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2004 Subaru Impreza Outback Sport, Manual Transmission, 170000 miles, EJ251 SOHC

A mechanic has told me that I have a leaking camshaft seal. I have a few questions. Background is that I had my head gaskets and timing belt redone 1 year ago using this Conti TB kit, which apparently does not come with camshaft seals, my invoice doesn't include new ones, and so they probably have not have been replaced. I wish I could ask them, but they went out of business!

  1. Because it's hard to get in there and see the camshaft seal, I'm skeptical that it can be diagnosed properly without taking the car apart. Could an apparent oil leak (there's some drippage on a hose underneath the left head) be caused by anything else? How should I go about independently diagnosing this leak? Should I bring this somewhere else for another opinion?

  2. I understand that a leaking camshaft seal can compromise the timing belt, leading to a catastrophic engine failure and damage (see this post). Supposing I do have a camshaft seal leak, and the timing belt, pulleys, water pump, and thermometer are all gross and oily, what should I replace? Keep in mind that I replaced the timing system one year ago (see above). What if all these components don't look dirty/oily?

  3. I am an amateur, but enthusiastic auto (and bicycle!) mechanic, but I've never done any engine work. I had no problem with rear strut replacement and two front axle replacements -- both of these are relatively easy on my car. Who of you have confidence in me? What could go very wrong that I should look out for? Do I need any specialized tools? I have one small and one large torque wrenches, and many sockets. No air tools. I'm hoping to avoid a rusted-part disaster since the whole thing was taken apart and reassembled 1 year ago.

  4. Do I need to remove my radiator for this job? How about drain the oil? Drain the coolant?

Thanks in advance.

  • Special tools for this job: 1 ) 32 and 34 mm axle sockets for installing the cam and crankshaft seals, respectively. 2) disposable timing belt for locking camshaft sprockets, 3) wrench-extending pipe for adding torque to camshaft and crankshaft bolts and bracing against body for crankshaft bolt removal trick (using the starter), 4) disposable AC or steering pump accessory belt, for installing crankshaft bolt to appropriate torque. – tim.farkas Dec 6 '15 at 15:24
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  1. Because it's hard to get in there and see the camshaft seal, I'm skeptical that it can be diagnosed properly without taking the car apart. Could an apparent oil leak (there's some drippage on a hose underneath the left head) be caused by anything else? How should I go about independently diagnosing this leak? Should I bring this somewhere else for another opinion?

You can always go to a separate mechanic for an independent opinion. In fact, I would recommend it. However, it isn't that hard to diagnose. All you have to know is what you're looking for, which in this case is where the oil is coming from. If it's leaking from the front cover (which covers the timing belt) just below where the cam sprocket is located, it's a pretty good bet the seal is what's leaking.

  1. I understand that a leaking camshaft seal can compromise the timing belt, leading to a catastrophic engine failure and damage (see this post). Supposing I do have a camshaft seal leak, and the timing belt, pulleys, water pump, and thermometer are all gross and oily, what should I replace? Keep in mind that I replaced the timing system one year ago (see above). What if all these components don't look dirty/oily?

If it is leaking and there is oil on the belt, change it. Oil will deteriorate the belt and it's one piece of equipment on your vehicle which you don't want compromised. Since timing belts are most easily obtained as kits (which are usually not much more expensive than a the belt itself), your best bet is to replace all of the same parts so you can be assured of another 60k trouble free miles.

  1. In the timing belt removal section of my repair manual, it says not to rotate camshaft sprockets after the timing belt has been removed, else the valves will be damaged. However, in the camshaft sprocket section, it says I should remove the timing belt assembly before loosening the camshaft sprocket bolts, which seems super risky if they're not supposed to be rotated. Doesn't it make sense to loosen these bolts with the timing belt on, then remove the TB, then remove the sprockets?

I believe they are saying this so as you don't put undue stress on your timing belt (coming off and/or going on). When you are removing the sprocket, you still don't want it to turn any. You need to lock the cam in place and then loosen the bolt for the sprocket.

  1. I am an amateur, but enthusiastic auto (and bicycle!) mechanic, but I've never done any engine work. I had no problem with rear strut replacement and two front axle replacements -- both of these are relatively easy on my car. Who of you have confidence in me? What could go very wrong that I should look out for? Do I need any specialized tools? I have one small and one large torque wrenches, and many sockets. No air tools. I'm hoping to avoid a rusted-part disaster since the whole thing was taken apart and reassembled 1 year ago.

