Low boost, cracked exhaust manifold , intercooler leak, turbo

[joslawrence]

I have received so much help on these forums in the past without ever asking a question and often find myself too busy to post I thought I owed the forum some information that may help others.

I have a 2000 Monaco Dynasty with a Cummins ISC 350 Hp that is rated at 1050 lbs of Torque @1400 rpm. I have owned the coach for 5 years and put about half of the 100,000 miles that are on it. I operate it most of the time around Michigan where there are not too many excessive grades however I have begun to notice that I could not keep speed up on even moderate grades and from 70mph it would drop down to about 55-60. I did not pay to much attention to it initially and chalked it off to the fact that I have begun to tow a heavier Lexus LX 470.

I started to realize however that I was not getting the power I thought I should have. I run other diesel equipment in my business so I changed my fuel filters, having had experience with clogged filters restricting fuel flow and reducing power, but only noticeable under high demand conditions. But performance stayed the same…I began to watch my boost gauge and noticed that my maximum boost pressure was only getting to about 18psi (on the dash gauge). I unfortunately could not remember for certain, but I thought in the past the gauge would get past 20. In addition we have had some 95deg weather recently and on a trip during this weather I also had the water temp light flicker on and off and the temp gauge show above normal. While still pondering this I had my muffler fail and I replaced it with a combined Aero and FTE free flowing exhaust which did improve performance marginally. This threw me off track for a bit, but I began to notice that I gradually had a hard time seeing the boost pressure get much past 10 now.

After doing a bit of reading I decided to inspect the turbo and exhaust. I found an obvious crack in the rear manifold at Cyl 2 or 4 (depending how you count) and sooty deposits on the cylinder head at 4 of the exhaust manifold gaskets. I also found that the waste gate on the turbo appeared to be seized (although later I found in the closed position). At this point I determined that replacement of the manifold was in order and the turbo was certainly in need of some work but considering the age and the difficulty of getting everything apart and the fact that the turbo would need to come off anyway I decided to replace both the turbo and manifold with new components. I made some calls and came up with a new OEM manifold for about $500 with shipping gaskets and new bolts. I also was able to find a new “Cummins” turbo with my spec number (the turbo is actually a Holset HX40W) that I could get without a core charge for $1073 (one dealer wanted $1689) I also ordered a new air filter to complete the job.

After the parts arrived I set to work…fortunately, for this repair, I do not have a rear slide in the coach and have good access under the bed to the top of the engine. I took the intake air boot off the turbo, disconnected the discharge air horn at the first hose connection, removed the oil supply hose, loosened the rubber hose on the turbo oil drain pipe, at the engine, and then carefully removed the manifold bolts without breaking any. I pulled out the turbo and manifold together. I did a coolant and oil filter change, with the manifold and turbo out, which was easier then from underneath. I Put everything back together with new gaskets, bolts and studs.

The manifold is in two pieces so I put the front section on loose and then installed the rear section and torqued both down to spec. I put “copper high heat” antiseize on all bolts and studs. I then put the oil drain tube back on the turbo, while on the bench, because one of the bolts is behind the waste gate bracket and would be difficult to install from underneath, once in place. Unlike the way I took it out, I then put the studs into the manifold and lowered the turbo into position and secured it with the nuts. In order to torque the turbo nuts I used a 15mm crows foot and 3/8 torque wrench to get them to spec. Kind of hard to get to them all but it can be done with exception of the nut toward the front at the bottom of the turbo flange. For this nut, I tested one of my already torqued nuts with a Box wrench and tightened the one, that I could not get with the torque wrench on, to the same hand “feel”. I pre installed the discharge air horn onto the hose below and connected the aluminum joint up at the turbo once the turbo was installed. The aluminum discharge airhorn has an o-ring seal but I put a thin coating of hi temp (red) RTV silicone on before securing it with the clamp I finished hooking up all the remaining pieces and took a test drive. Now I had boost pressure past 15 but still not to the 24-25 that I thought I had observed in the past.

