Knocking in 2.25

[rbbailey]

OK, so many of you have helped me in getting this thing back together, and I'm happy to report that all the front end seals, the oil pan, gaskets, etc... all seem to have turned out just right. No leaks! After clearing the apparent vapor lock in the upper fuel line, she started right up for the first time in 2.5 years. I ran it a little yesterday with the wings off so that I could closely inspect for leaks and such. And while she ran fine, I did start noticing what I thought might be a little knock in the back end of the engine.

Today, I ran her for about 10 minutes and the knock seems to be for real. At the same time, the oil pressure light is coming on at idle.......

So.

What do I do? where do I start? What do I inspect?

I can tell you that when I first pulled the oil pan off I was impressed with how clean the lower part of the engine was. No sludge in the pan. Very clean, metal still showing, dark brown oil, that's it.

I have not seen under the valve cover. The engine has always been a good runner, smooth, but has always liked a bit of a fast idle or she sputters a bit. These past few days I've seen gray smoke at start up. Not heavy at all, enough to notice.

[bobzinak]

My S2A original owners manual says that the oil light may come on at idle. and it is nothing to worry about. as far as the knocking goes I can't really say. if it a heavy knock or just a tapping. My advice is to let the engint gt to operating temp to see if it goes away. I have hasd an older engine that would have a slight knock untilit reached operating temp, that about all I could recommend you to do. ROVE ON bobzinak.

[rbbailey]

Never knew the manual actually said that. Interesting.

In years past, the light has come on at low idle -- I'm worried about it because this is a long time since it has run, and because of the knock.

I'm going to have to investigate it.

[o2batsea]

Well, no good deed goes unpunished. Now that you have the oil pan gasket squared away it is time to pull the pan again. This in order to pull the caps off the rods and plasti gauge the bearings. If they are indeed shot, which is likely, then you will have to take off the cylinder head in order to get the piston and rod out for repair. The engine can stay in the truck.
Thing is, that a rod bearing renders the entire engine's health suspect. It may be rebuild time.

[SafeAirOne]

The oil pressure light illuminates around 7 or less PSI IIRC, so there isn't a whole lot of pressure in the system when the light illuminates. Excessive clearance (wear) between the connecting rod bearings/main bearing and crankshaft as O2batsea suggested, combined with not enough oil filling the normal lubrication space between the bearings and crankshaft could cause a knock.


Engine Fault Diagnosis from the 90/110 WSM:

[rbbailey]

Thanks, but no thanks, if you know what I mean....

It started instantly this morning with little exhaust. I'm letting it idle to get warm and then I'm going to check for the noise with a video. Is there anything else I should do before pulling the pan again to check that oil is flowing where it should?

[jonnyc]

What weight oil are you using? I made the mistake once of running with 10/40 'cuz that's what I had. Returned to 20/50 and it quieted right down.

[I Leak Oil]

A) What is your idle set at when the motor is warmed up?
B) What does your oil pressure gauge [you have one right?] reading at various RPM's?
C) Have you checked your timing? Sometimes poor timing can mask itself as an engine rapping.

[stomper]

Are you sure it is a knock, and not a really loud tappet? I agree with the two above posts. oil viscosity and timing, as well as verifying the pressure of the oil by a mechanical gauge.

[o2batsea]

Honestly if it were me in your position, I would just drive it. As suggested go up one viscosity on the oil.

[rbbailey]

Yeah, I am thinking of just driving it for a bit, carefully, to make sure I know what I'm hearing and such.

Moving to higher oil -- I did think 10/40 was a bit thin as I poured it in, but I was thinking that this is higher than what I usually use... on my Audi and Discovery...

If the gauges are to be believed, I'm running at about 5psi at low idle (I do not have tachometer). It runs at 8-10psi at smooth high idle. And when I rev it and hold it at driving RPM's, I'm in the 40psi range. This is with engine at temps of about 150 to 160.

[o2batsea]

You can go for quite a while with a loose rod bearing. While you are out there tooling around contemplating the ultimate demise of the old 2.25, you should be saving up a for a transplant donor. It is way easier on your entire feng shui to rebuild a second engine and have it ready and waiting for that Cosmic Convergence Saturday when you yank out the old and drop in the new.

[I Leak Oil]

If the gauges are to be believed, I'm running at about 5psi at low idle (I do not have tachometer). It runs at 8-10psi at smooth high idle. And when I rev it and hold it at driving RPM's, I'm in the 40psi range. This is with engine at temps of about 150 to 160.

I run 10w40 all year with no troubles. At temp and speed my engine is between 40 and 50 psi. However, that 5-10 psi at idle does sound low, mine hovers right at 20 psi at idle. Sounds like you need to do some more trouble shooting before you pronounce it or go driving off too far from home.

[NC_Mule]

Sometimes you can pin point a knock/noise with a wooden dowel. One end in your ear the other on the engine. Actually pretty cool how much you can hear doing this. You said the knock is at the back of the engine, any chance something in the clutch is sticking from sitting? Have you taken it for a drive, does it get worse under load? Is your gas 2-1/2 years old or are you using new stuff?
Are the points in spec? These engines have such low compression I don't know if pinging could be a problem. Never heard a engine ping at idle but may be with crappy old gas and poor timing.
Just rambling out easy things to check.
Engines are very tough and they don't know if they have been sitting for 30 minutes or 30 years. 2-1/2 years is not that long, if it didn't knock before and you didn't do any internal engine work (sounds like you just changed seals) then I would look outside the engine and make sure it's in a proper state of tune before you get worried about a major internal repair.

Edit: Whoops I read the first few posts on the first page then posted, didn't see all the posts on the 2nd page. Carry on, looks like you have a plan.

[bugeye88]

Another thing to consider is "piston slap" that occurs when an engine has had a few rebuilds, with some boring going on with each. I've heard engines sounding like a Diesel knock or rod knock due to piston slap. Some engines can go quite long with this though.
Rob