NewZed Posted September 8, 2013 Share Posted September 8, 2013 Does anyone know how to tell for sure if a wrist pin is bad? I thought I had a timing chain noise but did some more inspecting and find that removing the #1 injector plug removes the noise. Loose wrist pin is the only thing that seems to fit (Honsowetz Rebuild book as my source), aside from possibly a small exhaust or head gasket leak. The engine (used, probably high mileage) has a light thumping noise that goes away after 4-6 thumps when started in the morning which is apparently a sign of a worn bearing. The inside of the engine had much sludge, which is slowly washing away with detergent oil usage, so it's probably had a hard life. But it runs great, except for the irritating ticking noise. Lash is adjusted, oil level right. Any insights on how long you can run with a bad wrist pin, and what happens when it gets too bad (does something break or does it just get super noisy?) would also be appreciated. Odd topic and I won't be surprised if it's just another one of my DOA threads. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 9, 2013 Share Posted September 9, 2013 There is a basic test involving pulling the spark lead, but I'm not inclined to argue about it. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted September 10, 2013 Share Posted September 10, 2013 Pulling injector does the same thing without getting the willys from a big shock. So you're saying it only makes the noise on cold start? If so, high mileage L28s do get loose on the rod bearings and will rap on cold start and certain oils may make the condition worse if it takes too long to get pressure on start. Quote Link to comment Share on other sites More sharing options...
Domzs Posted September 10, 2013 Share Posted September 10, 2013 It sounds like a rod bearing to me . Would it make noise with RPM ? Quote Link to comment Share on other sites More sharing options...
Xnke Posted September 10, 2013 Share Posted September 10, 2013 Wrist pins have a pronounced double-click, they sound like a lifter, but tap-tap, tap-tap, tap-tap...instead of tap-tap-tap-tap-tap-tap. Rod bearings are lower in the block; use a long screwdriver or a mechanic's stethoscope to locate the noise. Rod noise may go away with an injector clip or a spark lead at idle. Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 11, 2013 Author Share Posted September 11, 2013 (edited) The thumping noise is at cold start. It goes away and doesn't come back, I assume when oil is supplied. The other noise follows RPM exactly so doesn't seem like it would be a timing chain flopping around. That's why I thought it might be the wrist pin, after looking through Monroe's book. Removing the injector plug is a variation on his recommendation of removing spark. The motor has always had a ticking that remained after adjusting lash and I've kind of blown it off as just a noise that this particular engine makes, maybe from a loose mouse-trap spring or something. But I decided to find the source and here I am. Can't find it, except I know now it's associated with the #1 cylinder. Everything's adjusted, the mouse-traps all seem tight, the noise seems to come from somewhere besides the valve train. I've put about 10,000 miles on it so hopefully I'll get some more noise as it gets worse if it's about to go. I have another engine that will go in eventually. If I knew what to look for on the ticking engine I might take it out sooner and fix it. Thanks for the comments. The only blown up L6's I've personally seen all had rods thrown through the side of the block, but they weren't mine so I have no idea how much warning the drivers had. Mystery noises make me nervous. Edited September 11, 2013 by NewZed Quote Link to comment Share on other sites More sharing options...
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