I have been having rear main problems since I got my 69 8 or so months ago.
I put on a new carb and intake manifold now it leaking in the front. I have installed manifolds before and rear main seals. So I was baffled by why I was having all of these problems. I just put in an old oil pressure gauge and was pretty amazed at what I saw. 100 PSI (cold/start-up) in 75 Degree weather. It drops down to about 75 PSI after 10 or 15 min of driving then finally down to 40 ish after half hour of driving and it will slowly make its way to 30. I noticed that I was having this problem because I looked in my rearview mirror and I had a trail of smoke for a half mile down the road.Turns out My dip stick is getting blown out of the tube and squirting oil down on the manifold. Now I am guessing the P/O had installed a high pressure pump, I believe this is my problem unless anyone else has an idea. I did notice that the first time I changed the oil the P/O had some really think oil in it, not sure what viscosity but it was thick. I used synthetic 5W-30...
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Cody
69 Bronco, 351W, Edelbrock performer, Holley 670 T/A 35'S 5.5'' Wildhorses lift, Locker rear, F-100 power steering and a slight rear main leak
87 Bronco XLT, 302, rust, rear locker, tape player + IPOD, and the most comfortable (stock) seats ever.
Hi. It really does sound like ring blow by. But. As a last chance try you should thoroughly check your crankcase ventilation system. If you get vapor out of the side that connects to the air cleaner at warm idle and the pcv valve is good then it's probably blow by. A clogged ventilation system can blow out dip sticks and gaskets as well as seals.
Hi again. I forgot to mention that you should feel a small bit of vacuum at the hose to the air cleaner in the ventilation system at idle. The pcv valve should be supplying enough vacuum in the crankcase for you to be able to feel a small amount with your thumb over the hose coming from the valve cover vent at idle or where ever it vents from.
Also the oil pressure sounds pretty much ok to me. I would expect a little less of a drop when the engine gets hot though. 100 psi is a bit high but since it drops so much I'd leave that alone. Too high an oil pressure can damage crank and cam bearings but I think 100 is probably ok.
Well after the new carb and intake, I used a aftermarket air cleaner assembly. The aftermarket cleaner didnt have the bung for the crank vent tube from the pass. side valve cover so I replaced the cap with just a breather cap. Would that cause this? I should run a compression test then on each cylinder I suppose to make sure. She has devoloped a stumbling idle lately, I wonder if that is could be tied into this....
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Cody
69 Bronco, 351W, Edelbrock performer, Holley 670 T/A 35'S 5.5'' Wildhorses lift, Locker rear, F-100 power steering and a slight rear main leak
87 Bronco XLT, 302, rust, rear locker, tape player + IPOD, and the most comfortable (stock) seats ever.
The breather cap should be ok if it's not clogged. Since it's blowing the dip stick out I would guess that there's lots of oily mess around the breather cap on the valve cover. A compression test is always good to do. Do the dry then wet tests to compare. I wouldn't worry about the idle until you get the main things out of the way.
I know its pretty oily on the drivers side where the PCV/Oil Fill goes to the carb. There is no oil coming out on the pass. side breather cap at all. Its leaking real bad at the front of the intake now. Im going to run a compression check tomorrow. I pulled all the plugs the other day trying to diagnose the Idle problem they all looked great a perfect tan.brown and no oily deposits or anything, You would think that if I was getting blow by Id have at least one oily plug....
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Cody
69 Bronco, 351W, Edelbrock performer, Holley 670 T/A 35'S 5.5'' Wildhorses lift, Locker rear, F-100 power steering and a slight rear main leak
87 Bronco XLT, 302, rust, rear locker, tape player + IPOD, and the most comfortable (stock) seats ever.
You may be blowing gaskets and seals because that breather in the valve cover is clogged. Can you blow air through it. If you put a clean hose on it then use your mouth to blow through it you shouldn't feel any resistance. That crankcase has got to be vented.
I don't think that's all your problems so do the compression test too.
I checked the PCV hose and air flows through it freely. The breather is new and clean but ill try what you mentioned above, blowing thru that too. I hope its not rings.
