Blown head gasket~1996 750iL

[1fatcat]

First off, I want to apologize to those of you that helped me on this post: http://forums.bimmerforums.com/forum/showthread.php?2116684-750iL-vacuum-leak I should have done some more testing before assuming. Thank you for your help.

So I just bought this 1996 750il for a dirt cheap price, $950. The seller told me that the head gaskets needed replacing but I didn't believe it because the engine ran so smooth, but didn't have any power. I thought for sure it just needed a sensor.

It didn't smoke, didn't use coolant, didn't overheat.

Well it turns out that the head gasket IS blown between cylinders 9 & 10. Not blown to the cooling jackets, so it doesn't burn or use coolant and it doesn't overheat either...and it idled smooth as could be! I guess that's a side-effect of 12 cylinders. :) I went into this knowing full well that it may need head gaskets, so I'm not at all upset that it does. I was just hoping that it was something simpler.

The gasket blew out between cylinder 9 and 10 causing the explosion from one cylinder to enter the neighboring cylinder. When this happens, that neighboring cylinder had the intake valve open and the pressurized charge ran through that open intake valve and into the intake manifold which flooded the manifold with exhaust gas so the other cylinders on that bank can't run efficiently either.

I'm pretty good with repairing engines and plan on doing the repairs myself. I know some of you might be thinking that this is over my head, but I'm actually pretty good at fixing stuff. This big V12 doesn't scare me one bit.

I've done head gaskets on Cadillac Northstars, Chevy Trailblazers, Pontiac Grand Prix 3.4L 4 valve DOHC, Ford 4.6L 4 valve DOHC, and countless others. Those are just some of the more difficult ones I've done.

Anyways, I'm not at all trying to brag. I've never done head gaskets on a BMW V12.

There is a wealth of knowledge here and I'm open to any tips or advise I can get!

To start with, would you guys recommend I get parts through a BMW dealer, or should I buy an aftermarket head gasket kit on-line?

Can the head bolts be reused or do they need to be replaced? I'm guessing they need to be replaced.

[psjr]

Here is a quick price list (all parts from dealer) I threw together last year for a 99-01 V12 (doing both sides):
$400 gasket set 11129068137
$200 2x head gaskets
$66 all head bolts
$570 intake gaskets

[iDreadnaught]

Can the head bolts be reused or do they need to be replaced? I'm guessing they need to be replaced.

Nope, they stretch when you torque + angle them down. Going to need new ones.

[rahee006]

before you even start getting new bolts and head gasket/ or try to rebuild the engine, get the head off, and check for warpage on the head with a gauge tool. Check the spec for your 750iL head. ( For the max warpage ) and then if you do find irregularity or a warpage, get the head replaced and then check the block for cracks ( you have to send the block to a machine shop ) they will charge you around $50 for inspection. ( from what i know ) now if you cannot find any warpage? you should be a little worried. send both your block and the head in the machine shop and see what they say. Chances are you have a cracked block, now about the bolts. never reuse them because if there is a warpage, the bolts will not torque correctly, which will make you do the job twice! you either have a cracked block, warpaged head, broken valve ports so get it inspected thoroughly and by a professional, if you want to save your e38.

Good luck!

[GSXRliterbikz]

Wouldn't it be cheaper an easier to just swap motors? Pre facelift v12's are cheap.

[Binjammin]

I seriously doubt the intake valve on an adjoining cylinder would be open at the same time as the power stroke next door. It also helps if you stop thinking of it as an explosion, thinking about it like that will seriously cloud your thoughts when it comes to diagnostics.

If you had an open intake valve with a burning charge entering it, you would get major league backfiring into the intake plenum. It would be the opposite of smooth operation. You also wouldn't be flooding the plenum with exhaust gases, because you're only talking about one cylinder's pulse on one stroke. There's 5 other cylinders drawing from that plenum at the same time, and they're all continuously drawing fresh air in. Lots of cars draw exhaust gas in during normal operation anyway, it's called EGR.