I decided to do a boost pressure test next to see if there were any leaks…I got some connecting parts and made a makeshift rubber boot I could attach to the intake of the turbo and put some pressure in from a compressed air source…well as you might guess I could not get it to hold pressure…I heard air hissing out near the side discharge radiator and after pulling the grill off I found a 12” crack running up the side of the intercooler end cap toward the front of the MH. Fortunately the intercooler is in front and the crack was totally visible and exposed. I did not want to remove the thing and I had a trip planed in a few days so here is what I did. Because of the situation and location of the crack I was able to aluminum (Tig) weld the crack without removing it from the coach. After welding I pressurized it again and this time I could get it to hold pressure, although I was not able to get more than 5lbs or so of air into it before my test rig blew off. I only had regular band clamps and the turbo intake flange is smooth so with the size of the boot being 4” it does not take much pressure to break the grip of my rubber boot and blow it off. Be careful if you test boost pressure this way as even with low pressure the boot can blow off violently so keep out of the way! I could see though that it was holding pressure so I put it back together and took it for a test drive….WOW! what a difference…A job complete! I now had excellent acceleration and a boost pressure of near 25 at 2100 rpm under load!

Ok some thoughts…there is more information on this under an old post titled “Poor Boost” from 02-11-2013 which I only found after I had found and repaired my problem…go check it out http://www.irv2.com/forums/f115/poor-boost-151112.html

There is an indication, that on these coaches, a crack in this location is somewhat typical. You might think that if you do not have the ability to weld aluminum you can’t fix this as easily as I did…well here are some suggestions…if you have a crack accessible like mine was from the outside of the coach you could easily take the coach to a welder that can do “Tig” welding and let him weld it on the coach…it is not hard to do for an experienced welder and should not cost you more than a few hundred, if that (I had mine done in under two hours, including going to my shop for my welder and cleaning the joint with a stainless brush and acetone). If I had not had the ability to weld the crack I would have used an epoxy product like JB weld which should last very well on such a situation. There is only moderate heat, very little pressure (under 40psi) and no liquid flowing in the coil. If you have a similar situation but the crack is not accessible without removing the coil I would still look at getting it welded after removing, or even use epoxy…I think the fault is more a manufacturing defect than deterioration, and a repair I would expect to last very well. A new intercooler could cost several thousand so repair savings could be substantial and I believe very long lived. Haven’t yet been able to say for sure that my overtemp problem is gone as well but I suspect so!

Hope this helps someone else…Thank you to all the contributors to this forum and others that take the time to share their own experiences, knowledge and information!

Joseph

[walt2137]

There is also a post on this forum posted in I think 09 on how to remove the CAC without removing the radiator in about 2 hrs or less, if anyone needs the info and can't find it pm me.
When I tested my CAC I used soap and just idled the engine on fast idle and it made lots of bubbles where the tubes went into the alum header

[jacwjames]

Last year I had road debris come up and take out my radiator. While that was being fixed I decided to take the CAC and have it cleaned and tested. I did not expect a problem since I was getting ~22 psi boost. I got a call that said the CAC was bad so I went down there to see for myself. They plugged the holes and put air to it while it was submerged. It looked like a big Jacuzzi tub, leaked really bad on one side. Ended up getting it rebuilt for ~$1500.

After the radiator repair was complete I did notice that I now get ~24 psi boost with some improvement in power.

The next short trip we took, after returning I noticed a high pitch sound from the engine area. I went back and accessed the top via the hatch in the closet and found the exhaust manifold cracked. I know it was not like this before that as I had done a close inspection of the engine after getting the coach back from Cummins after radiator repair. Cost ~$600 in parts to fix and took me ~6 hours doing it myself.

[Papa_Jim]

The Holset HX40W turbo is capable of producing high turbo boost. However, the actuator that is supplied with the new turbo is usually set at about 20 lb. You can adjust the actuator rod connecting the actuator to the waste gate valve to increase the turbo boost. Failing that, you can purchase a boost fooler valve from TST products which will simply and easily increase your turbo boost by about 5 lb. There's a tremendous improvement in engine performance to be realized by simply getting that turbo boost increased into at least the high 20s, as close to 30 as possible.

Jim

[10Boomer]

Originally Posted by walt2137

There is also a post on this forum posted in I think 09 on how to remove the CAC without removing the radiator in about 2 hrs or less, if anyone needs the info and can't find it pm me.

When I tested my CAC I used soap and just idled the engine on fast idle and it made lots of bubbles where the tubes went into the alum header

Good to know!


