Low turbo boost

[jimsimrv]

I've been slowly migrating to South Padre Island for the winter months, and I'm almost there (200 miles out.) Everything has been working just fine until today's drive. I noticed the coach was very sluggish on hills and not maintaining 65mph on the slightest of inclines...

I started to watch the turbo boost psi while under load, 7 psi was the highest I saw it go. Normally, I'll see 21 or 22 when under a heavy load.

I found a post over in Country Coach forum with the exact same symptoms on the same motor I have (CAT C12). That turned out to be the waste gate stuck open.

I don't see anything amiss on my initial visual inspection, but I'm waiting for it to cool down before I take a closer look.

Lucky I'm about as flat as you can get for the last 200 miles, but I'm wanting to know if I risk any further damage to anything driving it in this condition?

[RamiDav]

Look down this page and there is a window titled similar threads.
You may find help there.

Many times a sudden drop in boost is simply a hose blown loose at the turbo or intercooler.

Ray 03 Windsor

[Sspdiesel]

Yes usually makes a vacuum type sound when into boost with a blown hose , make sure simple check also air cleaner clean ..
no boost can also mean no fuel , need fuel to make boost fuel filters are easy ..

[twinboat]

Go with fuel filters first if they haven't been replaced recently.

[jimsimrv]

Both fuel filters were replaced in Colorado before I left. I can change them againA, but I procrastinated after service a couple months ago and I'm sad to say that I don't have them on hand at the moment.

Aside from crappy performance, is it OK to drive down to my spot tomorrow and deal with it there?

Also, is there a way I can check if its any better without driving it and figuring out some sort of hill to go up?

[Sspdiesel]

Dirty fuel filters ( fuel restriction ) is a bad thing c-12 has unit injectors there about 800 each no fuel they run hot and seize the plunger to the barrel .
If it’s a e engines there more .
I can say this so many times , before major engine issues diesel show a sign a symptom before major engine parts fails . Don’t drive something with a issue ..
CAt filters can be found at any truck stop , they can quick change them .

Best way is to just get in and look at things you will see a failed hose or broken clamp if you look .

I personally rebuild tons of c12 in boats there was a class action law suit with a c12 , salt water after-cooler issue . Trucks don’t have them ..

We , use to do stall test on the nyc buses when we could not road test them.
We would put it in gear hold the brake and throttle it up .. we even block the wheels , the boost will come up fast ..it’s how rods with diesel take off bring boost up first ..in the old days it was call power braking .

[BonS]

Perhaps a crack leak in your charge air cooler or perhaps your engine is de-rated due to another issue? My Cummins de-rates to around 7 psi but normal is 37 psi.

[jdw1]

Did you notice this all of a sudden going down the road or after a stop, that might indicate what’s going on!

If you have a boost leak your exhaust will run pretty hot because it’s not getting enough air!

I would think it would be best to resolve the issue before you arrive at your destination, imo!

I would check your aftercooler tubes for leaks, check the boots from the tubes to the aftercooler in case one has broke or a boot tore, check all the clamps on the charged air system, it’s possible it’s something very simple. If it was mine I’d be headed for a Cat dealer or someone that understands these systems, I’m fortunate that I understand it, I’d wouldn’t drive it any further than I had to!

It’s possible to have a split in the aftercooler too!

Jmo

[jimsimrv]

I found the exhaust pipe where it connects to exhaust manifold with 4 nuts. There is a metal gasket hanging out and the top two nuts are missing.

I went thru my nuts and bolts and don't have anything that matches...

I'm going to limp on down the road and stop at the first truck stop to see if they can help me with it.

Thanks everyone for your suggestions/guidance on this.

[Orrin]

Looks like you found the problem and it will be a cheap fix. Good for you.

[garage man]

How often do we get to say "a cheap fix".
This forum is great!

[Sspdiesel]

Keep in mind that might be the cause but what did it do to the engine that made it low boost .
Exhaust leak in engine compartment
One air cleaner full of soot from exhaust
Charge air cooler full of soot from exhaust leak
Look deeper ..
It would have to be a exhaust manifold , or turbo mounting gasket failure to
Cause low boost .

[jdw1]

Just make sure you get the proper nuts, those exhaust manifold nuts are a special material, there’re not hardware store nuts! FYI.

Also fwiw, a person should be able to actually hear a manifold leak just standing at the back of your coach listening!

[Tooltime2]

Good catch, if the exhaust is able to go somewhere other than through the turbo it will certainly decrease boost.