Perkins engine noises that I can't put my finger on

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eetherington
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Joined: Thu Apr 12, 2012 10:15 pm

Perkins engine noises that I can't put my finger on

Post by eetherington » Fri Mar 08, 2013 8:35 pm

Hello everyone,

I have just rebuilt a Perkins 152 with chrome liners and rope seal. I've replaced the pistons, rings, little ends (professionally bored), big ends and liners and new head, and had the injectors reconditioned.

On first fire up I notice two distinct noises that I've never heard before on a rebuilt engine.

First noise: a high pitch rat-a-tat-tat-tat that reduces in volume by the last tat and changes speed with rpm. It sounds a bit like hammering metal in a foundry.

Second noise: a knocking noise that is a constant volume and is of a dull noise it isn't very loud but you can hear it. and isn't in a sequence it is just tap tap tap tap tap all the time, it is louder than the first noise and also increases speed with rpm. This is more prevalent at cyl 3

Observations: when installing the new liners they just slid straight in. I did not put shims in as they are in tolerance. I tightened up all big ends to 95Nm. on the third galley of the crank, I noticed that it wasn't smooth so I wet and dry papered it so it was with 1200ppm paper (the old bearings had distinct tracks in them). Using a long driver as a stethoscope I have established that it is top end and not bottom end. However there is some smoke that comes out of the oil filler however there is a lot of compression and once warm it starts on the second crank (it won't start on second crank when cold as the wrong ignition switch has been installed). I have also adjusted the tappets and readjusted them. I have run the engine without the rocker cover on and its not the valves.

Extra observation: there is very slight lateral play in each con rod. The crank has been ground to +0.010" when it was first rebuilt. There was very low compression and oil spurting out of the exhaust (use a pint of oil in an hour) i rebuilt the engine because I was only getting about 200-250psi on each cyl. I assume its meant to be double that for a diesel. Plus a lot of leakage (so much that the leakage tester couldn't pressurise the cyl)

What I think could be the problem:

The liners knocking against the head even though they are intolerance.

Apart from that me and my dad can't figure it out!

Anyone else who has any thoughts?

Thanks very much in advance



Norvin
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Location: Sunshine Coast, Queensland, Australia.

Re: Perkins engine noises that I can't put my finger on

Post by Norvin » Fri Apr 26, 2013 7:56 pm

From your description,
Re first noise:
Possibly a combustion issue related to second noise.

Re second noise:
I would bet that it is at least the #3 piston hitting the head. This must be addressed before the engine destroys itself, the hammering is likely to have already jammed the top rings in grooves and the big ends and main bearing bolts will also be over-loaded. When I worked on re-building Perkins engines 30 years ago it was normal practice to measure the assembled height of every piston and invariably re-machine the tops to the spec clearance (critical on any high compression diesel)

eetherington
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Joined: Thu Apr 12, 2012 10:15 pm

Re: Perkins engine noises that I can't put my finger on

Post by eetherington » Fri Jun 07, 2013 11:57 pm

Thanks for your reply, the pistons were hitting the head (they even had the machine serial that was imprinted on the crown imprinted on the head) and they were sold to me as finished pistons but anywho I've changed the pistons back to the originals and kept the new rings and put a few shims in so they are 0.005" proud. the foundry noise has now gone, thank you very much :)

Norvin
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Joined: Tue Aug 21, 2012 3:24 am
Location: Sunshine Coast, Queensland, Australia.

Re: Perkins engine noises that I can't put my finger on

Post by Norvin » Sat Jun 08, 2013 8:46 am

No worries, glad some of my experience has been useful, hope you never have to look inside it again!

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