Leaky valves - avoid head removal?

[IMColor]

01 525i..

Long story short, doing an engine swap due to second blown head gasket on outgoing motor. This is the third engine I have gotten from the junkyard; on the first one, the compression numbers were all over the board, second didn't even have compression because all of the exhaust valves were bent (somebody must have thought they were smart enough to play with the cams, but ran out of talent)...

Now for #3... this time I got smart and rigged up a jig that would allow me to install the starter directly on the motor so I didn't have to install it before checking compression. The numbers are good with the exception of cylinder 1, which is at 90. I have the motor on the bench (floor, actually) with the intake off. I screwed my homemade smoke generator into the spark plug hole and, with both sets of cam lobes up, sent the smoke in. I immediately saw smoke swirling from all the way around the front intake valve ( nothing from the rear intake valve) ; there was also smoke from both exhaust valves, but significantly less than the intake.

My question is this: any ideas on how to remedy the situation shy of removing the head? I'm paranoid to remove the head as I don't want to upset the sensitive little threads for the head bolts and have to play head gasket games again. I did spray some carb cleaner into the intake and filled up the bowl then sent compressed air down the spark plug hole in hopes that the agitation combined with carb cleaner would eat away at any deposits that might be sitting on the valve seat. That didn't seem to have any effect.

[bmwdirtracer]

90 psi on an engine that hasn't run for a long time is nothing to worry about. It's likely you've just got a sticky lifter. Put a wooden or plastic dowel on the lifter and hit it sharply with a hammer. Personally, I'd use a leak down tester rather than a compression test, for an engine that's sitting on the floor.

[IMColor]

You nailed it my friend, a couple of sharp pops and the compression jumped up to 170, consistent with the rest of the cylinders. Thanks for the quick and accurate reply.

[IMColor]

For future readers of this thread, don't do what I just did...

You obviously have to pop the follower (lifter) when the valve is closed, otherwise you're not going to solve your problem. They're only a couple Windows of opportunity within the stroke to get a dowel that is thick enough to withstand to the blow to make contact with the follower. In one of those windows of opportunity, the piston is up, and it's not going to get out of the way when the valve opens due to you popping it..

After 3 weeks of %^&* around with junkyards not doing what they say they're going to do or delivering what they say they're going to deliver, I finally saw the light at the end of the tunnel; and it was, in fact, an oncoming train. Looks like I now have no choice but to take the head off

[ross1]

For future readers of this thread, don't do what I just did...

You obviously have to pop the follower (lifter) when the valve is closed, otherwise you're not going to solve your problem. They're only a couple Windows of opportunity within the stroke to get a dowel that is thick enough to withstand to the blow to make contact with the follower. In one of those windows of opportunity, the piston is up, and it's not going to get out of the way when the valve opens due to you popping it..

After 3 weeks of fck'ing around with junkyards not doing what they say they're going to do or delivering what they say they're going to deliver, I finally saw the light at the end of the tunnel; and it was, in fact, an oncoming train. Looks like I now have no choice but to take the head off

what are you saying? You bent a valve?
Junkyards and promises

[bmwdirtracer]

I don't get it. Suddenly, after a few taps, you had perfect compression. 2 hours later, the head's coming off? Why?

[IMColor]

It seems not. After successfully sealing up cylinder 1, I decided to go after the little whisps of smoke that we're coming out of a couple other cylinders using the same approach, and suddenly cylinder 2 started pouring smoke out. Buy something was that I had knocked the piston with the valve and either bent the valve or somehow damaged the follower.

I removed the Vanos and exhaust cam and confirm that with no cam or follower installed, the cylinder was still leaking a significant amount of smoke out the exhaust port. But I thought I would smack the valves a couple more times before I jumped into taking the head off.

And that sealed up the exhaust. Banging on the followers must have caused some build up to shake loose and sit between the valve and the seat. All valves seem to be sealing up well now so I'll put it back together and pretend today never happened...

[bmwdirtracer]

Whew !
Okay, I was starting to feel guilty. And certainly, I should have registered a couple of cautions and disclaimers.....so I'm going to go ahead and do that now, for posterity: (THIS IS NOT DIRECTED TO YOU, but to future readers)

I have done this before, including on my own (used, very expensive, replacement) M5 motor. I know several master techs which swear by this technique, and they've never had any negative results from it, like bending a valve.

In fact, I'd really find it hard to believe that any reasonably mechanical person could possibly bend a valve, doing this. After all, we're just trying to free up a sticky lifter.... How can I quantify the correct amount of force, in writing?

I can't, I guess....1/4" wooden dowel? 1/2 pound hammer? (Sorry, let me translate into worldview: 6mm diameter dowel, or 250 gram hammer) And maybe a 4 inch swing on that hammer (100mm). In other words, TAP it.

OR, make sure that the piston's not there: put a screwdriver down the spark plug hole, make sure the piston has dropped at least half an inch (13mm)


Sorry, Imcolor; I'm a day late and a dollar short. Sometimes I forget the warnings....but you really do seem quite adept, from your single original post. And I see no reason to doubt that now, either. (I've made far more car mistakes than you ever will)

I apologize for the fact that it seemed my technique had caused you extensive grief. I'm very glad that this didn't end up being true, aside from having to reset the timing (which is bad enough, I know)

Oh....this is important: You MUST draw those cams down with the very greatest care! The official directions have you using a special tool to pull them down evenly. You CAN get around this, by setting the cams in a respect that prevents full loading on any lobe, and then tightening the nuts, 1/4 turn at a time,evenly. Do not cheat this, because those cams are hollow, and fragile.

Make sure that the crankshaft is backed off from TDC by ~15 degrees. Use the correct timing tools.

I sincerely apologize for your grief, Imcolor. The technique is quite valid, but probably requires mechanical sympathy bred from a couple of decades of messing with BMW motors.

[IMColor]

I used the instructions from GermanAutoSolutions, and fabbed my own crank pin and cam holder. All seemed to work out well.

Beemers on dirt, eh? I raced outlaw late models on dirt, 25 years ago. They had a big power, but were heavy, wide and long, so they flexed a lot. That is unless you added a lot of extra braces in to stiffen them, but that added to much weight.

These things are pretty stiff, I had the whole front end on stands and then jacked up behind the driver's front tire and it lifted the passenger side off its stand too. With that kind of stiffness, these things must really get down into the track coming out of the corner...