Assessing a motors condition.

[Sycostang67]

I am trying to determine the condition of the motor in this 1991 F-250 we just got. I have a feeling it may have been rebuilt or replaced at some point. It runs very smooth, has only one small oil leak, hardly any blow by, and no smoke out the tail pipe at all. The oil pressure is good, 20psi at warm idle, 40psi when cruising and cold start. The sticker on the valve cover is even in really good shape as they usually wear off or the writing smears. The ODO reads just over 43k but I can tell the rest of this truck was worked hard, goose neck hitch, bumper pull welded to the frame and air brake hose running from under the column to the engine compartment. The oil is black with no signs of coolant, but the coolant is mostly water with a bit of oil on top. I opened the drain plug and light green fluid came out but I can feel an oily film up top under the cap. I was thinking of running some dawn or other cleaner through it and then going back to water to see if the oil returns. Someone did a crappy job replacing the water pump so I am hoping the oil intrusion is coming from there. There is RTV all over the front of it and I saw a bit floating in the radiator as well. If this motor had been rebuilt or replaced, would there be a physical indicator like a tag or something?

 

[USNENFTS]

The only way to know for sure is the condition really. I dont know of any tags. My engine was replaced 100,000 miles ago and I know because the owner had the receipts. My engine is still mostly shiny black and really clean with little to no oil leaking. My guess would be you have a good engine. The oil in the coolant is sketchy but good on ya for checking the water pump first.

 

[CDX825]

Run a compression test and do an oil analysis. If it has good compression and oil analysis shows no abnormal wear its safe to say its in pretty good shape. Oil pressure seems good.

 

[Shadetreemechanic]

Run a compression test and do an oil analysis. If it has good compression and oil analysis shows no abnormal wear its safe to say its in pretty good shape. Oil pressure seems good.

What he said. The only issue you will have from that approach is that you don't know when the oil was last changed, so if you have elevated metals it will be harder to determine whether it is from lack of change or excessive wear. You will still know a lot more than when you started, and analysis is pretty cheap.

 

[OLDBULL8]

There is usually two places for oil to get into the coolant system, the bolts on the water pump, the oil cooler O'rings. With that oil pressure, it appears the bearings are in good shape.

To take an oil sample, warm the engine til the Hi idle shuts off, let set for 10-15 minutes, catch the first quart of drained oil, use that for the sample. Have Blackstone Lab's send you the sample bottles, before doing that, or save the oil until you get the bottles.

With oil in the coolant system, your going to have to flush/clean it. plenty of threads/posts on here on how to DIY.
When re-charging the coolant system, use the Antifreez with the SCA added in it.

The engine oil gets black within 30 miles even after an oil change, just change the oil filter use the FL1995 filter or equivalent, that's the one PSD's use, it filters a lot finer.

 

[junk]

Normally if it has good compression and good oil pressure I'd run it. I'd also check the coolant for traces of oil. If that all looks good I'd run it.

Now since it's in a vehicle, I'd drive it around as much as I could before I pulled it. Like put 20-60 miles on it if you can.

 

[Sycostang67]

I forgot about oil analysis, that's a good idea. I will flush the cooling system and see if the oil returns, if it does then I will change the water pump gasket properly and flush and fill again. I have a compression tester, but not the adapter to use it on these motors. I will have to try and find one somewhere. I was asking about tags because a few years back I bought a reman 460 from a guy who was parting a truck and it had a small tag attached to the block indicating it was rebuilt, the date and the builder.

 

[laserjock]

I am going through this same thing. I have 2 running motors (they were when pulled) and now I'm trying to decide which one to freshen up to go in my 91. I picked up a compression tester and a couple oil analysis kits. As soon as I get the chasis rolling so I can have some space, I built a cradle that will let me crank the engine at least if not start it so I figure I'll get these done then. BTW, if you check amazon, you can pick up Wix oil analysis sets for like $12-15 a sample. I did some reading and the lab got good reviews. I even found a comparison where a guy sent a duplicate sample to Wix and Blackstone. Watching this closely.

 

[79jasper]

BTW, if you check amazon, you can pick up Wix oil analysis sets for like $12-15 a sample. I did some reading and the lab got good reviews. I even found a comparison where a guy sent a duplicate sample to Wix and Blackstone. Watching this closely.

I'll have to look into that.


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