Blackened Posted April 7, 2011 Share Posted April 7, 2011 (edited) Hey guys,Im having a bit of a issue with a 2004 CX 613 Mack tractor. A month ago after a 150 mile trip up to Albany NY, the expansion tank in the truck filled up with coolant and built up pressure like it was going to burst. I shut it down and cracked open the line on the upper radiator hose to relieve the pressure. Once I did that I was able to hear the coolant start flowing through the engine again and I drained out the expansion tank. I refilled the upper tank and kept a eye on it the ride back. The truck never overheated or ran hot the entire time this happened but it just pressurized the expansion tank. When I got back to the shop I installed 2 new thermostats and found that the radiator cap wouldn't hold pressure so I replaced that too. I have no oil in the coolant, no coolant in the oil, no white smoke, no bubbles in the coolant, no exhaust smell from the coolant, no coolant consumption,and nothing that would point towards head gasket. I also checked the air tanks to be sure the compressor wasn't at fault. I drove the truck hard all around the neighborhood and lugged it down as much as I could but I couldn't replicate the problem so I figured it was fixed. That was until I took the truck out on a short haul into NJ and had the same issue within the first 40 miles of the trip. Now here's what I noticed. If I baby the truck and keep it running at 1/2 throttle with no load, the temp and the coolant will be normal and not build pressure. If I keep it at full throttle with a load on, it will build up pressure and start blowing out the expansion tank. On some extended drives at full throttle with the cruise control on, I would get the electronic malfunction light on the dash and I would loose all turbo boost for a few seconds then it would clear and the truck would pull like normal. Lately it hasn't been doing that but started building this pressure under a load. I been reading about the EGR coolers failing so I'm wondering if this would sound like something related to that problem or am I looking at something more serious?Within the last 2 yrs,the oil cooler filter was replaced. The water pump was replaced 3 months ago due to it leaking out the weep hole along with the water filter and a full coolant flush was done.Thanks for any info. Edited April 7, 2011 by Astoria Mechanic Quote Link to comment Share on other sites More sharing options...
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