Just entered the E38 world with a 750iL needing a lot of care. Drivetrain help sought

[M I C H A E L]

Wow. You went in head first!! Sucks this has all happened and been neglected. Psjr is right. Sourcing a used one would be cheaper... Good luck moving forward.

[1fatcat]

I would say the pistons, rings and cylinders are fine. 200+ psi is great compression and your readings were within 10 percent of each other or better. But guy, do me a huge favor and get some better supports under that car before you crawl under it again.


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Also, looks like your head gaskets were replaced once before. I can read "VICTOR REINZ" on your engine block. I don't know for sure, but I don't think BMW used victor reinz gaskets from the factory.

While you have the heads off, turn the engine over by hand and check all 12 pistons to make sure they all come up to the same height relative to the deck of the engine block. If a connecting rod is bent, that piston will not come up as far. This can cause a vibration and rough idle. I highly doubt you have a bent rod as that will also cause a low compression reading, but since it's all apart why not check?

[CDO5OO1A]

1. Mostly you've got a lot of cleaning, replacing gaskets for new and a new set of cylinder bolts, as they are NOT reusable(torque to yield using two passes and angle measurements) ahead of you.
Even beyond your mileage the inside of the cylinders shouldn't look like that. It's as if crankcase vapor(oil) was being sucked into the intakes. The huge light bulb over my head was when another poster noticed Victor-Heinz. So somebody has been here(inside this engine) before. Mal-functioning crank case ventilation could also be a source of oil vapor in the intake mixture.
Possibly of improper installation of valve seals. When valve seals are placed on valve stems you use a protective tube to keep the top of the valve stem from damaging the seal.
2. Valve to seat can be checked by placing a bit of water w/ dish soap at the sealed valve then blow compressed air in through the intake or exhaust ports and watch for bubbles. If you get bubbles you'll need to re-polish the valve to the seat w/ paste.
3. You need to ask way more questions.

(edited)

[psjr]

Not sure what everyone's on about... I see jack stands holding up the car and some decorative stones holding up the brake caliper.

[1fatcat]

Not sure what everyone's on about... I see jack stands holding up the car and some decorative stones holding up the brake caliper.

Doh! That was me. I didn't even notice the jack stands, all I seen were cinder blocks and I was like, WHAAAAT? Looks like OP has things under control.

[dburt86]

I would for certain not waste the time and money rebuilding a stock engine when you can get a used long block for a fraction of the cost. These motors do not typically have issues like this so i wouldnt worry about getting a used engine with issues becasue its not likely to happen.

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I can only assume that the scratches in the cylinder walls are from the pistons grabbing carbon from the tops of the clyinders when the last owner was hot rodding it around. (evident that he drove it hard from the fact he put an aftermarket exhaust on it)

Those carbon rings on the top of each cylinder is common to see in older engines, so when someone revs the engine beyond what it typically sees, the pitons make it into that carbon ring.

The nicks on the tops of the pistons do not really concern me at all.

The amount of oil in the chambers probably indicates crappy OSV's

[board57796]

Take many photos! The ones you have are great, I love seeing the inside of these engines.

[mboor]

Nice job so far on all the work. Glad to see someone really going through this car from bumper to bumper. Cant wait to see it back together in all its former glory. I'd be sure to send the heads out and have the vales checked, it would be a real bummer if one was bent slightly when it hit the piston. I have had this happen before a few times (not with BMW's) and lucked out with no damage. Im my experiance the valve springs usually dont have enough force to damage the valves when the slip and hit the piston. I have only seen them damaged when the engine is running and piston to valve interference occures...

[atakordie]

I would say the pistons, rings and cylinders are fine. 200+ psi is great compression and your readings were within 10 percent of each other or better. But guy, do me a huge favor and get some better supports under that car before you crawl under it again.


- - - Updated - - -

Also, looks like your head gaskets were replaced once before. I can read "VICTOR REINZ" on your engine block. I don't know for sure, but I don't think BMW used victor reinz gaskets from the factory.

