'91 M5 S38 3.6L Cylinder Head - I'm Going In - The Unofficial BMW M5 Messageboard (m5board.com)

LoneRyder · 29th October 2009, 05:25

Just a quick repeat from my previous thread looking for info then I'll continue.

"Bought a 1991 E34 M5 (production 10/1990) with S38 engine. It sat up for almost a year due to a deer hit. Replaced fender, hood and radiator. Engine fired right up when battery charged but idle was rough. Checked all spark plug wires, replaced spark plugs, distributor cap and rotor, pulled injectors and had them cleaned. No reaction with engine running when I pulled wire from #5 cylinder so I check compression on all cylinders. All cylinders read 175 to 185 PSI except #5 which reads zero compression. No needle movement at all on gage however fuel/air mixture will blow out of hole when spark plug removed. No apparent blow by as none is noticed when dipstick pulled while engine running. I'm suspecting stuck valve or burnt valve not allowing cylinder to seal during compression cycle. I checked valve settings on all cylinders. Most were .012" with a couple at .011" or .013". Cylinder #5 was .012" for exhaust and intake. My obvious next step is to remove the head for valve inspection. "

That's where I'm at now. Valve settings were all good so the head has to come off. I'll be taking pictures at each step and posting them here with observations. Hopefully this might help someone else one day. If I'm taking up too much bandwidth, etc then let me know. I'm not a mechanic by trade but worked inside a few engines (GM) in my younger days. My buddy has been inside a few BMW engines so I'm not too far out on a limb. If anyone sees a glaring problem in a picture that I didn't pick up on then please speak up.

I'll be starting the removal end of this week and weekend. Initial observations were:
1. The head bolts require a 6mm allen wrench for removal. I thought they would be torx.
2. Same size allen wrench is used to remove the timing chain top shield bolts. Bolts were VERY tight. Twisted one allen wrench 45 degrees trying to break loose.
3. You won't see much oil around exhaust valve shims. Already siphoned it up. A $1 turkey baster works very well.
4. All cam lobes looked great. No pits or grooves.

First pic is of head over cylinders 1 and 2.

More Friday. If anyone would like a picture of a particular part location, etc let me know.

Don

davidoli · 29th October 2009, 11:41

Great early thread ......thanks for sharing .

Take plenty of pics for reference and take your time noting how everything comes apart / goes back together .

I look forward to seeing your progress and wish you all the best with this restoration .

D

Lantz · 29th October 2009, 17:36

I love these technical threads! Really is an aid to those of us with less technical expertise but aspirations of mechanical greatness.

Can't wait for the updates!

Lantz

OT: Would it not be great for someone to film a full strip and rebuild of an S38 and then put it on DVD? I realise the market would be small but willing to spend a little extra when it comes to their cars. I bought a swedish DVD on how to remove, strip and rebuild (using highperformance parts) a chevy 350 V8. It was an extremely interesting and informative 8 hour DVD.

Anyone with the knowledge want to take this on? Faz? David? The Dutch?
I would be more than willing to donate my car to the experiment

XaQ · 30th October 2009, 04:37

I just did this on my '91. After you pull the throttle bodies, you should get a pretty good view of the intake valves. Maybe it will give you some clue as what to expect.

TIP: set motor at -60 degrees TDC (all pistons part way down bore) then you can turn the cams after you pull the sprockets without worry of piston/valve contact.

LoneRyder · 2nd November 2009, 05:47

XaQ - Thanks for the tip!

Got tied up Saturday so started removing parts today (Sunday) to access the cylinder head. I've renamed all the pictures to give all an idea of what they are looking at. Even if you are not removing a head maybe you'll see something useful in the pictures. I've resized all the pictures to between 110K and 220K (from 2M) to keep from eating up bandwidth and to reduce load time. I'm also breaking them into separate posts so it doesn't take so long for a single post to load.

Lessons learned today -
1. Keep a magnetic parts retriever handy. It's easy to drop tools when you can't see your hands.
2. Place the front tires on ramps. You will need to access points from the underside. See next.
3. Don't try to remove the oil separator from the air accumulator to release the air accumulator. Two bolts hold the oil separator to engine block. Very easy to access from under the car.
4. Seeing the location of the starter you Must remove the air accumulator to access/remove the starter. Very easy access once this is done.
5. Various hoses have to be removed. Most are obvious. One is below the oil separator, one is below the air accumulator. Once the air accumulator is "moveable" you can get between it and the throttle bodies to remove the valve cover ventilation hose. There is also a small hose from the dipstick tube to the oil separator. I'm assuming this returns any oil which enters the separator back to the crankcase.

In one of the pictures you'll see the timing chain shield which is located under the valve cover. This is a plastic piece. In the picture you'll see some very minor wear from the timing chain. The wear lines are on the input side of the timing chain shield. This appears to be the OEM shield. If it is I'm very glad to see such little wear. FYI the engine has 212K miles.

On with the pictures.

Don

LoneRyder · 2nd November 2009, 05:53

I thought the picture names would show but they don't. You'll have to hover over picture with your mouse or click on properties for the picture.

LoneRyder · 2nd November 2009, 06:00

Oil separator and removed air accumulator/oil separator assy.

LoneRyder · 2nd November 2009, 06:03

Some pictures of the top side of the intake showing the fuel injector ports.

LoneRyder · 2nd November 2009, 06:07

Pictures of the throttle body intakes.

LoneRyder · 2nd November 2009, 06:14

Pictures of the Timing Chain Shield (under valve cover). I will be measuring the wear on the shield with a micrometer and will report that in a post later this week.
Starter pictures are just for info.