Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Thu Jul 04, 2013 9:05 pm Post subject: M38a1 - oil in carb
I have noticed for a while now that I am getting oil dripping down the shaft that the choke is on out of the air horn. There is a buble on it and if I remove the cross over tube I see s slight puddle of oil there in the air horn at the choke.
It has to be coming up the dip stick tube and through the little hose that connects to the cross over (I doubt that its being sucked out of the air cleaner). My concern is could this be blow by or what would cause this?
My Motor has less than 10k on it and Im pretty sure I had the cylinders bored out and over size pistons when I rebuilt it. Had good compression last time I did a valve adjustment on it.
Is there any tests I can do or something to stop the oil running up the dipstick tube? _________________ "Those who enjoy freedom must endeavor to preserve it"
You should recheck all PVC plumbing. Make sure the PCV valve is functional.
And, yes, an over serviced air oil cleaner can allow oil to make it's way to the top of the carb. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
As Wes pointed out the air cleaner might be too full of oil. One other question is... does your jeep have the original air cleaner?
The vacuum on oil bath air cleaners is rated to the engine technically. So, if you have a non original oil bath air cleaner the vacuum may be greater than the ability of the air cleaner to keep the oil contained in the canister... allowing it to escape to the carb.
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Sat Jul 06, 2013 10:02 pm Post subject:
I do have the original air cleaner that was in the jeep when I got it from the CAP and it is the correct one for a 54 m38a1 by the photos and other details.
The PCV valve isnt a valve to my recolection, its just a restriction hole right. I mean nothing moves inside it right?
I do not have any fording valves installed. _________________ "Those who enjoy freedom must endeavor to preserve it"
If your A1 has the fording system installed make sure the valves are not in the fording position. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Mon Jul 08, 2013 9:48 pm Post subject:
I just went and looked at my pcv,
It is mounted between the vacuum wiper pipe on the back of the pump going to the valve cover.
Its not mounted in the place on that graphic, where it shows its mounted off the oil cap breather.
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It turns out mine is new (relatively) I now recall having issues a while back and I changed it based upon someones suggestion. It is in the same place as orignal was, the new one is silver.
Maybe I put it on backwards. Is it supposed to allow air pressure to escape the engine or allow air to suck into the engine? Since I have oil coming up my dipsick tube blowing into the carb I would think that the pcv would allow air pressure to escape and stop this? _________________ "Those who enjoy freedom must endeavor to preserve it"
The PCV valve (positive crankcase ventilation valve) does exactly that. It positively removes blow by gasses from the crankcase by allowing the intake manifold suction to suck the crankcase fumes into the intake and then they are burned in the cylinders.
An easy check for too much crankcase pressure is to remove the dipstick and the valve cover caps and hold your palms over both. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Mon Jul 08, 2013 10:09 pm Post subject:
Ok so then I dont have a PCV valve, there is just a hose from my dip stick tube to the carb cross over tube.
(What is the silver aparatus in my picture I thought was a pcv?)
When checking the pressure on the oil cap and valve cover caps, how would I know what too much pressure is, and is this done at Idle or high RPM?
What can I do to stop the oil sucking (or blowing) up into the tube? I take it I cannot just remove the hose and block off the ports on each side. _________________ "Those who enjoy freedom must endeavor to preserve it"
Ok so then I dont have a PCV valve, there is just a hose from my dip stick tube to the carb cross over tube.
(What is the silver aparatus in my picture I thought was a pcv?)
It's a PCV valve. I never said it wasn't!
Quote:
When checking the pressure on the oil cap and valve cover caps, how would I know what too much pressure is, and is this done at Idle or high RPM?
Check at both idle and full power. At idle there should be absolutely no pressure. At full RPM there should be some pressure but you should be able to keep the two openings plugged. If the dipstick tubes has a side exit to the crossover tube then plug that hole as well.
Quote:
What can I do to stop the oil sucking (or blowing) up into the tube? I take it I cannot just remove the hose and block off the ports on each side.
If the hand plugging test shows no problem then to rule out the oil source being the engine crankcase just plug off the vent hose from the dipstick tube to the crossover pipe and drive it a bit. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Apr 15, 2005 Posts: 162 Location: San Diego CA
Posted: Tue Jul 09, 2013 9:17 pm Post subject:
I removed the pcv vent cap on the side of the valve cover and ran the jeep up in throttle. It was hard using a stick on the linkage with my left hand also over the dipstick tube and my right on the hole of the valve cover. Didnt really feel any pressure at all, I kinda expected to feel some.
The vaccuum was sucking hard into the pcv valve, I put my finger on the orofice inside the cap and confirmed it sucked hard. Then I took off the pcv and vefied everything was loose inside and allowed pressure to escape the engine block side, and that it did not open backards from the vaccuum to the block.
It all looks ok.
I took the air filter apart and checked it again, I also took the cross over tube and corrogated rubber hose off (its original from when I got the jeep and never found a new one but it doesnt leak)
I would think that if the oil was coming from the air filter I would see deposits in the ribbing of the corrogated rubber hose to the cross over tube.
I will pull the hose off the dip stick tube and plug it and the intake side on the cross over tube and just see what happens.
Assuming that the oil is coming from my dipstick tube, what else can I check that could cause this... Vaccuum on the manifold? Valve adjustment? Compression? _________________ "Those who enjoy freedom must endeavor to preserve it"
Run it first for a while with the air intake cut off from the engine's PCV system and crankcase vent.
Then run it with the oil bath air cleaner disconnected from the cross over pipe. You can put a temp filter or clean white rag over the end of the intake hose.
No sense in assuming we already know which is the culprit. Let's first determine the source of the oil. With that knowledge it will be much easier to then figure why the oil is moving from that location.
Let us know which of the two tests above resulted in continued oil deposits in the top of the carb. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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