Center section of manifold cracking..

[marek4792]

What would cause one to crack at the mounting flange, or on the outside of it? Pre doc EGTs and boost are in range for Volvo's small piping. Had RR demandate it using a proper 565 overlay verified by Rawze and had overseen the gutting process. We did briefly run a higher boost tune but the truck didn't like it drove coolant and oil temps into the red and since brought it back down. Engine has 665k miles and it is tired, and have an appointment in GA would like to get it figured out before hand. CAC is new and tested good. Tried Oem and {aftermarket) exhaust manifolds just to see. Using the correct turbo from the Chicago rebuildler I've mentioned on Haggais recommendation. At one point it didn't want to hold mounting gaskets pre and post demandate. Thoughts?

[Rawze]

.
Putting big power (above 500+ HP) in a Volvo truck is part of the issue.

Those Volvo's have beyond horrible engine compartment cooling, and severely restricted air flow. The turbo and exhaust manifold runs hotter on them than any other brand of truck because of this.

Figure out a way to cut out all the Volvo plastic crap and guards and other trash that restricts free-flowing air from getting around the engine and you will find everything runs much cooler.

(my own opinions only ... the beer is talkin') ...
Personally, I don't know why anyone would want own that brand of truck. They are the least fuel efficient of ANY truck that is aerodynamic.. they have horrible air flow and everything runs much hotter under the hood than it should.. the I-ST%it tranny is garbage (for those who have them), they have a toothpick of a drive train, and are not designed around high profitability in my book.

===========

What make/model engine? .... what is the boost seen under higher operating loads?. .. and What are the EGT's (and oil temps) getting up to?

[marek4792]

2020 x15 4343 factory 505 1850, Boost was at 31-32 lbs at 1500rpm higher it tapers off. EGTs were under 1000 pre doc prior to it cracking. Oil temp doesnt get higher than 243F What I don't understand it was fine for years and now it just starts doing it..

[Rawze]

EGT's should run about 1050F (post turbo) under full sustained operating loads.

Oil temps should be running about 235~ish max.. maybe 240 only if you torture it up a long incline. your temps describe that maybe the injection timing is a bit on the high side.

It should be about 32-33~ish boost max, so your boost sounds like it is in range.

Maybe Slipped cam, intake sensors reading badly.. leaky injectors, maybe altitude sensor reading high,. or a temp sensor .. or it could be set a bit high the programming too.

[marek4792]

Oil Temperature has always hovered in the high 240's stock in this truck and in low 240's with Uni and RR Tune. Got really lucky with the aftermarket and they actually warrantied their manifold without me having to send it back.. I do have a spare stock manifold if needed, Anyway. Got the glowshift pyro tapped and installed post turbo now like it should of been instead of the Pre DOC inlet like I had it. Cruising bobtail at 65 was sitting around 475-500F. Changed out the crankcase filter too, My friend's shop experience with them makes me suspect these X15's crankcase filters aren't as "maintenance free" as we think they are.. Will update once I'm loaded.

[tree98]

I've seen and heard of many X15's with oil temps that high. Cummins must have engineered them that way for some reason??

[marek4792]

Update. Egts are in range post turbo 875 to 900 at 1400-1500 RPM and 925 to 1075 in sustained pulls above 1500 to 2000 RPM especially in higher elevation until I back out of it, BUT also, it miserably fails the fuel rail pressure test 15k psi in a minute just about although I've changed the relief valve and sensor months ago and it held then. So I have some investigating to do before I go firing the parts cannon...

[marek4792]

Bumping the post yet again. So it cracked the 2nd aftermarket manifold. Noticed white smoke on start up and when it first gets going and an occasional haze prior to and after overhaul. At this point we're strongly suspecting an injector is running afowl in a loaded condition, while passing a leak down test with 500 psi loss in a minute. EGTs 1075 at its highest since removing the radiator shrouds.

[Rawze]

(01-18-2025 )marek4792 Wrote:  Bumping the post yet again. So it cracked the 2nd aftermarket manifold. Noticed white smoke on start up and when it first gets going and an occasional haze prior to and after overhaul. At this point we're strongly suspecting an injector is running afowl in a loaded condition, while passing a leak down test with 500 psi loss in a minute. EGTs 1075 at its highest since removing the radiator shrouds.

Cracking an exhaust manifold is not a common thing. Its usually due to improper install or some form of engine abuse (excessive hp/torque vs. the components). Are you pushing the engine past its factory HP/torque ratings?. What is the average engine loads looking like in the graph?.

are you sure your not over-tightening the manifold bolts and they are not allowing for heat expansion?. Are the expansion joints of the 3 sections seized up?. Has anyone surfaced the manifold as a whole to ensure it sits flat and there is not stress?.

1050F exhaust temps are not excessive (post turbo). Above 1100F+ would be.

Has I reviewed the programming to ensure its not abusive?.

also, aftermarket manifolds... I don't trust em, and there are no engine/efficiency/etc. gains for using them.