While you have the heads off, turn the engine over by hand and check all 12 pistons to make sure they all come up to the same height relative to the deck of the engine block. If a connecting rod is bent, that piston will not come up as far. This can cause a vibration and rough idle. I highly doubt you have a bent rod as that will also cause a low compression reading, but since it's all apart why not check?

The high compression doesn't make sense to me (BMW TIS says 145-174psi) unless that carbon buildup is causing that much increase. And yes, I do have the car on 4 jack stands at the jack points; the blocks are holding the brake caliper while I change out the suspension. If someone's been this engine before, that explains the carelessness of not torquing all the head bolts correctly (or at all ). I will try to look at the piston travel height at TDC for each cylinder, good call. I've never done this before, so I'll look for a procedure...unless you think I could eyeball it?

1. Mostly you've got a lot of cleaning, replacing gaskets for new and a new set of cylinder bolts, as they are NOT reusable(torque to yield using two passes and angle measurements) ahead of you.
Even beyond your mileage the inside of the cylinders shouldn't look like that. It's as if crankcase vapor(oil) was being sucked into the intakes. The huge light bulb over my head was when another poster noticed Victor-Heinz. So somebody has been here(inside this engine) before. Mal-functioning crank case ventilation could also be a source of oil vapor in the intake mixture.
Possibly of improper installation of valve seals. When valve seals are placed on valve stems you use a protective tube to keep the top of the valve stem from damaging the seal.
2. Valve to seat can be checked by placing a bit of water w/ dish soap at the sealed valve then blow compressed air in through the intake or exhaust ports and watch for bubbles. If you get bubbles you'll need to re-polish the valve to the seat w/ paste.
3. You need to ask way more questions.

(edited)

1. Yes, I have new head bolts and am aware of the TIS torque specs and tightening sequence. If there is a bolt coming off of this engine, I have a new one from BMW ready to replace it when assembly time comes. I've already had 3 bolts shear apart when trying to remove them: one on the rear coolant manifold, and two on the valley pan. I'm not using air tools on the engine except to remove the exhaust manifold nuts. Regarding the crankcase vapor, there is a decent amount lining the walls of the intake manifolds. The manifold gaskets had several ports where significant oil seepage had occurred. I'll probably take the intakes to a machine shop to have them cleaned (along with everything else). Good hear your thoughts on the matter. I saw the Victor-Reinz too, but didn't think anything of it until you guys responded, thanks.
2. Hopefully the machine shop will find any bent valves on the heads. I was planning on changing the stem seals myself, so if there is a messed up valve that needs replacing that the machine shop can't fix, I'll use your method for checking for leaks.
3.haha, I'm sure I'll have more soon.

I would for certain not waste the time and money rebuilding a stock engine when you can get a used long block for a fraction of the cost. These motors do not typically have issues like this so i wouldnt worry about getting a used engine with issues becasue its not likely to happen.

- - - Updated - - -

I can only assume that the scratches in the cylinder walls are from the pistons grabbing carbon from the tops of the clyinders when the last owner was hot rodding it around. (evident that he drove it hard from the fact he put an aftermarket exhaust on it)

Those carbon rings on the top of each cylinder is common to see in older engines, so when someone revs the engine beyond what it typically sees, the pitons make it into that carbon ring.

The nicks on the tops of the pistons do not really concern me at all.

The amount of oil in the chambers probably indicates crappy OSV's

makes sense. I have new OSVs to put in, so hopefully that part will be solved.

Nice job so far on all the work. Glad to see someone really going through this car from bumper to bumper. Cant wait to see it back together in all its former glory. I'd be sure to send the heads out and have the vales checked, it would be a real bummer if one was bent slightly when it hit the piston. I have had this happen before a few times (not with BMW's) and lucked out with no damage. Im my experiance the valve springs usually dont have enough force to damage the valves when the slip and hit the piston. I have only seen them damaged when the engine is running and piston to valve interference occures...

Yeah, it'll be nice to finally have it going. The heads are at a machine shop now, waiting to hear back about their condition and what needs to be done to them.