What's happening in your car is that you've got two blown out fire compression rings in your head gasket. When one cylinder is on a power stroke, there is no seal, so there's no compression. The charge has been pushed to the adjoining cylinder. The burn of whatever is left is incomplete, and no, it won't burn out the complete charge in the other cylinder. The process is reversed for the other cylinder when it is on its power stroke. You have two cylinders that are making no power. That's your cause of power loss.

[TxDarth]

For some reason there seems to have been more blown head gaskets on the v12's over the v8's - there has been 5 or 6 members of several forums with v12 gaskets where I can only remember 1 v8 blowing...... Most occurred after overheating as I recall.

[Binjammin]

For some reason there seems to have been more blown head gaskets on the v12's over the v8's - there has been 5 or 6 members of several forums with v12 gaskets where I can only remember 1 v8 blowing...... Most occurred after overheating as I recall.

IIRC there was a recall on head bolts a million years ago.

[1fatcat]

If you had an open intake valve with a burning charge entering it, you would get major league backfiring into the intake plenum.

That's exactly what it's doing

I did a compression test on all 12 cylinders with all the plugs removed. Results were:
#1 180
#2 185
#3 185
#4 175
#5 180
#6 190
#7 190
#8 200
#9 10
#10 10
#11 190
#12 185

So 9 and 10 have next to no compression and when testing the compression in #9, you could hear the pressure coming out of the #10 plug hole. When testing #10, you could hear the pressure coming out the #9 hole. So I'm pretty sure the gasket blew between 9 & 10. I won't know for sure till I get the head off but I think it's a safe bet for now.

As far as swapping a used engine in, yes, the thought has crossed my mind. I can get one for $600 with 170,000 miles on it but it's a 10 hour round trip to get it so add $200 for gas. I could pay to have it shipped here, but that brings the price closer to $1,000. And then in the end, I have no idea what condition that used motor is in.

I would rather put head gaskets in the engine I have just for that peace of mind of knowing they are new. If I get it apart and find a cracked block or a damaged cylinder wall, well then I will go the route of a used engine.

[Binjammin]

That's exactly what it's doing

I did a compression test on all 12 cylinders with all the plugs removed. Results were:
#1 180
#2 185
#3 185
#4 175
#5 180
#6 190
#7 190
#8 200
#9 10
#10 10
#11 190
#12 185

So 9 and 10 have next to no compression and when testing the compression in #9, you could hear the pressure coming out of the #10 plug hole. When testing #10, you could hear the pressure coming out the #9 hole. So I'm pretty sure the gasket blew between 9 & 10. I won't know for sure till I get the head off but I think it's a safe bet for now.

As far as swapping a used engine in, yes, the thought has crossed my mind. I can get one for $600 with 170,000 miles on it but it's a 10 hour round trip to get it so add $200 for gas. I could pay to have it shipped here, but that brings the price closer to $1,000. And then in the end, I have no idea what condition that used motor is in.

I would rather put head gaskets in the engine I have just for that peace of mind of knowing they are new. If I get it apart and find a cracked block or a damaged cylinder wall, well then I will go the route of a used engine.

If it were backfiring into the intake plenum you would feel a severe skip and pop every time it happened, it would be the antithesis of smooth driving. :confused

[1fatcat]

Ok, I should have been more clear on that. It idled pretty darn smooth with no popping/backfiring. If you tried to accelerate, it would pop and backfire along with very little power. Let off the throttle and it would go right back to a smooth idle.

[atakordie]

I'm dealing with a similar issue on a recently acquired 2001 750. Thread about it here: http://forums.bimmerforums.com/forum/showthread.php?2105932-Just-entered-the-E38-world-with-a-750iL-needing-a-lot-of-care-Drivetrain-help-sought

My compression numbers were relatively similar to each other, but high (~215 psi range). Two head bolts are snapped on bank 1. I'm still waiting on the timing tools from a supplier before I rip inside the engine. Not sure what's going on with the wait on my tools, but you may want to make sure you have access to the tools before removing the head.

