I have a new 1948 Cub that I have started refurbishing. It had several electrical issues that I have corrected and now it starts easily and runs smooth. It smokes a little after idling for a while but clears after revving up. Oil pressure is above 20 psi at idle and holds steady above 35 psi at higher RPM. ( my guess is above 750-800 rpm. No Tachometer). The problem is there is a knocking noise at low rpm. It is almost like a small diesel at idle. It sounds internal near #1 cylinder. There is no discernible vibration. I thought at first it was fan belt noise but cannot see any slap in the belts. I know what a knocking rod sounds like in a larger engine and this is somewhat similar. As soon as you increase rpm it goes away. Also when I changed the oil and first cranked the engine there was no noise. When the engine warmed up and I idled it down the noise came back.
I would appreciate hearing what the probable cause is and the also the cure. I'm thinking rod bearings.
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Knocking Noise
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LeoM
- 5+ Years
- Posts: 137
- Joined: Sun Dec 07, 2014 7:02 pm
- Zip Code: 32713
- Tractors Owned: FARMALL FORUM
1966 Cub w/ IH 1000 Loader
1958 LoBoy w/ Wagner 45 Loader
1952 Cub w/ Woods 48" Bush Hog
1948 Super A w/ Finish Mower
1944 A w/ 3 Point Hitch - Circle of Safety: Y
- Location: Central Florida
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Eugene
- Team Cub Mentor
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- Zip Code: 65051
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- Location: Mo. Linn
Re: Knocking Noise
Check to see if the fan is hitting the shroud.
Stethoscope. Length of tubing or fuel line hose. One end to ear, other end to various locations on the block. Should be able to closely isolate the location of the knock.
Stethoscope. Length of tubing or fuel line hose. One end to ear, other end to various locations on the block. Should be able to closely isolate the location of the knock.
I have an excuse. CRS.
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CubHunter
- 5+ Years
- Posts: 48
- Joined: Sun May 28, 2017 6:26 pm
- Zip Code: 45862
- Tractors Owned: 1948 F Cub " Massey"
1948 H w/ McCormick 31 loader - Location: Mendon, Ohio
Re: Knocking Noise
For the sake of ruling out, did you lube the fan pully?
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staninlowerAL
- 10+ Years
- Posts: 4991
- Joined: Fri Oct 29, 2010 11:34 pm
- Zip Code: 36558
- Tractors Owned: Cubs: (3)'49's, (1 is for parts), (1)'57 IH Cub LoBoy w/FH, (2)154 Number Series Loboys, (1 is for parts), '76 Longstripe w/FH, Mowers: C-22, Bush Hog 412, Pennington 59, Woods RM42CF, Woods 42, assorted FCub plows, planters, discs, etc. OTHERS: '49 AC B & Ind. Sickle mower, '61 AC D12 Ser 2, '52 8N, '56 Ferguson 35 Deluxe, '47 & '49 Avery V, '53 MM BG (offset), '51 JD M (regular), '56 JD 420C, with Blade and fire plow, '85 JD 850 (Yanmar) w/72" belly mower, '76? Yanmar 2TR15 1500 & Bush Hog SQ42S-2 mower, '78? FORD Dexta, '86 FORD LGT14D & 48" Mower, (2)Cub Cadets & Mowers (MTD), (4) Sears Surburban's, other MTD mowers, Jeeps & other misc. "treasures"
- Circle of Safety: Y
- Location: AL (Southwest)
Re: Knocking Noise
Someone told me that #1 is the last one to get oil because it's the greatest distance from the oil pump and therefore the first to show symptoms of wear. Makes sense but I've never verified it. Might be time to drop the pan and have a look at the front main brg and #1 rod bearing.
Stan in LA (lower AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)
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LeoM
- 5+ Years
- Posts: 137
- Joined: Sun Dec 07, 2014 7:02 pm
- Zip Code: 32713
- Tractors Owned: FARMALL FORUM
1966 Cub w/ IH 1000 Loader
1958 LoBoy w/ Wagner 45 Loader
1952 Cub w/ Woods 48" Bush Hog
1948 Super A w/ Finish Mower
1944 A w/ 3 Point Hitch - Circle of Safety: Y
- Location: Central Florida
Re: Knocking Noise
I did not check the fan pulley lube. I will check it and get back to you.
Thanks
Thanks
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LeoM
- 5+ Years
- Posts: 137
- Joined: Sun Dec 07, 2014 7:02 pm
- Zip Code: 32713
- Tractors Owned: FARMALL FORUM
1966 Cub w/ IH 1000 Loader
1958 LoBoy w/ Wagner 45 Loader
1952 Cub w/ Woods 48" Bush Hog
1948 Super A w/ Finish Mower
1944 A w/ 3 Point Hitch - Circle of Safety: Y
- Location: Central Florida
Re: Knocking Noise
Please refresh my memory. Remove the screw in the hub and fill with 30 weight oil. Turn the fan so the screw hole is at the bottom and allow the excess to drain. Replace screw. ?????????
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staninlowerAL
- 10+ Years
- Posts: 4991
- Joined: Fri Oct 29, 2010 11:34 pm
- Zip Code: 36558
- Tractors Owned: Cubs: (3)'49's, (1 is for parts), (1)'57 IH Cub LoBoy w/FH, (2)154 Number Series Loboys, (1 is for parts), '76 Longstripe w/FH, Mowers: C-22, Bush Hog 412, Pennington 59, Woods RM42CF, Woods 42, assorted FCub plows, planters, discs, etc. OTHERS: '49 AC B & Ind. Sickle mower, '61 AC D12 Ser 2, '52 8N, '56 Ferguson 35 Deluxe, '47 & '49 Avery V, '53 MM BG (offset), '51 JD M (regular), '56 JD 420C, with Blade and fire plow, '85 JD 850 (Yanmar) w/72" belly mower, '76? Yanmar 2TR15 1500 & Bush Hog SQ42S-2 mower, '78? FORD Dexta, '86 FORD LGT14D & 48" Mower, (2)Cub Cadets & Mowers (MTD), (4) Sears Surburban's, other MTD mowers, Jeeps & other misc. "treasures"
- Circle of Safety: Y
- Location: AL (Southwest)
Re: Knocking Noise
LeoM wrote:Please refresh my memory. Remove the screw in the hub and fill with 30 weight oil. Turn the fan so the screw hole is at the bottom and allow the excess to drain. Replace screw. ?????????
If memory serves me right the filling should be done with screw hole in the horizontal position, then when turned to the bottom the oil drains out via an internal "standpipe" to the desired level.
Stan in LA (lower AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)
USAF & Reserves, Reg ARMY, ARMY NG (AL)
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