engine ?

[bigd1981]

I was thinking of buying a 95 2500 4x4 diesel. The owner told me that a mechanic told him that the main bearings where bad. causing the truck to run for about half a mile then it shuts down. does that sould like an acurate diagnosas. if so is it as simple as droping the oil pan removing the mains a changing the bearings out?

[hraney]

I think someone is confused or misinformed. I don't see the main bearings causing that kind of symptom. Low oil pressure, noise, are main bearing symptoms. Sounds like a good candidate for the classic PMD replacement on the injection pump.
And no, its not as easy as dropping the pan. These things aren't built like big trucks... I've never heard of anyone doing an "in-frame" on one. You would have to pull the engine.

[Chevylover]

Yep, sound like PMD !

Cu,
Sven

[bigd1981]

ok here is the deal looked at the truck this evening, and its knocking pretty bad and is blowing white smoke from the exhaust. Was told by the owner that they replaced the heads drove it for awhile then it started knocking so they parked it. mechanic told him that the mains where out. it also makes a noise similar to an exhaust leak. his neighbor told him that the pvc valve was bad. Im thinking that they overheated it causing the heads to crack along with mains and posibly the bottom of the block tell me what yall think

[carolinastreaker]

sounds like its time for a rebuild if the block is not cracked!

[torque454]

I dont see any way a main bearing can knock unless theyre all worn out and allow the crank to flop. Usually in that case tho there is enough downforce to keep the crank in place, it will squeel really loud tho as it chews thru the bearings and starts spinning in the block. I've seen that happen on gas engines its a very annoying sound. I tend to think that with the engine having overheated that the noise is (A) a busted piston or more likly (B) a rod bearing. Just this past summer I had two rod bearings on the same journal go out (got really really loose) when I overheated my old 72 chevy truck which had a 350 gasser in it. The gauge did not indicate that the engine was as hot as it was. The point of me telling this is that overheating an engine will cause rod bearings to fail and knock (other bearings too, but generally rods produce a loud knocking noise. Generally it is quiet or absent at idle but gets louder as engine rpms increase. Altho this is all pretty irrelevant tho because bottom line is the engine needs internal work.

[hraney]

I wonder why the heads were replaced? I would guess overheated and cracked. Also, they could have missed/damaged a gasket when reassembling the engine (white smoke).
Basically, yeah the engine is going to need to come back out and have internals worked on.

[turbostorm]

if antifreeze has gotten into the oil that will take out bearings