Scratching nois after engine brake is on. Volvo 670 cummins isx 400

If you have an ISX with a DPF the engine brakes work a little differently. The ECM will actually command the turbo to close to increase exhaust back pressure to increase load on the engine to increase the engine braking power. Air rushing through the turbo or the change of flow that is going through the turbo could be what you are hearing. Is this noise something that just started? Any way you could make a video of it and upload it to youtube or something?

 

might be the turbo, might not be. But if it is, here is some basic info on what you might be hearing...

The VGT turbo has a travel range from 0 to 100%. From about 5-70%, it will provide boost for combustion, but above 70%, although it will provide boost, it will provide the excess back-pressure needed to force exhaust gases into the EGR system, so that it can 'Overcome' that boost at the intake manifold. It is this same excess in exhaust back-pressure that is needed for the engine brake, so between 70% and 100%, there is little increase in boost gain, but much back-pressure gain. When this is happening, the turbo's actuating ring is extended past the main housing and relies on a keyed retainer ring in the most rear housing to keep it in place. This retainer ring suffers heat expansion on a constant basis and has been known to vibrate at high frequency as it gets worn. The sound is almost Identical in nature to the sound produced if the turbine were to touch the housing. This annoying 'squeal' is actually not nearly as harmful as it would seem, but can easily confuse a driver or mechanic into thinking the turbo is bad. If this vibration becomes severe to the point of fluctuating the engine during over-closed conditions, then it is time to replace the turbocharger. Usually, by the time it gets this worn, the rest of the turbo will show signs of failure as well.

 

is it a CM870 or 871? who did the delete?,...It is not likely to have been re-programmed correctly, it has only been since may of this year that it was documented that ALL the ISX deletes by ALL the butcher-shops were done incorrectly, causing constant excess heat and head pressures, killing turbo's, cracking heads, etc. The CM871 is the engine that suffers the most from these bad deletes, and the CM870 was not quite as bad, because of intake restrictions, etc. Just keep that in mind when you are working on it...

just in case you are not aware of this...

http://www.thetruckersreport.com/tr...s-deleting-egr-create-heat-2.html#post3372206

and...

http://www.thetruckersreport.com/tr...s-eighteen-wheelers/220280-isx-600-turbo.html

 

When u replaced the rockecrs did u check that they properly sat down in place they have what i would call washers on both sides on the shaft and that has to spin freely even if u tight the rockers down also check for any kind of boost or exhaust leak