Massive Mystery Leak!

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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Bryan
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Massive Mystery Leak!

Post by Bryan » Mon Jun 29, 2020 5:03 pm

After Radiator, Water pump, Muffler and other fixes, after short test drive a massive oil leak developed, we can not find the source! its above the crossmember, the oil pan gasket is good, im thinking at one time their was water in the pan and sitting for years the pan rusted a hole and my preasure washing opened it up, my Question is am i on the right track? How hard is it to replace the oil pan while the engine is in? is it possible to replace the pistons thru the oil pan? (while we are there anyway) this is my sons first MV and were doing it on the cheap side when possible, thanks
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Rickf
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Re: Massive Mystery Leak!

Post by Rickf » Mon Jun 29, 2020 5:19 pm

It is not possible to remove the pan with the engine in unless you drop the front suspension subframe. Much easier to remove the powerpak as a unit since it was designed that way. Check to make sure it is not coming from the back of the valve cover first. If you had the valve cover off a lot of the time they get hung up going back on on the inner metal lip that holds the gasket. It looks like it is on but it isn't. And as far as removing pistons it is so easy to take a head off of this engine going out the bottom is not even an option, why remove the crankshaft if you don't have to? Drop the flywheel cover and see if the rear main seal is leaking behind the flywheel. And last but not least, if you have a fording valve is it in the open postion? If it is closed the crankcase pressure will push oil out past the rear main, the front crank seal and any other place there is a seal. The fording valve has to be open at all times other than when actually fording deep water. Check the PCV valve for proper operation also since a clogged valve will do the same as a closed fording valve.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Massive Mystery Leak!

Post by Bryan » Mon Jun 29, 2020 5:53 pm

just took another look its still leaking bad after an hour, the oil is dripping off the front diff just foward of the input shaft, probally a Qt an hr, thanks for the help!
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markrdje
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Re: Massive Mystery Leak!

Post by markrdje » Mon Jun 29, 2020 5:55 pm

I wonder if the side cover for the push rods is leaking? Oil filter?
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Re: Massive Mystery Leak!

Post by Bryan » Mon Jun 29, 2020 6:11 pm

my sons jeep is a 151a1 no fording gear i can see, does a A1 have a PCV Valve? and where?
41 GP 14935
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43 Kubelwagen
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Trailers, Bantam T-3,Converto,M-100
M-416, Ben Hur (Checker)USN MKII

Rickf
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Re: Massive Mystery Leak!

Post by Rickf » Tue Jun 30, 2020 4:31 am

All 151's have a PCV, it is mounted to the brass fitting coming out of the intake manifold next to the valve cover. Has a U shaped tube that goes to the valve cover. That brass fitting is the fording valve on vehicles so equipped. You can tell the fording valve since it will have a movable handle on it with a hole for a cable. So it is leaking in the front? That is the front subframe, I thought you meant the rear of the engine where the frame cross member is. Have you had the valve cover off of this engine? If there was water in the pan then there will be a lot of rust inside the valve cover. And probably everywhere else inside the engine. But I have never seen a pan rust trough from the inside and yet still start without serious work to get to that point.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Bryan
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Re: Massive Mystery Leak!

Post by Bryan » Tue Jun 30, 2020 6:53 am

So if we disconect the line to the valve cover this should bypass the pcv valve? we had the valve cover off to adjust the valves, it seems like with the oil fill cap fitting so loose and rattling pressure could not be an issue, but ill try anything at this point, thanks for the input!
41 GP 14935
42 MB II6359 Slatgrill
51 CJ3A
43 Kubelwagen
53 M-170
Trailers, Bantam T-3,Converto,M-100
M-416, Ben Hur (Checker)USN MKII

Rickf
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Re: Massive Mystery Leak!

Post by Rickf » Tue Jun 30, 2020 7:19 am

Take the oil cap off, do you have a lot of vapor blowing out of the hole when it is hot and idling? If you do then either the PCV is clogged or the engine has excessive blow by.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Bryan
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Re: Massive Mystery Leak!

Post by Bryan » Tue Jun 30, 2020 11:21 am

PCV valve seems like its a 1 way valve when blowing thru, blowing in the female end its clear, blowing in the male end its restricted, i guess thats why they call it a valve
41 GP 14935
42 MB II6359 Slatgrill
51 CJ3A
43 Kubelwagen
53 M-170
Trailers, Bantam T-3,Converto,M-100
M-416, Ben Hur (Checker)USN MKII

User avatar
Bryan
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Re: Massive Mystery Leak!

Post by Bryan » Tue Jun 30, 2020 5:15 pm

i think the mystery is solved, last night all the oil drained out thru the leak, we wanted to compession check again for blowby, took the pvc valve out and oil cap off, added a couple of QTS of oil did not even turn the engine over and it all leaked out,it has to be a hole in the oil pan, looking for a power plant now,
41 GP 14935
42 MB II6359 Slatgrill
51 CJ3A
43 Kubelwagen
53 M-170
Trailers, Bantam T-3,Converto,M-100
M-416, Ben Hur (Checker)USN MKII

Rickf
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Posts: 5086
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Re: Massive Mystery Leak!

Post by Rickf » Tue Jun 30, 2020 6:21 pm

Did the engine run good? If so why not pull it and check it out before dropping a ton of money on another engine? Maybe it is just me but I don't believe in spending money until a positive diagnosis has been made. An oil pan is a lot cheaper than an engine.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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