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Front main seal

Tiny
RLAMJA89
  • MEMBER
  • 1979 FORD F-100
  • 3.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 166,000 MILES
The front main seal on a 302 started throwing out large volumes of oil all of a sudden. I replaced the seal and the balancer. After two hundred miles it started again. But on a new timing cover, and another new balancer, and a new seal. Lasted for two thousand miles and it now it is doing it again. It is not a small leak. Throwing oil up in the fender weld. Was over hauled 20,000 miles ago with new bearings. There is no blow by.
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Tuesday, April 24th, 2018 AT 3:02 PM

20 Replies

Tiny
MHPAUTOS
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Have you checked that the crank end float is with in specs? Crankshaft thrust bearings may have been worn and to replaced with the overhaul.
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Wednesday, April 25th, 2018 AT 12:27 AM
Tiny
RLAMJA89
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Yes, PVC valve and crankcase filter working, new oil pump, checked pressure in crankcase at fifty five mph and it is zero. You can idle it all day and it will not leak. You can run the engine at any speed sitting and it will not leak. Drive it at fifty five mph and it will leak a lot. Was overhauled 20,000 miles ago, no bearing noise and oil pressure light does not come on. Have not checked the pulley for balance. Could that be an issue? When the leak started it was instant, not building up over time. Thanks for your help! Bob
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Wednesday, April 25th, 2018 AT 5:13 AM
Tiny
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What is the oil pressure at idle and at 1,500 rpm's hot? The problem will have to be a seal failure flooding of oil in the timing cover or excessive oil pressure. I cannot really see it being anything else.
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Wednesday, April 25th, 2018 AT 6:54 AM
Tiny
RLAMJA89
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I do not have a set up to test oil pressure. Just has a light in the truck. It was doing it and I changed the oil pump and it is still doing it. Also changes the oil filter. Pressure in the crank case at idle and 1,500 rpm hot is basically zero. The is no blow by. Just made a test run. Idle and and rpm 1,500 sitting I do not have a leak. At forty five mph I have no leak. At fifty mph it has a few drops leak and at fifty five it pours out. Crank case pressure at fifty five is basically zero. Thanks for your help! Bob
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Wednesday, April 25th, 2018 AT 9:31 AM
Tiny
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I really need to know what the oil pressure is at the higher rpm as the pressure relief valve may not be working and engine oil pressure may be through the roof, this is nothing to do with crank case pressure so please try and get the coil pressure check done.
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Wednesday, April 25th, 2018 AT 4:15 PM
Tiny
RLAMJA89
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Thanks, will see what I can do. Bob
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Wednesday, April 25th, 2018 AT 6:46 PM
Tiny
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Just a foot note, excessive oil pressure can also blow out a rear main if not checked and oil flooding the rocker gear can cause excessive oil burning through the valve stem seals as well.
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Thursday, April 26th, 2018 AT 2:49 AM
Tiny
RLAMJA89
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Checked the manual and it says the valve is in the oil pump which I replaced. It does the same thing with both pumps. Guess the new one could be bad? Seems to me it comes back to the front bearing even thought it was checked. Running with no load and okay on the road up to fifty mph. At fifty five the crank sets up a vitiation and out comes the oil?
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Thursday, April 26th, 2018 AT 3:52 AM
Tiny
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Do not presume anything is okay until it has been tested. We need to eliminate things out of the equation. Bearings are staked and basically locked in place, with no play, apart form oil clearance, if the bearing was loose in any way it would knock its head off and the engine would have seized by now.
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Thursday, April 26th, 2018 AT 6:40 AM
Tiny
RLAMJA89
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Okay, Will follow up on oil pressure test. Thanks, Bob
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Thursday, April 26th, 2018 AT 6:58 AM
Tiny
RLAMJA89
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Hi,
About 42 oil pressure idle, 55 at hot rpm. New oil pump, no problem with filter leaking, rear seal does not leak, No other oil leaks on engine, no blow by, Does not leak unless fifty five mph or higher and then leaks badly. Going back to your original answer, would the front thrust bearing (been checked and okay) do that? Thanks so much for your help! Bob
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Friday, April 27th, 2018 AT 10:45 AM
Tiny
STEVE W.
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Okay, you can set still and rev the engine and no leaking even up to the same rpm as driving fifty five. But if you drive the truck it starts leaking oil. That would seem to indicate it is something to do with under hood airflow pulling oil out. When you stop and it has leaked can you see oil behind the balancer? Or is it just on the front of the engine so it seems to be from there? No oil dripping out of the oil pressure switch? Loose dip stick seal? Which front seal are you using? Maybe they are not made to spec?

