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Pete

Turbo booster gauge needle erratically bouncing

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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

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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.

 

  

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The Cummins ISC engine is known for cracked/broken exhaust manifolds. Remove the engine cover in the rear(bedroom) of the coach, use a flashlight to inspect the exhaust manifold and turbocharger  where it mounts onto the manifold for black streaks, which is a telltale sign of an exhaust leak, and obvious cracks in the manifold.

I had my broken manifold replaced last August, total bill was $3,1xx dollars. The new style Cummins manifold is heavier and thicker, as the entire weight of the turbocharger and associated piping is supported by the manifold. I haven't noticed any mileage change, but the increase in power is obvious.

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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).

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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.

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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.

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On 11/19/2018 at 6:05 PM, wolfe10 said:

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).

I had to have a HDT repair shop do the work, a 76 yr old man with COPD has no business standing on his head attempting to remove and replace anything, especially when you can't even see the bottom manifold bolts. 😞 The mechanic had to remove both pieces of the manifold and remove one with the turbo attached, then use a torch to heat the turbo bolts so they would't break, 2 manifold bolts did, which contributed to the total repair cost @$135/hr.

 I had removed the entire bed  framework and covered the carpeting with wall-to-wall carpet protector film for ease of access. Shop owner said I was the only one to ever have that consideration for the mechanic. It was really the MH and bill that concerned me.

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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.

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