c-mac

ok the cooler took care of the one I posed the pick of. The next one has a new cooler and compressor. I guess someone else has been chasing this problem too. I checked the newish cooler, it was clean and dry. I clamped pinch off the coolant line to the compress and ran the engine at 1000rpm. The cooling system got up to 13psi. I left the system a little low of coolant so as not to blow it back out. I pulled the overflow hose up and stuck it down a bottle of water and light bubbles were present and the coolant tube from the back of the thermostat housing to the coolant tank was jumping. I cant thing of any other way of determining if it is cups or a head problem. This one is an 08 model built date is 11/07. Not sure if it has copper or stainless cups of if they have been changed

Ok I pulled the cooler because I seen what looks like tiny red droplets of coolant and the inside of the housing is damp and sooty. I’m not sure if what appears to be red droplets is coolant. What do y’all think? You may need to blow up the pic to see

I edited my post. It’s a 12 model and I have an 08 with the same problem. I’m not sure if either has had the cups and injectors replaced. I work on a large fleet and they don’t keep good records..(oilfield). My self I write on the date and hours on the valve cover. I thought I had seen all the symptoms til now.

I’ve got Mack chi 613 with an mp8 that’s blowing coolant out the overflow hose of the coolant tank mounted above the radiator. I’ve already pinched off the coolant lines to the compressor and it builds up to 15 psi in the tank. Is there anything other than a head or head gasket problem that will cause this?

Put a new 7th injector on and took care of the problem. thanks

I just cleaned the Tee on top of the seventh injector where the air and the fuel connect. Now its been on regen 45 mins and only reaching 768deg on outlet temp and the fuel pressures are both steady at around 68psi. and 12% duty cycle. Theses numbers have been the same for 10 mins. The adaptive factor is holding and 1000. I would think it should rise if the temps were not coming up.

Turned out to be the “dump” valve on the trailers air tank.

Dang! Thought someone would have seen this.

Got a 2012 chu613 that when you set the trailer brakes air blows out the yellow exhaust line on the firewall for several seconds then the trailer brakes pop. Air continues to vent at the firewall for a while. I’ve been working on a large fleet of these and I remember having this problem a long while back but can’t remember what it took to fix it. Oh and also the tractor park brake don’t apply until a lot of air escapes. So when you pull both brake buttons air rushes out the firewall vent lines for several seconds until you here a dump at the trailer then all brakes apply

I have a 2012 chu613 MP8 that as the duty cycle gets to 10% or so, the A'treatment fuel pressure drops from 8 to 15 psi under engine fuel pressure which is running in the upper 60's. The exhaust temps never get higher than 750deg or so and wont complete the regeneration. This particular unit has a 7th injector with the "T" fitting on top where the air and fuel lines connect. Just wondering if any of you have seen this and what you've done to correct it. I thinking it could be either the 7th injector, the shut off valve or the T fitting on top of the 7th injector. I've been working on a large fleet of these trucks from 08 t0 13 models for 8 years and haven't ran into this before.

I have had the problem you've described that was a bad engine ECU but it always set a trouble code.

OK, I"m kinda embarrassed to say I think I have figured it out. when I started the engine cold it stumbled for a second which seemed odd, the oil pressure looked good 45 idle and 75 running high, then started dropping back to what it was prior to attempted repair. To make a long story short, fuel is getting into the oil ..how? past a bad injector oring? Thats all I can come up with anyway. I work on a fleet of 150 2008 and up macks eveyday and haven't ran into this problem. I've had fuel in the coolant several times, but not this. This engine has had cups and injectors about 1000 hours back. Do you think I can get away with just injector orings or maybe ya'll know of something else that may be the problem?

looked ok about to go back with all new orings, thanks

I'm not sure whats going on here. I though I recognized the tractor number. I looked through the service history and saw where another tech replaced the oil pressure sensor, then a month or so later in May I had it towed in due to low oil pressure. I put a manual gauge on it and it got down to 15psi at Idle and 35psi and dropping at WOT. Driver said the shutdow light came on at highway speed. At that time I remembered another guy had the same problem after injectors and cups. Turned out he had cut the oring on the engine brake oil control valve tube where the tube goes into the rocker shaft. I checked this one and the oring had a notch cut out of it. I replaced both tube orings and I thought it was fixed. The oil pressure was good. Now, two months later we have the same problem. I have already had the pan off to inspect the screen and it was all good. I think that I'm about to pull the valve cover and check the oil control valves orings again.

