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Keffer inc

2011 Mack MP8 pushing coolant out of the overflow tank.

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Hey guys, I have a 2011 Mack CXU613 with a 455 hp MP8 motor. The truck started pushing coolant out of the reservoir tank when climbing up mountains and long hills. The problem seems to be getting worse.

I did replace the coolant tank with one of Ebay some time ago, and its maybe possible that I have a higher percentage of water than coolant so that may be boiling over? I plan on draining the coolant and replacing with fresh coolant to see if that's my issue, but else might it be if it's not simply that? What are some test I can do on my own? Thanks.

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A few months ago, I'll change that too. You think that may be all that's wrong? Guess it would make sense.

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I had the same issue what I did on mine i poor a stop leak from gas station I poor it stop the leak
N I clean Raines all and put new antifrezze and I been running 7 months with any issue on my coolant


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Remove the egr hose at the front of the cooler and c if it’s wet there! Possibly failure however your symptoms are more similar to injector cup failure 

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That's what I'm leaning towards as well. I dont see any "steam" coming from my exhaust or any bad smell from the exhaust pipe. I have noticed my coolant temp is getting hotter, faster than usual.

Today I have any empty trailer and in 10 seconds of flooring it uphill, the temp goes 15⁰ hotter and the truck overall is running warmer than usual. Not overheating, but just hotter. The engine fan keeps coming on to.

It did cross my mind this could be simply a bad coolant water pump or thermostat?

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Ah hell, I just noticed air bubbles in my fuel filter globe. That's almost a guarantee it's an injector cup isn't it? 

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Posted (edited)

If it’s hard to start in the morning it’s a guaranty check egr before getting carried away. The hard pull comment kind of raises my eye brow a bit!

Edited by fjh

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Could possibly be a cracked injector cup at the body to tip area, seen that many times. Could also be a leaking egr cooler, worst case could be cracked head. I don't think a bad water pump would cause pushing coolant unless the engine overheated and cracked the head or damaged the egr cooler. 

If the upper radiator hose is hot to touch and the lower radiator hose is cold the you may have a water pump issue(vanes spinning on w/p shaft). Even if the water pump is determined to be bad its not the reason for pushing coolant. 

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My cousin had a Pete with a Cat motor, the piston cylinder walls were eaten through and air bubbles were getting into the coolant that way.

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Well I took the egr apart at the outlet side, its dry soot inside like it should be. I'm going to buy a cheap harbor freight temp lazer to check the radiator like you suggested, all signs kinda point to something injector related I think. The truck has an appointment with the dealer for tomorrow so tomorrow evening I'll probably have some idea what's going on and how much it will hurt to fix it. Any want to buy a 2011? I'll sell you one half price. ;)

20190530_092209.jpg

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Also I notice the fuel level in the fuel filter is going down all the way out of sight. Fuel is leaking back some where.

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I measured the radiator inlet and outlet with a lazer temp gun and it was a 25⁰ difference between them. I feel like that's kinda lower than it should be.

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So have you got any farther with this problem 

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Looks like it was a faulty pressure cap on the over flow side. Seems to be holding coolant now.

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Good news!   👍  Keep it simple!

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Posted (edited)

My truck uses a normal spin-on style filter, just a filter wrench is all you need on an MP8.

Edited by Keffer inc

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I have 6 Mack engines that I would like to delete the DPF. Any advice??

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