mp7 engine coolant issue

[eltiablo]

I have an 07 Mack Pinnacle with a mp7 engine. The coolant is pushing through the surge tank and into the reservoir. I took it to a Mack dealer who ran a diagnostic on it. I was informed that there is exhaust in the coolant and was told that to fix this issue, I would have to either buy a re manufactured engine or rebuild mine. I plan on getting a second opinion but am wondering if anyone has had the same issue or knows what the problem might be. Thanks.

[wheeler73]

Could also be an egr cooler. Seen that more than once. Have the egr cooler checked. Also have seen injector cups, air compressors, and liners with erosion cause the issue. But if there is exhaust in the coolant I would check the egr cooler and injector cups first.

[bbigrig]

Injector cups is the usual suspect for that issue. I've had the same issue with my MP8's which is the same basic design. EGR coolers will usually blow coolant into the intake and combustion chamber causing white smoke out of the exhaust.

[eltiablo]

Im taking it to a different dealer and that service manager was leaning towards the egr cooler. We'll see. I think the dealer its at now just wanted to sell me a reconditioned motor.

[eltiablo]

But wouldnt injector cups make it hard starting?

[wheeler73]

Only if they burnt where they meet the injector. Coolant goes around the cups and if the cup leaks at the head exhaust goes into the coolant

[eltiablo]

Thank for the info. Very helpful. The dealer did check the egr cooler as well as the compressor and did a computer compression test and some other things but im taking it to a different dealer that charges less in labore rates and will pinpoint the problem and not try to rebuild or try to sell me a remanufactured motor without tryin to save this one. The motor runs fine other than this coolant issue. Lol

[eltiablo]

It doesn't even overheat. Lol

[br549]

Had a couple of truck doing that and it was a bad radiator cap.

[bbigrig]

1 of my MP's pushed coolant out of the tank on start up. As it heated up it sealed the combustion chamber to coolant passage in the cup slightly. It would pressurize the cap fairly quickly. This was an engine that was on its second set of stainless injector cups at the time of the leak.

[wheeler73]

Hey bbigrig it sounds like improper installation of the cups. I have seen that before.

[eltiablo]

I already replaced the cap. Needless to say it wasnt that easy unfortunately lol

[jnr_ate]

there was a mod in Australia where we put a "shuttle valve" in the bleed lines to the header tank. as the engine was turned off it would force coolant into the tank from engine overflowing it and then losing coolant. as it cooled down you would be low on coolant.