Richpwb

Earlier today I noticed a really noticable clatter come fom under the drivers side of the hood. The sound was like a really loud fast injector clatter, after some more investigation I realized that it was the vaccuum pump for my cummins jake brake and after a test drive I am now sure of it as though I can barely hear it engage there is no resistance at all. The clatter however is very loud and Im not sure whether it is the diaphram or the pump or if there is any way of disengaging it until I can replace on or both items. Has anyone else had any expierence with this?

carl48

yes most people with jakes will have experienced this. you have to get a stock belt to remove the pump. the pump is most likely failing usually the diaphragm does not make noise when it fails. when the pump fails it locks up and burns the belt into. leaving you stranded. ask me how i know. they seem to fail at the most inconvenient time and place. if you fix the pos carry you a stock belt for the next time. we got some of our pumps from cummins some from genosgarage.com the diaphragm is $169 the pump with pulley $359 and without $299. the dealer cost can some times near $1,000 once we smartened up we started changing out to a bd every time we had a failure in the jake then we started changing the jakes out on the trucks we send out of town and using the parts to keep the in town trucks going. down to two jakes. the bd has a huge amount more stopping power than the jake.it will hold 60 lbs back pressure from 700 rpm to 3,200 rpm and sea level to the highest elevation where the Jake at sea level and 3,200 rpm is barley 60 and goes to nothing at 700 rpm12,000 feet

edtyler

I don't think that the pump seizing is the most common failure, unless you ignore the ruptured vacuum diaphragm, which then sucks the oil out of the pump.

As to replacements, search for a GMC K2500 vacuum pump - cost about $95 complete with a lifetime warranty. Be sure to remove the old pump from the engine and then swap vacuum assemblies, The vacuum inlet is in a different position, but the old hose will hook up just fine.

shep1

Mine was making a rattle sound. Got a new Jacobson pump (complete) rom Cummins for just over $200. Brotherinlaw helped and two hrs. later back on the road.Good as new.