Could you take a couple pictures of the area showing where the oil is hitting and the pan/cover area.
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Sunday, April 29th, 2018 AT 6:54 AM
Tiny
RLAMJA89
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Well, I have been working on this for about six months off and on. There is a national in there now and had another brand before but do not recall. Could not find a ford seal going back that far. No other leaks from valve covers, dip stick, distributor, and etc. The oil leaks behind the harmonic balancer and streams down the front of the oil pan and then blows on everything on the right side of the truck and up in the fender well. I can see it has oil dripped off the front of the seal. Oil is not coming out of the front of the harmonic blancer.
As I was thinking what I can try. The fellow who overhauled the motor said to use 20-50 oil. My books say 5.5 quarts but he said 5. I had 5.5 in it and 20-50. So, I took the filter off and but a new one on reducing it some but probably not half. The filter only had about 25% full with oil but it on its side and above the pan. Oil was very thick in filter. So, with a new filter and less oil I drove it and it did not leak. Do not know if this was a one time event or if it will leak next time I drive it. Will get you a picture when I can. How does the airflow issue work? Thanks for your help! Bob
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Sunday, April 29th, 2018 AT 10:46 AM
Tiny
RLAMJA89
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Good guess, but the switch is on the other side of the engine and I put a new one in. I sprayed foot powered on the engine to confirm the oil is coming from the seal only. Thanks,
thanks, Bob
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Sunday, April 29th, 2018 AT 1:31 PM
Tiny
STEVE W.
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Airflow under the truck acts like a vacuum to pull the heat out of the engine bay. At 55 there could be enough airflow to pull oil out.

Read the lower oil level suggestion and that it seems to work.
In operation your engine should be showing a slight vacuum internally if the PCV valve is working and the air inlet hose is connected properly. As engine rpm increases the manifold vacuum lowers but it should never show internal pressure if the PCV is working.
I see you say that crankcase pressure is basically zero, it should show a slight vacuum at least. Check that the PCV system is functional.
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Monday, April 30th, 2018 AT 7:19 AM
Tiny
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Hi.
The PCV system is working. Put a new valve on it. When you put your thumb on the valve it has a strong vacuum. Other side of the engine has a open hose to a filter that goes into the air clean. Has a cleaner of its own also. Can check again but as I recall it was basically zero at all rpm's. So, as far as I know PCV is functioning properly? Thanks, Bob
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Monday, April 30th, 2018 AT 10:34 AM
Tiny
STEVE W.
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Okay, if it is pulling a vacuum it should be holding the oil in. When you installed the seal was the gaiter spring removed to press the seal in and forgotten?
Running the lower oil level would drop it away from the seal but that seal should not have an issue even if it was fully under oil. High oil pressure would push oil out of a "loose" bearing clearance but that oil cannot spray against the seal directly, it hits the timing chain and sprocket before it gets to the front cover.
As a last resort item you could install a speedi-sleeve on the new balancer to increase the seal lip pressure some.
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Monday, April 30th, 2018 AT 3:33 PM
Tiny
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No, I made sure the spring was in place. It takes a lot of pounding to get the seal in place. Guess you never know if the spring could be dislodged. I had considered the speedi sleeve and is probably worth a try. If that does not work I will probably put in a new engine. Any thoughts on remanufactured engines? Thanks for your help! Bob
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Monday, April 30th, 2018 AT 4:37 PM
Tiny
STEVE W.
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If the engine runs good I would probably keep it. Do you still have the OEM balancer that first leaked and the replacement? Maybe measure the snout on each and see if maybe the new ones are made a bit smaller. It could be that the seals are made a bit larger and the snouts are a bit smaller and the seal just isn't tight enough to work. You may want to ask the builder what bearing clearances he set it up with and if the block was line bored/honed. If it was that would put the crankshaft a very small amount higher in the block then if the balancer and seal was already marginal it could be enough to create a very light seal on the bottom of the snout. It is a long shot but in the realm of possibility. If you wanted to test that theory out you could use a dial gauge set up on the nose of the crank and use the tip to run around the bore of the seal surface. If you rotated it and saw that the crank not centered that could be the problem.
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Tuesday, May 1st, 2018 AT 11:27 AM
Tiny
RLAMJA89
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I did compare them visually but not with a micrometer. Do not have the original now. I did fit the seal over the balancer and it was a perfect tight fit. I put new timing chain cover on and visually lined it up before tightening the bolts. If it is of it very minor. Thanks for your thoughts! Bob
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Tuesday, May 1st, 2018 AT 1:34 PM

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