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Cody
69 Bronco, 351W, Edelbrock performer, Holley 670 T/A 35'S 5.5'' Wildhorses lift, Locker rear, F-100 power steering and a slight rear main leak
87 Bronco XLT, 302, rust, rear locker, tape player + IPOD, and the most comfortable (stock) seats ever.
So I ran a compression test today, all cylinders were close to 115 to 130 PSI. I removed all the spark plugs and tied the throttle wide open, Then I did one cylinder at a time. I cranked it for a couple seconds and recorded the reading. If I let it keep cranking (4-5 seconds) it would build up to almost 150 PSI. I only did this on one or two of the cylinders. That seemed a little high...
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Cody
69 Bronco, 351W, Edelbrock performer, Holley 670 T/A 35'S 5.5'' Wildhorses lift, Locker rear, F-100 power steering and a slight rear main leak
87 Bronco XLT, 302, rust, rear locker, tape player + IPOD, and the most comfortable (stock) seats ever.
Those 2 cyls. compression seems good. Cranking for four or five seconds getting 150 is good. Now you need to do all the rest and compare the readings. There shouldn't be any more than a 20% differnce between all the cyls. Then squirt the equivelant of about 2 tablespoons of oil in 1 cyl. crank the eng a couple of revs then check the compression on that cyl. Then each cyl until they're all done. They all should be a bit higher maybe a max of 15psi higher than the dry readings. Any more than that and the rings are leaking. If any of the cyls were low without the oil and don't show hardly any increase with the oil in the cyl. test (wet test) then one or all the valves on that cyl. are leaking. A blown head gasket can have some effects on the readings too. Once I determine a problem on one or more cyls. I set the bad cyl on tdc of the compression stroke and hook an air hose to the spark plug hole and supply between 100 and 150 psi to that cyl and check all the places it could come out for sound or bubbles ie radiator cap off bubbles, crankcase throuth the breather, Carb or throttle body open, the exhaust pipe and the other spark plug holes. Be careful when applying the air. Watch the crank pulley it should not turn because of the air. If it turns that means it wasn't exactly at tdc of the compression stroke. If it's at tdc of the exhaust stroke air will come out both the carb and the exhaust.
If all this tests good it should not be blowing the dipstick out and making an oily mess around there.
I wet tested every cylinder they went up just like you said about 15 PSI. They were all in the 170- 180 range. I hooked up a different oil pressure gauge and it was the same. (Didnt really trust the one I had it it, I found it in the trunk of my mustang when I bought it) My problem is elsewere.. Any other ideas?
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Cody
69 Bronco, 351W, Edelbrock performer, Holley 670 T/A 35'S 5.5'' Wildhorses lift, Locker rear, F-100 power steering and a slight rear main leak
87 Bronco XLT, 302, rust, rear locker, tape player + IPOD, and the most comfortable (stock) seats ever.
Congratulations on the great compression readings.
I guess the next thing I'd concentrate on is the crankcase breathing system. You already tested the side that goes to the air cleaner assembly. On the vacuum side with the engine off you should be able to shake the PCV valve and it should rattle. Then you should be able to feel vacuum with your thumb over the engine end of the PCV valve and the engine rpm should drop a little or some kind of rpm change should be obvious. If you listen when you put your thumb over the eng. end of the valve you should hear one click like the clicking when you rattled it.
They make a PCV system checker it just reads crankcase vacuum on the vent side. It just sits on the valve cover where the hose connects that goes to the air cleaner. You don't need the checker. Just put your thumb over the air cleaner end of the hose. After about 10 or 15 seconds you should feel some vacuum as you pull your thumb off and a small rush of air should be heard as the air rushes into the crankcase. If all this checks OK then you're in pretty good shape. I know the dipstick blowing or rattling out of the tube shouldn't happen.
When an engine is at full throttle the PCV valve usually can't handle the increased pressure in the crankcase and the system is designed so the pressure that the valve can't handle escapes through the air cleaner end of the system and the fumes are then reburned through the intake system. Even under the most severe blowby the dipstick should stay in. If the dipstick rattles out this can provide a path for the blow by gasses to escape where you don't want them. Maybe as a trial you could bungee the stick in to the tube and see if the mess still happens.
If none of this works maybe someone else near you can take a peek at it and see something that I obviously can't.
Good luck, Dave
