 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / 4x4 Cars / July 2004Part time engine knock
Hi Group, I have a 1991 GMC K-2500 with the 350 CID engine {5.7 Liter}, 217,000 miles, runs great, doesn't use oil. It developed a water leak and the garage replaced the intake gasket. When I picked it up the oil pressure was very low, about 15 highway, 0 at idle. I assumed they had loosened a wire or something, until the engine started knocking. OF course the garage claims there is no way changing the intake gast would cause a loss of oil pressure, so I'm on my own. I pulled the oil pan and checked the rod bearings with plasti-gauge, number 8 was worn to much to get a reading with the green, but the others all ran from .002 to .003. I replaced that bearing with a new standard bearing and rechecked it, it was now .002. I installed a new oil pump and reassembled it. Now I get several hard knocks as soon as the engine starts, which stops as soon as the oil pressure rises. Oil pressure cold is 60 PSI. The engine sounds perfect at all speeds cold, no trace of a knock. As the engine warms up, the oil pressure drops a bit. At about 150 degrees the oil pressure has dropped to 45 PSi and the knocking starts again. It sounds low, like a rod knock, increases in speed with the engine, but is not very loud, and at higher engine speeds it can't be heard over the fan noise. At normal operating temperature the oil pressure is down to 15 PSI at idle, 30 highway, with a constant knocking from the lower engine. My best guess is that the crank itself will have to be replaced, with all new bearings. I welcome comments from anyone who might know more than I what is wrong. Thanks. The coolant is what did in the bearings: not the shop replacing the manifold gaskets. So there are several factors at work here, mainly. The main bearings were never checked. Secondly, why did you only replace the one bearing, the sides of the others could be egged at the parting line. Thirdly, The cam bearings were also etched by the zombie juice that was in the crank case when the manifold leaked. So, if you would have replaced all the rod bearings, all the mains, there would have been 12 less chances for a knock. The mains are most likely lose and leaking pressure, and the rod bearings are more than likely egged at the sides, so when the oil thins out at operating temperature. You lose the oil strata that normally quiets the knock hydraulically. You might be able to save it in vehicle, but would you want to take that chance again, with the price of a good kit, with Sealed Power pistons, cam, rings, bearings will most likely be sealed power and not cleveite. but, if you want the best you'll have to pay more. Machining it won't cost a lot and the timing chain, cam bearings and freeze plugs will be in the kit too. I hope this helps? Refinish King PS Don't buy the kit with cast pistons, pay a few bucks more and get the : Hypereutectic pistons. > Hi Group, > I have a 1991 GMC K-2500 with the 350 CID engine {5.7 Liter}, 217,000 [quoted text clipped - 23 lines] > wrong. > Thanks. > The coolant is what did in the bearings: The coolant leak was external, no coolant was ever in the oil, and the garage changed the oil after replacing the gasket to insure there was no contamination from the gasket change. > not the shop replacing the manifold gaskets. So there are several factors at > work here, mainly. The main bearings were never checked. > > Secondly, why did you only replace the one bearing, the sides of the others > could be egged at the parting line. Only one failed the plasti-gauge check, so I only replaced the one. I expected it to still fail the test, but it did not. > Thirdly, The cam bearings were also etched by the zombie juice that was in > the crank case when the manifold leaked. [quoted text clipped - 14 lines] > > I hope this helps? Every suggestion helps. Thanks. I'm of the mentality: If one bearing is lose, another one is lurking to get me! So if I sounded brash, I wasn't at all. I just get nervous that something is going to bite me in the back, and usually does. I was married, if you get my drift? Refinish King > > The coolant is what did in the bearings: > [quoted text clipped - 38 lines] > > Every suggestion helps. Thanks. > I'm of the mentality: > [quoted text clipped - 6 lines] > > Refinish King hehehee, oh yeah. Another reason I only replaced one was because I figured I would have to replace the crank anyway, and most reconditioned cranks are at least .010 undersized, so I would be wasting the money I spent on a whole set. I just bought one so I could get an accurate reading from that journal, and was quite surprised when it read so good. Being somewhat eager to have my truck on the road again, and hoping for the best, I reassembled it and went for broke. I've made a couple of trips to town and back and the knocking is not getting any worse yet, hopefully it will last until I can budget the funds to fix it right, whatever it takes. > > > The coolant is what did in the bearings: > > [quoted text clipped - 42 lines] > > > > Every suggestion helps. Thanks. Just remember: When it knocks like that, a rod is getting egged. So it will pay you to have all 8 rods reconed when you do the motor. Refinish King > > I'm of the mentality: > > [quoted text clipped - 75 lines] > > > > > > Every suggestion helps. Thanks. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.