I'm not going to tell you what to do, but needless to say, this isn't a job for the uninitiated. There are a lot of gotchas. The big one being aligning your cam timing. You didn't say, but I believe your engine has four cam shafts which have to be time along with the crank. If you don't get this right, you will most likely have cost yourself an engine. If this is something you fell you must do, have a competent friend come help/watch to ensure you are doing things right. You can watch some of the videos on YouTube, which may be of assistance.

NOTE: I just looked online at the engine which you probably have. Depending on which one it is (2.0TC, 2.5, or 2.5TC), it could have 2 or 4 cams. If this is one with 4 cams, I believe it has cam phasers (used in variable valve timing). If so, I WOULD HIGHLY RECOMMEND YOU NOT DO IT YOURSELF. There are just too many variables to try and tell you to avoid while doing the work and putting it back together.

  1. Do I need to remove my radiator for this job? How about drain the oil? Drain the coolant?

For the most part, no.

  • The 2004 Subaru Impreza Outback Sport has an EJ251 engine, which is SOHC, so only two cams. – tim.farkas Dec 6 '15 at 15:17
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Post repair answers to

  1. On my SOHC model, there is a left-side timing belt cover that can be removed without taking any other components out, so you can easily take a look at the camshaft sprocket and with a flashlight you can see back to the seal. The sprocket is definitely in the way (and definitely cannot be removed at this point), but you can see through the large holes in it. To see the whole seal, you can use a large socket wrench (22 mm) to rotate the engine (clockwise) from the crankshaft pulley, which will move the holes. I never did this procedure, but I think it's doable.

  2. Audience says yes, you must replace the belt at least. Makes sense to check the idlers, sprockets, tensioner, and water pump for damage, or just replace the whole assembly. See above comment, my leak didn't contaminate the timing belt assembly at all!

  3. This is not an issue on the SOHC models. My left sprocket kept turning a bunch, because it is very annoyingly spring-loaded and needs to be returned to the proper position if knocked out of place. In any case, the trick of wrapping the old timing belt around the cam and crank sprockets and fixing it with two vice grip pliers worked very well, but I wouldn't reuse this belt. Best to have a old belt on hand (get from auto shop) just in case you decide not to replace the belt (which is what I would have done).

  4. This job really wasn't so bad, and I stress that I'm really an amatuer -- it took me about 6 hours, and I was intentionally going slow. The hard parts were 1) removing the cam and crankshaft seals, and 2) installing the final timing components. My trick for removing the seals was to drill small holes in them (they're rubber on metal) so as to compromise their physical integrity, allowing me to crush them with a screwdriver and pull them out. There's plenty of space behind the seals, so you don't really run a risk of damaging the engine block -- just don't go too deep and make sure not to slip and gouge the sealing surfaces. For the timing belt installation, I had a friend help add slack in the system to ease things up by pushing on the belt.

  5. Remove the upper radiator hose, remove the radiator fans, and remove the overflow coolant reservoir. There is enough room for this job without removing the radiator. If you're going to replace the water pump or thermostat, however, you might as well remove the radiator for luxurious space, since you'll be draining the system anyhow. This will be especially useful if you plan to drill into the seals. I also recommend lifting the front end of the car up on stands just a little so that 1) you can easily get under there occasionally (eg to unplug fans), and 2) so that coolant does not dribble out of the engine while you're working, which will ultimately cause smoke to come off the engine when you start it up again totally freaking you out, because it looks like it's coming from the timing belt cover.

  • Drilling a hole in the old seal is not a good way to go, as you have many small metal shards which can cause damage later on if not completely cleaned out. Use a small/thin screwdriver and punch a hole directly into the metal part of the seal, then pry it out using the screwdriver in the hole you just created. Much easier and cleaner. The reason the cam is "spring loaded" is because the cam lobe is being forced in one direction or the other as it is pressing down on the valve/valve spring. The valve spring is what causes the cam to clock over. – Pᴀᴜʟsᴛᴇʀ2 Dec 6 '15 at 15:26
  • sounds like a fair concern about drilling, though the Haynes manual does suggest this approach. – tim.farkas Dec 22 '15 at 11:59
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A tip from experience:

Use the Subaru OEM camshaft seals. I have seen multiple timing belt jobs where aftermarket seals leaked, sometimes immediately. One car went through two sets of aftermarkets before the Subaru seals fixed the problem.

The timing in this car is especially challenging to do, there's no reason to gamble with cheap seals. For vital engine components, I always buy OEM.

  • I realize this post is old but as these cars age and this becomes more common, I hope it helps someone in the future. – Chris Feb 25 '17 at 3:10

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