Community Forums

Montrealer · 08-11-2013, 09:50 AM

Guys, here's an "interesting" one for you.

My 2005 Mandalay has a Cummins ISL 400 with approx 65,000 miles. Engine runs fine, with no smoke either at startup, idle nor under load. However, when I activate the Jacob brake, light blue/whitish smoke from the exhaust pipe. Nothing dramatic but easily visible from my mirror nonetheless. Smoke ceases immediately after I deactivate Jake. Jake brake seems to be a little less effective than in the past. Zero coolant loss (I monitor the level regularly) , but noticeable oil consumption approx 3 quarts after 500 miles. Normal oil pressure, temperature and boost readings. Has anyone experienced something similar or have any thoughts?

Thanks
Gary

KSCRUDE · 08-11-2013, 10:02 AM

I have been around trucks for over forty years and have never seen what you are describing. I think you may have a head or valve problem. You engine is probably using some oil at all time and it just looks worse when you use the jake. I would take it to Cummins and talk to them and maybe they could check it out. That is a unusual amount of oil usage for any engine.

Skip426 · 08-11-2013, 10:06 AM

Turbo , or exhaust valve seals, not able to handle the added heat and pressure, it can only get worse.

X2, on have it checked out.
Question though.
Is your Jacobs brake; an exhaust brake or an engine brake ?
I'm not sure if both types are available on the ISL.

Montrealer · 08-11-2013, 11:14 AM

Thank you gents for your replies. Definitely will have it looked at by Cummins.
Skip 426 - Mine is definitely an engine brake.
Thanks.

jacknife · 09-11-2013, 03:04 PM

Been a trucker and had cimmins engines for 30 years and they do use more oil when useing the engine brake. Just the nature of the beast but it shouldn't use a very large amount, just more.

jacknife · 09-11-2013, 03:07 PM

That color smoke is normal. You may need a readjistment of the jake and valves

Steve Ownby · 09-11-2013, 04:20 PM

Quote:

Originally Posted by Montrealer

Guys, here's an "interesting" one for you.

My 2005 Mandalay has a Cummins ISL 400 with approx 65,000 miles. Engine runs fine, with no smoke either at startup, idle nor under load. However, when I activate the Jacob brake, light blue/whitish smoke from the exhaust pipe. Nothing dramatic but easily visible from my mirror nonetheless. Smoke ceases immediately after I deactivate Jake. Jake brake seems to be a little less effective than in the past. Zero coolant loss (I monitor the level regularly) , but noticeable oil consumption approx 3 quarts after 500 miles. Normal oil pressure, temperature and boost readings. Has anyone experienced something similar or have any thoughts?

Thanks
Gary

Did you just have an oil change? Could it have been over filled? If over filled the engine will get rid of the overage pretty quickly and could account for the oil loss. Is the smoke coming from the exhaust for sure or could it be from the crankcase vent tube?

rock5986 · 12-18-2021, 11:59 AM

My 2006 Isl 400 is doing the exact same thing. It even sprays a bit of raw fuel onto my tow vehicle. Mine is an exhaust brake. Did you ever determine the problem! It runs great other than that terrible smoking when braking.

wolfe10 · 12-18-2021, 12:04 PM

Quote:

Originally Posted by rock5986

My 2006 Isl 400 is doing the exact same thing. It even sprays a bit of raw fuel onto my tow vehicle. Mine is an exhaust brake. Did you ever determine the problem! It runs great other than that terrible smoking when braking.

So, the fuel spray only comes out when using the exhaust brake? Or anytime the throttle is closed? OR Other?

Really makes no sense, as it should be injecting ZERO fuel with a closed throttle until just above idle RPM.

rock5986 · 12-19-2021, 09:31 AM

Only getting white smoke and seeing some wet spots on my tow vehicle when I use the engine/exhaust brake. No smoke or anything if I leave it turned off. At first I was told it had what’s called the 7th injector or doser valve which spray diesel fuel to burn out the soot. I was sure this was going to be the problem, but Cummins said my engine doesn’t have this. But Cummins also made some other costly mistakes while it was in the shop. I was sure thinking they would be the experts and know exactly what causes it.

HarryStone · 12-19-2021, 05:10 PM

Quote:

Originally Posted by wolfe10

Really makes no sense, as it should be injecting ZERO fuel with a closed throttle until just above idle RPM.

If it was injecting "zero" fuel, then the engine would shut off because of lack of fuel. It's got to get 'some' fuel to stay running.

n2zon · 12-19-2021, 06:30 PM

Quote:

Originally Posted by HarryStone

If it was injecting "zero" fuel, then the engine would shut off because of lack of fuel. It's got to get 'some' fuel to stay running.

Many fuel injected engines stay on with no fuel when coasting but stay "on." Some manufacturers call this "fuel cutoff," and it's done deliberately because it saves fuel and reduce emissions. (If it's cold enough, and the hill is long enough, you can actually lose effective dashboard heat in fuel cutoff in some cars and trucks.)

For our ISL9, the Scangauge D indicates 9999 MPG when coasting until the RPM drops near idle or we get to the bottom of the hill and the computer starts to fire the injectors again.

twinboat · 12-19-2021, 07:11 PM

Quote:

Originally Posted by HarryStone

If it was injecting "zero" fuel, then the engine would shut off because of lack of fuel. It's got to get 'some' fuel to stay running.

The engine is windmilling, meaning its being turned by the drive train .

It doesn't need fuel to coast so it gets cut off.

The transmission is in gear and the torque converter is locked. The fuel comes back on at idle RPMs.

rock5986 · 12-20-2021, 07:22 AM

All good common sense replies but this seems to be a mystery to everyone. If it were oil, the smoke would be dark and the wet spots on my tow would be black. Crazy.