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Take many photos! The ones you have are great, I love seeing the inside of these engines.

Thanks, I'll be posting more when things happen.

[1fatcat]

That bit of carbon will not cause high compression, I don't know if I'd worry about that yet. It could be that cam timing was off a tooth, or it could be that BMW under-rated the power of the engine and fibbed about compression ratios? At any rate, the only reason compression would be too high on a stock engine is if the cam timing was off slightly. You will have to re-time it anyways.

With the compression numbers you had, the pistons, rings and cylinders should be fine. Also, the valves should be fine. BUT, since it's apart I would certainly clean & check the valves, valve seats, valve guides and most certainly the valve seals. Worn valve seals will definitely cause carbon build-up in the combustion chamber. Also, poorly seating intake valve can cause carbon build-up in the intake manifold, but that is usually associated with low compression readings. A cylinder leak-down test would tell more, but the engine needs to be together for this.

As for checking the piston travel to check for bent rods, yes, you can eye-ball it. If one is bent, you will see it. Like I said though, I highly doubt you have a bent rod because if you did the compression would be considerably low in that cylinder. But why not give it a quick check while the heads are off?

[atakordie]

Two things:

1. Machine shop said the heads were way out and it needs some valve love. I gave them the BMW stem seals to do while they're in there, and (hopefully without offending) let the guy know there was a machining limit. I didn't think to tell him they had been off the block once before. I hope they turn out alright.
2. I checked the block again after thinking about those 2 loose head bolts on bank 1, and whaddya know, they have been helicoiled I tried one of the used bolts, threading it in a little and it just isn't right. Plus, from what I know (not a whole lot), I don't think helicoil is the answer for an engine block like this. Part of the helicoil was breaking off as I started the bolt in one of the bores. It looks like only those two were helicoiled, as they are visibly different in diameter.

At this point, I am tempted to throw in the towel for this block, and find a used one...and still change all the seals, gaskets, etc. since they are already waiting here at the house. I haven't checked the piston travel yet as 1fatcat suggested, as there is some debris stuck to the cylinder walls (even though the block is covered for now with a a large bag) and I need to clean it up first.

[psjr]

As soon as the machine shop said there was any issue with the heads, I would have had them stop right there and just swapped another motor. I think the $500-800 purchase cost of a whole motor would be less than all the trouble you're considering going through.

[1fatcat]

Sorry to hear about the helicoils. There is a thread repair insert out there that is a much better design than a helicoil, it's called a "time-sert" but is a bit of a specialty insert (made specifically for head bolt thread repairs in aluminium engine blocks and other applications). It requires some carefully planned drilling, taping and installation along with some special tools to install them.
Just google "time-sert" and you'll find all kinds of info on them. The main advantage is that they are one solid piece instead of coils of thread.
Time-Sert-VS-Helicoil-1.jpg

The only problem with trying to use a time-sert now, is that someone already tried a helicoil. So the hole may already be drilled too big or tapped to the wrong thread size for a time-sert. If the hole/threads are of the right size for a time-sert, then you may be able to use them yet. Getting the old helicoils out will be a challenge too.

[M I C H A E L]

So conclusion... The car had overheated in the past at some point and now the head is toast.. Aw man. Im sorry you have to go through this. Definitely not something someone wants when they buy their first 7.

I'm happy to know you're going to put it back on the road. Just get a used head and replace everything and the seals.

The banjo bolts coming loose is a common occurance with these engines.

[BOBS750il]

Two things: 1. Machine shop said the heads were way out and it needs some valve love. I gave them the BMW stem seals to do while they're in there, and (hopefully without offending) let the guy know there was a machining limit. I didn't think to tell him they had been off the block once before. I hope they turn out alright. 2. I checked the block again after thinking about those 2 loose head bolts on bank 1, and whaddya know, they have been helicoiled I tried one of the used bolts, threading it in a little and it just isn't right. Plus, from what I know (not a whole lot), I don't think helicoil is the answer for an engine block like this. Part of the helicoil was breaking off as I started the bolt in one of the bores. It looks like only those two were helicoiled, as they are visibly different in diameter. At this point, I am tempted to throw in the towel for this block, and find a used one...and still change all the seals, gaskets, etc. since they are already waiting here at the house. I haven't checked the piston travel yet as 1fatcat suggested, as there is some debris stuck to the cylinder walls (even though the block is covered for now with a a large bag) and I need to clean it up first.

