35 replies to this topic

[whoa]

Oil will drip down the intake valve stems, and if the vacuum is low enough (idle), will pool in the intake passages and not get sucked into the pistons for burning until you rev the engine. Hence the diagnostic test of idling for ten minutes and then revving the engine. (My 1996 850 Turbo makes a wonderful blue cloud, almost like a SeaFoam treatment.)

But if the exhaust valves are worn too, I'm wondering if there might be exhaust gases blown past the valve stems into the cam compartment, which is part of the oil system? Now, you might say, no, because the exhaust stroke happens with the exhaust valves closed. Good point! But there certainly is never vacuum in the exhaust, right? And there is even back-pressure there, surely, during the rest of the cylinder cycle, particularly with a stock exhaust, and particularly in California... So my totally uninformed, armchair hypothesis, is that worn exhaust valve stem seals could lead to increased pressure in the oil system, and hence the same sorts of symptoms associated with clogged PCV stuff: oil oozing out here and there, some smoke out the dipstick tube, . . .

How wrong am I?

Mark

(BTW, I am going to do an in-car valve-stem seal replacement, and will document it here, where you can see my plans now...)

[Ihatespeedbumps]

I like your post.

I think it would be difficult to push that much volume and air pressure between such a tight fit, even with valve stem seals that are hard as a carp.

I dunno though

[ozzimark]

I think it would be difficult to push that much volume and air pressure between such a tight fit, even with valve stem seals that are hard as a carp.

Indeed, but also consider that the exhaust manifold pressure is always higher than the intake manifold pressure. If there is 20inHg of vacuum in the intake ports that is drawing oil into the cylinders, that's just under -10psig. At full boost, the exhaust manifold pressure is probably around 15-20psig on a stock setup, more if you're running more boost... which is an even higher pressure difference to force a thinner fluid (air) through the valve seals. I think Mark is onto something here.

[whoa]

Well I have gotten to the valves, and the seals are completely hardened and basically are no longer seals.

Hoping to get her back together tomorrow---fiddling the keepers back in is a real ... assertive woman. Any tricks? I've been using a small magnetized screwdriver and an unmagnetized one, a gob of grease on the keeper, and then hope I get lucky. Only 20 more keepers to fiddle in...

Mark

[whoa]

Here are some observation after the first day working on this:

http://sites.google....ct-updates/day1

[whoa]

So here's what happened:

http://sites.google....pdates/write-up

[ozzimark]

Nice detailed write-up!

So I take it the blue smoke after idling has gone away?

[whoa]

Nice detailed write-up!

So I take it the blue smoke after idling has gone away?

Yes. There are before and after videos in the write up so you can see the big difference.

[ozzimark]

Ah, I watched the before video, and the initial start-up video at the end, but didn't see a video of you revving it after idling for a while to check for the same blue cloud, thus why I asked. Definitely looks like a monumental challenge to do all that stuff with the head on the car still. I'll be sure to replace all those seals whenever the head happens to be off next

[whoa]

The "after" video (as well as the "before" one) is a rev after 10 minutes of warm idle. So that problem seems to be fixed. I'm tempted to bring it to a smog test place to see how the emissions are affected. I'll keep an eye on oil consumption and leaks.

Yeah, it would be easier out of the car. For me the alternative was to get a new head. This was certainly cheaper, but probably no less work.

[Gilhuly]

Nice write up!

If I read you correctly and also from experience the cam sprockets don't need to come off the shafts, right?

So here's what happened:

http://sites.google.com/site/incarvalvestemsealreplacement/project-updates/write-up

[whoa]

Nice write up!

If I read you correctly and also from experience the cam sprockets don't need to come off the shafts, right?

Thanks!

Well, the sprockets do eventually have to come off, since you have to press in the front-end camshaft seals during reassembly. Next time I would wait until after the bolts come out at the other ends of the shafts, though.

[Gilhuly]

The sprockets don't have to come off. I just take the whole thing out and put it all back in with seals already in place. When replacing seals they can be worked over the shaft into place.

I'm the guy who bought the tools off whoa and wanted to comment on this job.

1. This will fix a smoking at idle 850 which is not from a blown turbo (diagnose by much oil in intercooler), bad rings or bad valve guides. The valve seals looked to have been re-used in a cheap ebay rebuild ($300 rebuilt head last year).

2. I highly recommend this to be a two man job. There is plenty to keep two busy and operating the schley tool really should have a dedicated person. It was helpful when replacing keepers to be able to call, "half way up, no back down, up.....". We used 4 ft of cheater pipe on the schley handle and this made things much easier.

3.Take your time on cam cover removal. This is the riskiest part of the job, IMO as you can crack the head where the shafts fit in.

4. Cover all the open holes, including the intercooler piping in back and handle the keepers over the head only. We still had two runaways, one dropped in the engine compartment and another made a break for it and shot out of the head and fell downon the cross member heat shield at bottom.

5. I highly recommend the compressor method for securing the valves using a spark plug hole fitting that can be purchased almost anywhere cheap. The rope trick for us was tricky and the rope got stuck I think 4 ways on the first cylinder. We switched afterward to air.

