37blackwood@comcast.net Posted December 17, 2006 Share Posted December 17, 2006 I have a 1974 RD 685 w/237. I'm burning about 1 gal of oil in 8-10 hrs. Lots of blue smoke out the stack, however no excesive blowby out the crankcase breather. I'm wondering if the valve guides and seals are junk, not pistons and rings Quote Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/ Share on other sites More sharing options...
whodunny Posted December 17, 2006 Share Posted December 17, 2006 if you are getting blue smoke all the time it's probably your rings, does it get a lot of idle time? if it does you might be able to reseat the rings by covering part or all of the radiator and put it on a hard pull for a while. remember to watch your temp gauge though. you should be ok up to about 260 degrees F you would need to keep it above 230 degrees for about an hour. if you have a LOT of miles on the engine though you'd be better off with new rings and sleeves. if you only get blue smoke from start up to operating temp. it probably is your valve seals and guides. Quote Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/#findComment-9028 Share on other sites More sharing options...
bulldoggin' Posted December 17, 2006 Share Posted December 17, 2006 Most likely the rings Quote KEEP THE BLACK SMOKE ROLLIN Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/#findComment-9029 Share on other sites More sharing options...
37blackwood@comcast.net Posted December 17, 2006 Author Share Posted December 17, 2006 I pretty much figured it was the rings, just wishfull thinking. Truck still pulls a load very well, Just using an awfull lot of oil in the process. Quote Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/#findComment-9033 Share on other sites More sharing options...
HK Trucking Posted December 17, 2006 Share Posted December 17, 2006 I have a 1974 RD 685 w/237. I'm burning about 1 gal of oil in 8-10 hrs. Lots of blue smoke out the stack, however no excesive blowby out the crankcase breather. I'm wondering if the valve guides and seals are junk, not pistons and ringsCould be that the seals are out of the impeller shaft in the turbocharger. That would cause exhaust smoke, and high oil consumption.Every engine I've seen with bad rings or valve guides had extreme blow by out the crankcase breather tube, and if it's really bad it would pressurize the crankcase to the point of blowing oil out the breather.You state there is no excessive blowby, therefore I'm thinking turbo sealsPull the intake & exhaust pipes off the turbo & look for oil in there, also grab the turbo impeller & try to move it sideways. If it has sideways motion, the turbo bearings are bad.If you find oil in the intake end of the turbo, the turbo is junk.If you find oil in the exhaust end of the turbo, remove the turbo from the exhaust manifold. If the exhaust manifold is dry, but the exhaust end of the turbo is oily, then the turbo is junk.If the exhaust manifold is full of oil, then you've got bad exhaust valve guides.Check these things first- no sense doing a complete engine overhaul if the problem is in the turbo or valve guides. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/#findComment-9034 Share on other sites More sharing options...
37blackwood@comcast.net Posted December 17, 2006 Author Share Posted December 17, 2006 Thanks HK, Turbo has been replaced because the seal was bad and filled the intake with oil. The oil has since burned of. I did however notice some oil streaking out of the rear ports of the exhuast manifold. Quote Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/#findComment-9042 Share on other sites More sharing options...
bulldoggin' Posted December 17, 2006 Share Posted December 17, 2006 Rebuilt 2 350's that had bad rings and had no blow by. And used way too much oil. Oddball luck maybe. Quote KEEP THE BLACK SMOKE ROLLIN Link to comment https://www.bigmacktrucks.com/topic/1872-blue-smoke/#findComment-9043 Share on other sites More sharing options...
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