Leaking oil at highway speeds 258 - JeepForum.com
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post #1 of 9 Old 09-10-2017, 07:40 PM Thread Starter
Diver151
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Leaking oil at highway speeds 258

I have owned my CJ8 for a few months. I bought it partially disassembled and reassembled it. It runs and drives well. I usually just drive it to work and around town but recently I had it on the highway for 30 minutes and when I got home I noticed an oil spot on my drive way. Did the same thing a second and third time. Oil level hasn't seemed to change much but it looks like a lot of oil. Here is what I know. At first I thought it was the valve cover gasket. Then I realized it's coming from the breather and running down the back of the engine. I put on a new PCV but the one I took off looked new. It had been replaced by the last owner wishing the last 18 months. It is also leaking from around the dip stick but that was already there. Pressure gauge isn't currently working. Just replaced sending unit but I think it's something behind the dash so I can't tell the pressure. Gronk performance carb, leaking around the rear of the exhaust manifold a little bit because of a missing bolt. Hard to tell how much because the oil that drips down on it smokes. Did a compression test and got 110 on 4 cylinders, 100 on 1 and 118-120 on 1. Not sure how accurate the gauge was because that's low and the engine runs and sounds good. No catalic converter. I'm about to do an oil change but wanted to solve this before incase I need to do something that wastes the oil. Please help!

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post #2 of 9 Old 09-11-2017, 06:01 AM
HoDad
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Make sure you have vacuum at the PCV, otherwise, sounds like a lot of blow-by, time for a rebuild.
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post #3 of 9 Old 09-11-2017, 08:46 AM
pedal2themetai
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HI yes make sure you have lots of suck at the PCV valve.. with the motor running pull the valve out of the valve cover and feel the end should be a ton of suck.. if not something isn't working (plugged into the wrong port).
good luck
tim
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post #4 of 9 Old 09-12-2017, 04:51 PM Thread Starter
Diver151
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Thanks for the help! Lots of suction at the PCV. I removed the valve cover and it was very dirty under there. Lots of grime. I noticed a very slow coolant loss and tracked it down to a pin hole in a hose that only sprayed out when it was bumped. Glad it wasn't leaking into the oil from a crack!
If I was having blow by from bad rings would I see it on my spark plugs? They were super clean.
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post #5 of 9 Old 09-13-2017, 06:19 AM
jeepdaddy2000
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Quote:
I usually just drive it to work and around town but recently I had it on the highway for 30 minutes and when I got home I noticed an oil spot on my drive way.
Most of us consider a spot of oil a good sign.

While folks can get their rigs sealed up for a time, generally speaking, sooner or later you're going to have to deal with various drips from just about every cavity that holds lube.

Oil spreads THIN. A drop or two can cover a square foot in a couple of days. You can continue to chase down the leaks or slap a piece of cardboard down and forget about it.


Quote:
If I was having blow by from bad rings would I see it on my spark plugs? They were super clean.
compression is a bit low, but the rig runs good. This means you should have plenty of time to decide if an overhaul is in your future....

Compression loss doesn't have to tie to oil consumption (gooey plugs). The upper cylinder walls may have wear in them and this allows pressure (compression) to push past the rings and pressurize the crankcase. The oil rings may still be sealing on the intake and compression stroke, keeping excessive oil from entering the cylinder.

bazinga
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post #6 of 9 Old 09-13-2017, 06:35 AM
Matt1981CJ7
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This may help:

http://home.sprynet.com/~dale02/vac-pcv.htm

Sounds like you have an air leak in the system.

Matt


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post #7 of 9 Old 09-13-2017, 07:42 AM
TIPPEDITOVER
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Regarding the low compression numbers, did you have the throttle held wide open? If not, that will significantly reduce your numbers.
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Shaun

1978 CJ5 to CJ6 - Build in progress......


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post #8 of 9 Old 09-13-2017, 09:16 AM
LumpyGrits
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Cj

Lots of different PCV valves were used by AMC over the years. Make sure you have the correct one for YOUR engine and year.
LG
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Have'n you along, is like loose'n 2 good men
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post #9 of 9 Old 09-13-2017, 08:29 PM
kirbot
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X2 on the blowbye.

Mine has the same problem. I bandaided it by running two PCV valves. Now it just sucks in and burns what it would have dripped, but at least it keeps the driveway clean until it's time for a rebuild/replace.

1981 CJ7, AMC 258, MC2100, T18, Dana 300, OME 2.5" lift, front locker, 32" Kenda mud terrains
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