Troywright68 Posted May 4, 2018 Share Posted May 4, 2018 Hi everyone. I have a 2002 Mack RD688S with E 7, 350 HP with 621,0047 miles on it. Yesterday when I checked the oil I noticed it appeared to have diesel in the oil. The truck doesn't miss or smoke. So what could be causing this? Quote Link to comment https://www.bigmacktrucks.com/topic/53290-diesel-in-oil/ Share on other sites More sharing options...
Jamkar Posted May 4, 2018 Share Posted May 4, 2018 Sounds like EUP seals/orings. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53290-diesel-in-oil/#findComment-398215 Share on other sites More sharing options...
Troywright68 Posted May 4, 2018 Author Share Posted May 4, 2018 Thank you. Looks like it's time to get oily and greasy. Thanks again Quote Link to comment https://www.bigmacktrucks.com/topic/53290-diesel-in-oil/#findComment-398216 Share on other sites More sharing options...
fjh Posted May 4, 2018 Share Posted May 4, 2018 Yup oilly! also fairly common as strange as it may seem is injector orings fuel can leak up by the injector hold down threads ! and the fuel transfer pump shaft seal can leak another semi common issue! Quote Link to comment https://www.bigmacktrucks.com/topic/53290-diesel-in-oil/#findComment-398229 Share on other sites More sharing options...
turckster Posted May 4, 2018 Share Posted May 4, 2018 Fuel transfer pump can leak fuel into the oil, there is an fuel galley plug under the front cover that can leak fuel into the oil as well. Usually there is fuel weeping around the fuel galley plugs on the front cover if the plug(s) are leaking. Best thing to do is remove the oil pan, use the fuel hand primer pump to charge the fuel system and try to find where its coming from. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/53290-diesel-in-oil/#findComment-398236 Share on other sites More sharing options...
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