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Old 12-01-2013, 09:13 PM   #1
stangcoupe1970
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Default leaky valve seals

So I noticed a nice blue could and burnt oil smelling exhaust the last 2 times i started up my car. She has 152k on the clock, o/r x-pipe, and I run full synthetic oil.

No doubt its the valve seals, someone told me it's because of the synthetic oil I run and its working it's way around the seals. I've had the car since 132k and I've run nothing but synthetic oil. Could this be true and all I have to do is go back to conventional oil?(that's what he told me but I think once they leaky they're always leaky) is there another cause for the seals going bad or is it just age taking its tole on a 15 year old car?

As for changing them is it a PITA or not to bad? anyone have experience with the head still on the car? I assume if the head stays on the cam does not? If I have to tear into the motor to do this I might as well swap the heads for PI heads and intake while I'm at it. I can get them for next to nothing although my long term goal is DOHC.
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Old 12-02-2013, 04:56 AM   #2
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Originally Posted by stangcoupe1970 View Post
someone told me it's because of the synthetic oil I run and its working it's way around the seals.
Stop listening to that person. He/she doesn’t know what their talking about. Seals wear out. It is not unheard of for seals to start to go after 150k miles. Its kind of expected actually.


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As for changing them is it a PITA or not to bad? anyone have experience with the head still on the car?
I’d first verify that it is the valve seals leaking by pulling the headers and having a look inside. If the inside of the headers are oily, then the valve seals need to be replaced. I would advise getting the factory service manual for your year/model ride. It will have a step by step instructions, with pictures, on how to do this job and the proper torque specs (which are critical for a properly running valve train). Avoid the Haynes & Chilton type manuals. They are the Cliff-Notes of the service manual world.

You shouldn’t need to pull the heads. The key is to not let the valves fall into the cylinder once you’ve removed the keepers for the valve springs. You can do this with a compression gauge attached to an air compressor to use air pressure to keep the valves up. Its also a good idea to rotate the engine so that the corresponding piston is at its highest point when you release the valve spring so if it does fall it may not fall all the way into the cylinder. There are a bunch of video’s online on how to keep the valves up with air pressure. If the valve does fall into the cylinder you will have to pull the head to get it out.

Good luck...
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Old 12-02-2013, 06:27 AM   #3
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You can do the job in the car. But the in car valve spring compressor is a pain in the butt. If you wanna PI swap it anyway and you can get them cheap I would almost say just go that route.
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Old 12-03-2013, 08:08 PM   #4
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[QUOTE=petrock;8315847].......Its also a good idea to rotate the engine so that the corresponding piston is at its highest point when you release the valve spring so if it does fall it may not fall all the way into the cylinder..../QUOTE]

If you use air pressure to keep the valves closed you piston will move to BDC once the pressure is applied......that what happens to me every time I do that kind of job! Much safer that way anyway since nothing will move once the piston is at BDC and you know that both valves are closed.
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Old 12-04-2013, 06:46 AM   #5
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If you use air pressure to keep the valves closed you piston will move to BDC once the pressure is applied
If that happens you are using too much air pressure. It doesn’t take a lot of pressure to keep the valves up. Also, if the car is a manual, put it in gear and the motor won’t spin at all. If its an automatic, or the motor is out of the car, you can put a wrench on the crank bolt to prevent the motor from spinning.


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Much safer that way anyway since nothing will move once the piston is at BDC and you know that both valves are closed.
You want it at TDC (Top Dead Center) not BDC (Bottom Dead Center) to ensure both valves are closed and more importantly to prevent the valve from dropping into the cylinder too far if it does drop. Depending on the compression ratio of the motor and the length of the valves, with the piston at TDC, if the valve drops and hits the piston you should still have enough of the valves shaft exposed to be able to pull it back up. If the piston is at BDC, the valve will most definitely drop all the way into the cylinder and your in for a long day pulling the head to get it out.
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Old 02-15-2014, 07:05 PM   #6
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........You want it at TDC (Top Dead Center) not BDC (Bottom Dead Center) to ensure both valves.............
Just set the record straight and for your information I attached the correct procedure right out of the Ford service manual.........take a close look at Sep 3.
Attached Files
File Type: pdf Valve Seals (4.6L 2V).pdf (118.3 KB, 6 views)
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Old 02-15-2014, 07:05 PM
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