Cam seal change question
09-20-2002, 01:33 AM
#1
Racer
Thread Starter
Cam seal change question
I have a 1973 911T with MFI. After many hours of burnt knuckles and creative speach, it appears the source of my oil leak is coming from the left side (drivers side) cam seal. The MFI pump is driven from this cam.
With the heat exchanger off, can this seal be changed without dropping the engine?
If it can be changed without dropping the engine, is it a job that should (could) be undertaken be the back yard mechanic. I have limited Porsche mech. knowledge, mostly American engines. I really need help on this one. I am tired of the oil smoke, and there is a great deal of it too. All on the left side (drivers side) <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Scott Harris
1973 911T 2.4L MFI
731-587-3487
With the heat exchanger off, can this seal be changed without dropping the engine?
If it can be changed without dropping the engine, is it a job that should (could) be undertaken be the back yard mechanic. I have limited Porsche mech. knowledge, mostly American engines. I really need help on this one. I am tired of the oil smoke, and there is a great deal of it too. All on the left side (drivers side) <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Scott Harris
1973 911T 2.4L MFI
731-587-3487
09-20-2002, 04:26 AM
#2
Race Car
Although a bit difficult, I would imagine it could be done. What I would do is drop the engine down a bit to facilitate access as you'll pretty much need clear access to the chain housing.
...unless your leak is at the rear of the engine, meaning towards the front of the vehicle where the MFI pump is driven by the belt...I don't have much experience in fixing a leak back there as I have only worked on 2.7s and above...they are sealed at the rear of the cam housing.
There is a large "O"-ring and a triangular, three-hole gasket (shaped like a Mazda rotary) at the front of the cam housing.
Let us know where your leak is, front or rear, if it's front I can give you the rundown, rear, I'll have to do some homework.
...unless your leak is at the rear of the engine, meaning towards the front of the vehicle where the MFI pump is driven by the belt...I don't have much experience in fixing a leak back there as I have only worked on 2.7s and above...they are sealed at the rear of the cam housing.
There is a large "O"-ring and a triangular, three-hole gasket (shaped like a Mazda rotary) at the front of the cam housing.
Let us know where your leak is, front or rear, if it's front I can give you the rundown, rear, I'll have to do some homework.
09-20-2002, 04:50 AM
#3
Race Car
Okay, after re-reading your original post, one could surmise that you're referring to the seal at the rear of the cam housing. 
Meaning closest to the trans. bellhousing.
Now I understand why you removed the heat exchanger. <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Again, as I have limited experience with an MFI setup, if any at all, I would imagine you would have to remove that pulley and I'm thinking it would be similar to the power steering pulley on a 3.6, then the seal might be like that of a main and rear seal for the crankshaft?? ...just guessing.
If so, then it would take a 19mm socket to remove the bolt that would secure the pulley...once pulley is removed you could pry out the old seal and pop a new one in. I will check my "secret" CD when I get home.
Although I'm sure there's a factory tool to drive the new seal in correctly, a large 1/2" drive socket might be handy to facilitate proper installation??
I would think that could be done without even dropping the engine down a bit...but then I'm just trying to picture it. <img src="graemlins/oops.gif" border="0" alt="[oops]" />
Maybe someone will "chime in" that's been there, done that.
Good luck! ...let us know how you do and if I was COMPLETELY wrong - my feelings won't be hurt, I promise. <img src="graemlins/crying.gif" border="0" alt="[crying]" />
Meaning closest to the trans. bellhousing.
Now I understand why you removed the heat exchanger. <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Again, as I have limited experience with an MFI setup, if any at all, I would imagine you would have to remove that pulley and I'm thinking it would be similar to the power steering pulley on a 3.6, then the seal might be like that of a main and rear seal for the crankshaft?? ...just guessing.
If so, then it would take a 19mm socket to remove the bolt that would secure the pulley...once pulley is removed you could pry out the old seal and pop a new one in. I will check my "secret" CD when I get home.
Although I'm sure there's a factory tool to drive the new seal in correctly, a large 1/2" drive socket might be handy to facilitate proper installation??
I would think that could be done without even dropping the engine down a bit...but then I'm just trying to picture it. <img src="graemlins/oops.gif" border="0" alt="[oops]" />
Maybe someone will "chime in" that's been there, done that.
Good luck! ...let us know how you do and if I was COMPLETELY wrong - my feelings won't be hurt, I promise. <img src="graemlins/crying.gif" border="0" alt="[crying]" />
09-20-2002, 07:08 AM
#4
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Hi Scott,
yes it can be done without dropping the engine! I have changed the camshaft - MFI pump drive seal recently on my 1972 911S.
