I would recommend taking the pistons out and measuring them and check they haven’t bulged out on the side of the piston or pushed the land down onto the top ring.
If the pistons are good then do rings and bearings then you’re good for another 500,000.

Thanks for the response, he's a 80 year old stuck in a 22year old body haha so can't see any turbos or super chargers anytime soon, but he wants it too go for a really long time.

My money would be on "sweet as"

Sump off to remove the pistons.
If money is tight go around the side of each piston with a feeler gauge to check the top ring is tight against the bore and not broken then put it back together.

if ya want cheaper original parts goto partsouq.

Originally Posted by Konev

if ya want cheaper original parts goto partsouq.

Thank you, looked into it and prices look awesome

I used to own and operate a machine shop - we used to have this issue many times on Toyota diesel engines.
If it was not burning oil before this then it wont after this. The downward force from the valve onto the piston is straight - and not on an angle. The valves in these engines take the hammering. If the head checks out A OK then the piston assembly will be good. Diesel engines are built tuogher than petrol cause of such higher compression and it takes a massive amount of energy to break a diesel engine piston. I'm not saying its impossible but in this cause its only a valve touching - You should see them when a valve breaks and pummels itself senseless in the combustion chamber.
I'd be happy to let it run however it all depends how good it was before the incident.
The secret to long life in any diesel engine but especially toyota's is regular oil and filter changes. They used to start on new ones at 10,000kms but that was reduced to 7500kms to stop thinning of the oil - once the oi became diluted it reduced bearing clearance resulting in the con rod going up that little bit further thus allowing the valves touching the pistons and Vola - Same result as you have.
Be care on aftermarket cheap parts - they are cheap for a reason - no one ever regretted paying for good quality parts. As me how I know LOL
Parts like pistons etc are like rifle scopes. You pay for what you get.

Originally Posted by 35desoto

I used to own and operate a machine shop - we used to have this issue many times on Toyota diesel engines.
If it was not burning oil before this then it wont after this. The downward force from the valve onto the piston is straight - and not on an angle. The valves in these engines take the hammering. If the head checks out A OK then the piston assembly will be good. Diesel engines are built tuogher than petrol cause of such higher compression and it takes a massive amount of energy to break a diesel engine piston. I'm not saying its impossible but in this cause its only a valve touching - You should see them when a valve breaks and pummels itself senseless in the combustion chamber.
I'd be happy to let it run however it all depends how good it was before the incident.
The secret to long life in any diesel engine but especially toyota's is regular oil and filter changes. They used to start on new ones at 10,000kms but that was reduced to 7500kms to stop thinning of the oil - once the oi became diluted it reduced bearing clearance resulting in the con rod going up that little bit further thus allowing the valves touching the pistons and Vola - Same result as you have.
Be care on aftermarket cheap parts - they are cheap for a reason - no one ever regretted paying for good quality parts. As me how I know LOL
Parts like pistons etc are like rifle scopes. You pay for what you get.

Thanks for your response, heard back about the head and valves aren't bent but the camshaft is. Gives me a bit more confidence to put it all back together once head is sorted, was a good runner before this happened
Cheers

Originally Posted by DLW

Thank you, looked into it and prices look awesome

I have used them. Legit.