BucketTrucker688 Posted April 23, 2019 Share Posted April 23, 2019 I posted about this topic before but could not find the thread. I have a mechanical E7 350 in a 1991 rd688s. At around 1600 rpm my engine brakes start going intermittent. It's not just one head it's both. I was told to check the relay but low and behold I cannot find any engine brake relay it's blank on my fuse panel. Where the other wires go into the heads to the solenoids there is some oil seapage nothing major but this engine brake cutting out when I need it most is getting ageravating. Any help would be greatly appreciated. I'm getting annoyed trying to chase this down. Sent from my Pixel 2 XL using Tapatalk Quote Link to comment https://www.bigmacktrucks.com/topic/56856-e7-engine-brake-going-intermittent-above-1500rpm/ Share on other sites More sharing options...
Mack Technician Posted April 23, 2019 Share Posted April 23, 2019 From the title..... does that mean the E-brake starts becoming intermittent above 1,500 and gets worse as RPM's descend, or the E-brake is only intermittent above 1,500 but stable at lower engine speeds? Quote Link to comment https://www.bigmacktrucks.com/topic/56856-e7-engine-brake-going-intermittent-above-1500rpm/#findComment-421165 Share on other sites More sharing options...
BucketTrucker688 Posted April 23, 2019 Author Share Posted April 23, 2019 From the title..... does that mean the E-brake starts becoming intermittent above 1,500 and gets worse as RPM's descend, or the E-brake is only intermittent above 1,500 but stable at lower engine speeds?It works fine below about 1500 then above that it gets starts cutting out as the rpms get higher. Sent from my Pixel 2 XL using Tapatalk Quote Link to comment https://www.bigmacktrucks.com/topic/56856-e7-engine-brake-going-intermittent-above-1500rpm/#findComment-421168 Share on other sites More sharing options...
Mack Technician Posted April 23, 2019 Share Posted April 23, 2019 (edited) I'd check oil pressure spec, I'd run a continuity checker to the pump switch to visibly watch when my pump position sensor is opening/closing relative to heads coming in and out of function (maybe even a makeshift test light), adjust overhead brake according to attached sheet and last, (if that didn't help) install a rebuild kit/update if they still make them. Timber.pdf Edited April 23, 2019 by Mack Technician Quote Link to comment https://www.bigmacktrucks.com/topic/56856-e7-engine-brake-going-intermittent-above-1500rpm/#findComment-421171 Share on other sites More sharing options...
fjh Posted April 23, 2019 Share Posted April 23, 2019 Check the mico switch on fuel pump these tend to get glitchy after years of operation! Quote Link to comment https://www.bigmacktrucks.com/topic/56856-e7-engine-brake-going-intermittent-above-1500rpm/#findComment-421182 Share on other sites More sharing options...
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