HappyAndy UltraDork
5/9/15 8:42 p.m.

Over the winter my wife's e34 525 quit running on the coldest day of the year. It was running normally the night before, but in the morning it would crank and sputter for a few seconds, but not actually run.

I did a compression test and found very low compression in all six holes. I think the highest I found was 50 psi, the lowest was under 20 psi. I also pressure tested the cooling system and found that the coolant tank had a leaky seam. This radiator is only about 6 months old and a good brand.

I'm thinking that the HG let go during that last drive and the combustion pressure leaked into the cooling system and popped the coolant tank.

Fast forward to today, I finally have had time to tear it down.

I don't think that I found a smoking gun, but I found some more clues.

I doubt that this would affect the compression, but the vanos piston is completely shot, it feels like the piston has no seal ring at all.

Most of the cylinder head bolts came out way to easy, like they were only torqued to the second stage during assembly.

The old HG didn't have any burnt, melted or eroded fire rings, but it looked like there may have been less than perfect sealing between some of the cyls. Also, the openings in the gasket near the cooling passages near the fire rings were all puffed out. I wonder if combustion pressure escaping caused that?

I feel reasonably confident that a new HG will fix it.

If I get a top end gasket kit it will include new valve stem seals. There is evidence that the stem seals were leaking, so I would like to replace them. I'm not sure if I want to do that myself or have a machine shop do it.

My Bentley manual mentions a special tool for removing the cams on these engines. It holds the cam down while the bearing caps are all removed together. I think that is to keep the cam from getting bent. Is that tool really needed, and do these cams bend easily?

Any good advise for repairing the vanos cylinder? I repair hydraulic cyls frequently at my day job, so I think I should be able to handle it, but what is the deal with the anti-rattle ring? I can't quite wrap my mind around what it's supposed to do.

Slippery GRM+ Memberand Dork
5/9/15 9:03 p.m.

This guy will have all you need:

Dr. Vanos

He will even rent you the cam tools.

Slippery GRM+ Memberand Dork
5/9/15 9:05 p.m.

BTW, if you dont have to have the head decked I would do the valve seals myself. Its quite simple.

Also get some valve grinding compound and the suction cups on a stick (harbor freight has them) and reseat the valves while in there.

HappyAndy UltraDork
5/11/15 6:31 a.m.

Bump for the weekday crowd.

rcutclif GRM+ Memberand Dork
5/11/15 8:39 a.m.

re: the cams. Never done it myself but considered many times (and even got so close as to take the valve covers off and look...) this is what I know.

Yes, they bend easily (or just break) they are hollow - and 6 cyl so they are long. The tool holds the cam so it cannot rotate and then you can unbolt the cam slowly. Key is to have one lobe pointing directly down (at max lift on that valve) so there is little pressure on the rest of the cam lobes. Then you can unbolt the 'unloaded' cam bearing caps, leaving the loaded one until last, then you can slowly unbolt it against spring pressure. or unbolt them all in an even pace or something. Bentley should have the unbolt procedure.

You can do it without the tool, but I suggest getting another person just to hold the cam with a big wrench (there are flats on the cam for this). The cam will want to twist during the whole process, and if it does while you are in the middle of unbolting, the cam will be ruined quick.

Giant Purple Snorklewacker
Giant Purple Snorklewacker MegaDork
5/11/15 8:57 a.m.

1) VANOS setup is easy with the right tools. The Bentley instructions are spot on.

2) If you are just doing the gasket and not decking the head or messing with guides, you don't need to touch the cams. Just leave them locked in the tool and the motor at TDC.

3) I think #2 would be a mistake. I'd take it to a machine shop and let them dip it, check it, deck it, replace guides/seals and cut new seats. So, unbolt the cams gradually, on the bench. Do it evenly so you don't spike the spring pressure in any one place. Leave the lock tool on so the cams don't twist.

4) The tools can be had for around $100 from a bunch of different sources. Here is one example: http://www.ebay.com/itm/BMW-Single-Vanos-Valve-Alignment-Timing-Engine-Cam-Repair-Tool-/171765599631?hash=item27fe070d8f&item=171765599631&vxp=mtr

Jamey_from_Legal New Reader
5/11/15 12:26 p.m.

I have never tried it myself, but:


Slippery GRM+ Memberand Dork
5/11/15 4:36 p.m.

I dont think the cams on the "M" engines are hollow, the "S" (M3) engines yes.

The website I posted will rent the tools for around $30.

spandak New Reader
5/11/15 4:53 p.m.

Removing the cams isnt that hard. I put them at TDC and loosened each bearing cap nut half a turn at a time. Keep everything even and its really quite easy. Timing everything is a little more tricky but doable with basic tools.

HappyAndy UltraDork
5/11/15 5:05 p.m.

I own a vanos tool kit, its the special tools for removing the cams to service the stem seals that I was curious about. I'll have to read that article in the link to Pelican parts tonight, it looks like it may have the information that I need.

I was also wondering if anyone had ever seen a head gasket failure like the one that I described.I'm not used to seeing head gasket failures that arent fairly obvious.

rcutclif GRM+ Memberand Dork
5/11/15 5:47 p.m.

well, i don't know if it was my head gasket or not, but I lost my m50 on a REALLY cold morning in wisconsin and a compression check later showed it at 30-40 on like 3-6. I was cranking, sounded normal, caught, then instantly died. Cranking afterward sounded like a broken timing belt (very little compression).

I didn't tear it down to inspect past the valve cover (timing chain was still intact), so this is of no help to you. But I did tear it out to make way for a 302...

I assumed that I had hydro-locked and mashed the valves or I had a vanos issue that let timing get so far off I mashed the valves. But thinking back that may not have been the case at all. It could easily have been a head gasket.

Streetwiseguy PowerDork
5/11/15 8:45 p.m.

I hate to be the bearer of bad news, but I'd bet you $1000 it was just flooded, and washed the rings. Warm it up, oil the cylinders and crank the E36 M3 out of it, and it would have started.

We see it up here all the time.

Desmond Reader
5/12/15 12:32 a.m.


Get a rebuild kit for your vanos there. Its like 60 bucks.

Also, go with an Elring headgasket or better. I hear nothing but bad about the Victor Reinz headgaskets for some reason.

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