6. Special implements: I had a dental pick for helping free the keepers which was awesome and also for helping manipulate the keepers back in after seal replacement. Also for keeper replacement using a long slender screw driver and some thick grease gun grease. Put a very small amount of grease on the screwdriver tip and stick the keeper to it and put it in with dental pick or other tool in other hand. Also, have a small diameter telescoping magnet that will fit inside the schley tool for valve keeper retrieval.

Again, I really call this a two man job. We did it in a long day (11 hrs incl lunch). Other skills required are timing belt removal/replacement skills. TDC on #1, crank shaft gear mark lined up on the block and slots on the camshaft ends level with head suface, exhaust slot cheats below the centerline, intake cheats above.

It was very rewarding to take this car back from being a smoking embarassment (it was bad and came on almost immediately) to a fine runnning car again.

[TorqueSteer]

If the sprockets are removed, and lets say you are replacing them with brand new sprockets, assuming that the cams are lined up correctly and locked into place, the new sprockets can go on at any angle right? Then once they are on, the new timing marks are made. In other words, there is no specific TDC location on the sprockets, it all depends on the cams, right?

Edited by TorqueSteer, 25 July 2010 - 02:24 PM.

[whoa]

If the sprockets are removed, and lets say you are replacing them with brand new sprockets, assuming that the cams are lined up correctly and locked into place, the new sprockets can go on at any angle right? Then once they are on, the new timing marks are made. In other words, there is no specific TDC location on the sprockets, it all depends on the cams, right?

There is a specific procedure to get the sprockets on at factory angle. It does affect the precise timing angle of both camshafts. You use a camshaft-locking tool to lock the slots on the rear of the shafts to horizontal position, put the cam sprockets on loosely, install the belt and tensioner, press the belt hard twice at the top (between sprockets) and left (between water pump and exhaust sprocket), and then tighten the sprocket bolts to 15 foot-pounds.

If you don't have the cam locking tool, try to get the slots horizontal with the belt well seated in each sprocket, and then tighten the bolts. Installing the sprockets in the middle of their range of slop is probably an okay hack.

[TorqueSteer]

There is a specific procedure to get the sprockets on at factory angle. It does affect the precise timing angle of both camshafts. You use a camshaft-locking tool to lock the slots on the rear of the shafts to horizontal position, put the cam sprockets on loosely, install the belt and tensioner, press the belt hard twice at the top (between sprockets) and left (between water pump and exhaust sprocket), and then tighten the sprocket bolts to 15 foot-pounds.

If you don't have the cam locking tool, try to get the slots horizontal with the belt well seated in each sprocket, and then tighten the bolts. Installing the sprockets in the middle of their range of slop is probably an okay hack.

So there is a top and bottom to the sprockets? They seem to be circular to me. I have sprockets with absolutely no timing marks and I am mating them to a set of new camshafts.

I am referring to the process of physically bolting the sprockets to the camshafts, before the belt is on and any timing has taken place.
I am looking at the sprockets, and I see three eccentric holes on them, and they are all spaced evenly. So there are 3 ways (directions) to attach them to the camshaft, the only distinguishing mark is a "M" engraved at the bottom of the gear.

I had assumed that since the gears appear to be circular and symmetrical, that I can bolt them on at any one of the three possibilities. I just wanted to make sure before I do this job tomorrow.

I have the cam locking tool.

Edited by TorqueSteer, 25 July 2010 - 04:54 PM.

[whoa]

I haven't ever put in new sprockets. but given the symmetry I don't see how it could make any difference which hole goes where.

[TorqueSteer]

I haven't ever put in new sprockets. but given the symmetry I don't see how it could make any difference which hole goes where.

Ok I thought the same, just wanted to confirm. Thank you!

[Gilhuly]

I always thought the sprockets were indexed so they could only go on one way, but I could definitely be wrong as I've never had reason to separate them from a shaft. But, let'say you can put them them on however you want for argument's sake. Then, yes, absolutely if you start with cylinder #1 at top dead center and the crank notch on the mark on the block just lay the shafts in with the slots on the other end of the shafts level with the head surface, exhaust slot below center and intake above center. the lobes on cyl #1 will be up and pointing in at each other at about 45 deghrees. The sprockets and their marks could be in any position assuming they go on the shaft.

[TorqueSteer]

I always thought the sprockets were indexed so they could only go on one way, but I could definitely be wrong as I've never had reason to separate them from a shaft. But, let'say you can put them them on however you want for argument's sake. Then, yes, absolutely if you start with cylinder #1 at top dead center and the crank notch on the mark on the block just lay the shafts in with the slots on the other end of the shafts level with the head surface, exhaust slot below center and intake above center. the lobes on cyl #1 will be up and pointing in at each other at about 45 deghrees. The sprockets and their marks could be in any position assuming they go on the shaft.

Thanks for the reply! Have you taken off the large black stabilizer bracket on the side of the engine in order to make and attach the cam locking tool?