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GU713 MP8 head issues


KyleThomas
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So I have 2 trucks so far at around 250k+ miles started to misfire. 2016 Mack Granite GU713 with the MP8.  Both start loosing coolant internally. 

Computer diag showed mechanical failure in the turbo, and one had cly 5 misfire, and the other was cly 6. Upon removing the heads we found the heads to be cracked, and chip missing off of a exhaust valve on both heads, which traveled to the turbo and jammed them up. 

The egg coolers are not leaking. No coolant in the oil. It seems the heads crack allowing coolant to hit the valve and causing it to crack. 

Has anyone seen anything like this. I'm worried this is working through my fleet. 

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  • 1 year later...

One of our trucks developed what i can only describe as a rough idle/running issue codes came up for the turbo and Cyl 5 misfire and what appeared to be a fuel oil mixture coming out of the exhaust (grass burner) after research we figured it was a failed injector combined with turbo oil seal failure (probably just wishful thinking and hoping we didn't have to remove the head) we replaced the turbo, and put in a whole new injector set and ran an overhead. after doing so during our test run it still had a rough idle and couldn't even get it up to speed. no codes so we pulled it apart again thinking maybe we mis-seated one of the injectors and decided to do a rudimentary pressure test (really should've done that the first time but hey) every cylinder passed except #5 of course, so reluctantly we pulled the head. and lo and behold #5 cyl exhaust valve was chipped, couldn't find the piece, and no scarring on the cylinder sleeve or marks on the piston and no valve piece, presumably the valve chip worked its way through the exhaust damaging the turbo.  we took the head in to be rebuilt and after a 6 week wait due to the shop being over booked they tested the head and it checked out, no cracks, fluxed clean just a bad valve. then we were told apparently the shop can't grind the new seats at the right angle or something and we decided to order a remanufactured head, then allegedly the first head was lost in shipping and now the second head is held up for some valve sleeves that allegedly can only be found in California and Europe which also got lost in shipping from California. currently that is where we are sitting, and i came across your post while researching info because I want to make sure i get the timing right and such when i finally get a head to put on. this particular truck is new to us its a 2013 CHU613 so far the general consensus is the cause may have been from neglecting to do any overhead adjustment in the life of the truck or an improper adjustment, or the #5 injector did fail and created localized temp issues or dry slap that caused the valve failure.

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On 7/28/2021 at 2:26 PM, KyleThomas said:

So I have 2 trucks so far at around 250k+ miles started to misfire. 2016 Mack Granite GU713 with the MP8.  Both start loosing coolant internally. 

Computer diag showed mechanical failure in the turbo, and one had cly 5 misfire, and the other was cly 6. Upon removing the heads we found the heads to be cracked, and chip missing off of a exhaust valve on both heads, which traveled to the turbo and jammed them up. 

The egg coolers are not leaking. No coolant in the oil. It seems the heads crack allowing coolant to hit the valve and causing it to crack. 

Has anyone seen anything like this. I'm worried this is working through my fleet. 

The most common issue is injector cups ! You are quite fortunate for the piece to have just got into the turbo ! We have seen several of these failures ! where by a piece would fall out of the valve end up on one side of the piston and take out the liner as well! Because the piston has no skirt to speak of the piston will cock in the bore and easily  break the liner  !As for the heads cracking I'm not sure its a pandemic by any means shit happens some times ! Also  if have deleted the egr this can cause a bit of problems if the proper tune was Not  installed into the program to account for the lack of EGR!

Edited by fjh
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Has the emissions been deleted? If so , seen several trucks with valve issues. Mainly if the EGR has been deleted. Disregard, just noticed that FJH was ahead of me on the EGR delete issue 

Edited by Mackpro
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19 hours ago, Mackpro said:

Has the emissions been deleted? If so , seen several trucks with valve issues. Mainly if the EGR has been deleted. Disregard, just noticed that FJH was ahead of me on the EGR delete issue 

Didn't realize we were racein ! 😅

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