Community Forums

mque · 11-07-2014, 08:24 PM

I have been developing a whistling noise noise when at high altitude using my engine brake. Mostly in 3rd gear but some in 4th and 5th. It is a high pitched whistle but then it disappears when I am down at a lower altitude and flatter ground. It has progressively gotten worse over the last 3 years. I do not seem to be suffering any power loss or Braking loss. I still can generate 30 psi of boost. Has anyone experienced this?
Thank You Mike Quinn

Bumps · 11-07-2014, 08:33 PM

Yep ... same thing for me. Subtle whistle sound at higher altitudes. Sounds "normal" at lower altitudes (no whistle). I put it on the list of things for the shop to check out every year. And every year they tell me that it is nothing to worry about. I guess it bothers me more than anybody else. \ken

Twomed · 11-08-2014, 10:42 AM

Get ready for exhaust gasket replacement. If replaced while in the whistling stage you may save the cost of warped/eroded manifold.

palehorse89 · 11-08-2014, 10:44 AM

Quote:

Originally Posted by Twomed

Get ready for exhaust gasket replacement. If replaced while in the whistling stage you may save the cost of warped/eroded manifold.

mque · 11-09-2014, 05:22 PM

Bumps, see the comments from Twomed. I found an exhaust manifold leak and will get it fixed. Most likely causing my whistle when I use the engine brake. Thank you for the input.

Bumps · 11-09-2014, 05:25 PM

Thanks! ...I've put it on the list for my next trip to the shop. Maybe if I tell them what it is they will agree(?) that the whistle is not normal. Thanks! \ken

MnTom · 11-09-2014, 07:10 PM

Bumps, if you can take a look at where the exhaust manifold bolts onto the engine. See if you can see any black steaks indicating where it is leaking.

smlranger · 11-10-2014, 12:35 PM

I don't get a whistle but (especially if I travel across a bridge or in a tunnel) I can hear much air movement from the rear of the coach when the engine brake engages. It sounds like the radiator fan is running at top speed. It is just a very loud rush of air. Mine is the 2007 clean diesel ISL. Are there other symptoms associated with a exhaust manifold gasket leak?

ShapeShifter · 11-10-2014, 02:58 PM

Quote:

Originally Posted by smlranger

I can hear much air movement from the rear of the coach when the engine brake engages. It sounds like the radiator fan is running at top speed. It is just a very loud rush of air.

I assume you have a rear radiator. If so, yep, completely normal: the radiator fan IS running at top speed. When the exhaust brake engages, the transmission downshifts so that the engine speed is increased. The increased engine speed pumps more air through the engine, so that the restriction of the exhaust brake generates more backpressure -- that's what gives you the braking action. Since the rear radiator fan is driven by the engine, when the engine goes fast, the fan goes fast as well. While it's noisy, that spinning fan also burns off a few horsepower, adding a little to the braking effect.

Quote:

Are there other symptoms associated with a exhaust manifold gasket leak?

When my leak developed, it was a horrible screeching noise when the exhaust brake came on. When parked, it could also be heard at fast idle and when coming down from fast idle. It was such an awful noise that my mechanic's first thought was that the bearings on the turbocharger were shot. Fortunately, it turned out to just be a small exhaust leak. Also fortunately, it developed at the end of a long trip when I was just 10 or 15 miles from home -- I could easily limp home, and then over to the shop a few miles away.

smlranger · 11-10-2014, 03:08 PM

Quote:

Originally Posted by ShapeShifter

I assume you have a rear radiator. If so, yep, completely normal: the radiator fan IS running at top speed. When the exhaust brake engages, the transmission downshifts so that the engine speed is increased. The increased engine speed pumps more air through the engine, so that the restriction of the exhaust brake generates more backpressure -- that's what gives you the braking action. Since the rear radiator fan is driven by the engine, when the engine goes fast, the fan goes fast as well. While it's noisy, that spinning fan also burns off a few horsepower, adding a little to the braking effect.

When my leak developed, it was a horrible screeching noise when the exhaust brake came on. When parked, it could also be heard at fast idle and when coming down from fast idle. It was such an awful noise that my mechanic's first thought was that the bearings on the turbocharger were shot. Fortunately, it turned out to just be a small exhaust leak. Also fortunately, it developed at the end of a long trip when I was just 10 or 15 miles from home -- I could easily limp home, and then over to the shop a few miles away.

No, I have a hydraulically-driven side radiator (Country Coach did not use any rear radiator configurations). This if my first side rad DP and the first with Jake brake so it may be my side rad fan plays a role in the process. It gets all its instructions from the engine ECM.

ShapeShifter · 11-10-2014, 03:27 PM

Quote:

Originally Posted by smlranger

No, I have a hydraulically-driven side radiator

Well, then... I have no experience with that, so you're on your own.

koda59 · 11-10-2014, 08:22 PM

What you might be hearing is the compression from the Jake brake. Does it sound the same as when a big truck lets off the accelerator and his Jake kicks in.?

MnTom · 11-10-2014, 09:03 PM

Quote:

Originally Posted by koda59

What you might be hearing is the compression from the Jake brake. Does it sound the same as when a big truck lets off the accelerator and his Jake kicks in.?

Not the same sound as an exhaust brake. They are two separate animals.

smlranger · 11-11-2014, 04:56 AM

My ISL has the two stage Jake brake. It sounds nothing like the big trucks which give the characteristic bap, bap, bap sound. It just sounds like lots of rushing air.....a loud hissing sound.

Someone on another forum suggested it was the variable geometry turbo used on my engine. The vanes on the turbo flatten out during application of the engine brake causing the sound. I just would like to verify that and wondered if others with the 2007 and later ISL's hear the same noise.