Sudden serious problem!

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
rb6874
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Sudden serious problem!

Post by rb6874 » Thu Dec 19, 2013 7:46 pm

I have been visiting this forum for some time and have been able to solve several issues just by reading others' posts, but I haven't had such luck this time.

I bought my M38A1 about six months ago. The engine has ran okay since, though with a slight skip in the engine (possible sticking exhaust valves?). Yesterday I added two quarts of oil (10w-30). This morning I drove the jeep and soon heard a sputtering sound. I then saw white-ish smoke, and noticed a definite loss of power. I drove it back home, parked it, and discovered a MAJOR oil leak, though I was never able to identify the source, it appeared to be coming, at least partially, from the area near the base of the carburetor or bottom of valve cover. The oil leaked stopped shortly after the engine was shut off. I pulled the dipstick and discovered that fuel was mixed in with the oil. I could clearly smell the fuel, and the oil was significantly less viscous then normal. Also, I could feel air movement from the oil filler tube, in sync with the engine speed. I don't know if that is normal, I never thought to check that before this issue.

I could guess at the fuel entering the crankcase due to a damaged fuel pump diaphragm, and possibly the oil leak due to the same. I don't know what other possible issues that could cause this, and more confusing to me, what caused the sudden sputtering, smoking, and power loss.

Any help would be greatly appreciated!


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zepher11
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Re: Sudden serious problem!

Post by zepher11 » Thu Dec 19, 2013 8:07 pm

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Last edited by zepher11 on Fri Dec 20, 2013 6:25 am, edited 2 times in total.
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Re: Sudden serious problem!

Post by artificer » Thu Dec 19, 2013 9:16 pm

Doesn't seem all that odd.
Fuel in the oil & loss of power go hand in hand & the diaphragm in the fuel pump is the likely culprit.
Do not drive drain oil & filter & refill with new oil & new clean filter.
Fix fuel pump with an overhaul kit from Ron & re-fit.
Now you can start & drive away into the sunset.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Sudden serious problem!

Post by Jeeps4Brains » Fri Dec 20, 2013 3:59 am

Check the valve cover to make sure it is snugged down. If the gasket is in place for the cover it should seal. There is also a oil feed pipe that is external that goes from the block to the head. It is on the drivers side near the firewall. Make sure that line is not loose or broken.

Gas getting in your crankcase can cause bearings to fail if you don't catch it fast and fix the source of the gas getting in there. Check the fuel pump like suggested. Change the oil in the crank case and the oil filter canister. You might want to change out the filter as well.

You say the smoke was white and not blue? True white smoke can be a sign the head gasket has given up and is letting coolant leak into a cylinder. That would cause a loss of power and make that cylinder not have power.

Alan
45' MB, ??' MBT, 47' CJ2A, 48' CJ2A,
51' M38 #1, 51' M38 #2, 51' M100,
52' M37, ??' M101A1 (1st Gulf War Vet),
53' M38A1, 53' M211, 65' M151A1, 67' M416,
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Re: Sudden serious problem!

Post by rb6874 » Fri Dec 20, 2013 4:41 am

It is definitely possible that the smoke would be considered more blue than white, just certainly not black. The oil dripping was charcoal black. Also, the loss of power felt like a cylinder was not functioning. I have parts on the way, so hopefully it is a bad fuel pump and will run better after it is fixed and the oil and filter have been flushed through and replaced!

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Re: Sudden serious problem!

Post by Joe Gopan » Fri Dec 20, 2013 5:43 am

First thought when an otherwise healthy M-38/M-38A1 suddenly starts running rich (as if the choke were out) and dripping fuel from the carburetor is that the neoprene diaphragms have failed due to age. It is a typical symptom. OEM Diaphragms would usually last 6-7 years.
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Re: Sudden serious problem!

