Pete Report post Posted November 19, 2018 I have a 2005 Monaco Knight with a Cummins ISC 330 with a Allison 3000MH 6 speed Transmission. I had been traveling for about 6 hrs towing a jeep liberty when my fuel consumption went way down and my Turbo booster gauge needle began bouncing all over the dial, All the other gauges looked fine, the coach was handling normally, I got to a good stopping point and set up for a stay, any thoughts on what I need to consider? I am new to running a diesel coach so I would appreciate some advice. Thanks! Pete Share this post Link to post Share on other sites
dickandlois Report post Posted November 19, 2018 Pete, Did the fuel Consumption go down or did you mean to say it went Up? Did the acceleration drop off, with a decree in power to climb? Sounds like a leak in the boost system. That could be a number of items. Leak in the silicone coupling hoses or just a loose clamp, then it might be a blown gasket, at the exhaust manifold, turbo connection or gasket, cracked in the exhaust system. Then it might be an issue with the Turbo bearings - causing a speed change of the turbo spools / causing rapid changing Boost pressure. How many miles on the coach and has the Turbo or exhaust system been serviced ? Not going into the CAC / inter-cooler at this time. Rich. Share this post Link to post Share on other sites
wolfe10 Report post Posted November 19, 2018 Ray, Same for the ISL. I replaced mine (cracked exhaust manifold). Plenty of penetrating oil and gently persuasion and all the bolts came out. Look for both cracks and if the crack is bad enough, for black deposits (soot from exhaust escaping). Share this post Link to post Share on other sites
kaypsmith Report post Posted November 20, 2018 I had to replace the manifold on the left side in 2015, then the right side in 2017, both times, drastically reduced power. Share this post Link to post Share on other sites
Pete Report post Posted November 20, 2018 Thanks for the responses, the fuel consumption went way up( less miles per gallon) there was no noticeable loss of power, it ran fine, the coach has 84,000 miles on it, I don't have a copy of the records. Share this post Link to post Share on other sites
kaypsmith Report post Posted November 21, 2018 If fuel consumption has gone up, I would definitely check out the entire exhaust system, all clamps and look for any trace of black soot, it is a tell tale sign of a leak. Both times that I had a problem, fuel mileage went down before the big problem arose. First time, I heard a big bang, sounded like a large glass breakage from the rear of the coach then immediate power loss, when checking it out, the turbo pipe had actually broken into, inspection showed that there was a crack in the turbo pipe for a rather long time, and further checking revealed a small crack in the left manifold. After making those repairs all went well for two years, then the exact same scenario on the right side, only difference was the manifold on that side actually developed a gaping hole in it. In most cases someone with good hearing can actually hear these type leaks with the motor running. Share this post Link to post Share on other sites
rsbilledwards Report post Posted November 21, 2018 I had to replace all the exhaust gaskets on a 3126B CAT and I used a lot of "PB Blaster" to make sure the bolts would come out, spraying days ahead of the effort. All came out cleanly. Share this post Link to post Share on other sites
manholt Report post Posted November 22, 2018 At 75+ and 6 foot 8 inches, I don't bend the way you all do! Happy Thanksgiving! Share this post Link to post Share on other sites
