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RV_rob · 02-20-2019, 09:28 AM

Thanks Jon_C! I'm headed off to storage here in a bit to get working on it, and i'll stop by the hardware store and get some PVC. I have my portable compressor with me, so I will just screw a quick connect into the pvc end cap and pressurize that way. That sounds MUCH better than trying to look/hear bubbles while the motor is running, especially if I'm not building up pressure to begin with.

And that's perfect as far as boost at idle goes, that was one of my main questions, so now I know for sure not to expect much of anything while just sitting and pushing the throttle. I will get her out on the hwy right after all these little fixes. Would be nice if all coaches just let you lift them off the ground with the leveling jacks and had a built in resistance/dyno device attached to the axle.

I'm taking pictures as I go, will post a few tonight of my progress. BTW, I gave my motor an "air bath" last night from my compressor, that makes a huge difference in getting all the grime off. I think I'll put that as part of my yearly maint schedule. It literally turned some of the CAC pipes back to metal color. I was careful around all the fitting though, afraid I might "cause" a leak by blowing off corrosion and such.

RV_rob · 02-20-2019, 05:55 PM

Holy freaking Turbo Batman!!! Fixed exhaust manifold leak, and hole in wastegate actuator, lit the fire and WOW, I haven't heard her purr so quietly in years. That crack must've been there a while and just kept growing. I immediately showed boost of .7 at idle, and got up to 2 when throttling up. I shut her down and my buddy had a clean air filter for his Ag tractor, so we temporarily hooked it up to my intake and what do you know, boost climbed to 1.1 at idle.

So we took her out on the hwy and she climbed right on top of 32# at 2100 rpm, with about 240 horses. Mostly during flat road accelerations it sat around 8-10# at 1500rpm. My new air cleaner should be in next couple days, and I'm guessing I'll get even more air, because the Ag filter was about 3/4 size.

I will also be ordering a new manifold, the patch was just temporary to confirm I didn't need to fix something more expensive first, like if it turned out to be a fuel problem, God forbid. That CAPS pump scares the jeebies out of me. If anyone reading this in future needs advice on that thing, I will be glad to help. Cummins wanted nearly 11k to put on a new one (replace only pump, no parts from them). I ended up sourcing some parts from a couple school districts where the mechanics of the bus fleet had bench parts, and I was also able to order a new ICV from a distributor. But I did have to time the rotor and pull the mid section pumping assembly apart and clean it, along with the 2 pressure pistons, so I gained a lot of knowledge.

Anyhow, to summarize this whole thread for anyone who might have similar issue. Yes, the crack in my manifold was large enough to cause almost Zero boost, and patching it up alomst entirely solved the problem, except I also discovered that even tho my filter minder showed about half life left, my filter is completely clogged and not letting the big lady breath so she can sing!

I want to thank you all for you help with this, I would have needed to replace those parts regardless of help here, but you guys sure answered some much needed questions, and gave me some advice on how to test things correctly. I will make sure to stay active and try to help anyone else if I can to pay it forward.

Jon_C · 02-20-2019, 09:32 PM

Thats fantastic!! And thanks for letting us know!!

Jon_C · 02-20-2019, 09:42 PM

The wastegate actuator is an overspeed protection device for your turbo, the spring tension in it is set to open at a specific pressure if it fails to work you can catastrophically damage your turbo in a hurry. Uf u have any doubts about the repair holding up id replace it. It will make a squealing noise when it overspeeds ( dont ask me how i know)

I thought wastegate on stock turbo would open at less than 32 psig but im not familiar with ISC.

RV_rob · 02-20-2019, 11:25 PM

Jon_C, I went over and played with it some more this evening, and now that I have the hole sealed on the wastegate, I tried to do the standard "air blower" into tube test and I think it's seized in the shut position, so if it's was supposed to not let me build up to 32#, that's probably why it didn't. I tried to take off just the wastegaste assembly and I sheared on of the bolts. I have a good reverse out set, but at this point I think I'll just go ahead with my original plan and replace the whole turbo for the $218. I think for anyone with a ISC that's as old as mine, that's a "No Brainer". It could almost just be considered a maintenance item at that price and ease of access.

Until then, If I must drive the rig, I will just watch the boost like a hawk, and better yet, I'll probably work to get a physical gauge like you recommended in the next few days.

Jon_C · 02-21-2019, 08:50 AM

Id be cautious about a $200 turbo. A new holset hx35 for mine was $1500. I pulled both the manifold and turbo off mine still together seemed easier that way but i have good top access to my motor. And on your new actuator u need to set it on the bench to open at the proper pressure. Call cummins and find out what is correct for your motor. With too high pressure she runs like a beast but with stock head bolts and gasket you run risk of blowing gasket. There are good videos on how to set the actuator just turn a bolt but u need an air regulator to send pressure and watch when it begins to open. Its not hard i set mine to 30 but ive got good bolts and gasket. If u get into this and have questions let me know.

And on the bolts if youll work them back and forth slowly theyll usually come out. I have worked out bolts on my offshore boat outboard some im sure took 30 min each but thats still quicker than a repair.

Jon_C · 02-21-2019, 09:05 AM

On second thought i have a Banks big head actuator on mine and it was banks who told me i needed to set it. If u get one from cummins for your motor it may be preset, id check that before installing. And i think id stay with your turbo before replacing with a cheap one, they can last for several hundred thousand miles. Just turn the turbine and make sure it has little to no play left to right and back and forth and spins free.

RV_rob · 02-21-2019, 03:32 PM

Again, thank you for the advice. I did not realize I would be buying a piece of junk, for some reason I thought that turbo WAS a Holset, but I went back and looked and it is some aftermarket manufacturer . Everything on the existing turbo seems like it’s in good shape except the actuator housing, so I will heed your advice and just try to replace the actuator itself from Cummins, or find a good aftermarket piece, and I ordered a new oil delivery hose.

There’s also been lots of talk about stronger aftermarket lift pumps to lessen the chances of a CAPS pump failure, so I think I will do that as well. The coach is 18 years old but has been completely remodeled on the inside and I absolutely love how smooth the Spartan chassis is so, I plan on keeping her for quite some time, and want to do what it takes to keep it running well.

Jon_C · 02-21-2019, 06:25 PM

I have a raptor lift pump on mine, my vp44 injector pump uses excess fuel for cooling and will burn up if not enough pressure. I also installed a fuel pressure sensor and dash gauge on the inlet line to the pump so I could adjust to correct pressure on the raptor and monitor if i have any filter plugging.