Doffer Posted March 7, 2013 Share Posted March 7, 2013 (edited) My Engine brake isn't disengaging when its cold for some reason. When I am using the engine brake and then hit the throttle the exhaust makes a weird noise (kind of like the engine brake is still engaged, but only partially), blows out all kinds of smoke and bangs and pops blowing flames out the exhaust then the engine brake turns off and it runs normal. When the engine warms up, there is no issue with the engine brake.Its a 1999 Mack RD688SWhat is causing this ????? Edited March 7, 2013 by Doffer Quote Link to comment Share on other sites More sharing options...
staxx Posted March 7, 2013 Share Posted March 7, 2013 If this is E-tec engine could be worn jake srews or defective jack housing pluger or in correct adjustment ,sticking solinoids. Quote Link to comment Share on other sites More sharing options...
BKrois Posted March 7, 2013 Share Posted March 7, 2013 You're not supposed to use engine brake until the truck gets up to operating temperature..at least that's what i was taught Quote BryanMy Photo Albums Link to comment Share on other sites More sharing options...
RFCDrum Posted March 7, 2013 Share Posted March 7, 2013 Joe Gulino's 01 Tandem does that. You have to let it warm up. Some do it worse than others. RFC Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted March 7, 2013 Share Posted March 7, 2013 You're not supposed to use engine brake until the truck gets up to operating temperature..at least that's what i was taughtThis is very true. Quote glenn akers Link to comment Share on other sites More sharing options...
Doffer Posted March 19, 2013 Author Share Posted March 19, 2013 Oh really? I didn't know this. I was pretty much just thrown onto a truck after I got my CDL and they said "Good Luck!" LOL Quote Link to comment Share on other sites More sharing options...
Don Hancock Posted March 19, 2013 Share Posted March 19, 2013 And you're not supposed to use it to shift, Bad for the valve train. Quote Don Hancock Link to comment Share on other sites More sharing options...
2stacksuperdog Posted March 19, 2013 Share Posted March 19, 2013 I thought you're suppose to use it to shift? Quote Matt Link to comment Share on other sites More sharing options...
tdk1982 Posted March 19, 2013 Share Posted March 19, 2013 Had this happen a couple of times .......it could be worn rocker shafts if it has dynatard brakes.....if it has Jake Brakes pry solenoids or bad check valves... Always a good idea to let the engine warm up. Quote Link to comment Share on other sites More sharing options...
RFCDrum Posted March 24, 2013 Share Posted March 24, 2013 It's nice to shift with the Jake if you are in the middle of a hill. Quote Link to comment Share on other sites More sharing options...
mack1928 Posted March 24, 2013 Share Posted March 24, 2013 Check each head selenoid unplug one and check it then the other usually it's just the selenoid sticking in the valve cover happened to me a few times then just change the one you ruled to be popping back. Quote Link to comment Share on other sites More sharing options...
mack1928 Posted March 24, 2013 Share Posted March 24, 2013 The jake is hard on the valve train no matter using it for shifting or decelerating I get about 350-400k miles out of them and about 600k out of heads got 661k on one truck with still original bottom end still has cross hatches it's all in the maintenance and a good driver is always a help! Quote Link to comment Share on other sites More sharing options...
RFCDrum Posted March 24, 2013 Share Posted March 24, 2013 You're right the pitfalls of a Mack. Weak cams and valve trains. It is what it is. I got to do the cam in my R Model. Rob Quote Link to comment Share on other sites More sharing options...
mack1928 Posted March 24, 2013 Share Posted March 24, 2013 I haven't done a cam yet in any Mack I've had even my new ones I've heard horror stories about them but never had the issue just the valve train getting slapped or dropped a valve once or twice and plenty of jake issues Quote Link to comment Share on other sites More sharing options...
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