$976 air leak

[jwlce]

Just as an FYI the IXS 870 has a small box perhaps 3x3.5x5" that is a variable geometry turbo control valve. There was more than one version and this is known as a lower control. Long and short of it, it began leaking air and would deplete brake air pressure in 6 to 8 hours. Replacing it resolved the issue but I would add the comment that Cummins is on the 6th revision of this part. 5 since my engine was built. Replacement was 2 bolts 2 air lines and one electrical connector. Took longer to go into town and get it than it took to replace it. I have gone 24 hrs without any loss of air pressure. I will say engine seems to run more smoothly but no engine errors or warning lights occurred.

[Smitty77]

Thanks for sharing Jim!

Can I add on a recommendation from a grizzly tech of Cummins in Coburg, OR (A gent I've worked with on now two coaches, several times, and I consider knowledgeable and a straight shooter!).

He explained that many RV'er's with the ISX and VGT, when Jake Brake was activated in High/Stage 3 position, did not like what they considered a 'double engine braking assistance' kicking in. First Braking Assistance was when all 6 Cyl kicked in to provide Braking Assist. Second Braking Assistance, was within seconds of the first - which is when the geometry of the VGT changed, and added further back pressure Braking Assist. (Which, is the Maximum Brake Assist configuration.

He said especially in moderate traffic conditions, where the Jake, along with VGT Assist, could come off and on multiple times. As the ISX600 CM870 was new to me, I purposely went out and drove with Hake in High/Stage 3 position, to see if I could detect what he was talking about. And yeah, it's noticeable. Really did not bother me too much, but then again, it was a limited test.

The Tech also pointed out that BIB BLOCK's compression in Med/Stage 2, was rather robust at Braking Assist. So he said many coach drivers he had talked to, elected to just leave it in the Med/Stage 2 position for most driving conditions.

The reason he, and other Tech's at Coburg Cummins were talking with these RV Owners - is because due to lack of use High/Stage 3 Jake - the 'rod' that adjusted the position of the VGT reversing the vanes to provide the final Braking Assist - were becoming 'frozen' in the open position, which removed that extra assist of the VGT vane adjustment. (I'm assuming the control box that caused your air leak, controls this rod's movement(?).).

So his recommendation, and what I'm doing each time we drive the coach, is to 'Exercise' High/Stage 3 Jake position, so that the Rod does not end up frozen.

(Sorry the was so long winded, but it's my nature - and I was trying to describe what he had explained to me...).

This Tech, said that the number one reason that RV's with ISX (CM870/CM871's (As that is what I was asking him about, prior to our purchase of the CM870.) came into their shops - was to repair the 'frozen rod' supporting the VGT. He also said that he could not remember any CM870 coming into their shop for the #6 valve problem. And yes, he said they had a few (He estimated about 15), come in for either fixing the Drop #6, and or, pro-actively replacing the head with the latest and greatest - all CM871's. He personally did not recall a CM870 owner doing a preventative head swap out.

As I'm sharing his input, he said OTR ISX's, CM870/CM871 - most prevalent visit to their shop - was EGR related. Newer generation Cmxxxx's, he said had a disintegrating Ceramic component in their fuel pumps - that could be very costly to repair when the Ceramic component came apart...

===

My apology to you if you feel this not appropriate to tack onto your info sharing, but it was ISX related... So, wanted to share!

Smooth sailing on our freeways ahead for you (And please let us know where those smooth freeways are!) - and best,
Smitty

[wfalch]

Will be at that Cummins service center on Thursday, April 22th.

[f360racer]

Originally Posted by jwlce

Just as an FYI the IXS 870 has a small box perhaps 3x3.5x5" that is a variable geometry turbo control valve. There was more than one version and this is known as a lower control. Long and short of it, it began leaking air and would deplete brake air pressure in 6 to 8 hours. Replacing it resolved the issue but I would add the comment that Cummins is on the 6th revision of this part. 5 since my engine was built. Replacement was 2 bolts 2 air lines and one electrical connector. Took longer to go into town and get it than it took to replace it. I have gone 24 hrs without any loss of air pressure. I will say engine seems to run more smoothly but no engine errors or warning lights occurred.

Thanks for post. The Silverleaf mechanic, Robert works on diesels as well and he thought my issue may be related to VGTCV as well. In my coach I feel power is not all there. I also get a lot of black smoke under load. I filmed this while driving under load and the video shows a 4sec ON and a 4sec OFF cycle continuously of black smoke evident from tail pipe. If I’m next to a wall the sound sounds almost like ticking sound heard up front. Again I don’t know what’s normal as it’s the same since I first drove it. I need to call Cummins in Coburg while I’m still here.

Inverters are in but they are not showing up on House or VMS-240 panels. Power is there so they work but no communication yet to old boxes. They are continuing to T/S issue at Silverleaf. TM-102 box test fine but something on network causing issues. If you change to new inverters expect system upgrades as well.