Thread: Run in period

Originally Posted by The Mutt

I ran the motor at idle for about an hour,

Which is probably about the worst possible thing you can do to a rebuilt engine .

There is every chance that you will not be able to cure the blowby without another rebuild now .

Find some hills to drive up, give it a decent work out and see if you can get a reduction in blow-by. You might be lucky. It's what I used to call ruining in...

Otherwise it means another hone of the bores, possibly rings, too.

yep, bad move doing the extended idle thing, that'll kill a diesel even after its run in.

you needed to get it started and then loaded, not full load full noise loaded but enough to get it working.

theres some very nasty things you can try to bed it in but in reality you are more than likely going to want to run a bottle brush hone down the bores and re-ring the pistons.

the nasties included dusting the intake with ajax/baking powder or misting petrol into it while its running at full rpm. I DO NOT Recommend these methods as anything else than the act of a madman, a desperate fool at the end of his pitiful rope

In addition to the above comments, where did you get the rings from and what are they made from?

The rings the aftermarket places try to sell you for these engines are wrong and will cause no end of trouble.
The standard Isuzu rings are cast iron with a chrome top ring, tension isn't that high.
The aftermarket rings are all chrome and have a lot of tension. When used with chromed liners cause rapid wear, blue smoke and blowby that will never go away.

I got the rings from a supplier we know in Canley Vale NSW, Mekong Spares, They are'nt Isuzu parts but are Made in Japan, I was told they are made better than the original rings, same with the Pistons and Cylinder linings, all made in Japan.

Mekong Spares supply a lot of Mechanic shops we do work for, I felt I could trust them.

I didn't get a chance to go out on a drive over the weekend, when I do if things don't settle down can I replace the rings with something slightly larger in diameter?

Glenn

Originally Posted by The Mutt

On for the brains trust ....

We have recently finish rebuilding our 4BD1 after a piston let off a chuck damaging the cylinder liner.

We have rebuilt using new pistons, rings, cylinder liners, new gaskets and seals everywhere. The head has been skimmed, tested and the valves se-seated, probably forgot something in the list.

I ran the motor at idle for about an hour, I was on a business call, when I went back to the vehicle I found that there is still blow-by coming out the seperator on the firewall, when we can we will do a compression test to confirm nothing is wrong internally.

My question is, do we have to drive it for a while for everything to bed down or should we be looking somewhere else?

Glenn

What you have done is glazed the bore. Try towing 2 ton behind it and drive it like you stole it. This was a common problem with the 2 stroke GM diesels and people not driving them properly. A really good workout will probably tgake the glaze off the bores.

Thanks Dave, I'll try to get out for a drive this weekend, a few trips up and down the Hawkebury Road might be a good start ... I hope.

Glenn

Hi Glenn,

Not trying to be rude but do you understand why you need to work a freshly rebuilt engine to run it in? and hence why you need to change the oil after the first ~500/1000kms.

there are heaps of differing opinions on how to running in an engine, and i think the reasons behind softly running in an engine are outdate with the quality of the oils nowadays.

Regards, Steve.