Dal3 Posted July 1 Share Posted July 1 https://comancheclub.com/topic/55531-89-comanche-vacuum-diagram/ Diagram shows PCV hose running to back of air cleaner. No corresponding fittings there though, There is a 1/2" plastic hose from the PCV valve running toward the front which ends at a strange round plastic manifold with about 12 round fittings of varying-size. One plastic outlet about 1/2" diameter goes from there through a 90 degree elbow heading toward the air cleaner hose, but no connector candidate in the vicinity. The PVC hose is not clearly visible in the link as viewed on my Comanche. Clear photos showing complete properly routed and connected PVC hose, header, and adjacent hoses would be helpful. I don't have much to go by at this point. The fitting at the back of the valve cover wasn't connected properly. I have rerouted that hose to the unidentified manifold fitting (just behind what is labeled in the diagram as "vacuum fitting.") What could be happening to the engine oil with the oil cap on. I was about to change the rear seal because a lot was dropping off at the back. Now I want to get things properly buttoned up, then clean the engine bay before doing anything else. Link to comment Share on other sites More sharing options...
jdog Posted July 2 Share Posted July 2 Some pictures of what you've got and or year and motor will help out greatly Link to comment Share on other sites More sharing options...
89 MJ Posted July 2 Share Posted July 2 Out of curiosity, what does your engine air filter look like? It could be that the engine isn’t getting enough air, so it is sucking more from the crankcase. Link to comment Share on other sites More sharing options...
Dal3 Posted July 2 Author Share Posted July 2 It's an "89, 4.0, as described in the title. I'm not equipped to send pictures. I've learned a lot about Comanche hose connections from the linked YouTube video featuring a 1988 Comanche. I now have matching components on my 1989 connected as the video instructed, changing most. The video doesn't discuss systems, but illustrates the connections well. Can anyone tell me which hose connections might have changed between 1988 and 1999 models? Dale Link to comment Share on other sites More sharing options...
Htchevyii Posted July 2 Share Posted July 2 Only 2 of the hoses have to do with the crankcase ventilation. The small one in the back going to the intake and the large one in the front that goes to the filter. The small one has a small metered orifice and can become plugged. There's also Cruiser's (RIP) tip of modifying the inside of the cover. Is there excessive blowby coming from the valve cover when it's running with the cap removed? https://cruiser54.com/?p=131 Link to comment Share on other sites More sharing options...
Dal3 Posted July 4 Author Share Posted July 4 Htchevyii , I just checked and no blow-by or pressure at the filler opening or pvc hose. Recall that originally there was large oil consumption, which stopped when I lost the oil filler cap, actually, stimulating my suspicion of engine control dysregulation as possible cause of the loss. Then, I found the intelligible video guide to the engine vacuum hose connection locations. I already knew they were somewhat incomplete and likely a mess. I've mostly implemented the video recommendations, getting needed vacuum line and connectors from auto salvage. and the engine is performing better. It seems to have cleared up a persistent jumpy throttle/surge. I replaced the oil cap. I haven't driven enough since to check consumption, but after driving a few miles now with the cap on there was only about 1 drop on the floor, a big improvement. I doubt the loss was caused by blow-by, but still don't know what, exactly. Thanks. Dale Link to comment Share on other sites More sharing options...
AZJeff Posted July 5 Share Posted July 5 Loss of the oil cap opens a HUGE leak to the crankcase, which is pressurized to at least some degree on a perfectly working engine. The fact that oil loss drops dramatically without the oil cap tells me a couple of things: 1. Your engine may be quite tired and venting lots of combustion gases past the rings into the crankcase. 2. Your crankcase vent system is not working as designed by Jeep. With the cap in place, it is sealing the crankcase up to a level that the malfunctioning (plugged) crankcase vent system can not deal with. I would run a compression test on the engine to get an idea of how much blow by the rings are allowing to enter the crankcase. I am guessing you have a tired engine spewing lots of blow by gases, and a compression test would affirm or refute that. In addition, I would do the upgrades to the older 4.0 valve cover and crankcase vent system. This will help vent a tired engine more effectively. Link to comment Share on other sites More sharing options...
AZJeff Posted July 5 Share Posted July 5 On 7/2/2024 at 3:41 PM, Dal3 said: It's an "89, 4.0, as described in the title. I'm not equipped to send pictures. I've learned a lot about Comanche hose connections from the linked YouTube video featuring a 1988 Comanche. I now have matching components on my 1989 connected as the video instructed, changing most. The video doesn't discuss systems, but illustrates the connections well. Can anyone tell me which hose connections might have changed between 1988 and 1999 models? Dale The 1999 engines have an improved crankcase vent hose and valve cover that deals with blow by much better. Link to comment Share on other sites More sharing options...
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