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Discussion Starter · #1 ·
1997 Chevy C3500HD 6.5 248K miles
Replaced rear main seal. Replaced oil pan seal, since I was there (rubber in back, black rtv for the rest, cork in trash can). Started today, oil leak seems as bad as before (was leaking one quart every 150 miles). Next today, dug under fuel filter to reveal the oil pump drive "hatch". Not sure what I'm looking for as far as leaking. Oil cooler lines replaced with Leroy Diesel lines last year, it's not there. Any ideas?
 

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While doing the rear main you should have been able to see pretty much everywhere on the back of the engine oil could have been coming from and I would think by looking at the mess been fairly sure you were fixing the correct thing. Where was most of the goo? In the bell area or over the top of it? Auto or manual trans?
 

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Make sure the 3 IP hold down nuts are tight.
I've seen loose nuts cause oil leaks several times.
 

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Discussion Starter · #4 ·
Most of the goo was in the bell area. The leak had progressed over 2 years, so I did a power wash underneath before working on it. Manually felt behind valve covers: dry. I could see the oil pump drive lid and did not notice any leak from said lid. Wasn't sure where those leaks normally are, at the lid? Oil cooler lines look good. The new rear main seal was manually set in a tad past flush to account for any wear. The old seal did have wear on inside/spring side. Thought I did a good job on oil pan, checked back bolts yesterday: tight. Didn't rtv the rubber seal in the back, made sure it was seated in the groove nicely. New tuna can. OPS doesn't look to be leaking, checking further today. Will also check IP hold down nuts.
 

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I was looking at my block in the stand today and it looks like all the oil plugs in the back are threaded in plugs vs pressed in so seems unlikely that those would be leaking.
 

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Discussion Starter · #6 · (Edited by Moderator)
I thought I'd update my fix and conclusion for any future "rear main" candidates. I decided to drop the trans again and give it another whirl by myself this time. I purchased a seal installer tool from Ebay for $80, just for peace of mind. Resealed the oil pan as well. This time I also rtv'ed the rubber seal in the back of the pan on the bottom side and corners at the lip. Finished in two days and 24 beers. Started up and leaked like before. Sigh. The "improved" leak (more than before first seal replacement) seemed more viscous than before. Stuck a piece of white paper under the drip and noticed it wasn't as dark as only oil, smelled of diesel. Turns out my optical sensor had backed off slightly on the IP. Tightened it up and now I only had a smaller oil leak. Investigated the OPS and realized I needed to clean the area (shine) around it to notice a leak. Used some brake cleaner, dried off and watched after starting. Viola. Ordered the socket, realized doesn't fit without taking off manifold. Returned socket and went back to my basin wrench, which I used to replace OPS a few years ago. Cranked her down and NO LEAKS!

Did repair over Memorial Day weekend so, only 1 day jack rental ($22) and new seal and rtv ($30). My beer practically cost more, IPA's.
I'm selling the seal installer tool. Thanks again for those who gave advice.
 

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I thought I'd update my fix and conclusion for any future "rear main" candidates. I decided to drop the trans again and give it another whirl by myself this time. I purchased a seal installer tool from Ebay for $80, just for peace of mind. Resealed the oil pan as well. This time I also rtv'ed the rubber seal in the back of the pan on the bottom side and corners at the lip. Finished in two days and 24 beers. Started up and leaked like before. Sigh. The "improved" leak (more than before first seal replacement) seemed more viscous than before. Stuck a piece of white paper under the drip and noticed it wasn't as dark as only oil, smelled of diesel. Turns out my optical sensor had backed off slightly on the IP. Tightened it up and now I only had a smaller oil leak. Investigated the OPS and realized I needed to clean the area (shine) around it to notice a leak. Used some brake cleaner, dried off and watched after starting. Viola. Ordered the socket, realized doesn't fit without taking off manifold. Returned socket and went back to my basin wrench, which I used to replace OPS a few years ago. Cranked her down and NO LEAKS!

Did repair over Memorial Day weekend so, only 1 day jack rental ($22) and new seal and rtv ($30). My beer practically cost more, IPA's.
Thanks again for those who gave advice.
Glad you got the issue resolved. Once you hit 25 posts then head on over to the Marketplace and list the tool in an ad
Thanks for giving us an update!
(y)
 
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