You MUST remove the heat exchanger first, and then some sheet metal from the engine.
On my car I actually discovered that the seal was OK (30 years old, 80000km original engine never disassembled) but that the oil was coming from leaky rocker shafts. The shafts had drifted in axial direction, and allowed oil to pass by.
Be careful when removing rocker shafts and do only use wood or plastic bars to drive them out. The material of the shafts can become very brittle. Best is to heat the camshaft tower first.
For reassembly I suggest to use RSR rocker shaft seals. (-> pelicanparts).
Good luck
Andreas
yes it can be done without dropping the engine! I have changed the camshaft - MFI pump drive seal recently on my 1972 911S.
You MUST remove the heat exchanger first, and then some sheet metal from the engine.
On my car I actually discovered that the seal was OK (30 years old, 80000km original engine never disassembled) but that the oil was coming from leaky rocker shafts. The shafts had drifted in axial direction, and allowed oil to pass by.
Be careful when removing rocker shafts and do only use wood or plastic bars to drive them out. The material of the shafts can become very brittle. Best is to heat the camshaft tower first.
For reassembly I suggest to use RSR rocker shaft seals. (-> pelicanparts).
Good luck
Andreas
09-20-2002, 01:42 PM
#6
Racer
Thread Starter
Thanks for the quick replys.
I can't find the camshaft MFI pump drive seal part number anywhere.
Andreas, how long did it take you to change the seal? Any special hints or procedures to make it easier?
Scott Harris
1973 911T Targa
2.4L MFI
I can't find the camshaft MFI pump drive seal part number anywhere.
Andreas, how long did it take you to change the seal? Any special hints or procedures to make it easier?
Scott Harris
1973 911T Targa
2.4L MFI
09-20-2002, 01:45 PM
#7
Racer
Thread Starter
I had forgotten to mention that this engine was rebuilt less than a year ago.
Rocker shafts drifting axially? How would you fix that? Would the engine have to come out?
Scott Harris
1973 911T
2.4L MFI
731-587-3487
Rocker shafts drifting axially? How would you fix that? Would the engine have to come out?
Scott Harris
1973 911T
2.4L MFI
731-587-3487
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09-21-2002, 10:43 AM
#8
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Hi again Scott,
I believe the most critical part is taking off the heat exchanger. Be careful as it is easy to shear off the struds. Usually the nuts are badly rusted onto the struds. My personal trick is to soak them 1 or 2 days before with brake fluid. But read rennlist thoroughly, it seems that heating the nuts to red is best for getting them off.
Maybe you are lucky as your engine was rebuild only a year ago.
For the camshaft seal, if you mark the position of the belt to pulley to camshaft and if you secure the belt properly on the pump itself then you may reassemble without readjusting the MFI pump phase.
changing the seal itself is easy, I used a screwdriver and a small hook to pull it out (you destroy the old one) and a piece of wood to push the new one in. Be careful not to scratch metal surfaces!
It is a known fact that the rocker shafts can shift slightly. In my case it was ~5 mm shift in 30 years. Just loosen the shaft and reposition it properly as shown for example in the haynes manual. DO not use much force, rather do heat the camtower around the rockershaft area to ease the movement.
To install rsr seals, drive the loosend shafts out with a wooden bar or similar, clean everyting and reassembe. Postition the camshaft as for valve adjustment, so that there is play between rocker and valve before you drive out the shaft. Probably you do not need to readjust valves!
I believe the most critical part is taking off the heat exchanger. Be careful as it is easy to shear off the struds. Usually the nuts are badly rusted onto the struds. My personal trick is to soak them 1 or 2 days before with brake fluid. But read rennlist thoroughly, it seems that heating the nuts to red is best for getting them off.
Maybe you are lucky as your engine was rebuild only a year ago.
For the camshaft seal, if you mark the position of the belt to pulley to camshaft and if you secure the belt properly on the pump itself then you may reassemble without readjusting the MFI pump phase.
changing the seal itself is easy, I used a screwdriver and a small hook to pull it out (you destroy the old one) and a piece of wood to push the new one in. Be careful not to scratch metal surfaces!
It is a known fact that the rocker shafts can shift slightly. In my case it was ~5 mm shift in 30 years. Just loosen the shaft and reposition it properly as shown for example in the haynes manual. DO not use much force, rather do heat the camtower around the rockershaft area to ease the movement.
To install rsr seals, drive the loosend shafts out with a wooden bar or similar, clean everyting and reassembe. Postition the camshaft as for valve adjustment, so that there is play between rocker and valve before you drive out the shaft. Probably you do not need to readjust valves!
