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e7 460 jake brake


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i recently purchased a 2000 mack vision cx613 460 e7

recent documented inframe at mack dealer including new heads ( slightly less than 2 years ago 120k miles ago)

one issue is i belive the jakes are only working on the low stage. jake works in both high and low settings but dosent seem to be any different as far as braking power showing less than 5psi on the boost gauge at 2k rpm with jake on high setting (same on low setting). switch seems to be functioning properly as far as i can tell 5 leads on the switch two switched hots and looks like posibly two switched grounds and 1 constant ground (as far as i could tell plugging away at it with a volt meter and messing with the switch)

i pulled the two plugs off (one to each head) the connections look clean plugged them back in.

what else should i look at.

oil psi seems good 20 psi hot idle 50-60 psi running down the road.

engine pulls and runs good, but jaking is only slightly better than hanging your arm out the window...lol

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i found only the front jakes are working. unplug the pass threw connector on the rear head no change in jaking. plug it back in and unplug the pass threw on the front head no jake at all.

whats the best way to figure out if the problem is before the pass threw or under the valve covers.

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thats a good idea, i suppose if i have high jakes with a jumper wire i know that the problem lies in the wireing before it gets to the head, if its the same, id be looking at pulling the vave covers, inspecting the wire from the pass threw to the solinoid and if that looks fine replace the jake solinoid assuming nothing else looks out of place?

if the jumper wire does not activate both sets of jakes is there a way to test the solinoid?

if the jumper wire does work is there any harm in leaving it that way, about all i have ever used on any truck is high or off.

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ok so iv done more reading on jake brakes over the last few days than i care to think about (never had a faulty Jake before so never learned much about them) of course that's the upside now i get to learn about them.

according to a pdf i found online and a cheap ass shitty analog volt meater and a peice of wire (haven't made it home to my shop yet so i was messing with it in a truck stop parking lot and don't have a whole lot of tools with me.

from reading the pdf (witch i think is actually for 2003+ mack motors)

i should have a low amp 12v at all times on both jakes and when the jakes activate it is suppose to up the current to energize the solenoid. now i cant actually acitave the jake from under the hood but i found closer to 6 volts on both leads for the pass threw. (front jake works both got the same reading so should be fine and its literally like a 5 dollar analog volt meter) so this would indicate to me that the wireing prior to the pass threw is not suspect)

so now after that i got a little more gutsy and increased the idle rpm to 1000 unplugged both pass thews and used a peice of wire to jump the pass threw. front activated the jake when i did this. the rear did not.

now we get real technical both pass threw connectors gave off about the same small arch when touching my hot wire too them, (not a dead short arch just a small visible spark like you would expect on a 1-2amp draw. this would indicate to me that the wiring from the pass threw to the solenoid is good.

obviously im not going to tear the valve cover off in a truck stop parking lot so that is going to have to wait till i get home.

but would you think it would be a safe enough bet that the solenoid is the problem to call up mack at home and order up a Jake solenoid and have the wife go pick it up so its there waiting for me when i get home. (might not make it home till next weekend and mack is only open m-f)

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well i finnally made it home and got to check things out, i found that one of the freeze plug like plugs in the end of the rocker shaft had come out, found the plug in the bottom of the rocker valley.

i had no luck finding a new one on sunday and have to get heading back out so i just re-installed the old plug, would have rather not done that but put a little bit of loctite on it and re-installed it, the jake works now, i guess if it stops working again ill have to call mack and get a new plug.

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If any boost in oil psi its nominal at best

Rocker assembly seems fine without actually taking it apart. When I discovered the problem I had taken the valve covers off solenoid appeared to be functional. But i changed it anyway. I then started the truck with the valve cover removed to inspect the operation. Started walked around and notice the Jake spacer quickly filling with oil. Half a second of head scratching till I realized what was going on. Rocker assembly completely submerged in oil. Quickly shut it off and oil had already run over the top of the Jake spacer. And that was under key idle. Im sure while running down the road that head was probably full of oil to the top of the valve cover.

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