Post by artificer » Fri Dec 20, 2013 12:17 pm

Ben Dover wrote:First thought when an otherwise healthy M-38/M-38A1 suddenly starts running rich (as if the choke were out) and dripping fuel from the carburetor is that the neoprene diaphragms have failed due to age. It is a typical symptom. OEM Diaphragms would usually last 6-7 years.
That may be so, but will that cause dilution of the oil causing overfilling of the oil pan [sump]?
BTW white or whitish smoke can be caused by oil getting past the valve stem seals in F head or OHV engines.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Sudden serious problem!

Post by Joe Gopan » Fri Dec 20, 2013 3:03 pm

If it is driven with a flooding carburetor long enough, raw fuel will contribute to the oil level. Whatever the source, driving it in this condition will wear out the rings in short order. Best to solve the problem. Try removing the bottom cover off the vacuum booster portion of the pump and see what comes out.
Also,if your engine is equipped with the fording valves at the Crossover Tube and at the PCV, the valves may have gotten closed for some reason which will pressurize the crank case and blow oil all over hell.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: Sudden serious problem!

Post by rb6874 » Sun Dec 22, 2013 10:21 pm

The parts should (hopefully) be in tomorrow. Any recommendations for what oil to use in my well-aged F-134 with possible damage from this fuel/oil mix mess? From what I gathered from the previous owner, I'm pretty sure the engine hasn't been rebuilt in about 30 years.

I am wanting to rebuild it soon, but I wasn't hoping to HAVE TO right at Christmas :-/ We'll see what happens after tomorrow, hopefully she'll run just a little longer!

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Re: Sudden serious problem!

Post by artificer » Sun Dec 22, 2013 11:24 pm

Whatever you ran previously should be fine, if it was OK then.
The earth has not shattered yet!
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Sudden serious problem!

Post by Joe Gopan » Mon Dec 23, 2013 4:22 am

Avoid 10W-30 in tired Jeep engines.
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HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO

rb6874
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Re: Sudden serious problem!

Post by rb6874 » Tue Dec 24, 2013 3:32 pm

I believe we can definitively rule out this being a minor issue…

I drained the oil and saw there was definitely fuel in it. I replaced the fuel pump, flushed the oil, replaced the oil filter, flushed the oil and refilled it again. I let her sit idling for a while and she continued to sound either as if she was missing a cylinder, or possibly the valves aren’t moving. I opened the oil filler tube and there was clearly air flow moving from the filler tube. I couldn’t tell if it was all exhale, or pushing back and forth. I drove her around the block and brought her back. The engine had very little power and still wasn’t running smooth.

I looked underneath and saw something even more concerning. The oil was leaking again, but this time I did see where (at least some of it) was coming from. I saw oil dripping out of the vent hole on the bottom of the bell housing, along with smoke or vapor coming out of the same vent hole in little “puffs.” I don’t know what that could mean, but I’m certain it is significant.

I’m expecting this means engine rebuild for sure, but is there any other insight on those symptoms? Thanks

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Re: Sudden serious problem!

Post by Joe Gopan » Wed Dec 25, 2013 4:59 am

If your Jeep were in active Army, it would go to a support unit with a list of maintenance to be done.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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Re: Sudden serious problem!

Post by Jeeps4Brains » Wed Dec 25, 2013 1:56 pm

It sounds like the rear seal of the crank has gone bad. It is letting the oil that is under pressure at the rear main bearing get pushed past the seal. I am not sure about the puffs of smoke unless the oil has gotten on the clutch face and flywheel then got hot. This would also cause the clutch to start slipping and cause a loss of power.

It sounds more like now the engine needs a tear down and a good checking out. At the least have the rear and front seals replaced. If the clutch is inundated in oil then that needs to be replaced.

Alan
45' MB, ??' MBT, 47' CJ2A, 48' CJ2A,
51' M38 #1, 51' M38 #2, 51' M100,
52' M37, ??' M101A1 (1st Gulf War Vet),
53' M38A1, 53' M211, 65' M151A1, 67' M416,
MVPA #31724

Joe Gopan
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Re: Sudden serious problem!

Post by Joe Gopan » Wed Dec 25, 2013 2:02 pm

Are there fording valves installed on this engine?
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO


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