longshipconstruction

Thank you all for the help! Jakes are working very well now, even hot without fade. Truck has 47,000 hrs on the clock so I wasn’t optimistic this was all it needed, but I am very pleasantly surprised. Again, thank you for the responses. This forum has been a valuable resource for me, and I really appreciate it!

Think I found my smoking gun. control valves are all totaled.

Thank you fjh and Joey Mack. Mine does not have the upper feed, yet… but I do buy my parts from Portland now. This is the kit I got, I’m not seeing the pn you referenced, but it may now be a dirty Volvo number now. So far during disassembly I haven’t found a smoking gun, but some orings look pretty trashed. Only other thought I had was making sure the holes in the accumulator bore are not supposed to be plugged? Also I haven’t backed the slaves off in the picture, looks like an awful lot of adjustment left. Like they might have been way off? id settle for a weak jake, I’ve never had them function whatsoever in 4 years. Really appreciate the feedback!

Reviving my old thread for model 690 jake. I purchased the Jacob’s kit from Mack for almost $1400 with 2 new solenoids. Was told I got the “last kit in the USA” and they are out of production. My question is, am I missing something between the rocker assembly and the jake head for oil delivery? The 2 pictures are when I removed the Jake head, and nothing else. Doesn’t look like there is any o-ring or anything to seal it. There is also an open hole on the bottom of the jake head that looks like it’s missing something. (Shown in the first image to the far right) Any help is appreciated!

Great info thank you, ill check it out. I know someones been in it before. On the valve cover tag .015 is scratched out and rewritten as .021. Any suggestions on where to buy parts? Thanks again

Adjusted properly so thats ruled out now. Anyone have a source for the jake rebuild kits? I havent had any luck with google search, and local mack wants $750. Thanks

Thats always been my experience, higher pressure cold start before oil thins out. Both my macks are 45-50psi cold. What are you running for engine oil?

Confirmed electrical side is working properly to the solenoids. 5.5v constant, and 14.3v when jake operated. Oil squirts vertically during jake operation so I would assume the issue is not with the solenoids. Is there a way to check oil pressure to the jake manifolds through a port? Its just odd to me that at 70psi of engine oil pressure on gauge it wont give me any audible jake operation at 1500rpm.

Update: Pulled rear cover, all rivets and rocker plugs still in tact. Had someone hold throttle running and applied power to both passthroughs, no change in rpm. I can hear both solenoids click with truck off and power applied so im assuming they either work or they dont? Camshaft is $1400 and a jake rebuild kit is $780 from mack so im a little hesitant to start parts throwing. Is it possible the jake is just out of adjustment through wear, causing neither unit to work at all? Thanks,

Thank you for the explanation. Just did a road test, no change at all. Oil pressure 29psi @ idle, 60 ish at 1400rpm. Ill pull the rear cover today and inspect.

Update: Rivet hole is filled, so no more side spray. Ran a hot jumper to pass through with truck running and valve cover off. Oil shoots straight up from jake assembly when 12v applied but no change in engine sound. But now my windshield is covered in oil thanks to the fan. I havent pulled rear valve cover yet thinking id do one at a time, but now im thinking an oil leak on the rear portion may be enough to cause the other to not build enough pressure? I would have thought id get at least a stumble in rpm with one leak plugged. Thoughts? Thanks

Awesome thank you! Fingers crossed thats all thats keeping them from working. What are the ports for??

Evening folks, Hoping someone can shed some light on an issue I'm having with my jake brake on a 2000 E7-460 I just picked up. Truck is a CH 613 tractor with 1.1m miles, past history not known aside from what the seller told me. Driving it home after purchase I noticed the jake did not work at all. Read all the appropriate forum posts here for troubleshooting (learned a ton, thank you everyone), confirmed the electrical side was good. I ran a jumper to the pass-through on valve cover with engine off and confirmed both solenoids clicked when 12v applied. I then pulled the front valve cover and checked the rockshaft plugs were still in on both sides, which they were. I started the truck with the upper valve cover off to inspect, which covered the passenger side tire in engine oil within seconds. From other posts ive read it sounds like I should be able to start the truck with the top portion of the valve cover off without that much spray, correct? Attached is a picture taken from the passenger side. The oil spray is coming from a small hole shown by the center circle on one of the uprights. The left and right circles are the same holes but look like theyve been filled by a rivet? Any guidance is greatly appreciated, I hate parts throwing hoping something sticks.