[dburt86]

Do a leak down test if you wanna be certain. No point in spending big money on gaskets when you have a cracked piston or something alone those lines.

[xboss]

Have better bolts been made for the heads yet or are they the same old bolts?

[1fatcat]

Have better bolts been made for the heads yet or are they the same old bolts?
That's a great question! I haven't checked any of mine yet, but I did get this far today...
http://i727.photobucket.com/albums/ww279/1fatcat/bmwheadgaskets001.jpg (http://s727.photobucket.com/user/1fatcat/media/bmwheadgaskets001.jpg.html)

[xboss]

Nice, you got pretty far!

[1fatcat]

I won't have time to work on it again for a few days now, that sucks. I really want to get those heads off so I can start ordering parts, because I'll have to wait for the parts to come in too. I'm anxious to get it going. :)

[1fatcat]

So I got the heads off and sure enough, the head gasket is blown between cylinder 9 & 10. Parts are ordered, but will be a while before they get here. I still need to get the heads reconditioned just because it wouldn't make sense not to at this point.
http://i727.photobucket.com/albums/ww279/1fatcat/bmw3007.jpg (http://s727.photobucket.com/user/1fatcat/media/bmw3007.jpg.html)
http://i727.photobucket.com/albums/ww279/1fatcat/bmw3003.jpg (http://s727.photobucket.com/user/1fatcat/media/bmw3003.jpg.html)
http://i727.photobucket.com/albums/ww279/1fatcat/bmw3006.jpg (http://s727.photobucket.com/user/1fatcat/media/bmw3006.jpg.html)
http://i727.photobucket.com/albums/ww279/1fatcat/bmw3004.jpg (http://s727.photobucket.com/user/1fatcat/media/bmw3004.jpg.html)
http://i727.photobucket.com/albums/ww279/1fatcat/bmw3002.jpg (http://s727.photobucket.com/user/1fatcat/media/bmw3002.jpg.html)
http://i727.photobucket.com/albums/ww279/1fatcat/bmw3001.jpg (http://s727.photobucket.com/user/1fatcat/media/bmw3001.jpg.html)

On a side note, I noticed that the gaskets are Victor Reinz. I also noticed recently that another member here pulled the heads off his V12 and it also had Victor Reinz head gaskets. At the time, I thought his were aftermarket and had been replaced once already, but now I'm not sure? Did BMW use Victor Reinz head gaskets from the factory?

[M I C H A E L]

No those Victor reinz is oem "quality" not OEM. Oem is bmw logo stamped on it. Get them from the dealer. That's what I would do. Good job putting in work!

[WarMachine7]

No those Victor reinz is oem "quality" not OEM. Oem is bmw logo stamped on it. Get them from the dealer. That's what I would do. Good job putting in work!

I thought reinz was oem and bmw just stamped bmw like dinan does?

[CDO5OO1A]

Am doing similar with a M73. Initial cause was overheat due to pin hole leak in hose at aux water pump. New head bolts from dealer a must. (one time use). I'm confident with the Victor Reinz head gaskets. Remember it's mostly aluminum so you've got to follow the torque specs for most every bolt. Sometimes it will seem like it's not tight enough but that's from the feel of working with steel blocks and heads. You can check your valves by turning the head upside down in your lap with a bit of dish soap and water and a compressed air hose. Put a bit of soap and water around the valve and then blast air into the intake or exhaust port. If you see bubbles you'll need to use valve polish paste and re-polish the valve to the seat. Copper paste(anti-seize) on the exhaust fasteners is a good idea too.

[1fatcat]

I did buy new head bolts, and have torqued head bolts on aluminium block engines. The Cadillac Northstar V8 is scary to torque down, with an aluminum block and torque specs of 30 ft lbs + 70* + 60* + 60*! It gets scary on that last 60* pass!!! Very surprised that the threads hold!...but if you don't "time-sert" them, they probably won't hold.

I've done head gaskets on steel block/steel head, steel block/aluminum head, aluminum block/aluminum head. The specs on this V12 is pretty minimal compared to the aluminum block/aluminum head northstar. Next to nothing in comparison, really.

