valve stem seal nightmare

[crystalworks]

Originally Posted by ants_oz

I just can't be bothered doing some jobs myself anymore. I'm a qualified mechanic, but have many more enjoyable things I would prefer to do with my time that struggle in a home garage with things like lifting heads, doing timing chains, etc etc.

As much as it hurts the hip pocket, I would prefer to be shooting hoops with my son, or going for a ride with my wife on the motorbike than spending a day under the bonnet of a car.

As a new(ish) father. I can relate to this. I used to spend every weekend in the garage maintaining or modifying the 5 BMW fleet... but now it a rarity for me to get in there and spend any more time than it takes to replace belts or do oil changes.

[jmitro]

ants_oz thanks for the reply.

In reading about head removal, the camshaft timing tools are required. But I can't set the engine at TDC since I can't rotate the engine; so do I just leave the crankshaft and cams at their current settings, remove the head, then line it all up with the tools when I'm ready to re-assemble?

[Doru]

Originally Posted by crystalworks

^Yikes... now I am really not looking forward to doing this job. Is there another way to support the valves while working on them other than air pressure? Maybe magnets or even long nosed vise grips wrapped in electric tape or other non-marring material? I guess anything you use would just get in your way while you were trying to replace the valve though...

I've pulled and replaced I6 heads (m50, 52, etc) and I really don't want to pull these heads... lol.

When changing the valve stem seals using the AGA tool, you "can" change the valve stem seals without compressed air, and having the valve you work on resting on top of the piston. That is if you know what you're doing, and being 100% sure you're at TDC. At TDC, without compressed air, the valve rests on the piston. With compressed air it will stick out more. I did this job last year, and I haven't used compressed air on quite a few valves, but I also let air in as soon as I needed the valve to stick higher in order to place the retaining collets. When performing this procedure, you have to be very careful. Also, you have to cover everything up that is around the bank you work on. Absolutely no gaps. You will work with some very small parts and you will handle them with magnets. There are also springs, and small parts that can come lose and fly everywhere if not careful. They could land where you leave gaps, and then it's good-bye in the worst case. The repair procedure should NOT be rushed even if you want to have it done quick. Especially the last cylinder on bank1 & bank2 (close to the firewall) are very taxing on the back, and you might feel compelled to finish it off quick. Big mistake. Just take a break, have a beer (it's summer after all), return later. Take extra care and double & triple check that the parts seat correctly after assembly. You might want a helper after all the stem seals are replaced, to very slowly turn the engine over, so you can inspect every cylinder carefully - the valves & valve guides. the engine shouldn't bind, and the valves & roller guides should move smooth. For the cylinders close to the firewall you need a good small mirror for visual. Same for a few other spots. Actually you should take some pics on how the lifters & guides look prior to starting the job to have as reference.

GL

[Doru]

Originally Posted by jmitro

ants_oz thanks for the reply.

In reading about head removal, the camshaft timing tools are required. But I can't set the engine at TDC since I can't rotate the engine; so do I just leave the crankshaft and cams at their current settings, remove the head, then line it all up with the tools when I'm ready to re-assemble?

When you tried turning the engine with the valve resting inside, you might have hit the top of the head with that valve. It was probably resting on top of the piston on side, and it was pressing the piston down on that side. the piston isn't true anymore - it probably seats cockeyed in the bore and is wedged with that valve. I can be wrong, but this is what I think happened. Try to find someone that has a snake cam and slide it inside the cylinder to have a visual how things actually are. It might not be that bad. Once you know 100% why the engine is not turning/how the valve is caught, you might listen to the AGA guys and go from underneath without pulling the head. You have to know which way to rotate the engine, if you can remember 100% which was the rotation sense (clockwise or counterclockwise) when the engine seized, so you can try to go the opposite way. You might need a helper and build a small hook out of sturdy wire to pull on the valve to dislodge it. The snake cam and the hook should be able to fit through the hole. the sturdy wire might need a small bend before the hook.

[Doru]

Jmitro, maybe this thread can help you a little. It has some good pictures and descriptions of some procedures. It's a very long thread, but I would take my time and go through it, maybe it will shed some light on what you encounter. It's a different car, but the exact same engine.

[crystalworks]

Originally Posted by Doru

When changing the valve stem seals using the AGA tool, you "can" change the valve stem seals without compressed air, and having the valve you work on resting on top of the piston. That is if you know what you're doing, and being 100% sure you're at TDC. At TDC, without compressed air, the valve rests on the piston. With compressed air it will stick out more. I did this job last year, and I haven't used compressed air on quite a few valves, but I also let air in as soon as I needed the valve to stick higher in order to place the retaining collets. When performing this procedure, you have to be very careful. Also, you have to cover everything up that is around the bank you work on. Absolutely no gaps. You will work with some very small parts and you will handle them with magnets. There are also springs, and small parts that can come lose and fly everywhere if not careful. They could land where you leave gaps, and then it's good-bye in the worst case. The repair procedure should NOT be rushed even if you want to have it done quick. Especially the last cylinder on bank1 & bank2 (close to the firewall) are very taxing on the back, and you might feel compelled to finish it off quick. Big mistake. Just take a break, have a beer (it's summer after all), return later. Take extra care and double & triple check that the parts seat correctly after assembly. You might want a helper after all the stem seals are replaced, to very slowly turn the engine over, so you can inspect every cylinder carefully - the valves & valve guides. the engine shouldn't bind, and the valves & roller guides should move smooth. For the cylinders close to the firewall you need a good small mirror for visual. Same for a few other spots. Actually you should take some pics on how the lifters & guides look prior to starting the job to have as reference.

GL

Thanks for the info. I have your thread bookmarked as well as another from a 6 (or 7) series. I have rebuilt I6 heads before... but the V8 BMW engines I've only seen it done. It didn't look like fun and so would definitely use the AGA tool rather than pulling the head... and if I can use my snake cam to verify the piston is up on the valves I'm working on negating the need for consistent air... then awesome. That makes me feel a lot better.

BTW, when I do this job... I am going to budget a month for the job so rushing will not be an issue. I'm 6'8" and my back lets me know when I have been hunched over an engine bay for too long.

[Doru]

Yeah. Maybe the valve slid over a bit and is not sitting in the valve relief groove of the piston head, and could be only "slightly" jammed. With that sturdy wire you might be able to pull it so it slides down in the valve relief. Than you might be able to ever so gently guide it back in it's place, while barely moving the crank.

[jmitro]

Success!!
Got the valve pulled back up and keepers back in without removing the head. Basically had to pull the exhaust manifold and use mirror, pliers, and extreme body contortioning to feed the valve back up, then slowly rotate the engine to push the piston up which in turn miraculously managed to find the valve guide (after about 15 attempts). The motor rotates freely now without binding. The #2 piston is back up at the top of the compression stroke where it should be.


Anyway, i'm going to read up on removing the camshafts and if it seems easy to do I will change the valve stem seals that way. I am most of the way there, Just need to set the engine to TDC, Remove timing cover, sprockets, and cams. I think that is going to be much easier to change the seals.

Any suggestions "while I'm in there?"

[BigBlack48is]

Way to go jmitro!!!



I was actually thinking the same thing ( about going the route of removing the cams ) and then using something like this ( Compact Double BMW N62 V8 Valve Spring Compressor | eBay ). or just a standard valve spring compressor. Keep us all posted on how it goes and that is such a huge accomplishment!!!

[ants_oz]

How have you been able to determine there is no damage to either the piston crown, the bore, or the valve itself?