Perkins knock ad4.203

Rustbucket · Apr 27, 2017

I just got a MF 40B. The thing starts great and runs nicely for 4 to 5 minutes, then as it gets warmers I get a knocking sound that gets louder. I can not seem to pin
point it. I thought if it were a rod it would knock on start up. Any ideas or maybe someone has seen this before? Thanks Oh if this is a rod, can the pan be pulled
without splitting the tractor to check them?

John Deere D · Apr 27, 2017

Try installing a mechanical oil pressure gauge....Start engine ,monitor oil gauge. As engine is running, and as Knocking sound becomes pronounced loosen fuel line from PUMP to # 1 Injector, take note if Knocking sound is worse ,less, or absent. Tighten fuel line and continue with all fuel lines from main fuel pump to each individual Injector.
See if the Knocking ever becomes worse ,less, or absent.

Rustbucket · Apr 29, 2017

32 degrees here this morning. Tractor started just fine this morning, but the tick was there early on and got worse more quickly than before. I broke each injector,and with each one there was a drop in rpms, but no real difference in the severity of the knock. I am presuming that means I will have to open the engine up? All my diesel experience has been with detroits. Can I drop the oil pan on this tractor without removing the engine? I can block the tractor up and use my a-frame to support front end. I would just like to know how much damage before I start buying parts or another motor. Thanks for the help.

rockepg · Apr 29, 2017

Use a mechanics stethascope and move the probe around the engine. You will hear the knock all over but when you get close to the actual area it will get quite loud. Should help you narrow down the area at least.
If you dont have one a long screwdriver held to your ear will give similar results.

Working Towards 62 · May 1, 2017

Just got on for another reason and saw your post. I restored a 1962 Dexta which had a 3 cylinder Perkins diesel engine with a knock I could not figure out so I found me an old timer who has worked on Perkins engines for ever! Here is what he told me to do, sounded crazy at the time but I gave in and did it. I pulled my head and gasket and measured each piston at it's top dead center.They were all different. He told me that sometimes the valve would hit the top of the piston just enough to make a knocking noise. I pulled the piston and machined them down to be 10 under the lowest piston measurement. Put it back together and no knock. Power still seems to be the same also. Before you went to all that work maybe pull your head and double up the head gasket to get some extra distance in there and see if the knock goes away or changes. My 2 cents

JoeMartin · May 2, 2017

I had a 4 cyl gas engine that started fine and about the time the heat gauge started to come up it started knocking. It was a rod bearing, Joe.

Rustbucket · May 6, 2017

Thanks to everyone, I finally exhausted all the suggestions and then some. I dropped the pan and sure enough it was #4 rod bearing,I do not know why it did not knock
immediately, the oil passage was blocked with babbiting. There is some ribbing but no discoloring. Do not want to pour a lot of money into it, so I will clean out the
journal oil hole and smooth it with crocus cloth. Put a new bearing in and see how far it gets me.

John Deere D · May 7, 2017

Was the bearing Insert STANDARD or UNDESIZE? (Was Journal ever ground?)

Bob..

rockepg · May 7, 2017

If you had bearing material clogging the port then you probably have a blockage somewhere. Oil is not flowing into the journal and it just ate the bearing.
Since you just got this i would be having a conversation with the person you bought it from. Sounds like it had this problem and they slapped a new bearing in there to sell it.

Perkins knock ad4.203

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