ten 42 Posted November 25, 2017 Share Posted November 25, 2017 After head replacement truck runs fine for 50 miles then gets hot at 60 MPH and will cool down at 30 MPH immediately. Coolant system pressures up and then will push coolant out the cap at 1200 RPM, but no pressure at idle. My mechanic is stumped on this problem. Any help is appreciated. Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/ Share on other sites More sharing options...
Mack Technician Posted November 25, 2017 Share Posted November 25, 2017 What was the original failure? Pre-head replacement. Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385869 Share on other sites More sharing options...
ten 42 Posted November 25, 2017 Author Share Posted November 25, 2017 (edited) Pushing coolant out of the cap and the coolant was very dirty. Would overheat at 60 MPH and then cool down at 30 MPH. Used the NAPA combustion gas kit and it tested positive for exaust gas. So the head gasket was the first thought. I've just discovered the suction from the radiator is cold when at operating temperature, yet the rest of the system is hot The coolant smells strange as well, the short hose from the thermostat housing was also sucking flat at 1200 RPM and going back to round at idle. I changed it to a reinforced hose and that helped the overheating, but not the coolant purge out of the cap Edited November 25, 2017 by ten 42 Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385871 Share on other sites More sharing options...
fjh Posted November 25, 2017 Share Posted November 25, 2017 Did you guys replace the t stat? Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385877 Share on other sites More sharing options...
ten 42 Posted November 25, 2017 Author Share Posted November 25, 2017 1 hour ago, ten 42 said: Pushing coolant out of the cap and the coolant was very dirty. Would overheat at 60 MPH and then cool down at 30 MPH. Used the NAPA combustion gas kit and it tested positive for exaust gas. So the head gasket was the first thought. I've just discovered the suction from the radiator is cold when at operating temperature, yet the rest of the system is hot Yes, there is one on this engine. This is a 2002 CL 700 Oilfield Vac Truck Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385881 Share on other sites More sharing options...
ten 42 Posted November 25, 2017 Author Share Posted November 25, 2017 Yes, that was the same thought my mechanic had. The dirty coolant that smells funky is what is strange. I Bypassed the air compressor to check if the gasket was leaking on it and it did not even have the slightest bit of air coming out of the water jacket Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385882 Share on other sites More sharing options...
ten 42 Posted November 26, 2017 Author Share Posted November 26, 2017 Pulled a bypass hose and it was full of air and the truck began to run normal. Hopefully is a real fix and it's not a liner or wrinkled head gasket. Washed out radiator from bottom to top Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385924 Share on other sites More sharing options...
Mack Technician Posted November 26, 2017 Share Posted November 26, 2017 May be good to have the heads crack-checked too (during R&R). Can't always pick up everything with a naked eye. Retest for exhaust gas if continues. Quote Link to comment https://www.bigmacktrucks.com/topic/51777-2002-mack-e7-427/#findComment-385933 Share on other sites More sharing options...
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