Sent from my iPhone using iRV2 - 2008 Monaco Camelot 40 PDQ

[joslawrence]

Thank you Jim for the input...I took a look and with the turbo installed I could not access the rod very easily so to try things out I pinched off the pressure line from the turbo housing to the actuator. My unit according to the dash gauge must have been set to about 23 psi. With the waste gate disabled I now max out at about 26-27 psi.

On my engine there is no other waste gate control other than the direct pressure line from the turbo housing to the waste gate diaphragm...is there any reason not to just plug the 1/8" pipe thread in the housing and leave the waste gate disabled?

[barmcd]

I regularly get close to 25 lbs of boost going up hills and accelerating in my 2000 Dynasty so I'm assuming that's typical of the ISC. Nominal boost is around 5 lbs when traveling at highway speeds on the straight and level. Does that sound about right?

[walt2137]

Yes Dennis that is about right. I run the TST boost fooler set for 30# and a friend Bill D ran the 35# fooler on his 8.3 with the fuel plate that gave him close to 400 HP.

[Mr_D]

I installed a Banks PowePak setup on our '02 ISC 350. Banks dynoed this setup @ 435/1200 and Banks was known to be conservative on their reports.
I too had trouble with the bolts on the turbo as the Banks kit included a new turbo housing. Stock boost was about 24 max and 30+ after the kit. It also included a new actuator and reduced the turbo lag. Too bad they no longer make that kit.

[barmcd]

Originally Posted by walt2137

Yes Dennis that is about right. I run the TST boost fooler set for 30# and a friend Bill D ran the 35# fooler on his 8.3 with the fuel plate that gave him close to 400 HP.

Thanks Walt.

[Papa_Jim]

Originally Posted by joslawrence

Thank you Jim for the input...I took a look and with the turbo installed I could not access the rod very easily so to try things out I pinched off the pressure line from the turbo housing to the actuator. My unit according to the dash gauge must have been set to about 23 psi. With the waste gate disabled I now max out at about 26-27 psi.

On my engine there is no other waste gate control other than the direct pressure line from the turbo housing to the waste gate diaphragm...is there any reason not to just plug the 1/8" pipe thread in the housing and leave the waste gate disabled?

I really can't think of any reason why it wouldn't be OK to do that. The rod on mine is adjusted so the waste gate can barely open and I'm also using a TST boost fooler. When my coach is on a really steep grade, and the transmission is shifted back into 4th gear, and the engine is laying out absolutely everything it has, the turbo boost is pegged at 32psi. Lots and lots of power.

Jim

[joslawrence]

Originally Posted by Papa_Jim

I really can't think of any reason why it wouldn't be OK to do that. The rod on mine is adjusted so the waste gate can barely open and I'm also using a TST boost fooler. When my coach is on a really steep grade, and the transmission is shifted back into 4th gear, and the engine is laying out absolutely everything it has, the turbo boost is pegged at 32psi. Lots and lots of power.

Jim

That is what I did...and I am going on a short trip tomorrow and enjoy performance I have not seen in awhile, perhaps ever!

Excuse my ignorance here...Is there any reason a "Boost Fooler" would do any more then disconnecting the waste gate on my engine? Does it interface with the ECM to allow more fueling?
What product do you have from TST? Is it electronic?

[Papa_Jim]

Originally Posted by joslawrence

That is what I did...and I am going on a short trip tomorrow and enjoy performance I have not seen in awhile, perhaps ever!

Excuse my ignorance here...Is there any reason a "Boost Fooler" would do any more then disconnecting the waste gate on my engine? Does it interface with the ECM to allow more fueling?
What product do you have from TST? Is it electronic?

My coach has the mechanical C8.3 engine, so turbo boost and fuel delivery are simpler to manage. The turbo boost fooler that I bought from TST Products is a simple adjustable air relief valve that is inserted into the air pressure line that feeds from the injection pump to the waste gate valve actuator.

I agree that you can simply close the air line to the actuator. I've done that to test the available turbo boost and to make sure that the waste gate valve is actually functioning properly. I think it's wise to have the hose hooked up and the turbo boost adjusted to a specific setting. That way, if there's a sudden surge of turbo boost (for whatever reason) nothing in the engine or in the air intake system is going to get damaged.

TST Products have other methods of accomplishing the same thing with turbo boost for electronic engines. You might want to browse their website.

Jim