CletusLloyd Posted January 3, 2023 Share Posted January 3, 2023 Hello all, This is my first Mack Truck (RD688s 10 wheel dumper) and I absolutely love it but please forgive my ignorance. My mechanical skills and tools are fairly advanced but I have not worked on much heavy diesel, and never anything Mack. It has 9k hours and 235k miles on the E7350 and Eaton 10speed trans. I've had it for a year and put about 6k miles on it for my small rock business. It recently developed a small oil leak at the back of the pan, I hit it with the hot pressure washer and got it clean then drove it for a day, got under it and observed the oil just slightly seeping from between the pan gasket and block/flywheel cover interface. The isolators are pretty well shot around the area in question. My question is how likely it this to be the silastic seal between the block and flywheel cover? That would be a real bitch of a job and I just don't know if I could tackle that one myself. I bought a new pan gasket and isolators from PAI and planned to change the oil pan gasket in the next few days. Should I put permatex ultra black silicone on these interfaces (as well as the front cover interfaces) before I install the rubber gasket? I have read both to put silicone or it will leak, as well as just clean the surfaces extremely well and install. The E-tech service manual doesn't mention anything about silicone for this application. Looking for advice from guys with real world experience. Thank you for any help, it is greatly appreciated! Quote Link to comment https://www.bigmacktrucks.com/topic/70963-99-e7-350-oil-pan-leak-or-silastic-seal-leak/ Share on other sites More sharing options...
Solution Joey Mack Posted January 3, 2023 Solution Share Posted January 3, 2023 Ok.. it is very common for oil to leak/weep between the block and flywheel housing.. a lot of work to fix a minor issue.. the rubber gasket is to be installed dry, however, a small amount of Mack Gray RTV is applied at the seams where the flywheel housing mates up, and the front cover mates up. 4 points.. new bolt insulators are a must.. PAI sells a nice pan gasket set.. the E-Tech pan gasket is very good.. Good luck with your RD,, you are in the right place for info.. Jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70963-99-e7-350-oil-pan-leak-or-silastic-seal-leak/#findComment-519872 Share on other sites More sharing options...
CletusLloyd Posted January 3, 2023 Author Share Posted January 3, 2023 Thanks JoJo! I already got the kit from PAI with the new gasket and isolators. I will clean all traces of oil from everything then clean surfaces with acetone or similar. My main question was about putting the silicone at the 4 corners (it says nothing about this in the service manual). Anyway I appreciate your reply, I'll post up results when I finish. Probably going to tackle this one by myself tomorrow. Thanks again! Chris 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70963-99-e7-350-oil-pan-leak-or-silastic-seal-leak/#findComment-519893 Share on other sites More sharing options...
Popular Post CletusLloyd Posted January 5, 2023 Author Popular Post Share Posted January 5, 2023 I swapped out the gasket today and found a tear in the old pan gasket in the exact spot of the leak. Not sure how that would have gotten there. Must have been the previous owner which was the state of Arizona prying on it, or maybe re-used a bad one. Not too bad of a job took me most of the day by myself piddling around. Painted the oil pan and cleaned all the bolts and studs until all the threads were like new. Worst part was cleaning all the oil from underneath on the block etc. Thanks for the help! 2 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70963-99-e7-350-oil-pan-leak-or-silastic-seal-leak/#findComment-519991 Share on other sites More sharing options...
masterwelder Posted January 5, 2023 Share Posted January 5, 2023 Steam Jenny is a handy tool for a lot of things, especially cleaning grease and oil from equipment. Just spent about 4 hours with 240 degree wet steam getting the RD ready for the tranny swap. Spent some of that time on my oil pan as it will have to come down to change the flywheel housing. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70963-99-e7-350-oil-pan-leak-or-silastic-seal-leak/#findComment-520069 Share on other sites More sharing options...
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