If your looking for another block I may have what you need. Cylinders will need a honing and I'd have the block cleaned which I'm sure you would do during a rebuild anyway.

Sent from my iPhone5s using BF.com

[mboor]

A properly installed helicoil shouldnt be anything to worry about. Remember the caddilac northstar engines? GM has a "special" kit to install helicoils on the head bolt threads (i did the head gaskets on one and had to helicoil ALL the head bolts=nightmare). They pull the threads out of the aluminum block when you remove the heads. Supposedly a properly installed helicoil is stronger than the factory threads, but i dont believe that. It sounds like the two helicoils on your block are boogered. id start looking for a good used engine. even if you do get this one back together, it sounds like its going to be a ticking time bomb.

[pumpedTSI]

I'm with MB.......sounds like a used motor/short block is the way to go.....

[1fatcat]

Cylinders will need a honing

I don't know for sure, but I thought these engines had aluminium cylinders with a nikasil coating? If so, then they can not be honed without re-coating the cylinders. Big job, engine block would need to be stripped 100% and sent out to a re-plating company.

[mboor]

I believe the early M60 4.0l V8's had the nikasil lined cylinders, up to early 1996 model year. i dont think this was an issue on the M73 engines

[pumpedTSI]

I believe the early M60 4.0l V8's had the nikasil lined cylinders, up to early 1996 model year. i dont think this was an issue on the M73 engines

It wasnt..........early V8 only...no issues with the M70 or M73 V12...

[1fatcat]

OK, please don't be offended by this, I still can't say for sure, but this looks like a coated aluminum cylinder to me. Please correct me a second time if I'm wrong.
_MG_0960.jpg

[psjr]

Yes, the notorious problems were with Nikasil, used on the M60.
What seems to have been missed here is that subsequent V8s and the M70/73 use Alusil, a similar compound and application but without the corrosion issues.

AFAIK, there are only a few shops anywhere that can re-etch the Alusil properly after honing, and it certainly wouldn't be worth the cost compared to any other options here.

As I have suggested twice already, I would recommend replacing the motor entirely as the cheapest AND lowest labor option.

[1fatcat]

At any rate, the only reason compression would be too high on a stock engine is if the cam timing was off slightly.

Oops, I need to add to this. On a STOCK engine this would hold true, but your engine has had the heads off before. Your compression may be higher than spec if the heads were resurfaced in the past and a thicker head gasket was not used.

[Binjammin]

Oops, I need to add to this. On a STOCK engine this would hold true, but your engine has had the heads off before. Your compression may be higher than spec if the heads were resurfaced in the past and a thicker head gasket was not used.

Please stop being ridiculous. The amount of carbon buildup you would need to affect compression would foul out a plug long before it ever got to that point.

Want proof? Go find an engine and drop 1 cubic centimeter of oil into the chamber. It will have a greater thickness than carbon buildup. Play around with a displacement calculator, you can change chamber volume in CCs until you see how many it takes to make an appreciable change. Hint: it's more than some carbon will give you.

[daytonatrbo]

It looks like your engine has some piston slap, which is often the result of the engine being pushed too hard when cold.

The scoring may be from the over heat. The valve hitting the piston could be from carbon buildup preventing the valve from closing properly, but i'm not sure that these engines will strike that easily. Could be indicative of previous timing issues. The rings of carbon in the cylinder bores are not uncommon where the engine was sucking oil.

If it were me, I'd be looking into a used engine that comes with a warranty.

Either way, I'm really impressed by your can-do attitude and the amount of work you have put in so far. Happy to see such a wonderful car getting the love it deserves.