I have a truck running under 20psi oil pressure at idle hot. I changed out the pressure sensor and the pressure came up to 26psi at idle but I’m not sure if the oil was as hot. It will max out around 78 at wide open throttle, before and after pressure sensor replacement. 5500 hrs on engine.

don't forget the overflow valve for the extended cranking time. We have over 100 MP8's in our fleet and I know that I've replaced 60 of them. I didn't know the 7th injector could leak coolant into the exhaust. Thanks

Ok, Im in another truck right now doing a forced regen and the intake manifold pressure is ranging from 1.8 to 2.0 psi. If I get back on the the truck in question, If I have similar intake pressure would you say that the turbo is doing what it should?

I think I narrowed it down to a problem in the ecm or the short harness between the aftertreatment fuel pressure sensor to the ecm. I swapped the harness connectors from the oil pressure sensor and the a'treatment fuel pressure sensor. While monitoring the a/treatment fuel pressure I started the engine and pressure still read 0.0psi. Then I activated the a'treatment shut off valve and the dash oil gauge went from 0 to 60 psi. I checked the harness connectors to both sensors, three pins one 5v one ground and I cant remember the third pin but the both were the same. I unplugged the ecm connectors to inspect for oil or maybe a terminal corroded or bent over. I looked all good. I'm pretty sure its an internal problem in the ecm.

Well it seems like I'm always posting a doozie. i have a 2011 with an MP8 that wont heat up when regenerating. It gets to about 600 degrees and thats it. I noticed that the aftertreatment fuel pressure was reading 0.0 and it would only hit 7% duty cycle, it would go back and fourth from 7 to 0 percent no higher. Well first thing I thought was the shutoff valve was bad. I installed a new block with shutoff valve and pressure sensor. No change. then I set it on a forced regen and cracked the line to the 7th injector and fuel sprayed out like it would with proper pressure. I blew out the fuel line from the filter base to the aftertreatment block and everything else you can think off. what i'm coming up with is, the ecm is not getting the signal from the pressure sensor or their's a problem with the ecm. Anyone else have this problem?

Well I guess I'm in the clear. The boss called the Mack field tech to com look at it. 10 hours later he had nothing either. we just pushed it outside and will tackle it another day.

This one has the regulator in the right side of the block. I removed the return line and I get a drip from regulator, but I dont think its enough to cause a pressure problem. I just noticed that the engine oil is an inch over full and appears thin, like contaminated with fuel. I hooked up the pressure gauge as pictured. I had to turn the engine over for a long time to get 20psi.

Thanks a bunch! I read somewhere the pressure should be 90psi. Anyway you say it should be 58psi. Will it make that much pressure just cranking? Where is this ground relay?

Thanks for the link. Engine has a brand new pump. I was trying to find a way to test fuel pressure so I pulled the check valve out and was going to tap it there but the hole in the block is some weird size, I can't find a fitting to screw into it. The outlet of the lift pump is in a real bad spot but I guess I'll have to try to tap it there

Thanks, I've already swapped the four relay around and checked them individually. The eecu has no coolant in it but someone before me added some dielectric grease to the connectors. I've tried to get that out just to be sure I was making a good connection.

I have a 2007 Pinnicle with the gray Mack motor that turns over great but no start. I have tech tool but its not much help on the older stuff plus I have no shop manual either. When I first checked it out it had many dtc's but engine position sensor stood out. I cleared all the codes out and none came back. Anyway I swapped the cam sensor and crank sensors out with a running truck and nothing. I swapped the ECM also and nothing. Id kind like to check the circuit but I don't know where it goes in to the ecm. I check for voltage at the sensor but i've ohm'ed and tested so many things on this truck I can't remember what I had there but it wasn't 5v. I saw a pic online somewhere that showed the circuit to be five volts but I not even sure it was for the same engine.I guess tomorrow I'll start tearing into the harness unless you guys can help.