Well ain't this a hot pile of steamy. Thought I had a timing issue but am told by my mechanic he suspects a low bearing issue. This engine only had 6k miles on it since the PO rebuild. Not something I wanted to hear. Man oh man, what now. Had a gravel sound at light throttle like it was pre-igniting but mechanic says timing and vacuum advance was fine. This sound occurs after the engine warms up. No sounds at start up or initial run, sounds fine .

Sounds good, I ordered a oil test kit, so I hoping it's not a bearing issue. This is the second mechanic that said this. Just would expect some noise when it idles or when it accelerates, but it just does it at light throttle.

How is oil pressure? Any changes? A cracked flex plate or a bad harmonic balancer can make bout the same noise. I have one tore down now with same symptoms except low oil pressure and bad analysis. It is the main bearings down to the copper, engine has bout 5k since rebuild. I found it had a double row timing chain (brand unknown) and the oil slinger was rubbing the timing cover. Looks like maybe the gear was to thick but I need to do some more checking and comparing before I can state as fact. Crank end play was good and no other visible issues. I Did find specks of silicone gasket sealer in the oil screen.



tgeiger wrote on Fri, 13 March 2015 21:43

Sounds good, I ordered a oil test kit, so I hoping it's not a bearing issue. This is the second mechanic that said this. Just would expect some noise when it idles or when it accelerates, but it just does it at light throttle.

oil pressure is good when started, shoots way up...when going down the road after it warms up it is at 40 plus psi. at idle the needle does get down to the lowest tick...and at times even slightly lower...but comes back up to regular running pressure when going down the road.

If it doesn't do it a idle,but does start to rap at about1500RPM that may be a bad rod bearing. The sound is the piston rapping the ledge on the head. Ask me how I know

Ok, if I get my oil results back and it's not good news, which way is the better way to go, pull engine and rebuild or just get a new re-manufactured engine? This is if the oil results indicate a bearing had gone bad? Does this oil report get specific about whats wrong or does it just show metal floating around in the oil?

Ok, if I get my oil results back and it's not good news, which way is the better way to go, pull engine and rebuild or just get a new re-manufactured engine? This is if the oil results indicate a bearing had gone bad? Does this oil report get specific about whats wrong or does it just show metal floating around in the oil?

My oil analysis saved me a ton of money. I had a analysis not too long after getting our coach. It showed antifreeze in the oil and a fair amount of babbit material. A couple months later after some attempts to end the coolant leak, I did another test and it showed a considerable increase in the amount of copper in the oil. Copper can only come from the inner part of bearings. Both these tests were done by Blackstone labs. I then send a sample to Chuck Boyd's guy in Knoxville. Two days later the guy calls me and says "Take this engine off the road now. You are in the midst of an bearing failure that is not going to fix itself. Delaying will only increase your cost to repair." This is an older guy who has been doing this for decades.

Blackstone gave me back a ton of data that I did not understand. Chuck's guy gave me back INFORMATION.

I took his advice and pulled the engine. Turns out that there was a blown head gasket that was letting coolant get into the oil and break down the lubricity of the oil. There were two main bearings that were showing copper.

Because I caught it early, the crank was not damaged and still within factory specs. The cylinders were all good also except for one scratch which we had to take to 20 thou over to clear. Rather than boring all 8 to 20 over, I chose to do just that one. It's a 4000 rpm motor and won't care that it has one piston 20thou over.

We did completely replace everything in the heads, valves, springs, keepers. The engine had overheated and blown the gasket....that was the cause...everything else was the result. My engine guy, John Beavers in Americus Ga, wanted good gaskets so he ordered them from Mondello along with the crossover blocking plates.

I tell you this to explain why I am a believer in oil analysis.