Northstar = 30 ft lbs + 70* + 60* + 60*
BMW V12 = 22 ft lbs + 60*

Both engines use aluminum blocks and heads, but there is a huge difference in head bolt torque.

[xboss]

I did buy new head bolts, and have torqued head bolts on aluminium block engines. The Cadillac Northstar V8 is scary to torque down, with an aluminum block and torque specs of 30 ft lbs + 70* + 60* + 60*! It gets scary on that last 60* pass!!! Very surprised that the threads hold!...but if you don't "time-sert" them, they probably won't hold.

I've done head gaskets on steel block/steel head, steel block/aluminum head, aluminum block/aluminum head. The specs on this V12 is pretty minimal compared to the aluminum block/aluminum head northstar. Next to nothing in comparison, really.

Northstar = 30 ft lbs + 70* + 60* + 60*
BMW V12 = 22 ft lbs + 60*

Both engines use aluminum blocks and heads, but there is a huge difference in head bolt torque.
They are stretch bolts so the threads do not have to hold too much pressure

[CDO5OO1A]

I did buy new head bolts, and have torqued head bolts on aluminium block engines. The Cadillac Northstar V8 is scary to torque down, with an aluminum block and torque specs of 30 ft lbs + 70* + 60* + 60*! It gets scary on that last 60* pass!!! Very surprised that the threads hold!...but if you don't "time-sert" them, they probably won't hold.

I've done head gaskets on steel block/steel head, steel block/aluminum head, aluminum block/aluminum head. The specs on this V12 is pretty minimal compared to the aluminum block/aluminum head northstar. Next to nothing in comparison, really.

Northstar = 30 ft lbs + 70* + 60* + 60*
BMW V12 = 22 ft lbs + 60*

Both engines use aluminum blocks and heads, but there is a huge difference in head bolt torque.

I think there are three passes on the BMW V12 - M73.




Thoroughly clean all mounting surfaces and check the head for warpage. Check the condition of the head locating dowel sleeves and clean out the bolt threads with a tap.

Check the cylinder head and block deck surface to be sure they are true and install a new head gasket.
NOTE
Use a thicker head gasket if the head has been machined.



Apply sealant to the joints between the engine block and the upper and lower timing covers.

Mount the cylinder head on the block and use new bolts. Do not remove the coating on the head bolts, apply oil to the threads and torque following the tightening sequence in 3 steps as follows:


Step 1: 22 ft. lbs. (30 Nm)

Step 2: 60 degrees

Step 3: 60 degrees



Reinstall the timing sprocket to the camshaft. Be sure the camshaft is in proper time and use new lockplates. The camshaft for cylinder number 1 is at TDC firing position when the recess of the camshaft flange is flush with the bolt holding the oil baffle.

The balance of installation is the reverse of the removal procedure.

Fill the cooling system.

Start the engine and check for leaks. ...

[1fatcat]

Hmm, I'll need to look into that further. I'm using Mitchel On Demand for repair info, but maybe their info is wrong? Two 60 degree passes does sound more realistic than one. What source did you get your info from?

[mboor]

They are stretch bolts so the threads do not have to hold too much pressure

Ive done head jobs on north star engines. Def worse / more involved than our V12. I'd never pull another north star engine apart. They suck.

[psjr]

I just checked TIS, it's 30Nm + 2x 60 degrees.
Be sure to use official sources for your info :)

http://e38.org/bmw_torq.pdf has a large number of torque specs pulled from TIS.

[1fatcat]

Thanks psjr and CD05001A! I'm using Mitchell On Demand 5. Would have thought I could trust their info, but I guess not! Thanks guys for straightening this out, it would have sucked to put this together with loose head bolts!

I triple checked Mitchell and it must be wrong. It doesn't say anything about a second degree pass. My software is outdated by 3 years (was current in 2011), but you would think that in 2011 they had enough time to correct a mistake that was 15+ years old :rolleyes

[StylezP]

so what happened?